BIOL 286 Exam #1 Study Guide
BIOL 286 Exam #1 Study Guide Biol 28600
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This 13 page Study Guide was uploaded by Elissa Emily on Tuesday February 9, 2016. The Study Guide belongs to Biol 28600 at Purdue University taught by Joshua Springer in Spring 2016. Since its upload, it has received 48 views. For similar materials see Introduction to Ecology and Evolution in Biology at Purdue University.
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Date Created: 02/09/16
Biology 286 Notes EXAM #1 EE 129 8pm -10 pm Monday feb 15 January 19, 2016 Natural selection: chooses the best adapted • For the current generation ONLY • Not necessarily the best adapted for the next or subsequent generations • Sorts through allelic combinations that work or don’t work Size matters- evolution by natural selection does not lead to perfect (cost benefit to some structures) Cut-hunter hypothesis Darwin’s four postulates: 1. Diversity 2. Partly heritable 3. Some survive and reproduce better than others 4. Not random mating Trait composition of population changes- rate is not set in stone, but is visible over time Darwinian fitness- the ability to survive and reproduce Never say final population! Antibiotics are prescribed for a certain amount of time…never stop taking because some individual bacteria may have higher resistance and can reproduce and rebuild if it is not killed Drug Holiday- short break in drugs, used because some drugs can be hard on body. Allow the person to feel okay for a period of time Galapagos Finches- great way to study natural selection, Peter and Rosemary Grant Major take away was that severe droughts led to changes in population structure! Medium ground finches in the Galapagos are variable for beak depth The variation is heritable (offspring get characteristics from their parents) Some individuals survive better than others and that’s tied to traits Beak size in Darwin’s finches depended on weather • Wet years: small beak birds do better • Dry years: big-beak birds do better Adaptation: heritable trait that confers a fitness advantage to its carrier (by improving the reproductive success of the carrier, and thereby the transmission of that trait) Can be sharper teeth, stronger wings, winning smile… We also speak of individuals “adapting” to changes, Fitness: • Proximate: ability of an organism to survive and reproduce • Ultimate: relative representation of alleles in subsequent generations • Measures of fitness include absolute and relative o Absolute: survival and reproduction o Relative 3 ways selection acts on a trait 1. Stabilizing selection- favors average trait- selections against both extremes (bell curve) 2. Directional selection- favors one extreme 3. Disruptive selection- favors both extremes Genetic variance: • Stabilizing selection: reduces genetic variance on quantitative traits Frequency dependent selection: • Frequency-dependent selection, the fitness of a phenotype declines if it becomes too common in the population Phenotype vs genotype: What evolution is not… • Untestable • Perfect • A cause to believe in irreducible complexity • January 21, 2016 Cline vs phenotypic plasticity • Cline: change or variation in a phenotype over the range of a species. One phenotype but it varies slightly • Phenotypic plasticity: the ability for one genotype to produce more than one phenotype in the same local area Five evolutionary forces acting on population Rules for lecture: Think of each evolutionary force with two different population sizes What effect would each evolutionary force have on either population size 3 individuals must die at the end of each growing season. Selection • Important throughout the growing season or disease cycle (if talking about a pathogen) o Differences in phenotype lead to variable survival and reproduction o Some individuals have higher fitness § Evolution occurs if the trait under selection is variable, heritable, and differential in survival § If a trait does not have variation, selection cannot generally act on it • Traits have reached fixation Random Genetic Drift: • Not a selective force o Does not: lead to adaption o Does (can): lead to changes in allele frequencies by random chance • Alleles randomly reach fixation by chance o Decline in heterozygotes, increase in homozygotes • Most important when population sizes are small o By chance (sampling effect) alleles are represented in the next generation o As population size increases, effects of drift decrease o When population size is small random genetic drift can overwhelm selection Migration (gene Flow) • Mechanism of evolution if alleles inherited o Establish and become part of breeding population • Has largest effect when populations are small o New alleles make a larger proportion of the population • If migrants differ in allele frequency...then o Inhibit or promote adaptation § Maladaptive or highly fit individuals • Homogenization among populations o If selection is not acting o Counteracts drift by preventing divergence of populations § High levels of migration in a species can prevent speciation if no barriers to migration exist (or are very inconsequential) o Migration can counteract natural selection • Population divergence (Fst) o Measures proportional reduction in heterozygosity § So= increase In homozygosity § Sub-population divergence Mutation • Ultimate source of all genetic variation o Almost never changes allele frequencies o Most are quickly selected against (deleterious) • Chance of seeing mutation increases as population size increase o Constant mutation rate= more seen in larger populations because higher proportion Recombination • Important whenever it occurs o Creates new genotypic combinations § Therefore produces new, variable phenotypes on which selection can act Population genetics and disease epidemics, e.g. • Changes in