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The Theory of Evolution by Natural Selection Why Is It Important Revolutionary breakthrough in our understanding of the world one of the most important theories in science This explains 1 Diversity and similarities of organisms 2 Adaptation to environment One of the bestsupported theories in science overwhelming amount of evidence What Did People Believe In The 19th Century Special Creation leading explanation for diversity of organisms in mid19th century Pattern 1 Species independentseparate entities 2 Species staticdo not change over time Life on earth is young 6000 years old Hierarchy of species certain species were more superior larger more complex Humans were at the top Process gt Each species created separately and instantaneously by divine being The New Theory of Evolution By Natural Selection gt Formulated independently by Darwin amp Wallace 1858 gt Radical departure from prevailing View Pattern Descent with modification 1 Species related by common ancestry species descend from pre existing ones 2 Species change through time characteristics can be modified over generations Life on earth far older Process Natural Selection gt Explains how evolution occurs Pattern Modern Terminology Evolution Evolution Process Natural Selection gt Traits vary among individuals in a population gt Those individuals better suitedadapted to the environment Will leave more surviving offspring more of their genes in the next generation than less adapted individuals Variation within populations becomes more important Scientific testable theory In uential Figures 1 James Hutton amp Charles Lyell a Slow subtle continuous processes 9 substantial geological change b Earth is very old 2 Jean Baptiste Lamarck a Proposed mechanism for evolution Inheritance Of Acquired Characters b Traits in parents modified through use passed to offspring in modified form c Emphasized adaptation to the environment 3 Thomas Malthus a Potential of human population to increase faster than food and other resources Evidence Species Are Related Common Descent 1 Geographic Proximity of Similar Species 2 Homologies similarities that exist because of common descentrelatedness a Structural Homologies ex vertebrate limb bones b Developmental Homologies ex early vertebrate embryos c Genetic Homologies ex genes controlling development of animal eyes and limbs 3 Current Examples of Descent From Common Ancestor ex formation of new species Internal Consistency Data from independent sources are consistent gt Coelacanth morphology amp DNA Evolution by natural selection occurs when genetically based traits are passed to the next generation in different proportions Darvvin s 4 Postulates Natural Selection logical outcome of 4 conditions 1 Individuals Within a population vary in traits 2 At least some of the variation bust be heritable ie has genetic basis 3 Some individuals produce more offspring than others 4 Individuals producing most offspring not random subset of the population Result 9Population characteristics will change over time Evolution will occur Current View gt Distilled the 4 postulates to the essence gt Natural selection occurs when heritable variation leads to differential reproduction These conditions are very typical in nature happens very often It is pretty impossible for Darwin s 4 postulates to not be fulfilled Frequently Used Terms Darwinian Fitness The ability of an individual to produce offspring relative to that ability in other individuals in the population gt Individual that produces many surviving offspring is more t than one that produces few gt Measurable quantity Adaptation A heritable trait that increases the fitness of an individual in a particular environment relative to individuals lacking the trait gt EX Lungs of a lung fish gt The changing of a species that result in its being better suited to its environment Questions About Heredity gt To understand evolution need to know how 1 Variability in heritable traits maintained 2 Characteristics passed from parents to offspring Heredity the transmission of traits from parent to offspring Mendel s Experiments With A Single Trait gt Crossed pure lines homozygous differed in only one trait to create a hybrid o 31 ratio in F2 generation Mendel s Model Particulate Inheritance Hypothesis gt Hereditary determinants genes maintain their integrity from generation to generation 1 Do not blend together 2 Do not acquire new or modified characteristics through use gt Each individual carries 2 alleles of each gene gt The Principle of Dominance o In heterozygote Dominant allele expressed Recessive present by unexpressed gt The Principle of Segregation 0 Two alleles of each gene must segregate into different gamete cells during formation of eggs and sperm in parents Each gamete contains one allele of each gene Mendel s Experiments With Two Traits What patterns of inheritance do we observe when we cross parental lines that differ in TWO or more traits gt Two possibilities 1 Alleles of two genes are passed on together 2 Alleles of two genes are inherited independently If alleles of two genes stay together Ratio of F2 offspring genotypes A 12 1A If alleles of two genes do not stay together Ratios of F2 offspring genotypes 916 316 3 16 116 The Principle of Independent Assortment pairs of alleles for different traitsl genes segregate independently from one another during gamete formation A Little About Chromosomes gt DNA proteins gt Differ in lengthsize gt Different species have different numbers of per cell gt In many organisms there are 2 sets 1 from father amp 1 from mother Homologous pairs similar size shape same genes not necessarily same alleles Ploidy number of chromosome sets present numeral before the n gt Cells with one set of chromosomes haploid n gt Cells with chromosome pairs diploid 2n gt Cells with three sets of chromosomes triploid 3n Haploid number n the number of distinct types of chromosomes found in a species Replication Of Chromosomes gt Chromosomes can be replicated or unreplicated gt Copies held together by a centromere gt Each copy is a chromatid gt Chromatids of the same chromosome are called sister chromatids Cell Division Mechanisms Overview 2 Fundamentally different kinds 1 Mitosis a Makes cells genetically identical to parent cell b For growth replacement and asexual reproduction c In nonreproductive somatic tissues 2 Meiosis a Makes cells with half genetic material only one member of each homologous pair b For production of gametes sex cells c In reproductive germ tissues The Stages of Mitosis 1 Prophase o Chromosomes condense Chromatids unwoundlong strands Chromosome condensedcompact 0 Nuclear envelope begins to disintegrate o Spindle begins to form Spindles are built from microtubules Originates from centrosomes Radiate out from poles meet in the middle Moves chromosomes 2 Metaphase o Chromosomes move to center and line up single file along the equator of the cell 3 Anaphase o 2 sister chromatids separate and move toward opposite poles 4 Telophase o Chromosomes start to decondense 0 Nuclear envelope begins to form 0 Spindle fibers break down and disappear 1 Diploid cells 9 2 Identical Diploid cells The Stages of Meiosis Meiosis I called reduction division homologous chromosomes separate chromosome number is halved 1 Prophase I o Homologous chromosomes pair up synapse 2 Metaphase I o Homologous pairs of replicated chromosomes line up along the equator 3 Anaphase I o Homologs separate members of each homologous pair go to opposite poles o Chromatids do NOT separate 4 TelophaseCytokinesis o Cytoplasm divides to form 2 haploid daughter cells Meiosis II Sister chromatids separate and each daughter cell divides in two very similar to mitosis 1 Diploid Cell 9 4 UnIdentical Haploid Cells Generating Genetic Variation Sex cells produced via meiosis genetically variable due to 2 processes 1 Crossing Over a Occurs in Prophase I synapsis b 2 nonsister chromatids physically exchange DNA c Since alleles on 2 chromosomes may differ this leads to new genetic combinations on each chromosome 2 Separation amp Distribution of Homologous Chromosomes a Occurs in Metaphase I b Orientation of matemal vs paternal chromosomes at equator random c Different gametes end up with different combinations of matemal and paternal chromosomes d 2 different combinations possible Sexual Reproduction gt In sexual reproducing species gametes from different individuals combine to form offspring outcrossing gt Increases genetic diversity of offspring gt Without outcrossing for self pollinators genetic diversity also exists The Chromosomal Theory of Inheritance In 1903 Sutton amp Boveri hypothesized that 1 Chromosomes carry Mendel s genes 2 Mendel s rules explained by independent segregation of homologous chromosomes at meiosis I Chromosomal Theory of Inheritance Physical Basis for the Principle of Segregation Principle of Segregation Pairs of alleles are separated during meiosis in the formation of gametes gt One allele on matemal chromosome other on paternal chromosomes gt Meiosis I Homologs and alleles 9 different daughter cells 9 different gametes gt Each gamete carries one allele for trait not two Physical Basis for the Principle of Independent Assortment Principle of Independent Assortment The genes for seed shape and seed color assort independently because they are located on different chromosomes gt When genes are on different chromosomes gt Meiosis I each homologous pair carrying a gene lines up independently of others 9 different combinations of maternal and patemal chromosomes in daughter cells gt Different genes assort independently of one another Sex Linked Inheritance Discovered by Thomas Hunt Morgan through Work with Drosophila observed unusual patterns of inheritance reciprocal crosses did NOT give same results Sex Chromosomes gt In mammals and other groups females XX males XY gt X is larger carries more genes the pairs are NOT homologous gt Nonsex chromosomes are called autosomes Sex Chromosomes and Gamete Formation gt Pair at meiosis I segregate into different gametes gt All female eggs carry one X 12 sperm carry X and 12 sperm carry Y Inheritance of XLinked Genes gt Genes carried only on X not on Y 9 XLinked 0 Females 2 copies of gene one from each parent Males 1 copy from mother gt How to quickly spot an XLinked trait o Recessive phenotypes seen more often in males 0 A son cannot inherit X linked gene from his father Linked Genes gt Concept developed by Morgan gt Genes for different traits assort independently when located on different chromosomes When located on the same chromosome it displays linkage Predict linked genes 1 Inherited together end up in the same gamete 2 Produce fewer gametes and offspring genotypes Typically small of unexpected recombinant genotypes produced Due to crossing over Extensions of Mendel s Rules Mendel worked with the simplest kind of genetic system Phenotypes of traits based on single gene two alleles complete dominance and autosomal inheritance Not all genes follow Mendel s rules Incomplete Dominance gt Neither allele is dominant gt Heterozygote show phenotype intermediate between two homozygous phenotypes 0 Ex red ower white ower pink ower Codominance gt Both alleles expressed at the same time gt Heterozygote has phenotype of both homozygote 0 Ex red cow white cow cow half white half red Don1inant Recessive Relationships 1 Range of dominance complete 9 incomplete 9 codominance a Depends of mechanism and level examined i Ex TaySachs hh cannot break down lipids HH can break down fast Hh can break down but slow codominance 2 Dominant characteristics of an allele do not have anything to do with abundance or fitness of that allele in a population Genes One gene can have dozens of alleles 9 hundreds of alleles per locus Multiple Alleles the existence of more than 2 alleles on the same gene One individual cannot carry more than 2 alleles at a time Pleitropyz when a single gene affects more than one phenotypic trait 0 Ex frizzle gene in chickens feathers curl upward abnormal body temperature higher blow ow etc The environment has a strong effect on phenotypes produced by most genes ex Effect of food deprivation on growth fur color in Himalayan rabbits Presence of Other Genes gt Interactions can occur between genes at different loci gt Episasis when phenotype produced by an allele depends on actions of genes at other loci 0 Ex Fruit color in bell peppers RY red rrY yellow R yy brown rryy green Why Do Many Traits Vary By Small Increments Rather Than In Large Jumps Polygenic Inheritance gt Each locus contributes small amount to phenotype gt Produces quantitative trait range of phenotypes gt Continuous bellshaped normal distribution of phenotypes in population gt Opposite to Discrete Traits Ex Human skin color The Hardy Weinberg Model gt Given certain allele frequencies Hardy Weinberg predicts What the genotype frequencies of a population would be when evolutionary forces are NOT acting and mating is random gt Acts as a null model or base line for comparison p frequency of A allele q frequency of a allele frequencies add up to 1 The Hardy Weinberg Principle gt Allele frequencies do not change over time when transmitted according to rules of Mendelian inheritance gt If allele frequencies in a population are given by p and q then genotype frequencies Will be given by p2 2pq q2 generation after generation as long as certain conditions apply Assumptions Of The Model 1 No mutation a No existing alleles converted to other existing alleles b No new alleles created 2 No gene flow a No new alleles added or lost via migration 3 No genetic drift a No randomchance allele frequency changes 4 No selection a All parents contribute gametes equally to gene pool 5 Random mating Useful Equations Any time pq1 p fAA 12 fAa q faa 12 fAa Only when population is in Hardy Weinberg fAA p2 fAa 2pq faa q2 Determining if a population is in HW