Ecology and Evolution Bundle of notes Exam 2
Ecology and Evolution Bundle of notes Exam 2 Biol 202
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This 11 page Study Guide was uploaded by Katlyn Burkitt on Tuesday March 29, 2016. The Study Guide belongs to Biol 202 at Towson University taught by J. LaPolla in Spring 2016. Since its upload, it has received 187 views. For similar materials see Intro to Ecology and Evolution in Biology at Towson University.
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Date Created: 03/29/16
Green means Text and Lecture( 3/21/16) Red means Lecture 3/21/16 22.1 Learning outcomes Distinguish between the biological species concept and the ecological species concept Define the two types of reproductive isolating mechanisms Describe the relationship of reproductive isolating mechanisms to the biological species concept Sympatric Species Inhabit the same locale but remain distinct Phenotypically different and use different part of the habitat and behave differently Geographic Variation Within a species organisms that occur in different areas may be distinct from one another o May be classified as subspecies or race o In areas where the populations occur close together they may share characteristics of both populations Biological species concept and the ability to exchange genes (Further Explained in Lecture) Gene pool: All the alleles present in a species Gene flow can maintain geographical distant populations to continue to be connected Reproductive Isolation and its mechanisms (Lecture Notes) Ecological species concept Will not cover in notes due to his purposeful exclusion in lecture 22.2 Learning outcomes Define reinforcement in the context of reproductive isolation Explain the possible outcomes when two populations that are partially reproductively isolated and become sympatric Ch. 22 Biol 1 | P a g e o Species tend to look very different from each other in sympatric locations (Secondary Reinforcement) o Secondary reinforcement can only be seen in sympatric locations Selection may reinforce isolating mechanisms Formation of species is a continuous process Some populations that are ecologically or behaviorally isolated they still may be able to mate and reproduce and the Postzygotic barriers may be incomplete allowing for a viable offspring that may have a lower survival rate or reduced fertility. The concept that incomplete Postzygotic barriers are reinforced by natural selection until they are completely effective Allopatric: Geographically separated populations (By physical geographic barriers) are more likely to undergo speciation 22.3 & 22.4 Learning Outcomes Describe the effects of genetic drift on a population o Founder Effects o Small Populations o Population Bottleneck o Neutral Theory of Molecular Evolution( Not in book) Molecular Level Most of the variation observed between species is the result of genetic drift. Most are neutral at the molecular level (Deleterious: Negative) Neutral evolution: accumulation of neutral mutations at the molecular level, but the phenotypical changes are dominated by natural selection Explain how genetic drift and natural selection can lead to speciation o “Fruit Flies” Effected their courtship rituals (Hawaiian Islands) How does speciation occur? 1. Initially identical populations must diverge 2. Reproductive isolation must occur to maintain these differences Sympatric speciation o Speciation within the same location. o Can occur instantaneously Occurs when an individual is born that is reproductively isolated from all other members of its species Through polyploidy: Individuals have more than two sets of chromosomes Autopolyploidy Ch. 22 Biol 2 | P a g e o All chromosomes arise from a single species o Ex. When an error in cell division causes a doubling of chromosomes creating Tetraploids (Organisms with four sets of chromosomes) Tetraploids can self-fertilize or mate with other tetrapod’s but cannot mate and produce fertile offspring with normal diploid organisms. This is because they produce diploid gametes that produce triploid offspring when combined with the haploid gametes from diploid organisms Triploids are sterile because of the odd number of chromosomes Allopolyploidy o More common o Occurs when two species hybridize The resulting offspring is usually infertile due to have one copy of chromosomes from each species therefore they cannot match correctly However these species can become fertile through several events including the error that causes tetraploidity, may be able to reproduce asexually o Can also occur over the course of multiple generations Disruptive selection Can cause a population to contain individuals with two different phenotypes o This will only work if the two phenotypically different parties develop reproductively isolating mechanisms. o Ex. Adapting to eating a different food source 22.5 Learning Outcomes 1. Describe adaptive radiation 2. List conditions that may lead to adaptive radiation Adaptation o The differences in Dewlap Coloration Adaptive radiation o The existence of groups of closely related organisms that recently