population size o Can GREATLY influence relative importance of each genetic force • Population genetics can influence o Commonness or rareness of particular alleles o Presence or absence of alleles that cause disease or resistance to a disease January 26, 2016 Understanding the diversity we se in populations of species: • The central issue in population genetics is genetic variation o It extended within populations o Why it exists o How it changes over the course of many generations • Emerged as a branch of genetics in the 1920s and 1930s o Its foundations are largely attributed to mathematicians Genes in population • Population genetics is a direct extension of mendel’s law of inheritance, molecular genetics, and the ideas of Darwin • The focus is shifted away from individual and towards population • All the alleles of every gene in population make up gene pool o Only individuals that reproduce contribute to gene pool of the next generation • Population geneticists study the genetic variation Some genes are monomorphic but most are polymorphic • The term polymorphism refers to the observations that many traits display variations within a population • Hawaiian happy-face spider- differ in alleles that affect color Population genetics is concerned with allele and genotypic frequencies • Two fundamental calculations are central to population genetics o Allele frequency= # copies of allele in pop/ total # allele o Genotype frequency= # individuals with particular genotypes/ total# of individuals in pop Consider a population of 100 frogs • 64 dark green frogs with genotype GG • 32 medium green with Gg • 4 light green frogs with gg o frequency of allele g= (2)*(3)+32 / (2)*(64) +(2*32)+(2*4) o frequency of gg= 4/100~ 4% • For a given trait the allele and genotype frequencies always = or less than 1 • For monomorphic genes o Single allele with = 1.0 • For polymorphic genes o Frequency of all alleles should add up to 1.0 o Frequency of G allele + frequency of g allele= 1.0 Hardy-Weinberg Equilibrium • The Hardy-Weinberg Equation was formulated in 1908 o Relates allele and genotype frequencies in a population • The HW equation (*finish in notes) • Predicts an equilibrium-unchanging allele and genotype frequencies from generation if certain conditions exist in a population o No new mutations o No genetic drifts. Population is so large allele frequencies do not change due to random sampling effects o No migration o No natural selection o Random mating • Provides a quantitative relationship between the allele and genotype frequencies o P+Q=1 o P2+ 2pq + Q2= 1 o Can be used to predict the frequencies of carriers (heterozygotes) for a recessive genetic disease • In reality, no population satisfies the HQE completely • Some large natural populations there is little migrations and negligible natural selection – nearly approximated or certain genes in these populations • HW E can be extended to situations in which genes exist in 3+ alleles Haemochromatosis in people of northern European descent • 1/200 humans of this ancestry have both alleles • for Thursday calculate the frequency of heterozygous carriers Microevolution • genetic variation in natural populations changes over many generations • microevolution describes Natural selection • in the 1850 charles Darwin and Alfred russel Wallace independently proposed the theory of natural selection o according to this idea there is a struggle for existence o those individuals that are more adapted to their environment will survive and reproduce • recently populations geneticists have realized that natural selection can be related to mating efficiency and fertility o not just to differential survival o some are just better at mating • a modern description of natural selection can relate molecular genetics to the phenotypes of individuals o within a population there is allelic variations arising from various factors such as mutations causing differences in DNA sequences § distinct alleles encode proteins of differing functions o some alleles may encode proteins that enhance an individual survival or reproductive capacity o individuals with beneficial alleles are more likely to survive and reproduce o over the course of many generations, allele frequencies of many different genes may change through natural selection § this significantly alters the characteristics of genes Significant factors that effect • Bottleneck effect o In nature a population can be reduced dramatically in size by a natural disaster o Such a disaster randomly eliminates individuals regardless of their genotype o The period of the bottleneck when the population size is very small may be influences by genetic drift § African cheetah has lost nearly all of its genetic variation • Founder effect o Small group of individuals separates from larger population and establishes a colony in a new location o This has to important consequences § The founding population is expected to have less genetic variation § Found pop will have allele frequencies that may differ markedly from those of original population, as a matter of chance § Ex: old order Amish of Lancaster County, PA • Dwarfism is high (7%) Mating and phenotypes • Assortative mating : do not mate randomly • Positive assorative mating: occurs when individuals are more likely to mate due to similar phenotpyes • Negative assorative mating: occurs when individuals with dissimilar phenotypes mate Mating and genotypes • Inbreeding: between genetically-realted individuals • Outbreeding: between genetically unrelated individuals nd February 2 2016 Plants get carbon from atmosphere Plant Adaptation • Photosynthesis and respiration • Environmental controls on photosynthesis • Plant adaptations to o High and low light o Water limitation o Nutrient availability Conditions and resources • Conditions: are physical/chemical features of the environment o