Equilibrium Step 1 Figure out underlying allele frequencies Step 2 Determine what genotype frequencies should be in HW Step 3 Compare expected HW genotype frequencies with observed Evolutionary Mechanisms gt 4 mechanisms of evolution 1 Selection 2 Mutation 3 Migration Gene Flow 4 Genetic Drift gt Different consequences 9 adaptation amp genetic diversity Selection and Adaptation How does selection differ from other evolutionary mechanisms This is the only mechanism that brings about 1 Nonrandom change in allele frequency 2 Adaptive evolution increases ability of organisms to survive and reproduce Modes of Natural Selection 1 Directional Selection changes the average value of a trait a Allele frequency changes in one direction b Selection favors one end of phenotype rang these become more common and reduces other extreme c Consequences i Changes average value of trait ii Tends to reduce genetic diversity d Purifying selection selection that lowers the frequency or even climates deleterious alleles 2 Stabilizing Selection reduces the amount of variation in a trait a Selection acts against both extremes in population b Favors phenotypes near the mean c Consequences i No change in average value of trait over time ii Genetic variation in population reduced 3 Disruptive selection increases the amount of variation in a trait a Opposite to stabilizing selection b Eliminates phenotypes near mean and favor extreme phenotypes c Consequences i Average value of trait stays same ii Overall variation in trait decreases 4 Balancing Selection No single allele is favored Instead there is a balance of alleles in terms of fitness and frequency a Occurs When i Environment varies over time and space ii Certain alleles are favored when rare b Consequences i Genetic variation is maintained or increased Frequencv Dependent Selection gt Direction of selection uctuates 9 first selection favors one trait then it favors another gt Each trait is advantageous when rare gt Maintains two or more traits in a population EX Three mating strategies of a marine isopod Conclusion gt Natural selection can increase adaptation gt Different pattems of selection produces different outcomes of allelic diversity and direction of evolutionary change most forms of selection favors certain alleles and lead to a decrease in overall genetic variation SUMMARY TABLE 263 Modes of Selection Effect on Genetic Mode of Selection Effect on Phenotype Variation Directional selection Favors one extreme Genetic phenotype causing variation is the average reduced phenotype in the population to change in one direction Stabilizing selection Favors phenotypes Genetic near the middle variation is of the range of reduced phenotypic variation maintaining average phenotype Disruptive selection Favors extreme Genetic phenotypes at both variation is ends of the range of increased phenotypic variation Balancing selection No single phenotype Genetic is favored in all variation is populations of a maintained species at all times 0 901 5 our011 l lucnllon Inc Evolution and Natural Selection 1 Misconception Individuals evolvechange genetically 0 Correction Natural selection acts on individuals Populations evolvechange 0 Ex beak size in Galapagos finches peppered moth 2 Misconception Selection acts at groupspecies level 0 Natural selection promotes survival of species 0 Individuals act for the good of the species 0 Correction Selection promotes survivalreproduction of individuals Truly altruistic behavior selected against Note every altruistic behavior studied found to increase altruistic s fitness because beneficiaries are close genetic relatives or reciprocate 0 Ex prairie dog alarm calls lemmings commit suicide by jumping off cliffs 3 Misconception Evolution is progressive o Organisms have become better over time 0 Correction Tendency toward increased complexity organization and specialization But thousands of instances of group becoming simpler than ancestors 0 Ex tapeworms snake earliest birds bivalves echinoderms 0 Complexity can be costly energy and not necessarily superior 4 Misconception Evolution is goaloriented o Adaptation evolves because organisms want or need them 0 Correction Evolution is blind it does not look ahead The environment cannot direct the formation of mutations Adaptation Misconception organisms are perfectly adapted to their environments Not All Traits are Adaptive 1 Vestigial structures structures present in ancestors but not currently adaptive Ex goose bumps 2 Developmental holdovers ex rudimentary mammary glands of human males developed because this is developed before sex hormones kick in and say no need Functional Structures Are Constrained In A Variety Of Ways gt All adaptations compromises gt Constrained by 9genetics history multiple demands 1 Genetic Constraints a Lack of genetic variation Selection favors most fit variations from what is available 0 Ex salamanders and limb regrowth inability of some bird species to recognize interspecific nest parasites b Genetic correlations Selection for one trait causes correlated nonoptimal increase in another trait 0 Ex selection for tameness in the silver fox selecting for behavior but paired along other effects so these genes can have other affects in the animal Pleiotropic 2 Historical Constraints a Traitsstructures can only evolve from preexisting ones b May originally have had different structurefunction 0 Ex stingrays vs ounders both have attened bodies and swims near the ocean oor ounder looks awkward because its ancestors was laterally attened vs stingrays evolved from sharks 0 EX vertebrate vs cephalopod eyes 0 Ex vertebrate trachealesophagus connection bad design can choke This system of mouth and lungs evolved first in ancestors 0 Ex Whales live in the water but possess lungs and breathe air because they evolved from terrestrial ancestors Clicker Q 3 TradeOffs a Organisms must do many different things at once b Energy limited c Any strategy has positive and negative impacts 0 Ex vertebrate limbs puffin vs hawk puffin awkward at ying because it is better adapted to swimming therefore cannot be perfectly adapted for ying as well 0 Ex female offspring quality vs size Kiwi produces one huge egg with good surviving chances at once Quality Octopus makes thousands of small eggs with adequate surviving chances Quantity 0 Ex ecototherms vs endotherms Mutation Mutation How does a mutation arise gt When DNA copied errors random changes o Ex MeiosisMitosis gt May create new allele Where do mutations occur gt Somatic vs gameteproducing cells implications 0 In somatic cells not important will not be passed on even if it impairs physicality of organism o More important in gameteproducing cells because can be passed on to offspring How often do mutations occur gt Each gene has characteristic mutation rate probability of mutating during DNA replications gt 105 to 106 per gene locus per gamete each generation Statistics vary with different gene General Types of Mutation gt Mutation is a random process with respect to fitness 1 Deleterious mutations a Cause changes in structure function or behavior that decrease individual s fitness 2 Neutral mutations a Neither helps nor harms individual 3 Beneficial mutations a Bestows fitness advantage on individual b Rare because organisms are already adapted to their environment and to introduce a completely random change the chances to improve an organism are rare The effect of mutation depends on the environment Ex sickle cell anemia caused by a change in the gene that code for hemoglobin Will not carry oxygen as well Homozygous for sickle cell will die young But in areas of malaria sickle cell anemic will have slight resistance to malaria Can be considered deleterious in some areas beneficial in others Effect of Selection on Frequency of Mutated Alleles Beneficial 9 Should increase in frequency due to natural selection Deleterious 9Tend to be eliminated by purifying selection Purifying selection is more effective at reducing the frequency of dominant mutation expressed early in life Effectiveness As Cause Of Evolutionary Change 1 Mutation Alone At Single Locus a Change in allele frequency at single locus due to mutation alone 9 insignificant b Mutation by itself not potent evolutionary force too rare c What if considered effect of mutation i Over entire genome ii When population under selective pressure will become more important 2 Mutation In Combination With Natural Selection Over Entire Genome a Lenski amp Travisano 19946 experiment with bacteria determined that new population gradually increased fitness in comparison to early populations b Fitness increased in jumps when a beneficial mutation occurred Conclusion on Mutation 1 Mutation increases genetic diversity 2 Mutation is random with respect to fitness 3 Mutation is important when considered all genes and combine it with natural selection Mutation is sometimes called the ultimate source of genetic variation acted upon by other evolutionary processes This is because meiosis shuf es existing alleles into new combinations but only mutation creates new alleles Gene Flow Gene Flow How Does Gene Flow Take Place gt When individuals or gametes disperse from one population to another and breed 0 Ex long distance dispersal of juvenile animals 0 Transport of pollen seeds or spores by wind water or animals gt Amount caries with species gt A population receiving the migrants will increase genetic diversity Evolutionary Consequences 1 Effect on genetic diversity a Tends to eliminate genetic differences among populationsequalize allele frequencies b Can increase genetic diversity in small isolated populations that tend to lose alleles due to genetic drift 2 Effect on tness a Can reduce fitness of a population by introducing poorly adapted alleles from different environment Not necessarily great for adaptivity i Ex Migration in Lake Erie Water snakes unbanded versus banded snakes Genetic Drift Genetic Drift A change in allele equency due to luck gt Over time random changes in allele frequencies lead to fixation of one allele gt Which allele fixedlost is due to chance gt Occurs in all population more rapid in small ones Mathematical TheoryExplanation gt Caused by random sampling error gt The fewer times a chance event occurs the greater will be the variance from the expected outcome of that occurrence gt Applies every time random mating occurs in a population also random death o Ex Flip coin 1000 times 9 50 heads and tails ip coin 5 times much less likely Expected Frequencies Aa x Aa 9 AA Aa Aa aa fA 05 fA 05 fa 05 fa 05 Genetic Drift Aa x Aa 9 AA AA Aa Aa fA 05 fA 075 fa 05 fa 025 Genetic Drift In Natural Populations The Collared Lizard isolated small populations tested if there is still allele diversity Conclusion gt Effect on genetic diversity Over time can lead to loss or fixation of alleles Loss of genetic diversity gt Effective on tness Random allele frequency changes not adaptive gt Effectiveness as evolutionary force Insignificant in very large populations significant in small populations Bottlenecks Population Bottleneck a sudden constriction in population size gt Caused by disease outbreak natural calamity etc gt Much of population destroyed Often followed by Genetic bottleneck a reduction in allelic diversity resulting from the sudden reduction in the size of a large population due to a random event gt Allele frequencies altered at random due to drift EX Northem Elephant Seals originally few parents left to repopulate the population Not much genetic diversity and vulnerable to any environmental changes due to the bottleneck effect Ex Cheetahs in South Africa very inbred Two bottleneck effects as we know of and hunted in 19th century Low genetic variation vulnerable to change Founder Effect Founder event Founder effect Each time founder event occurs founder effect is likely Why Do Allele Frequencies Change 1 Allele frequencies of founders may not be same as those of original population 2 Genetic drift likely 3 Selection pressures in new habitat likely different Outcome can be stunning on isolated islands Ex Human populations Ellis Van Creveld syndrome in Pennsylvania s Old Order Amish which leads to extra digits and shortened limbs Recessive Carried by few at first married within own group allele shows Ex Hawaiian Flora Inbreeding Inbreeding gt Form of nonrandom mating gt Hard to avoid in small isolated population Eifect On Population Genotypes Homoygosity loss of heterozygotes with time Inbreeding does not change allele frequencies 9 does not cause evolution Evolution is the change of allele frequencies Effect On Fitness Inbreeding Depression gt Offspring of inbred mating tend to have lower fitness than progeny of outcrossed mating Inbreeding depression Inbreeding is not a mechanism of evolution changing genotype frequencies fewer heterozygotes more homozygotes Explanation 1 Many recessive allelesloss of function mutations Littleno effect when in heterozygous form one normal allele sufficient 2 Many genes involved in fight disease exhibit heterozygote advantage Ex Captive animals humans first cousin marriages Charles II of Spain Ex Inbreeding Depression in nature Isle Royale Wolves Inbreeding Avoidance Mechanisms Ex SelfIncompatibility Loci in owering plants Ex Animal dispersal pattems Ex Contemporary Human Societies Inbreeding As An Indirect Cause Of Evolution gt Inbreeding itself does not change allele frequencies How can inbreeding bring about evolution indirectly gt Inbreeding can unmask deleterious recessive by combining them in homozygous form Purifying selection would be more common gt Increases rate at which natural selection can eliminate deleterious recessive alleles from the population After all deleterious alleles have been eliminated much less inbreeding depression Sexual Selection Sexual Dimorphisms gt Males and females often differ in size appearance behavior gt Typically males show exaggerated traits 