diverged from a common ancestor but have adapted to different parts of the environment Ch. 22 Biol 3 | P a g e o Common in environments with few species but many resources Ex. New islands formed through volcanic activity or catastrophic events leading to mass extinction o Can also occur when a new trait called a key innovation evolves within a species allowing it to use resources or other aspects of the environment that were previously inaccessible o Requires both speciation and adaptation to different habitats Character displacement o Natural selection favors those individuals that use resources not used by other species so populations on different islands evolve to become different species causing the species to diverge. The finches were used as another example however since they are covered extensively in lecture as well as several other chapters I will not cover them here. There are several other examples of speciation in this chapter 22.6 Learning Outcomes 1. Define stasis and compare it to gradual evolutionary change 2. Explain the components of the punctuated equilibrium hypothesis Gradualism The accumulation of small changes over several generations Punctuated equilibrium Species experience periods of little to no change followed by periods of rapid evolutionary change Ch. 22 Biol 4 | P a g e Chapter 20 Biol Genetic Variation provides the raw material for evolution Evolution: An entity changing over time Population genetics: The study of the genetic composition of a population and how/why it changes Blending inheritance: Offspring are expected to be phenotypically intermediate relative to their parents HardyWeinberg Equilibrium: When the proportions of genotypes do not change in a population o This can only occur if No mutation takes place No genes are transferred to or from other sources (No immigration or emigration) Mating is random Large population No selection o Equation to calculate allele frequencies P= Dominant Q= Recessive P*p =p 2 P+q=1 2 2 P +2pq+q =1 o Why would a population have an excess of homozygotes vs heterozygotes? Natural selection favors the homozygotes Individuals choosing to mate with genetically similar individuals An influx of homozygous individuals from an outside population 5 agents that cause evolutionary change o Mutation o Gene Flow: Movement of alleles from one population to another o Nonrandom mating Assortative mating: When phenotypically similar individuals mate more often than different individuals produces an excess of Homozygotes Disassortative mating: When phenotypically different individuals mate, producing an excess of Heterozygotes o Genetic drift: The change in frequency of an allele by change alone Founder effect: When one or a few individuals of a population disperse and become the founders of a new isolated population can cause the allele’s that were rare in the parent population to be common in the new population Bottleneck effect: When populations are drastically reduced no matter the cause the surviving individuals will likely be a random genetic sample of the original population o Natural Selection There must be phenotypic variation in the population The variation must give some individuals a reproductive advantage The variation must be genetic Sexual selection: Selection based on mating success Frequency dependent selection: When the fitness of a phenotype depends on its frequency Negative: The rare phenotype is selected for Positive: The rare types stick out and are more vulnerable to predators Oscillating selection: One phenotype is favored then the other Heterozygote advantage: When the heterozygous condition provides an advantage over both homozygous conditions Disruptive Selection: When selection acts to eliminate intermediate types Directional Selection: When selection moves to eliminate one extreme in a population Stabilizing Selection: Selection that moves to eliminate both extremes of a population Lecture Notes Darwin argued o Species are not immutable Immutable: They do not change o Modification of the “normal form” are caused by abiotic and biotic changes Adaptations: Beneficial traits from modification o Populations over time become “fit” to local environmental conditions o Populations can become so different in form that they may become unique species Mechanics of natural selection o Observations 1. Every species on earth has an enormous reproductive potential 2. The number of organisms in a species cannot increase endlessly do to limited resources, meaning there is not such thing as unlimited growth Conclusion: Species can and do produce far more offspring than the environment can support. This leads to intraspecific competition or “struggle for existence” 3.If you look at any population individuals are not identical in form. Variation: Provides the raw material for natural selection The ability to survive and reproduce depends on form o Conclusion: Individuals with favorable traits “win” on average and survive longer and produce more offspring than those without those advantages 4. Natural selection only works with inherited characteristics If there is no genetic basis