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BIOL 301 Test 1
Ecology & Evolution Test 1
| Term | Definition |
|---|---|
| Ecology | the study of the distribution and abundance of organisms inluding the control and regulation of their numbers |
| Evolution | the study of the origins of biological diversity and the molding of the characteristics of species, including those traits that determine their distribution and ecological function. |
| Hypotheses my be tested using: | 1) Laboratory Experiments – contrived but highly controlled. 2) Field Experiments – much more natural but less well controlled. 3) Natural Experiments – take advantage of natural events to test hypotheses. Least well controlled. 4) Best: use all 3 |
| Mutation | Ultimate origin of all genetic variation |
| Point Mutations | Change single bases in the DNA sequences and are quantitatively the most important. Occur at a rate of ~10-5 per gene per generation. Each of us carries 1-3 new mutations. |
| Synonymous Point Mutation | Do not change the amino acid sequence |
| Non-Synonymous | Results in change in the amino acid sequence |
| Recombination | most variation within a population results from the reshuffling of existing variation by sex and crossing-over. |
| Gene Flow | New alleles may arrive in a population by migration from another population. Similar to mutation in that new alleles suddenly arrive but differs from mutation because the rate may be much higher. Example included polydactylism in cats. |
| Hardy-Weinberg Equilibrium | describes the distribution of genotypes in a population given the frequency of the alleles and certain assumptions. |
| Assumptions of Hardy-Weinberg Equilibrium | 1) No new alleles from either mutation or gene flow 2) Random mating 3) No selection 4) Infinite population size |
| Hardy-Weinberg Equilibrium Demonstrates | a) genetic variation persists through time b) the prevalence of a phenotype in the population is a product of the frequency of an allele in the population. |
| Genetic Drift | Caused by random change in allele frequency from one generation to next. Random variation will cause one population to diverge in allele frequency to another and alleles to be lost from the pop. Rate inversely proportional to the size of the pop. |
| Ecological processes leading to reduced population | 1) Population Bottlenecks: sharp reduction in size of a pop due to environmental stochastic events or human activities. 2) Founder Effects: loss of genetic variation that occurs when a new pop is est by a very small number of indiv from a larger pop. |
| Effective Population Size (Ne) | genetic drift is related to the number of individuals that are “effectively” contributing to the next generation. Ne is almost always smaller than the census size of the population. (Ne = 10% N) |
| Influences on Effective Population Size | 1) separate sexes: number of the rarer sex 2) Variation in reproductive success: those who leave behind most offspring. 3) Inbreeding: reduces Ne because there are effectively fewer “genetic” partners 4) Age Structure: only reprod portion contributes |
| Natural Selection | variation in reproductive success due to heritable differences in phenotype only force driving adaptation accumulate effects of multiple gene loci->causes changes in the avg phenotypic values of pop that far exceed mean & range that orig existed in pop |
| Origins of Novelty via Natural Selection | 1) Multigenic effects of accumulation 2) Building upon pre-existing structures 3) Genomic Duplication |
| Directional Selection | selection in favor of one of the extreme phenotypes and against the other and intermediates. Example: changes in frequency of melanism with variation in pollution in moths from England and the US. |
| Stabilizing Selection | selection in favor of the intermediates and against both extremes. Example: survivorship as a function of birth weight in humans. |
| Disruptive Selection | selects against the intermediates in favor of both extremes. Example: niche polymorphism for bill size in black-bellied seed crackers. |
| Frequency-Dependent Selection | selection where reproductive success depends upon the frequency of other phenotypes in the population. Example: right vs left faced cichlid fishes that prey on scales of other fish. |
| Co-Evolution | selection with respect to the frequency of phenotypes that occur in other species. Mimicry is on major category of coevolution. Example: mimicry of geographic variation in wing coloration pattern in Heliconius butterflies |
| Sexual Selection | selection for access to mates, usually selects upon males. May be either intrasexual or intersexual. Important because it can “run away” and can cause rapid divergence among populations. |