0 Weapons fighting o Ornaments and behavior courtship gt Females lack these and tend to be smaller and more subtle Why Natural Selection gt Weapons ornaments fighting displays energetically costly gt Size amp conspicuousness 9 vulnerable to predation Sexual Selection Selection for traits that enhance individual s ability to obtain mate gt Form of natural selection gt Form of nonrandom mating The Theory of Sexual Selection Fundamentally Asymmetry of Sex gt Eggs are expensive but sperms are cheap gt Females typically invest much more time and energy into producing and caring for offspring than do males o Ex orangutans mother carries baby for 8 months takes care of baby till 7 or 8 years old Consequences Females gt Females produce relatively few young in their lifetime gt Reproductive success limited by ability to gain resources not by ability to find males Males gt Males can potentially father huge number of offspring gt Reproductive success not limited by resources but by number of female mates Sexual selection more intense in males Males compete for females females are choosier Ex Mammals vs birds difference Mammals most expensive is to gestate and lactate for young Not monogamous Birds raising of young is most expensive incubation and feeding and can be done by both parent therefore tends to be monogamous Male Male Competition Males compete by assessment and fighting Ex Marine iguanas of Galapagos Islands Intermediate sizes survived the best Females usually reach the perfect weight for optimal survival Males would usually go over the optimal size Males are all competing for best mating territory and biggest males get best territories Big males do not get interrupted Explains body size of males Female Choice What do females look for 1 Resources a Food nest sites parental care etc b Ex bullfrogs chooses best site to raise young weaver birds selects nest c Big is not always necessary Ex moorhens females select the males with most body fat which in this case is small and fat 2 Good genes a When will this be particularly important to the female When the male has nothing else to offer b How can a female tell if a male has good genes Evidence that bright male coloration vigorous and complex songs and dances etc can be accurate indicators of male nutritional status and resistance to disease c Ex Mating success and parasite load Satin Bowerbirds ability to build an elaborate bower means less parasite 3 Sex Role Reversals a Sometimes male invest more time and energy in offspring b Ex Pipefish males brood eggs in their pouch while females provide the egg Male puts in more energy being choosier In this case the females compete for mates Female reproductive success limited by how many males she can find Both sexual selection and inbreeding are forms of nonrandom mating Genetic Divergence and Speciation Speciation Speciation is caused by isolation and genetic divergence Isolation is important because allele frequencies change independently in isolated populations What happens when gene ow between two populations reduced or eliminated gt Begin to evolve independently 9 diverge gt When diverge sufficiently 9 form distinct species Definition of a Species Species Distinct types of organisms in appearance behavior habitat use andor genetic characteristics How can we identify species gt Striped skunk amp Western Spotted skunk lifestyle coloration size gt Western amp Eastern Meadowlark by song 1 Biological Species Concepts Species gt Do not interbreed in nature or fail to produce viable and fertile offspring when mating takes place Reproductively isolated gt Strengths clear logical gt Weaknesses can t be applied with fossils and asexual species dif cult to apply to when closely related populations do not overlap geographically Mechanisms of Reproductive Isolation gt Prezygotic Isolation o Mechanisms that prevent individuals from different species from mating 0 Difference in when where or how individuals mate gt Postzygotic Isolation o Mechanisms that operate after mating of individuals of two species occur 0 Hybrid offspring likely to die early be infertile or be less fit I Ex mule sterile 2 Morphospecies Concept Species gt Strengths can be used for fossils asexual and sexual species gt Weaknesses Subjective how much distinction necessary Cannot differentiate cryptic species 3 Phylogenetic Species Concept Species gt Strengths Can be used for fossils asexual and sexual species objective gt Weaknesses Few well known species Ex Applying multiple species concept on Giraffes technically only one species currently but actually six groups who are reproductively isolated Models of Speciation How does gene ow between populations become reduced or eliminated 2 Basic Models gt Allopatric 1 dispersal and colonization 2 Vicariance gt Sympatric Allopatric Speciation Allopat c Speciation gt Population becomes physically separated gt Most common form of speciation Occurs in one of two ways 1 Dispersal and Colonization a Dispersal occurs colonists establish population in novel location b Speciation particularly likely i Founder effects and genetic drift pronounced ii Selective pressures may differ c Leading hypothesis for speciation on islands d Ex Hawaiian Dorsophila 2 Vicariance a A new physical barrier splits population into two or more isolated subgroups b EX change in course of river or glacier continental breakup rising of mountain range etc c How formidable barrier must be kept populations apart depends on ability of organisms to disperse d EX Squirrels of Grand Canyon north rim and south rim difference Pupfish of Death Valley in isolated pools species in each pool different from those in other pools Sympatric Speciation Sympatric Speciation gt No physical barrier gt Traditionally thought of as rare or non eXistent Although populations not physically isolated they may be isolated by preference for different habitats Ex Apple Maggot Fly mates on apples and chooses apples based on preference Low in hybrids hybrids not successful Polyploidy gt Errors in meiosis or mitosis can sometimes generate polyploidy individuals gt Have extra sets of chromosomes gt Common in plants Polyploids reproductively isolated from wildtypes Offspring cannot form normal gametes via meiosis Can selffertilize or reproduce like polyploids Speciation is instantaneous Normal and polyploidy individuals 9 no fertile offspring Ex Two species of anemone ower and their chromosomes What About Humans gt Human races differ in physical characteristics e g skinhair color facial feature height body build gt Differences arose due to lack of gene ow in the past gt Multiple studies have shown genetic divergence among human populations extremely low Phylogeny gt Usually summarized and depicted in the form of a phylogenetic tree Phylogentic tree gt Clarify who is related to whom gt Shows chronological sequence of branching during evolution of a group How Do Researcher Estimate Phylogenies gt Phylogenies are estimated from data cannot be known for certain 1 Measure traits 2 Identify shared derived characters a Ancestral traits possessed by ancestors b Derived traits not present in ancestors gt Focus on which groups possess similar new traits gt Ignore characters from common ancestors 0 Ex traits of hair in phylogeny of mammals Closely related species should share more derived traits How To Read A Phylogenetic Tree gt Tree constructed from a series of dichotomies 2 Way branch points gt Read from root to rip gt Root more ancestral traits tip more derived traits NOT primitive vs advanced Synapomorphies and Monophyletic Groups gt Synapomorphies identify monophyletic groups Monophyletic groups gt Monophyletic groups an ancestral population and all descendants gt Synapomorphy trait unique to a monophyletic group TaXa that share more recent common ancestor are more closely related Problems of Convergent Evolution Need to use homologous traits Homology Ex Vertebrate forewings H0m0Dla Y3 gt Common cause homoplasy convergent evolution Ex Body form of dolphin mammal sharks fish ichthyosaurs reptile all independently evolved due to environment homoplasy New World Cacti vs Old World Euphorbia evolved similar structure due to living in arid environment How can you tell the difference If the similar trait is due to common ancestrv it should be found in many intervening lineages Tools For Studying The History Of Life The Fossil Record Fossil How Fossils Form gt Partall organisms buried in sediment before decomposes gt 4 categories of fossil based on method of formation gt After many centuries fossils can be exposed at the surface by erosion uplift road cut quarrying mining etc Different Types of Fossils gt Intact complete organism that is trapped preserved still has living tissue gt Compression an impression of the organism that is attened gt Cast three dimensional organism was crushed by compression but left a mold What We get is the outside form of the organism gt Permineralized when decomposition is extremely slow and mineral deposits enter when living tissue is still present Shows form of internal structure Limitations of the Fossil Record gt Contains biases nonrandom sample of the past gt Fossilization more likely when organisms 1 Habitat Bias 9 in depositional habitats 2 Taxonomic amp Tissue Bias 9 have hard parts 3 Temporal Bias 9 recent 4 Abundance Bias 9 abundant Widespread and on earth long time Benefits of the Fossil Record gt Data still scientific treasure trove gt Only Way scientists have of examining physical appearance of long extinct forms and inferring how Where and when they lived Macroevolutionarv Patterns Adaptive Radiations Adaptive Radiation Hallmarks 1 Monophyletic group 2 Speciated rapidly 3 Diversified ecologically occupy wide array of niches What caused them to occur A period of high resource availability does not typically promote adaptive radiation 1 Ecological Opportunity a Availability of new types of resources b Often occur when habitat unoccupied by competitors c Ex Radiation of mammals 60 to 65 million years ago when dinosaurs died off a few lineages turned into many lineages of mammals due to change in environment d Ex Hawaiian Honeycreepers believed from 4 to 7 million years ago there was one type that was ancestor to all e Ex Cichlid fish of East Africa in land lock lake believed that there was one ancestor and due to environment now have hundreds of species In other lake fishes look the same but not closely related Adaptive radiation in each lake due to ecological opportunity 2 Morphological Innovation a Evolution of a key morphological trait that allows descendants to live in new areas exploit new sources of food or move in new ways b Ex Cretaceous explosion of owering plants or angiosperm 100 million years ago owers attract pollinators for reproduction very efficient Mass Extinctions Extinction ultimate fate of all species 1 Background Extinction a Species die due to normal environmental change emerging disease or competition with other species b Natural selection acting on individuals poorly adapted to normal or gradually changing conditions 2 Mass Extinction a Rapid global involve broad range of organisms b Result from extraordinary sudden and temporary changes in the environment c Species die from exposure to exceptionally harsh shortterm conditions d Largely random with respect fitness like genetic drift Palentologists recognize five mass extinctions Ex KT Extinction Addition And Loss Of Complexity Through Evolution Evolution of Complex Characters How can complex highly integrated structures evolve Some creationists claim cannot arise via natural selection process must be directed Complex structures evolve through series of intermediate stages Each step must increase fitnessprovide advantage Ex Mollusk eye VVVVV Loss of Character gt Why do characters disappear gt Always cost at least in terms of energy gt In character no longer carry advantageuse natural selection tends to reduceeliminate it gt Ex Eyes and pigmentation in cave dwellers Wings in island birds Bacteria vs Archaea Phylogeny 2 major prokaryote branches are bacteria and Archaea gt Bacteria was the first lineage to diverge gt Archaea and eukaryotes are more closely related What Do They Have In Common Structura1ly simple gt Virtually all unicellular gt Small All prokarvotic 1 Plasma membrane 2 DNA 3 Cytoplasm no membranebound organelles e g no nucleus How Do They Differ Fundamentally different in molecular structure and genetic machinery gt External cell wall o Bacteria unique polysaccharide peptidoglycan gt Plasma membrane 0 Archaea 9 unique phospholipids includes isoprene gt DNA 0 Archaea 9 associated with histones like eukarvotes gt DNARNA polymerase ribosomes etc o Distinct in bacteria Metabolic Diversitv Master of metabolism gt Metabolic diversity prokaryotes gt all eukaryotes gt Can use almost anything as source of energy and carbon gt Nearly all metabolic pathways originated in prokaryotes 9 evolved variations Source of Energy and Carbon gt 3 Sources of energy for ATP production gt 2 sources of carbon for synthesis of organic molecules 9 6 general methods for obtaining ATP and carbon Source of Energy Sunlight Organic Inorganic Source of Molecules Molecules Carbon Atoms Simple Molecules Plants Molecules From Other Animals Organisms Fungi This explains ecological range some extremophiles Harsh environments but some bacteria are able to survive due to ability to break down inorganic molecules Although environments are harsh evolution allows bacteria to grow there due to space and resources and due to lack of competitors Ecological Impact of Bacteria 1 Recycling of Chemical Elements in Ecosystems a Decomposers b Nitrogen Fixation i Converts atmospheric nitrogen into ammonium 9 form organisms plants algae can use ii Only certain prokaryotes possess enzyme iii Free living or in root nodules plant will get good nitrogen and bacteria will get food plant produces Mutualistic 2 Primary