Temperature, humidity, pH, ect o NOT CONSUMED by living organisms • Resources: are consumed o Once used, they are unavailable to other organisms in that original form o Plants sunlight water minerals o Animals prey organism Plant resources: • Plants are autotrophs- make own organic carbon form in organic nutrients • Plants are sessile (so not move once established—but seeds) o Grow towards nutrients § Or in environments Photosynthesis: conversion of Carbon dioxide to simple sugars • Involved gas exchange • Controls: o Light- tall plants better at catching light o Water o Nutrients o temperature Respiration: conversion of sugar into ATP & water Tradeoff • shade plants grow better in the sun than in the shade • but sun plants grow faster than shade plants in direct sun • shade plants survive well in either sun or shade • sun plants cannot tolerate shade Sun leaf • thicker • more cell layers • more chloroplasts • leaves at many angles • high saturation point • high compensation point • high respiration • less chlorophyll • enzymes limit photosynthesis Shade leaf • flat • thin • larger surface area/unit weight • horizontal leaves singl layer • low saturation point • low compensation point • low respiration • more chlorophyll Strategies for drought • Avoiders: o Short lifespan o Wet season o Seeds survive drought o Drought deciduous species § Leaves shed in dry season • Tolerators o Leaves transpire slowly o Change orientation of leaves o Sunken stomata (gas exchange organs) § E.g pines o More efficient photosynthesis § Eg C4à reduces photorespiration § Eg CAMà stomat Water absorption • Root hairs increase surface area Nutrients • Macronutrientsà needed in large amounts (C, H, O, N, P, K) • Micronutrients- trace amounts • Micro/macro refer to the quantity needed Evergreen leaves • Plants adapted to nutrient-poor conditions tend to have evergreen leaves Effects of temperature • Increase temperatureà increase biochemical reaction rate • At high temperature, enzymes denature o Death Leaf Temperature • > 95% of sunlight absorbed by a lead becomes heat • cooling of leaves o transpiration o convection (movement of cool air around a leaf) o keep a microclimate around leaves Response to cold • chilling injury o near > 0 degree C o cell membranes rupture • freezing o < 0 degrees o ice inside cells= death o ice outside cells= dehydration (might survive) o may kill juveniles only Closer to home (view power point) ANIMALS Effects of extreme temperatures • cold- the effects of freezing o physical damages to structures caused by the formation of ice the membrane bound structures are destroyed • heat o • heat and cold Body temperature • Law of tolerance: for most requirements of life, there is an optimal quantity, above and below which the organism performs poorly • There is much variation in the range of temperatures that a species can tolerate Thermoregulation • Maintenance of internal temperature within a range that allows cells to function efficiently • Ectothermy & Endothermy Ecothermy • An animal that relies on external environment for temperature control instead of generating its own heat • Cold blooded • Invertebrates, reptiles, fish (majority of animals) Metabolism and temperature • Ectotherms cant move very much unless the amient temperautres allows Endothermy • A warm-blooded animal that controls its body temperature by producing its own heat through metabolism • Evolved approximately 140 mya • Birds, mammals, great white sharks, • Swordfish Behavioural adaptations for thermoregulation Shiverng, sweating, and panting • Honey bees survive by clustering together and shivering, generates metabolic heat • Inefficent 75% of energy is lost to heat Torpor • Metabolism decreases • Heart and respiratory system slows down • Body temp decreases • Conserves energy when food supplies are low Hibernation • Long term torpor • Adaptation for winter cold and food scarcity • EG ground squirrels Aestivation • Summer torpor • Adaptation for high temperatures and scarce water supplies • Eg mud turtles, snails Endothermy and evolution of sleep • Evolutionary remnant Colour and posture • Change coloration • Posture change shape , orientation Chemical adaptations • Many Canadian butterflies overwinter further south and… Advantages & disadvantages • Advantages: o External temperature does not affect their performance o Allows them to live in colder habitats o Muscles can provide more sustained power • Disadvantages o Energy expensive § An endotherm will have to eat much more than an ectotherm in equivalent size Endotherms thrive • Higher latitudes & deserts • Terrestrial environments have more variation in daily and seasonal temperature which contributes to more endotherms in terrestrial environmenals Size and Theroregulation • Small mammals have greater dependence on internally-generated heat than big mammals • Leads to o Presence of insulation (large usually has less hair) o Voracious appetites of small mammals February 4, 2016 How to study for the exam: • Do all the reading #1 look at the slides #2 read the summaries at the end of the chapters #3 study questions at the end of the chapters #4 review the questions online Properties of populations Population: is a group of individuals of the same species that inhabit a given area • Populations have structure, including density, spacing and age distribution • Populations are dynamic, changing over time • Why is it important that the individuals are members of the same species? • Why is it important for a population to have a spatial boundary? o Human construct sometimes (we determine boundaries based on our studies) Organisms may be unitary or modular • Suckers- new stems that sprout from surface roots and may appear to be individuals • Genet- plant produced by sexual reproduction, a genetically unique individual • Ramet- module produced asexually by a genet (these are essentially