| Intrasexual Selection | males compete with one another for access to females female has no choice |
| Intersexual Selection | females choose which male they will accept |
| Divergence | Gene flow will interconnect local pops through exchange of individuals and alleles. Gene flow homogenizes pops while selection & drift causes them to diverge. Amount of divergence depends upon relative strength of selection and drift vs gene flow. |
| Allopatric Divergence | External isolating force (physical barrier) restricta migration between populations. Two populations will change independently – they will diverge because they are independently subject to selection, drift and mutation. |
| Allopatric Speciation | when sufficient allopatric divergence occurs between populations that they become biologically incapable of inter-mating (reproductive isolation) they may be considered separate species. |
| Reproductive Isolation | When allopatric divergence results in two populations no longer being able to inter-mate or produce viable offspring. |
| Pre-Mating Barriers | Individuals from two species (populations) no longer accept one another as potential mates. |
| Types of Pre-Mating Barriers | Behavioral: courtship etc; may be asymmetric (1 rejects 2 but not reverse) Ex: fireflies Seasonal: when reprod active Ex: flowering time Ecological: ecological req or pref; don’t occur in same habitat Ex: oaks and buttercups live in diff soil types |
| Post-Mating Barriers | those in which individuals from two species (populations) attempt to mate but the mating is unsuccessful. |
| Types of Post-Mating Barriers | Mechanical: physically incapable of exchanging gametes Developmental: embryos fail to complete development Fertility: hybrids are sterile; asymmetrical F2 breakdown: F1 hybrids inter-mate with F1 or parent species; doesn't work |
| Speciation | if populations have diverged to a sufficient degree that they no longer have the capacity to inter-mate they have become two separate species |
| Biological Species Concept | a species is a group of actually or potentially interbreeding populations that are reproductively isolated from other such groups |
| Problems with Biological Species Concept | |
| Variation in Allele Frequency | Gene flow homogenizes- interconnects local populations through exchange of individuals and alleles Selection and genetic drift cause divergence Amount of divergence depends on relative strength of selection and drift vs gene flow |
| Allopatric Divergence | caused by external isolating force two populations will change independently b/c independently subject to selection, drift, and mutation |
| Allopatric Speciation | sufficient allopatric divergence->biologically incapable of intermating->separate species |
| Reproductive Isolation | allopatric divergence resulting in populations being unable to intermate |
| Pre-Mating Barriers | individuals from two species (populations) no longer accept one another as potential mates |
| Pre-Mating Barrier Types | Behavioral: courtship; asymmetric (1 rejects 2 but not reverse) Ex: fireflies Seasonal: when reprod. active Ex: flowering time Ecological: ecological req/pref; don’t occur in the same habitat Ex: oaks & buttercups live in different soil types |
| Post-Mating Barriers | individuals from two species (populations) attempt to mate but the mating is unsuccessful |
| Post-Mating Barrier Types | Mechanical: physically incapable of exchanging gametes Developmental: embryos fail to complete development Fertility: hybrids are sterile; asymmetrical F2 breakdown: F1 hybrids intermate with F1r or with either parent species; doesn't work |
| Speciation | if populations have diverged to a sufficient degree that they no longer have the capacity to intermate they have become two separate species |
| Biological Species Concept | a species is a group of actually or potentially interbreeding populations that are reproductively isolated from other such groups. |
| Problems with Biological Species Concept | too much or too little sex Asexual species Long-term capacity for hybridization: distinct species still hybridize Ex: mules “Partial” speciation: not all or nothing; varying levels of reproductive isolation Ex: Streptanthus glandulosa |
| Post-Speciation | Majority of divergence still occurs after speciation New species will form diverging populations and speciation may occur again |
| Common Descent - Phase 1: Early Divergence | marked by the initial stages of allopatric divergence that lead to populations that are differentiated in numerous characters, including those that consequently lead to reproductive isolation and speciation |
| Common Descent - Phase 2: Intermediate Divergence | marked by the continuing divergence of populations after speciation and the subsequent splitting of daughter species to form additional species Phase II generates a variety of biogeographic patterns |