Production a Photosynthetic and chemosynthetic bacteria make organic compounds food 9 support food chains 3 Mutualistic Relationships a Ex Cellulose breakdown in ruminants 4 Historic Oxygen Revolution a Cyanobacteria put all oxygen in atmosphere 25 billion years ago b Allowed aerobic respiration Eukaryotes Who s Included in Eukarya gt Largest most morphologically complex organisms gt Plants fungi animals are all subgroups within Eukarya The Eukaryotic Cell gt Essence large compartmentalized cell gt Membrane bound nucleus and other organelles Fun i General Characteristics Eukaryotic chitin cell wall Mostly large and multicellular Nonmotile Extemal heterotrophs Filamentous bodies VVVVVV Mostly terrestrial anywhere organic material and moisture is available Structure gt 2 Growth forms 0 1 Multicellular filamentous mass mycelium o 2 Single celled yeasts Mushrooms are specialized reproductive structures gt Individual very thin filaments hyphae gt Divided by septa Incomplete cytoplasm and organelles ow freely Feeding gt Secrete digestive enzymes outside body at tips of hyphae then absorbs nutrients gt Mycelium grows toward food Dies back and releases spores when food is low Adaptations High surface area volume efficient absorption 2 Grows underin food tissue 1 Ecological Roles 1 Decomposition a b c d Saprophytic fungi major decomposer in biosphere Digest almost any organic substance Digest wood lignin cellulose completely Speed up carbon cycle carbon atoms locked in dead trees etc are released for re use 2 Mycorrhizae a b c Mutualistic association between fungus and plant Fungi grow on or in plants roots Extremely common 90 of land plants d Fungus gains carbohydrates plants gains nutrients without mycorrhizae host plants grow much more slowly or starve 3 Parasitism a b Parasitic fungi cause death and disease among plants and animals Ex ringworm yeast infection etc General Characteristics of Land Plants VVVVV Eukaryotic cellulose cell wall Large complex multicellular Autotrophs makes own food via photosynthesis Nonmotile Primarily terrestrial occupy almost all such habitats Diversity Land plantsmonophyletic Major groupings gt Nonvascular no vascular tissue no seeds 0 Ex mosses gt Seedless vascular vascular tissue no seeds 0 Ex ferns horsetails gt Seed Plants vascular tissue and seeds 0 Gymnosperm ex redwoods pines o Angiosperm owering plants Evolutionary Origins gt Evolved from multicellular freshwater green algae First major group of organisms to move onto land What was the payoff Massive amounts of sunlight and Carbon Dioxide Key Evolutionary Innovations for Life on Land gt Algae surrounded by Water and light 0 This is important because Water provides structural support and prevents Water loss Water is also necessary for reproduction gt On land much less Water typically found in soil Adaptation For Survival 1 Preventing Water Loss a Need to prevent cells from drying out b Cuticle i Prevents Water loss 0 Stomata i Bordered by guard cells changes shape to regulate amount of opening 2 Support and Water Transport a Need Support to avoid falling over gravity Wind transport of Water from roots to shoots i Both solved by vascular tissue Vascular System Tracheids gt Dead and empty at maturity gt Thickened secondary Wall With lignin gt Fits in secondary cell Wall Vessel Elements How do they differ Shorter fatter and Wider Ends with gaps in primary and secondary cell Wall Greer Algae NDNV SCUL aR Liwrwmts l Mnse fI39iIi39 f res C i P0 H fascnlartlszssulenn1a1gmm H r w rts E luma39la SEEHLE SS VASCU LPER H lquot39 IE39t iIlE Ferns Grmmlosrlmm A i laacuilar ti5393 uie RE dliW quot ads travcheidsi pi IllB5 Seed I Gnnet nph39te5 Vni ls I ANG l SPEREi tnjgtilue up Erm Vessels Flower Adaptations For Reproduction gt Nonvascular and seedless Vascular plants have naked male gametes that swim to the egg gt On dry land need a protect gametes and embryos against drying out b transport gametes in air Improvements in Seed Plants Pollen gt Resistant to drying out gt Transported by wind gravity or animals Seeds gt Seed coat protects embryo from drying out and mechanical damage gt Often attached to structure that aid dispersal by wind water or animals gt More effective dispersal survival and initial growth Further Refinements in Angiosperm Flowers gt Sophisticated reproductive structure gt Color shape scent and nectar attract animal pollinators gt Very efficient means of achieving fertilization Fruit gt Ovary tissue becomes swollen sweet perfumed gt Attracts animals gt Excellent means of seed dispersal gt Most abundant and diverse group gt250000 species Ecological Importance of Plants 1 Primary Production a Dominant primary producers in terrestrial habitats 2 Ecosystem Services a Add to quality of atmosphere surface water soil and other physical components of ecosystems i Produces oxygen build and hold soil hold water and moderate local climates etc 3 Carbon Cycle a Convert carbon dioxide into sugars organic molecules General Characteristics Eukaryotic with no cell Wall Large and multicellular Internal heterotrophs most hunt packets of food VVVV Motile during at least part of the life cycle uses neurons and muscles not all but vast majority have at least neuron Monophyletic Size microscopic 9 Whale Amazing diversity of body plan Most occur in the ocean unlike fungi and plants VVVV Architecture of Animals Major lineages defined by body plan 1 Embryonic Tissue a Diploblasts two layerstypes ectodermouter and endoderminner b Triploblasts three layerstypes mesodermin between Ectoderm 9 skin nervous system Endoderm 9 digestive track Mesoderm 9 circulatory system bones muscles 2 Nervous System amp Body Symmetry a Radical i Often cylinder like ii Most oat in Water or attached to substrate iii Diffuse nerve net iv intercept food from any direction b Bilateral i Long narrow body with distinct head and tail ii Resulted in Central Nervous System and cephlazation 9 formation of a head helps eat etc More nerves in head region will give advantage to hunting and chasing in one direction iii Unidirection movement can hunt 3 Body Cavities a Coelom 2 i Acoelum no cavity ii Functions Medium for circulation space for internal organs iii Hydrostatic skeleton 9 movement in limbless animals iv Basic design is tube within a tube 4 Early Development in Bilateria a Protostomes i Molluska annelida arthropoda ii Gastrula pore become month iii Blocks of mesoderm split to form coelom iv Majority of the animal species b Deuterostomes i Echinodermata chordada ii Gastrula pore become anus iii Mesoderm pockets pinch off gut to form coelom Not one is better than the other Humans are deuterostomes 5 Segmentation a Body divided into repeated structures b Improves locomotion different parts can move separately c Evolutionary exibility different parts can evolve separately and become specialized d gt90 animal bilateral symmetric triploblasts that have coeloms Phylogeny 2 fundamental splits Pnriferaf penges lI391tenephnra IZ ei1 h ireillies niulariar39 See jellies eerals anemquot1ene5 3tee eI5 diplulzuliisili i N FZletyl1e nriinit1l1ee Filatwnrme 5 1 Ei1Ii er Triplrjblast ISEgl39ELE 39I liD i 0L 5IEgIfIiIrEIliEITI wnrme Nlnlllliuelqm Eephnliz iimi 39EquotmeI1u m I len1a ti1 equot R eum lwnr me Eegm I139iItiunI1 1 JLrt1hrnpn a aj39Radial Symm w Eel1inuiJemeta ea st ers ureIrina E 1uralete If wHeI t ehrate5n J T SS fl39I 39II39quotI139IiliEll1 Illeulemstrmne T Diversification of Animals 1 Cool Sensory Organs 2 Feeding Specialization a Largest consumers in ecosystem b Diversity of mouthparts c Ex Flamingoes and ticks 3 Movement a Most based on contraction of muscle cells and skeleton b Diversity of limbs c Evidence that all animal appendages homologous d EX human vs grasshopper vs segmented Worm 4 Reproduction a Metamorphosis i Major innovation in many animal life cycles b Immature forms i Larvae different body habitat and food to adult ii Juveniles same body habitat and food to adult c Advantages to larval stage i Exploit different resources at different times 9 larvae and adults don t compete ii Specialization 9 efficient 1 Larvae feeding growth dispersal 2 Adult reproduction dispersal Who Are The Vertebrates gt Monophyletic group within phylum chordate gt Includes fish amphibians reptiles birds mammals gt Large active dominant organisms in most habitats Defining Features 1 Column of cartilaginous or bony structures on dorsal side of the body 9 vertebrae one species does not have this 2 A bony cartilaginous or fibrous case that encloses the brain 9 cranium all species have this 3 Have large 3 part brain Kev Innovations The Vertebrate Jaw gt First vertebrates Were jawless filter feeding fish with no paired appendages and cartilaginous endoskeleton Today hagfish lamprey gt Jaws first evolved in sharks gt Modified gill arches bars of cartilage support gills What did it do gt Enables fish to bite Allowed captureprocessing of wide array of food gt Spectacular radiation of jawed fishes followed The Tetrapod Limb gt First land vertebrates amphibians arose from group of bony fish with sturdy fins and lungs lobe f1nned shes gt Related to modern day lungfish and coelacanths gt Fins supported by bones 9 limbs gt All tetrapod limbs are homologous What did it do gt Allowed efficient movement on land gt Basic limb evolved into diverse forms for running swimming digging ying etc The Amniotic Egg gt Early reptiles evolved amniotic eggs and water tight skin 9 larger young and superior ability to conserve water gt Radiation of reptiles quickly replaced amphibians as dominant terrestrial forms gt Amniotic egg found in descendants modern reptiles birds egglaying mammals What is an amniotic egg and what does it do gt Provides water nutrients and mechanical support gt 3 internal membranes extra SA 9 good diffusion 9 Large eggyoung and will have better survival rate gt Leather or calcified shell Viviparity and the Placenta gt Various strategies for retention and nourishment of embryos Oviparity 9 Ovoviviparity 9 Viviparity Oviparity eggs laid outside body birds turtles Ovoviviparity Live birth embryos nourished by yolk Viviparity Live birth embryos nourished directly by mother gt Placenta 2 gt EX Sharks show entire range mermaid s purse yolksac placenta Advantages of Viviparity and Placenta 1 Constant favorable temperature for development 2 Offspring protected 3 Offspring portable 9 Increased offspring survival rate Disadvantage If the organism needs speed and agility taking your eggs everywhere would not be advantageous Other Forms of Parental Care gt Particularly extensive in mammals and birds gt Mammals evolved lactation Feathers and Flight gt Birds evolved from lineage of bipedal feathered dinosaurs gt Feathers evolved from simple projections came before ight What did they do gt Airfoil insulation camou age communication gt Still unknown whether ight evolved groupup or tree down Further Modifications for Flight Skeleton 1 Bones thinwalled hollow strengthened by struts 2 Elongated keel on sternum for ight muscles 3 Bill instead of heavy teeth Physiology gt Superior circulatory respiratory systems gt Endothermy generate own body heat for oxidation of food 0 Benefits can be active in the cold high metabolism 9 sustained activity 0 Cost need huge amounts of food Lampr Eyls 3 hag sh Sharks mys E skates 1quot39rEITIE39l39I re EI IlIiIlIIli Ilay I1I IIIE sh J wls 3 tseIsssntss st lung sh llru11gsi1ItEr11a l1auI 1 In imphihian L letil ns I g A M mtmals IiI1I1I1s l 7 if Hgephlxes Amni tine Egg 5 llfiir Feathers Z Introduction to Behavior What is Behavior gt The observable coordinated responses an organism makes to stimuli gt Organism receives information from environment acts in response gt Focus typically animals with sophisticated nervous and skeletalmuscular system Levels of Analysis in Behavior gt Biologists analyze behavior at two levels 1 Proximate or mechanistic 2 Ultimate or evolutionary 1 Proximate Mechanisms How Questions a Asks how mechanisms within animals operate to perform behavior b Answers involve Nervous system hormones skeletalmuscular system genes developmental mechanisms 2 Ultimate Cause Why Questions a Asks why animal has evolved ability to perform a behavior Explanations deal with adaptive valuefitness advantage of a behavior c Adaptive behaviors will evolve via natural selection and become more prevalent d Full analysis of any behavior involves both proximate and ultimate explanations Diversity of Behaviors Innate vs Learned gt Variation in how exible behaviors are in response to environmental conditions Innate Behavior gt Fixed not stereotyped gt Not easily altered by environmental in uences gt Ex Begging behavior in Herring Gull chicks Learning gt Flexible gt Dependent on experienceenvironment gt Ex Bird song observational learning in octopus Innate behaviors can sometimes provide greater fitness benefits than learned behavior Learned behaviors can sometimes be less exible Making Choices Cost Benefit Analysis gt When range of possible behaviors 9 how are decisions made Animal would have evolved to recognize when to use certain behavior in certain situations to increase their fitness All traits have positive and negative effects on individual reproductive success Animals unconsciously Weigh fitness costs vs benefits to particular behavioral responses Expect to observe behavior when benefits outweigh costs VVVV Ex Mobbing behavior in ground nesting gulls benefits the parent bird by saving their chicks cost parent may get injured and will cost a lot of energy Fitness Benefits Save current offspring from being eaten by predator Fitness Costs Neighboring gull could eat unattended chick adult may be injured or killed While distracting predator Migration Migration gt Will focus on migration in birds extensive studies gt Ex Arctic Tern one of the most impressive migrating birds Proximate Mechanisms Preparations 1 Intemal clock responds to increasing day length because day length