the form will not be passed on, individuals with favorable traits have more offspring that also share those traits. Over time the populations have an increase in favorable traits. Blending inheritance: An idea that offspring should be intermediate to their parents Population: A group of individuals of the same species in the same area that can interbreed Gene Pool: All alleles in a populatulation. Population genetics: The study of properties of genes in a population Convergent evolution: Similar forms having evolved in different areas due to similar selective pressures in a similar environment Phylogeny: An evolutionary tree Chapter 21 Biology Evolution by Natural Selection requires o 1. Phenotypic variation must exist in the population o 2. This variation must lead to differences among individuals in lifetime reproductive success o 3. Phenotypic variation among individuals must be genetically transmissible to the next generation Natural Selection occurs when there is a selecting factor that gives one phenotype an advantage o Examples in islands During droughts or dry years when the main type of seed available is large and tough the larger beaks hold the advantage During wet years small seeds are more available the smaller beaks hold the advantage Beak depth is genetic o Natural Selection can occur if something in the environment changes Example when pollution caused the trees in a forest to turn darker in color the population of black moths increased in relation to the population of “peppered” moths The theory being that light colored moths were more easy for predators to see on the darkened trees which made their coloration unfavorable Industrial Melanism: Refers to the phenomenon in which darker individuals come to predominate over lighter ones. Artificial Selection: Operates by favoring individuals with certain phenotypic traits allowing them to reproduce and pass their genes on to the next generation Domesticated breeds have arisen from artificial selection o They managed to domesticate foxes by selecting the most docile of the parent generation o Their ears, tails, and legs also changed with their temperaments. Homologous Structures o Structures with different appearances and functions that all derived from the same part of a common ancestor Most species are similar during the embryonic stage Not all features are perfectly suited for their use Vestigial Structures o Structures that have no apparent function but resemble structures their ancestors possessed Fossil Genes or Pseudogenes o Genes that have been made inactive through some mutation however still remain a part of the organisms genome Convergent Evolution o Evolutionary change that occurs parallel in similar environments Chapter 26 Biology Notes Debris from a meteor hitting earth formed the moon (4.6 BYA) Atmospheric temperature is 2000˚C Increased CO c2used Increased temperature Decreased CO 2 caused decreased Weathering increases in hot wet conditions and pulls CO f2om the atmosphere Plates o Ridged slabs of rock that forms earths crusts Plate tectonics o The movement of plates Supercontinents o Rodinia: All continents, during the Proterozoic era (early life) Broke up during 650 MYA o Gondwana: All southern hemisphere continents o Pangea: All continents Phanerozoic = Visible life o 12% of earth’s history Paleozoic era/ Cambrian period = High diversification of multicellular life Birds and mammals o 4% of earth’s history Humans o .2% of earth’s history Fossils are dated by the half-life’s of their isotopes o Carbon dating, uses carbons half-life which is 5700 years How did life originate? o Arose from early waters filled with ammonia, formaldehyde, folic acid, cyanide, methane, hydrogen sulfide, and organic hydrocarbons o Meteorites may have brought some of the organic molecules Example Tagish with 3% of its mass being organic molecules o Reducing Atmosphere (high hydrogen content) Makes forming molecules easier o Miller and Urey Experiment Step 1: Assembled a reducing atmosphere Step 2: Placed atmosphere over liquid water Step 3: Maintained at a temperature bellow 100˚C Step 4: Simulated lightning This created small organic molecules and amino acids RNA was the first nucleic acid that promoted self-replication Early membranes were made of fatty acids Craton: A rock layer of undisturbed continental crusts o Microfossils Stromatolites: Sedimentary deposits held in place by mats of micro- organisms Carbon Fixation: Changing inorganic carbon to usable organic carbon o Done by the Calvin Cycle and the reductive Krebs cycle Organic molecules are biomarkers o Example Hydrocarbons from fatty acids Climate: Temperature and water availability Atmosphere: Levels of O and2CO 2 o Volcanic Eruptions alter the atmosphere Highest temperature of earth was 2000˚C Lowest temperature of earth was -50˚C Snowball Earth: Ice or glaciers Glaciation results in massive extinctions Oxygenic photosynthesis produced O encour2ging the evolution of cellular respiration Increased O i2 the atmosphere caused O to int2ract with UV rays forming O 3 or Ozone
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