clones) Many species such as Aspens exhibit this trait Pando! Quaking Aspen in Utah • Pando- single living organism (one tree with many different stems), 6 million kg, root system 80 million years The Distribution of a population defines its spatial location • Ubiquitous- species have a geographically widespread distribution • Endemic- species have a geographically restricted distribution o Many endemic species have specialized habitat requirements § The shale-barren evening primrose is found only on hot, shale-barren environments, on south or southwest facing slopes in the Allegheny mountains • There are many types of geographic barriers that reduce or prevent individuals from moving and colonizing new areas o Bodies of water o mountains • Interactions with other species can also serve as barriers o Competition o Predation • The environment is heterogeneous o Thus most populations are divided into subpopulations that live in suitable habitat patches surrounded by unsuitable habitat • A metapopulation is the collection of these local subpopulations • These subpopulations are spatially separated but connected by the movement of individuals between them (migration!) Abundance Reflects population density and distribution • Abundance is a function of population density and the area over which the population is distributed • Crude density- the number of individuals per unit area o Square meter, kilometer • Or the number of individuals per unit volume • Place a grid over a population distribution and calculate the density for a given grid cell • Clumped- this is the most common spatial distribution and results from a number of factors o Suitable habitat or resources are found in patches o Species form social groups o Ramets formed by asexual reproduction • Spatial distributions of individuals may be described at multiple spatial scales • In the savanna ecosystem of southern Africa o The shrub Euclea divinorum has a clumped distribution o The clumps occur because Euclea grows under the canopy cover provided by Acacia tortilis trees o The clumps are uniformly spaced between…. Abundance • To account for the patch distribuions of some species, ecologists may use o Ecological density- the number of individuals per unit of available living space § Bobwhite quail prefer hedgerow habitat § Density can be expressed as the number of birds per mile of hedgerow rather than birds per hectare § However, it can be difficult to determine what part o a habitat is living space for a particular species Determining density requires sampling • Population size (abundance)= population density X the area occupied • How is density determined? • How accurate is this method? • Depends largely on the spatial distribution of individuals in the population o Look at slides • Can also be influenced by the choice of boundaries or sample units • Mark-recapture is the most commonly used technique to measure animal population size • This method is based on o Capturing a number of individuals in a population o Marking them with a mark that will no be lost during the course of the study o Releasing a known number of marked individuals back into the population o After an appropriate amount of time… • Of the individuals captured the second time (n), some will have been marked, or recaptured(R) • To estimate pop density • assume the ration n/R represents the ratio **view slide • signs of the presence of animals include: o counts of vocalization, such as bird song o counts of animal scat seen along a certain length of trail o counts of animal tracks, such a footprints in the snow • abundance does not provide any information on the characteristic of individuals within a population • why do populations with overlapping generations have n age structure? • What can the populations age structure tell you… Measures of Population Structure include age, developmental stage and size • A pop. With nonoverlapping generations does not have an age structure o Individuals reproduce and die within a signle season o Annual plants and some insects • A pop with overalapping generations has an age structure o There are individuals in different age classes § Reproduction is restricted to certain age classes • Populations can be divided into three ecologically important age classes o Prereproductive o Reproductive o Postreproductive • How long an individual is in each age class depends on the organisms life history o Some organisms such as mice have a • The most accurate method is to mark young individuals in a population and follow their survival through time • This is also the most difficult o Many individuals must be marked and subsequently • Less accurate methods include: • Examining a sample of bodies of individuals that have died and determine their ages at death • Look for characteristics that indicate age o Wear and replacement of teeth o Growth rings in the teeth or horns o Plumage changes and wear in birds o Annual growth… • It can be more challenging to estimate age structure in plants • Trees with seasonal growth produce annual growth rings • Dendrochronology-counting annual growth rings to determine the age of a tree • Size o the tree based on diameter at breast height can also be used o However, growth conditions can strongly affect this measurement An age pyramid is a graphical representation of the age structure of a population Sex ratios in populations may shift with age • In most mammalian populations, the sex ratio at birth is slightly weighted towards males at 107 males/ 100 females o The sex ratio shifts towards females in older age classes o Males generally have shorter life spans than females o Many species are characterized by rivalries amount males for reas… • In birds, the number of males tends to be higher than females o Nesting females are more susceptible to attach and predation
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