is very consistent and reliable 2 Release of hormones Testosterone cort Growth Hormone a Physiological preparations increased feeding fatmuscle build up etc b Zugunruhe behavior migratory restlessness when it s time to migrate Initiation gt Exact day to migrate is based on if they are ready physically gt Trigger sufficient fat and favorable Weather Orientation and Navigation gt Complex neurological mechanisms gt Cues 1 Visual landmarks secondary 2 Celestial bodies sun stars 3 Earth s magnetic field 4 Others polarized light ultraviolet light olfactory cues infrasound very low frequencies gt Redundant and hierarchical have multiple systems so there are backups and prefers certain cues over others Ultimate Causes Costs 1 Energy 2 Risk of exposure exhaustion physical calamities 3 Risk of predation 4 Investment in complex navigational mechanisms costly Potential Bene ts 1 Migrants exploiting temporarily favorable opportunities 9 increasing reproductive success by breeding in temperate zones better food and nest sites 2 Overwinter survival higher in tropics than if stay in temperate zone Tradeoffs mortality energy vs reproductive success overwinter survival Are certain kinds of animals more likely to evolve migratory behavior than others Depends on costs and benefits If an animal is very mobile and can get to new places efficiently then migration is likely Migration is mostly in animals that can cover big distances quickly and at a reasonable energy cost Selfish vs Helpful Behaviors Sel sh Behaviors gt Much of animal behavior is selfish behavior directly benefits individual performing it gt Ex Territorial behavior will have access to the resources in an area more resources more potential offspring gt Ex Infanticide in Langur Monkeys new male goes into a group of females and he kills the offspring so he can have his own offspring Helpful Behaviors gt Hundreds of examples of selfsacrificing behaviors exist in nature gt Altruism How can altruism exist 1 Kin SelectionIndirect Selection a Hamilton s Rule b Altruistic allele can spread if Br C gt 0 or Br gt C i C cost of altruistic act to the actor offspring lost ii B benefit to the recipient offspring gained iii r coefficient of relatedness fraction of alleles in actor and beneficiary that are identical by descent how closely are related Individuals can pass their gene on to the next generation not only by having their own offspring but also helping close relatives produce more offspring r Values for Familiar Pairs of Relatives Relationship r ParentOffspring 12 FullSiblings 12 HalfSiblings 11 UncleAunt NieceNephew 1 Grandparent Grandchild 1 Cousin Cousin 18 Simple Calculations Cornpare genes lost with genes gained EX An a1truist s action prevent the altruist from producing one offspring of its own but leads to the survival of three nephews who would otherwise have perished Will this behavior be favored by selection r offspring 12 r nephew 11 Cost l X 12 12 Benefits 3 X 11 31 The allele for this altruistic behavior would increase via natural selection because it confers a fitness advantage The benefits outweigh the cost EX Is it adaptive for an individual to sacrifice the produce of two offspring in order to save the lives of five cousins r offspring 12 r cousin 18 Cost 2 X 12 1 Benefits 5 X 18 58 No the cost outweighs the benefits Natural selection would not favor this behavior Definitions Direct Fitness Indirect Fitness Inclusive Fitness Kin Selection Meerkat A helps raise l sibling and 3 half siblings Meerkat B helps raise l halfsibling and produces 2 offspring r offspring 12 r sibling 12 r halfsibling 1 Meerkat A 1 X 12 3 X 11l11 Meerkat B 1 X 11 2 X 12l11 Same inclusive fitness Age matters Older would exhibit more altruism than younger Case Study gt Do animals really favor relatives when they act altruistically gt Most cases of altruism that have been analyzed are consistent with Hamilton s rule gt Ex Alarm calls and territory defense of Belding Ground Squirrels caller sees predator faces predator makes a distinct whistle Caller has a higher mortality rate How Does The Environment Affect Evolution of Helping Behaviors Via Kin Selection gt More likely to see helping behaviors evolve via kin selection when chances of successful reproduction for individuals who go it alone are low gt Ex Naked mole rats extreme case of altruism workers helping out the big reproductive females 2 Reciprocal AltruismTrivers Does not have to be related Does not even have to be in the same species Help another individual if that individual comes back and helps you a Reciprocal altruism b For reciprocity to persist i Pair must persist long enough to permit reciprocation ii Benefit to receiver must exceed cost to donor iii Donors must recognize cheaters and not help them individuals have to be able to recognize who they have helped and who has returned the favor c High frequency of interaction between individual critical In What kind of animals are we likely to nd to observe reciprocal altruism Likely to be characterized by 1 Long lifespan 2 Low dispersal rate 3 Clumped distribution social groups 4 Good memories EX Vampire bats will have a group of females that live together Relatedness is low in the group Young vampire bats will most likely be hungry Commonly a roost mate will regurgitate food to the starving one Found that if one bat is giving blood to another it is more likely to get blood in retum The benefit is must greater than the cost for the starving bat to get blood when it is close to starvation Human Social Behavior gt Reciprocal altruism likely mechanism to explain helpfulcooperative behavior commonly observed among unrelated humans Kin selection may also help explain some human behaviors Ex Increased likelihood of child homicide in families contain stepparents Ex Mother s brother often cares from sister s children in polygenous societies where VVV certainty of patemity is low What Is A Population Population Population ecology Life Histories Life History gt Includes age at maturity number of offspring number of reproductive bouts lifespan gt Vary Widely among population and species Individuals have limited time and energy therefore must make tradeoffs if have a lot of offspring they cannot be big etc Life history traits shaped by natural selection to maximize individual s fitness in environment gt Ex Clutch size in magpies 7 was the perfect number to give the most surviving chicks gt Variation in one s life history trait often correlates with variation in others Trait form continuum gt High fecundity low survival low fecundity high survival Population Growth Basic Model of Population Growth gt For continuous growt when individuals added to population continuously N0 initial population size t0 Nt final population size timet r instantaneous growth rate per cap birth per cap death e base of the natural logarithms approx 272 About 139 r varies depending on conditions When birth gt death 9 rgt0 population size increases birth death 9 r0 population size stays same birth lt death 9 rlt0 population size decreases Each species has rmax that does not change rmax varies with species Practice 1 In a population of 100 individuals there are 10 births and 8 deaths annually a What is r approximation 01 008 002 b Is the population increasing or declining Increasing r is positive 2 I release 20 ladybird beetles into my greenhouse to control the aphid population 10 years later I count the beetles in my greenhouse and find 110 Note N Noe 9 rt 1nNtNo a What is r rln11020 10 017 beetleyr b If this r is sustained how many more years would it take for the population to reach 200 beetles t ln200110 017 35 years ExponentialDensityIndependent Growth When 139 constant over time 9 exponential growth gt Can theoretically lead to huge numbers Growth is not affected by population density 9 Density Independent Growth gt Most populations have great growth potentials gt Observed when 0 Organisms introduced into new region with suitable environment 0 Population rebounds after a crash gt Exponential growth can occur over short intervals but cannot be sustained gt Ex Ringnecked pheasants on Protection Island started with 2 males and 6 females on a deserted island turned into over 2000 in 20 years Population RegulatiorMDensity Dependent Growth gt Most populations remain relatively stable gt As population increases in sizedensity 0 Run out of food places to live more social strife disease predators waste etc o Per cap birth rate decrease and percap death increase r declines 0 Population growth slows or stops Growth is affected by popu1ation s density 9 Density Dependent Growth Pattern of Growth Sigmoidal or S shaped curve Carrying capacity db tn Later growth 2 falls to zero E Early growth 3 is rapid E Growth begins to slow Time 2014 Pearson Education inc r at red positive and reasonably high r at redblue positive but magnitude decreasing r at blue zero If overshot carrying capacity r will be negative A grassland has held a stable population of 200 mice for many years You experimentally add 50 mice of the same species to the area and monitor the population over the short term If the previous population has already been stable for a long period of time it means the population is already at the carrying capacity Any addition r will decrease due to competition for resources will cause decreased births and increased deaths Carrying Capacity K Carrying Capacity K What happens to r and population size when the population is below at or above K Below positive At zero Above negative Is K xed K can vary in space and time K varies with specie type What will change K A fire destroys many largemature trees in which the birds build their nests will change K because K is dependent on how much resources there is Density Dependent Factors gt Alter birth and death rates Change in intensity as a function of population size Will act more strongly in a more dense population gt Usually biotic e g parasitesdisease that spreads better in more dense populations competition for mates and resources by conspecifics those of the same species predators etc Density Independent Factors gt Alter birthrates and death rates irrespectively of the number of individuals in a population gt Usually abiotic factors e g Weather natural disasters gt Ex Australian insect pest genus Thrips numbers are regulated by abiotic factors doesn t matter how many there are gt Most populations are dynamic 9 change in size and other characteristics through time and space gt To understand history and predict future behavior of a population need to also take into account of additional factors such as spatial distribution age structure etc Population Cycles gt Some show periodic cycles regular highs and lows gt Ex Population cycles of small mammals in northem Finland regular ups and downs Caused by time delays in response of populations to their own densities ie delays in the response of birth or death rates to changes in the environment Does not completely change in sync with what s happening in the environment 1 High birth rate at low densities 9 population grows rapidly and overshoot its K 2 Low survival rates at high densities 9 population compensates and decreases below K gt Ex Red grouse every 4 to 6 years there will be a very large change in population size Hypothesizes that there is a parasite When the population gets too dense the parasite will cause the population to dramatically decline Density dependent When a large population is treated with antibiotics for the parasite the population remains relatively unchanged and high Metapopulations Metapopulationz Why do we nd metapopulations in nature Have environment with patchy resources Most species will have specific preferences for habitats Humans also do a lot of fragmentation of habitats What happens to metapopulations over time gt When subpopulations wiped out reestablished by migration from nearby subpopulations 9 metapopulation size maintained What factors affect the extent of migration between subpopulations The distance between the two subpopulations the nature of intervening environment ex Fishes cannot migrate ponds the mobility of species Ex Snail Kites in southern Florida moves around easily one big habitat of kites Ex Oedura geckos in southwestem Australia cannot move around easily losing genetic diversity What factors affect whether a subpopulation survives or goes extinct Subpopulations are more likely to survive if they 1 Large 2 Occupy larger geological areas ample amount of resources 3 Closer neighboring populations good for migration 4 Genetically diverse Small isolated inbred populations unlikely to survive over long term Implications for Conservation gt Model being applied to design of nature reserves 1 Preserve large area 2 Connect smaller areas wit wildlife corridors 3 Preserve unoccupied habitat patches Small populations are most vulnerable so the creation of wildlife corridors will benefit the small populations because it will get new alleles via migration etc Human Population Growth gt Has increased dramatically over the past 200 years gt World population now over 7 billion Age Structure of Human Populations Age Structure Gives picture of recent history and future of population Ex Sweden vs Honduras Sweden has a stable age distribution which means population has been the same for a long time and will not change dramatically Honduras has a population that is very bottom heavy It has a lot of growth a large population of young people Would expect the population to keep growing due to the large amount of young people Even if the fertility rate is stable would take a long time before the population will stabilize Patterns Even Age Distribution Sweden gt Results from long period of no or very slow growth gt Not expected to grow very quickly Bottom Heavy Age Distribution Honduras gt Results from period of rapid growth gt Extremely rapid growth expected to continue even with decline in