| Common Descent - Phase 3: Deep Divergence | continuation of evolution by common descent generating so called “macroevolution” Generates biological patterns that represent the vestiges of descent and give evidence that even remarkably distinct groups shared common ancestors sometime in the past |
| Phase 1: Early Divergence - Lack of fixity | formation of species proceeds through innumerable steps of "partial speciation" changes with time (housecats vs wildcats) and space (pocket gophers, mimulus, east/west blackbirds) |
| Phase 1: Early Divergence - Species are polytypic | consist of distinct var, races, pops, & subspecies for every trait Ex: morph var rat snakes & flickers; fert diff pops & subspecies of jewel flower (Streptanthus glanulosus); morph diff distinguishing genera of plant family Compositae (Roxira vs Layia) |
| Phase 1: Early Divergence - Variation | variation within species is often the source of differences between closely related species- differences are a matter of degree. Ex: genetic differences among Drosophila; morphological (and genetic) differences of domestic cats compared to wildcats. |
| Phase 1: Early Divergence - Transition | Change of one species into another Ex: transition of stickleback fish from populations with full pelvic girdles to those with intermediate structures to those where the structure is absent |
| Phase 2: Intermediate Divergence - Biogeography | Geographically related areas should share related species even if the habitats are dissimilar. Ex: troglodyte; plants on islands similar to mainland; Continents connected by Pangea have similar species of plants/marsupials |
| Phase 2: Intermediate Divergence - History of Geographic Isolation | explains pattern of relationships among related species Ex: speciation of parrots in Malay Archipelago; relatedness of salamanders around CA valley; age of Hawaiian islands explains diversity of crickets |
| Phase 3: Deep Divergence - Fossil Record | Evidence of common descent should be present in the fossil record |
| Phase 3: Deep Divergence - Predictions of common descent proved by fossil record | 1) Earth is ancient (4.5 billion years) 2) Extinction: 9.8% of all species 3) Older the strata, lesser the degree of similarity 4) Gradual Change (Stickleback data) 5) Intermediate forms (Archaeopteryx & Sinornis; Therapsid reptiles; Basilosaurus) |
| Phase 3: Deep Divergence - Living Intermediates | common descent predicts that many “intermediates” should exist between major taxonomic groups and some of these will still be alive Ex: Basommatophora; “advanced” vs "primitive" flies |
| Phase 3: Deep Divergence - Homology | mod of pre-existing structures to new adaptations Structural (Morph): forelimb and skull bones Genetic: cytochrome c 104 AAs in all species, 37 identical Developmental: similar embryological dev & often have little in common with func state of adult |
| Phase 3: Deep Divergence - Vestigial Organs | some organs may lose their function but will be retained for some period of time Ex: non-functional eyes in cave dwelling species; disarticulated pelvic girdles in whales; retention of the capacity to develop teeth in chickens |
| Phase 3: Deep Divergence - Adaption | adaptation will be imperfect bc constrained to work with existing structures, not those ideal for task 1) better solution is obvious 2) other species produced superior adaptions Ex: mammalian reproductive system; cephalopod eye |
| Phase 3: Deep Divergence - Phylogenetic Concordance | phylogenetic classification will yield the same set of relationships among organisms regardless of info used to construct the classification Ex: salamander trees; morphological, immunological, DNA all same |
| Phase 3: Deep Divergence - Monophyletic vs Polyphyletic | Monophyletic: all members of the group share traits inherited from a common ancestor; recognized by uniquely derived traits Polyphyletic: members share a trait that was separately evolved from ancestors that did not have that trait |
| Phase 3: Deep Divergence - Derived vs Ancestra | 1) multiple states; which came 1st; uncommon 2) development; strong indication (anteater teeth as embryos ancestral) 3) outgroup method; ancestral trait occurs in related taxonomic group outside group of species being classified (moth & butterfly legs) |
| Phase 3: Deep Divergence - Cladistic Classification | Uses nested monophyletic groups |
| Phase 3: Deep Divergence - Classification Errors | separation of groups is very old, very recent, or tok place at almost the same time also fails in species like bacteria that spread genes without descent (horizontal gene transfer) |
Created by:
blackcm3
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