fecundity Exhibits momentum Top Heavy Age Distribution If the conditions don t change with a top heavy age distribution the patter of population will decline in size before stabilizing Clearly top heavy or bottom heavy age distributions are very rare to nonexistent in humans The Bad News gt Over population causes habitat loss species extinction decline in living standards mass movement of people political instability shortages of basic resources The Good News r has already peaked and begun to decline 1750 9 increasing 9 196570 peaked 9 declining gt Stabilizing human population depends on fertility rates of Women Species Interactions gt Populations are not isolated interact with populations of other species Classification gt Species interactions classified by effects on fitness of individuals involved 9 Positive negative or neutral effects on survival and reproduction Commensalism O Competition Consumption Mutualism Key Points Species Interactions 1 Dynamic and conditional Change depend on time and place 2 Can affect distribution and abundance of species 3 Over long period of time 9 coevolution What Is Coevolution Coevolutiom Sees coevolution in everything except for commensalism Ex Darwin s orchid and long tongued sphinx moth Competition Competition Ex Resources food shelter mates for plantssunlight water nutrients Will focus on interspecific competition The Niche Concept gt Every species has unique niches gt Niche Food type light temperature humidity space etc Fundamental niche Realized niche When does competition take place gt When two niches of two species overlap species use at least some of the same resources gt For competition to occur resource much be in limited supply in nature shortage is the rule Resource is in limited supply b Partial niche overlap competition for seeds of intermediate size A Species 1 Species 2 Number of seeds consumed V e o 0 0 Seed size Do species have to be closely related to compete Species do not have to be closely related to compete Competitors compete for the same resource Does competition have a negative effect on fitness Yes no shit gt Fewer resources available to each species gt Decreased growthreproduction in one or both populations gt Ex Two Great Smoky Mountain salamander species Experiment where a scientist set different plots of land Set plots where there was either one species or that there was both Result was that if there is only one species the population has grown The control plots have remained relatively unchanged How can you tell if competition is taking place gt If population size or distribution of one species changes following the addition or removal of another Consequences of Competition Competition Exclusion Species with same niches cannot coexist gt gt Species that uses the resources more efficiently will eventually eliminate the other 9 local extinction If niches do not overlap completely weaker competitor can retreat to the area of non overlap Outcome 9 species ranges do not overlap Ex Grause landmark experiment on coexistence of protozoan species in lab cultures puts two bacteria in the same ask The better competitor drove off the inferior competitor The two paramecium cannot survive together because their niches overlap so much Ex Two chipmunk species in Sierra Nevada Least chipmunk at lower end of mountain Yellow pine chipmunk at higher with pine trees Is this a habitat preference or because one is driven out due to competition 0 When Least chipmunks are removed from the lower end the Yellow pine chipmunks stay where they are When Yellow pine chipmunks are removed from the higher areas the Least chipmunks move up to the pines o Asymmetric competition Least chipmunk s fitness and survival being restricted because of less resources 0 Species 1 Yellow pine chipmunk Species 2 Least chipmunk A Species 1 Species 2 W strong competitor weak competitor E 2 8 5 2 5 Fundamental 392 3 E niche II 2 o m Realized 339 r E niche n n E 3 5 3 2 39 Niche range of resources used Is competition exclusion always reached Why do superior competitors not take over 9 Due to fitness trade offs 90rganisms cannot be superior competitor in all aspects of it niches gt Competitors can coexist if other factors e g predators parasites disturbance etc reduce population of better competitor gt Ex Coexistance of two species of pond snails due to ephemeral habitat When separate reproductive output of one species is higher than when together When environment changes the better competitor changes Niche Differentiation Resource Partitioning Species can coexist in the same habitat but subdivide the resource Niche differentiation is related to the use of a resource gt Competitive exclusion at finer levels Not fundamentally different Need to look at the habitat gt Ex East Coast Warblers They all eat on the same tree but the resource is divided some only eat on top of tree some only eat on bottom etc gt Ex Rocky Mountain Bumble Bees Blue specializes on big owers brown specializes on small owers When separated will use both owers When together will specialize on one ower gt Natural selection favors traits in both species that minimize competition gt Over time niche overlap and competition reduced Niche differentiation Both species end up benefitting Less overlap less competition 2 S 2 8 gt L g 3 Species 2 Time 1 an 1 on 3 in E 3 3 Z gt Niche differentiation 1 Nat ral Sdection favors 39 individuals that do not compete 2 ii 2 2 8 gt I 3 in 1 9 Species 2 Time 2 o 2 0 a in E 3 3 Z gt Niche range of resources used Character displacement In general when there is niche differentiation there will be character displacement gt Compare traits of populations in the presence and in the absence of competitor 9 do they differ gt Ex Indian Mongoose Found that Where there is no competition the canine tooth size is larger This is an example of character displacement This is because Where there is competition the larger mongoose will kill the larger prey so the smaller mongoose will have the smaller prey This restriction of resources meant smaller tooth Where there is no competition the original tooth size would stay large Mechanisms of Competitior How Do Species Compete gt Varied depends on species and resources 1 Exploitation Competition a More frequent 2 Interference Competition a Less frequent Ex Interspecific territorial defense in hummingbirds and others hummingbirds defend their resource gets very fierce when something gets close to their ower Interference competition Ex Mechanical and chemical Warfare for space Eucalyptus tree Sage brush sponges bamacles Interference competition Competition CANNOT lead to an increased fitness for the superior competitors At best the better competitor will keep the same fitness It is never beneficial to have a competitor around Coevolutionary Arms Races Applies to all consumption relationships 1 Parasite develops trait to better exploit host 2 Natural selection favors prey individuals better able to defend themselves 3 Frequency of defended prey individuals increases 4 Natural selection favors predators With novel traits that overcome new defenses etc Antagonists continually evolve in response to each other gt Can lead to speciation gt Ex Roughskinned Newts and Garter Snakes Newt has a lot of neurotoxin A lot of Garter snakes have developed a resistance to the toxin Areas with high levels of toxin and high levels of resistance match due to coevolutionary arms race Costly to the newt Parasitism Parasite gt Acquire resource from host at cost to the host gt Close and long term association gt Differs from predation 0 Usually smaller than host 0 Don t usually kill host May increase the probability of host dying from other causes or reduce its fecundity 912 of world s species live in or on bodies of other organisms Parasite Adaptations 1 Morphological Adaptation of Parasite a For attachment resource acquisition etc b Ex Tapeworm at absorbs nutrients from the predigested food 2 Change In Host Morphology and Behavior a MorphologyGrowth i Ex Oak gall formation by insect parasites insect parasite lays egg in oak tissue stimulates growth to facilitate the growth of the egg b Behavior i Ex GordianHorsehair worms causes host to drown itself The life cycle started in the water so the adult worm manipulates its host to continue its life cycle 3 Countering Host Defenses a Parasites have ways of circumventing the host s immune mechanisms b Ex Some schistosomes blood ukes avoid antibody attack by coating themselves with proteins of host before antibodies become numerous Predation Predator Prey gt Predator typically large than prey and less specific than parasites often exploit many different species AdaptationDefense of Prey StandingConstitutive Defenses 1 Hide run away Escape Behavior 2 WeaponsActive Defense a Foulsmelling or stinging secretions b Spines or armored body coverings 3 Camou age a Appearanceposture match background b Break up body form by using different colors and patterns 4 Warning ColorationAposematism a Contain noxious chemicals b Advertise with conspicuous color patterns c Innate or learned avoidance response by predator 5 Mimicry a Palatable organisms resemble noxious ones 6 SchoolFlockHerd Formation a Greater predator detection b Dilution effect statistically safer although a group can attract more predators the chance of one specific individual getting eaten is low c Confusion effect d Group defense ex Muskox Why are warning colors similar across species gt If there is any learned or innate behavior to avoid certain coloration in one species it will most likely avoid another species of the same coloration as Well Why aren t all prey species noxious or unpalatable gt Trade off if one can fool the predator Without actually producing poison it is a cheaper lifestyle Inducible Defenses gt Defense triggered by presence of predator gt Advantages o Energetically cheaper only produced when needed 0 Avoid other costs of predator defense e g camou age 9 loss of visibility to mates gt Disadvantages Time delay Might get suddenly eaten because no time to be defensive gt Ex Predatorinduced change in body morphology in Crucian carp When no predator Pike carps were pretty small When there is predator the carps will be much larger with a different body shape Pikes are gape limited so when Pikes are around carps changes body morphology and becomes bigger Why not always be large Larger body shape will require more energy to swim Effect of Predators On Prey Populations Can predators reduce prey populations below carrying capacity gt Predators can control prey populations gt More likely to occur when predators exhibit 0 High reproductive capacity 0 Strong dispersal powers o Ability to switch to alternative food resources Specialists will not survive as well gt Ex Cyclamen mites and predatory mites With both in population prey mite s population is kept under control When the predator mites are killed by pesticides the prey mite s population shoots up Hawk A eats frogs as first choice but also has altemative food source reproductive maturity at 1 year Hawk B only eats frogs reproductive maturity at 2 years Which predator would be more likely to control the frog population keep it below K Hawk A because it is not specialized and reproduces earlier Do The Dynamic of PredatorPrey Interactions Cause Populations to Oscillate gt Predator and prey populations often increase and decrease in regular cycles close synchrony gt Continue unchanged for long times gt Ex Lynxsnowshoe hare cycles Basic Sequence 1 Predator eat prey 9 prey numbers drop 2 Predator go hungry 9 predator number drop 3 Fewer predator 9 prey number rise 4 More prey 9 predator number rises gt Many predator prey interactions have response lag due to time required to produce offspring Herbivory Herbivore gt Typically remove tissue but rarely kill plants gt Champions are Insects eat the most plant tissue AdaptationsDefense of Plants gt Plants can t run away or hide 9 more limited options Tvpes of Defenses 1 Mechanical Defense a On plant surface spines thorns prickles sticky gums and resins tough seed coats etc 2 Chemical Defense a Toxic noxious and nutrientreducing compounds inside plant tissues either makes it taste bad kills the herbivore or makes the plant tissue harder to digest i Ex lignin tannins alkaloids b Source of our pesticides drugs and spices Bioprospecting i Ex Pseudoephedrine caffeine capsaicin Inducible Nature of Plant Defenses ConstitutiveStanding gt Always presentproduced e g tannins gt Energetically expensive Inducible gt Made when needed gt Toxins increase dramatically in many plants following defoliation by herbivores o In area of wound or systemically throughout plant 0 Response in minutes 9 next growing season gt Can substantially reduce subsequent herbivory Responses of Herbivores to Plant Defenses 1 Counter Plant Toxins a Containment some insects takes in plant toxin and uses for own benefit such as protecting self from predators b Breakdown 9 Specialization of insect herbivore to particular plant 9 Evolutionary arms race 2 Sequester for Defense a Some herbivores preferentially feed on plants with high toxin concentrations use chemicals again own predators b Ex Leaf beetle prefers to eat cottonwood trees that have resprouted after an attack because it has higher concentrations of toxins Tobacco plants produce nicotine when suffers a tissue damage Compared to undamaged plants what might you expect to observe Attacked plants will produce fewer seeds resources committed to defense can t be used for growth or reproduction Why Don t Herbivores Eat More Plants gt Levels of herbivory low in terrestrial ecosystems Two hypotheses Not mutually exclusive aka can occur at the same time 1 TopDown Control Hypothesis a Herbivore populations limited by predation and disease 2 BottomUp Limitation Hypothesis a Plant tissues are poor food sources low in Nitrogen and are well defended b The plants themselves limit the herbivore densities growth and reproduction Both important factors in limiting impact of herbivory Depends on plant species Mutualism Mutualism gt Provides participating individuals with food shelter transport of gametes or defense against predators gt NOT altruism with mutualism both individuals gain direct fitness With altruism the inclusive fitness is increasing gt Mutualistic dependencies thought to have evolved in many cases from antagonistic interactions e g pollination A bacteria in the stomach of the cow allows the cow to survive on vegetation that would normally be too low in digestible energy content How have the bacteria affected the niche of the cow With the bacteria s presence the cow s niche is larger than it would be without the bacteria Dynamic and Conditional Nature of Species Interactions EX Interaction between freshwater crayfish and branchiobdellid worms gt Nature of interaction depends on density of worms dynamic association gt Mutualistic at low numbers gt0 Parasitic at high numbers What is an Ecological Community Community gt Often named after most prominent species or physical characteristics sagebush community pond community etc gt Does not include abiotic factors What is Species Richness Species Richness gt Simple count of how many species present gt Ignore species abundance how rare or common Advantages and disadvantages of this measurement 9Disadvantage will not say anything about the abundance of a particular species Cannot compare species diversity between different communities 9Advantages not complicated Patterns of Species Richness gt Several largescale spatial and temporal pattems of species richness have been identified gt One of the most widely recognized patterns Greater species richness as it gets closer to the equator less species richness as it gets closer to the poles Islands Habitat Area and Remoteness gt Number of species on islands decrease as island area decreases and island remoteness increases gt Doesn t have to be a patch of land surrounded by water can be a cave a pool of water surrounded by desert etc How Can We Explain Species Diversity on Islands Basic Pattem gt Assume speciation too slow to be important gt Species added by immigration from mainland and removed by extinction gt As number of species on the island increases 0 Immigration rate of new species decrease because if there are already a lot of different species on an island the chances of a new species immigrating is low would probably already have been represented o Extinction rate increase because with more competitors life gets harder 9Reach equilibrium species number continual turnover Island Size and Location gt Islands large and close to mainland immigration rates higher because it is easier to find and get on the island if it is close by A larger island tends to have more diverse resources gt Islands small and far from mainland extinction rates higher because there would be smaller populations because there is a smaller carrying capacity smaller populations go extinct more easily An island far away would have smaller immigration rate Conclusions Species richness increases with island size and decreases with distance from colonization source gt Predictions have been verified for islands and islandlike habitats throughout the world Species Richness and Ecosystem Function gt Does species richness affect productivity and stability of communities Species Richness and Productivity Do the number and types of species affect community productivity Experiment Planted a total of 289 experimental plots each with up to 32 species and up to 5 functional groups Weighed biomass Result There was more productivity in plots with more species levels off though Conclusion Productivity increases when there is species richness Why 1 Resource Use Efficiency differences among species in resource use allow light water nutrients and space in a community to be used more completely 2 Facilitation Certain species or functional groups provide benefits shade nutrients etc to other species 3 Sampling effect Big Producer species more likely to be present There will be some that are very good at primary production therefore skewing the data Species Richness and Stability Does species richness affect resistance to disturbance Resistance Resilience Natural Experiment Compared biomass of experimental plots before drought and during peak of drought Results The plots with low species richness were more affected by the drought than plots with high species richness Conclusion Species rich communities are more resistant and resilient to disturbance Why gt When many species present some are likely to be redundant in the community rolefunction o EX many different types of herbivores carnivores pollinators etc gt Wiping out one or a few species is unlikely to affect the community as a whole if it is already species rich gt Response to invasive species Harder to get a foothold in communities that are species rich Mostall niches filled Community Structure Closed Communities Fredrick Clements quotIL Communities stable integrated orderly predictable gt Biotic interactionscoevolution prominent gt Develop via predictable stages 9 climax determined by climate gt If disturbance same community will re establish itself Open Communities Henry Gleason JL Communities neither stable nor predictable gt Short term association of species that shares similar climate requirements gt Biotic interactionscoevolution uncommon and diffuse gt After disturbance new communities will not necessarily be similar depends on history and chance How have these ideas been tested Experiments and analysis of species distributions Which is more accurate Communities are dynamic and not static Composition neither entirely predictable nor stable gt Biotic interactions and climate are important in determining community composition but chance and history also play a large role Effect of Keystone Species on Community Structure Keystone Species gt Entire community structure can be changed dramatically depending on presence of absence of a single species Community Development How do communities change through time What is a Disturbance Disturbance Ex Volcanic eruption tree falling etc Boreal forests are affected by a number of different types of disturbances Which is the least important in determining the impact of disturbance The age of the boreal forest prior to the disturbance What Determines the Impact of a Disturbance 1 Type of disturbance nature of disturbance 2 Frequency how often this disturbance happens 3 Severity intensity speed or duration of disturbance How predictable are disturbances In most communities disturbances are predictable Exhibits a disturbance regime disturbance that is expectedperiodic If altered community can change dramatically Ex Gulf and Southem Atlantic Coast pine forests community maintained by a periodic fire The fire kills the oaks and boreal trees The pines are resistant This disturbance VVVV regime maintains the ecosystem Succession Succession Primary Succession gt Ex Volcanic eruption glacier etc Secondary Succession gt Ex Fire What Determines the Pattern of a Successional Pathway II Species v Irait5 V Develupngl Epenises Gummlmniiityr innleractiuns 3 Histurinal 3 enmirunmenital farmrs chiance and histur3rquot 1 Species Trait r vs K Species r species good colonizers tolerate harsh physical conditions Kspecies good colonizers r species Kspecies Seed Many and small winddispersed Few and large animaldispersed Growth Rapid Slower Focus shoots seeds need light Focus roots stem shade tolerant Maturation Early Late Size Small Large Lifespan Short Long How Species Traits Affect When Species Appear During Succession New habitat colonized by pioneer r species Modify environment Changes inhibit pioneers make habitat more suitable for species that follow K 9 outcompete pioneer species EX Sanddune Vegetation south end Lake Michigan How Species Interactions Affect Succession Facilitation Tolerance Inhibition 3 How Chance Effects Succession Ex Mount St Helen exact timing of disturbance daytime therefore nocturnal animals would have survived There was ice on the lake which protected aquatic organisms Chance events are important The Climax Community Climax Community How Predictable Is It Predictable 9 climate species traits and interactions Unpredictable 9 history and chance Is it always reached No There are disturbancesdisturbance regimes How long does it take to reach gt Varies 20 to 40 years 9 1000 years gt Depends on nature of climax what climax is this Is it going to be a grassland which won t take so long or will it be a large forest and initial quality of soil are we starting from scratch or most of the soil seed and organisms still being there What is an Ecosystem Ecosystem gt Study how organisms interact with abiotic physicalchemical part of the environment gt Energy and elements ow through ecosystems and are exchanged between biotic and abiotic components Why is ecosystem ecology important Extremely important knowledge for conservations Need to understand how a healthy ecosystem works in order to fix it Classification of Organisms in Ecosystem Producers Consumers DecomposersDetrivores Organisms Within ecosystems classi ed according to feeding relationships Why is this useful It allows us to compare different ecosystems Why are ecosystem ecologists particularly interested in producers All the energy and organic molecules within an ecosystem originated with the producers Trophic Structure Food Chains and Food Webs gt Basic Way to describe the structure of an ecosystem Food chain Grazing vs Decomposer Food Chain What is the difference Grazing food chain producer alive Decomposer food chain producer dead Which one is more important Decomposer food chains are dominant in terrestrial communities particularly forests Grazing food chains are more important in planktonbased marine communities Food Webs Food Web gt Most food chains in an ecosystem is interconnected gt Consumers can eat more than one species or from more than one trophic leVel Energy Transfer low Through Ecosystems Energy ow is one Way 1 Energy enters food chainecosystem Via producers a Typically solar energy 9 chemical energy sugars 2 Producers use much of it for maintenance and respiration Only a fraction is used for growth and reproduction Net Primary Productivity N PP Why do We care about NPP This energy is the only energy available to consumers and decomposers 3 At each subsequent level again energy is used for maintenance and respiration and growthnew tissue and reproduction 9 next level a Energy transfer is inefficient energy is lost at each level b Energy stored in one trophic level l10 of that is stored in level below 10 rule c Total biomass declines Energy Pyramid Energy Pyramid gt Size of compartment proportional to amount of stored energy What Determines Efficiency of Energy Transfer gt Diet and activity levels How do diet and activity affect ef ciency of energy transfer from one trophic level to the next Activity If the activity level of the organism is low it can convert more energy it takes in to the next level Slow and lazy nice and fat lots of mass for eating Ex Hummingbird vs Tortoise Hummingbird has to produce own heat and constantly move around so it is not efficient in converting the energy it takes in to its biomass Diet Herbivores are less efficient than carnivores Ex Lion vs Hippo The lion is able to use a much greater percentage of the energy it takes in The hippo s food is not digested so Well Pollutants in Food Chain Biomagnification Biomagni catimn Mechanisms Persistent organic pollutant POP Environment 9 l producers 9 consumers Sequestered in consumer s body Consumer eats lOg tissue for lg of own tissue Concentration magnified at each trophic level VVVVVV Ex Methyl mercury levels in fish much higher in levels in larger fish that are high level consumers How Do Trophic Changes Effect Food Webs Same food chain different ecosystems Why gt Changes to food Webs can have farreaching effects TopDown Control gt Consumers depress trophic levels on which they feed BottomUp Control gt Increased production 9 greater productivity at all levels gt When effects extend through additional trophic levels this is called a trophic cascade Global Patterns of Productivity Primary production varies among ecosystems Terrestrial Ecosystems gt Productivity limited by 0 Lack of nutrients o Adverse weather conditions 0 Intensity of Sunlight 0 Availability of water 0 Intensity of grazing gt Highest Wet tropics gt Lowest desert and arctic Aquatic Ecosystems gt Productivity limited by 0 Availability of nutrients o Intensity of grazing 0 Availability of sunlight gt Highest coral reefs coastal algal beds estuaries Wetlands gt Lowest open ocean What Is Nutrient Nutrient 30 atoms found in molecules and ions of living organisms gt Matter nutrients are not lost in a global sense gt Elements are reused Continually cycle between organismsfood Web and the physical environment gt Each kind of atommaterial has its own unique biogeochernical cycle Nutrient Cycling Basic Features 1 Inorganic nutrients from soil carbon as atmosphere carbon dioxide 9 PLANTS 2 Plants eaten nutrients 9 consumers 9 detritus Plant dies nutrients 9 detritus 3 Detritus broken down by decomposers a Nutrients 9 soil organic matter 9 inorganic forms gt Nutrients can now be taken up by plants once more How Fast Do Nutrients Cycle Rate at which nutrients move through an ecosystem is usually limited by the rate of decomposition of detritus gt Decomposition rate depends on activity of decomposers fungi bacteria archae etc In uenced by 1 Abiotic factors oxygen temperature water a Faster when climate is Warm oxygen and Water available 2 Quality of detritus a Inhibited if detritus is low in nitrogen or high in lignin decomposition of a fruit will be faster than a tree branch b Ex Peat bogs and bog bodies bogs are Wet cold acidic and no oxygen Decompositions are extremely slow in bogs How Are Nutrients Lost and Gained gt Nutrients not gained or lost globally but can be gained or lost locally Nutrient Loss 1 Soil erosion by Water or Wind 2 Organisms physically leave an area Which human activities enhance nutrient loss 1 Devegetation This leads to greater erosion 2 When We bum stuff up EX Effect of acid rain Nutrient Gain 1 Chemical weathering of rocks nutrients trapped will become available 2 Deposition by wind and water 3 Activity of NitrogenFixing bacteria The Water Cycle Why is water important gt Essential for life cells are mostly made of water gt Required for photosynthesis gt Cycle involves predominantly physical changes gt gt 97 of the water in the biosphere in the oceans How does water get to land gt Evaporation gt Precipitation gt Water vapor 9 continents How does water return to the ocean gt Precipitation gt evaporation and transpiration gt Water 9 Ocean as runoff and groundwater How Are Humans Altering The Water Cycle gt Major problem groundwater depletion Using up aquifers especially in arid areas where it will be hard to be refilled This is a nonrenewable resource Aquifers take thousands of years to build up Cause 1 Asphalt devegetation etc 9 increased runoff and decreased percolation 2 Irrigation industry etc remove massive amounts of stored groundwater Effects 1 Wells dry up 2 Reduction of water in streams lakes wetlands etc 3 Deterioration of water quality salt water intrusion 4 Land subsidence increased risk of ooding Water table Dropping on every continent Ex Riparian habitat loss along the Santa Cruz River 1942 vs 1989 decrease in Water table lead to loss of trees and vegetation The Nitrogen Cycle Importance of Nitrogen gt Component of many organic molecules e g proteins DNA ATP chlorophyll gt 78 of air is nitrogen gas but most organisms can t use it in this form How does Nitrogen enter the food chains 1 Nitrogen fixing bacteria NH4 9 N03 nitrate 2 Plants can absorb NH4 and N03 3 Nitrogen containing organic molecules pass up food chain Lightening also causes nitrogen fixation How does Nitrogen return to the atmosphere 1 Nitrogen containing molecules returned to environment in urine and dead tissue 2 Decomposers convert these to NH4 N03 and eventually N2 gas How Are Humans Altering The Nitrogen Cycle gt Huge amounts of nitrogen are being added 0 Industrial fertilizers o Cultivation of nitrogen fixing crops 0 N03 from fossil fuels Problems with OverFertilization gt Terrestrial Ecosystems can decrease biodiversity There will be an increase in productivity of certain species and will outcompete the other species gt Aquatic Ecosystems nitrogen laced runoff can have disastrous impacts on aquatic ecosystems 0 Ex Anaerobic dead zone in Gulf of Mexico The Carbon Cycle Why is Carbon important gt Carbon atoms framework of all organic molecules gt Organic carbon is also a major source of energy for animals fungi and most microorganisms How does Carbon enter food chains gt As carbon dioxide is used during photosynthesis How does Carbon exit food chains gt As carbon dioxide is released via cellular respiration Additional Processes 1 Equilibrium between carbon dioxide in the atmosphere and dissolved form in oceans lakes and streams 21 CO2 H20 9H HCO3 2 Carbon extracted by marine organisms to build calcium carbonate CaCO3 shells a Limestone and dolomite 9 erode How are humans altering the carbon cycle Global Warming Human Activities That Increase CO Concentrations gt Humans causing significant increases in atmospheric carbon dioxide 1 Burning fossil fuels a Dramatic increase in fossil fuel use over the past 150 years especially in industrialized countries b Releases carbon atoms trapped for hundreds of millions of years in inactive petroleum and coal reservoirs 2 Deforestation a Reduces ability of area to take up carbon dioxide via photosynthesis b Release of carbon dioxide when fire is used for clearing or when dead tree parts are left to rot decomposers respire and put carbon dioxide in the air Consequences of Global Temperatures gt Carbon dioxide greenhouse gas traps heat infrared radiated from the earth and preventing it from being lost in space gt Average global temperature is already higher By 2100 it is predicted to further increase 11 to 640 C Residents of industrialized countries are largely responsible for global warming because they burn large quantities of fossil fuel Is global warming just a hypothesis or is it really true Evidence is unequivocal It is a fact The earth s climate has changed throughout its history so why is this a problem The average temperature currently is increasing at an extremely high rate one of the most rapid periods of climate change since life began Organisms do not have enough time to adjust The rate is What is causing the problem Ex Muir amp Riggs Glaciers 1941 has snow and ice 2008 is now a lake How Are Ecosystems Responding Positive Feedback makes things worse gt Changes due to global Warming result in further acceleration of Warming gt Ex Increased fires in North America and Canada this further increases the amount of carbon dioxide in the atmosphere gt Ex Faster decomposition of the tundra decomposition rate increases will make the situation Worse Negative Feedback make things not quite so bad gt Changes due to global Warming result in increased uptake of carbon dioxide and other greenhouse gases 9 global Warming reduced gt Ex Increased photosynthesis growth of some trees and crops more vegetation means carbon dioxide will be sucked back into plants gt Example of a negative feedback on global Warming Glaciers and icecaps are melting leading to larger volumes of Water in the seas and oceans carbon dioxide dissolves in Water Impacts On Organisms 1 Changes in geographic rages 2 Changes in timing of seasonal events 3 Increased extinction who is vulnerable a Arctic alpine tundra and pack ice habitat species b Beach and near shore habitat species c Ocean organisms With CaCO3 skeletons or shells d Slow dispersing species some species adjust by changing their geological range but slow or motile species are vulnerable due to inability to move to a better location 4 Evolutionary changes Impact On Net Primary Productivity Terrestrial Ecosystems gt Net primary productivity now decreasing due to draughts despite increased carbon dioxide and temperatures Although increase amounts of carbon dioxide food for vegetation and increased temperatures more metabolic action aided in photosynthesis global Warming has caused more draughts Aquatic Ecosystems gt NNP decreasing in oceans due to increased stratification Nutrients cannot reach surface Waters because density differences between Water layers have increased Nutrientrich water is i brought to the surface by currents 391 I r I I I I I I I I I I I I I I I I I I I 9201 Pearson Education Inc Current Extinction Rates gt 100 to 1000 times greater than averagebackground extinction rate gt Approaching rates observed during mass extinction gt Extinction is irreversible Threats To Biodiversity gt Causes of species loss gt Habitat loss is the most important factor overall gt Dominant problems 0 Terrestrial species 9 Habitat loss 0 Marine species 9 Overexploitation o Freshwater species 9 Pollution amp habitat loss gt Endangered species usually affected by multiple factors 1 Habitat Destruction a From logging plowing grazing mining construction b EX Atlantic coastal forests of Brazil over 40 years most almost all of the forest was delimitated Habitat destruction leads to Habitat Fragmentation amp Small Populations Habitat Fragmentation Habitat Fragmentation How does it affect species richness Larger the fragment greater the species richness Problems 1 Habitat fragments are too small to support some species e g large predators 2 Preventrestrict dispersal 3 Creates a large amount of edge habitats species that live on the edge of two habitats 9 decline in habitat quantity and quality Increased light temperature wind edge species Decreased humidity biomass gt Edge Effects 0 Ex Kentucky Warbler living in fragmented forests have more edge species The rate of parasitism on nests of Kentucky warbler by brown headed cowbirds varies with distance from the edge The cowbird lays an egg in the warbler nest decreasing the fitness of the warbler and its chicks Small Population Small isolated populations are more likely to go extinct than large ones due to 1 Stochasticchance events if there is a small population a catastrophic event ood fire disease will be more likely to be wiped out than a large population 2 Genetic problems inbreeding depression random loss of alleles due to genetic drift Ex North American big hom sheep population The population that had 100 individuals still existed after 70 years whereas the smaller populations all died off 2 Overexploitation 3 Overexploita onz Many species have been hunted to extinction Species must susceptible are large species with low intrinsic reproductive rates e g elephants whales rhinos etc Cascading Effect when there is Overexploitation Ex Global sh stocks if current over shing continues we won t have fish by 2050 3 Invasive Species a b c d Disruptions severe when exotic species from diverse continental biota are Can be competitors predators or pathogens to native species Arrive accidentally or introduced deliberately Process accelerated by ease of travel introduced to isolated island Ex Pythons in the Everglades huge pythons are accidentally released and the mammal species populations are suffering Traits Common to Invasive Species Fast growth and reproduction 5 VVVVVV High dispersal abilities Phenotypic plasticity ability to alter growth form to suit current conditions Tolerance for a wide range of environmental conditions Ability to live off a wide range of food types generalist Association with humans prior successful invasions Pollution a Pollution release of chemicals into ecosystems b Many types of major pollutant many persistent c Ex Intersex Fix in Potomac Smallmouth Bass had female eggs developing in male testicular tissue Found out it was due to a pesticide in their ecosystem This pesticide is a known endocrine disruptor Climate Change a Increasing evidence that climate change affects extinction rates b Which species are most vulnerable One that cannot change its geographic range and those who cannot evolve rapidly e g trees Why Biodiversity Is Important Economic Benefits 1 Crops improvement of traits and pollination 2 Bioprospecting a Bioprospecting 2 b Ex Madagascar periwinkle produces chemicals vinblastineVincristine that can be used to treat leukemia c Ex Naked mole rats are anticancer 3 Ecosystem services a Ecosystem Services b Ex Oxygen production cycling of nutrients through ecosystem soil formation and retention temperature and wind moderation Water retention Biological Benefits gt Biodiversity increases productivity and stability of communities Ethical Reasons gt Man believe humans have an ethical obligation to preserve species and ecosystems Preserving Biodiversity and Ecosystems Conservation of Biodiversity Genetic Restoration gt If small populations suffer loss of genetic diversity alleles can be restored by artificial gene ow gt EX Greater prairie chicken eggs stopped hatching with loss of genetic diversity so people brought in the same species from a different area gt How can one gure out if a problem has to do with genetic diversity Compared current genes to genes from decades ago to see if there is a loss of genetic diversity Ex Situ Conservation gt Ex Situ Conservation gt Zoos maintaining viable genetically diverse populations of species endangered or extinct in the Wild VVV Aim is to eventually reintroduce them into natural setting This program is costly Requires legislation land purchases and public education to control factors that threaten population in the first place Ex California condor There were 22 left in the 80 s Brought all 22 into captivity to bring their numbers up Made laws to promote condor survival The cost was over 35 million dollars cannot be used commonly Establishing Effective Protected Areas gt Cover ltl2 of Earth s terrestrial surface Not enough but it is increasing Where Should Protected Areas Be Located gt gt gt Few species richness hotspots in protected areas Gap Analysis Program identi es geographic gaps between species ranges and location of preserves Focus on identifying and protecting areas of high species richness endemism threat and unique ecological or evolutionarv characteristics Biodiversity Hotspotz Endemic Species EX The Kakapo New Zealand Parrot odd does not y low metabolism and can live up to a hundred years Used to be all over New Zealand but then people came and introduced predators cats dogs etc almost all died on the mainland How Should Reserves Be Designed l 2 If preserve carved out of area of uniformed habitat a The larger the better b Reduced of edge habitat circle c Connect isolated preserves via strips of undeveloped habitat wildlife corridors Preserving smaller areas of multiple habitats often preferable to larger area of uniform habitat because smaller areas of multiple habitats can support a larger variety of species Conservation of Ecosystem Function Ecosystem Restoration gt Ecosystem Restoration gt Includes removal of non native species manmade structures contaminated top soils re vegetation erosion control reintroduction of native species etc gt Thousands of projects underway around the world gt Ex Elwha River Restoration Project starting to remove the damns and take care of the silt that built up behind the dam planted native species and plants Hoping to get the salmon back with making the river free owing again Dealing With The Ultimate Causes of Loss Sustainable Development gt Use resources at rate at which can be replenished gt Avoid reliance on stored resources gt Ex Solar and wind power vs Oil and coal Stabilizing human population size