Definitions


Analogy


Simiar functions w/o close relationship

-similarity is result of convergent evolution (evolve independently of each other)


Homology


Similarity of structures due to common ancestry regardless of function


Vestigial Organs


Organs w/ no discernable function

ex: coccyx of humans legs of snakes and whales


Evolutionary Anachronisms


Products of nature that can only be explained in light of evolution ("ghosts of evolution past")

ex: avacado


Exaptations


Adaptations that evolved originally for a different function

ex: feathers on birds (evolved as thermoregulation as opposed to flight)


Embryology


-study of organismal development-more closely related organisms should share more of their development
ex: we all had gills at some point and had a 2 chamber heart


Molecular Biology


Genetics = Study of heredity

-we should share more of our DNA w/ those organisms we are more closely related to

ex: chimpanzees and humans share 98% of DNA


Natural Selection = unequal reproductive success


those individuals with traits (= adaptations) best suited to the local environment will generally leave more fertile offspring


Modern Synthesis (1930's)


Merging of evolutionary and genetic research/thought


Populations


a group of individuals of the same species in the same place, at the same time


Hardy-Weinberg Formula


p2 + 2pq + q2 = 1


Hardy-Weinberg Formula Assumptions


1 Extremely large population size2 no mutations are occuring3 no selection happening (ex: no evolution)4 random mating5 no gene flow


Microevolution


A generation-to-generation change in a populations frequency of allels


Genetic Drift


A change in the gene pool of a small population due to chance


The Bottleneck Effect


A drastic reduction in population size

-only a few survive--->therefore certain alleles are overrepresented and others are underrepresented (or lost)

ex; cheetas (10,000yrs ago & 19th century)


The Founder Effect


Only a few individuals w/ a different genetic make-up start a new population

ex: 1814, 15 British founded a colony on Tristan de Cunha (in the middle of the atlantic ocean)-one had rare retinitis pigmentosa allele-by 1960's, of 240 descendents, 4 had the disease and 9 were known carriers


Gene Flow


A gain/loss of alleles from a populationby the movement of individuals/gametes into or out of a population-if gene flow increases, it will decrease the difference among populations


Mutation


The raw (original) source of genetic variation


Natural Selection


Leads to variation between population = geographic variation

-bc environmental factors are likely to vary across the range of a species-the main driver of microevolution


Directional Selection


Select one phenotype over another phenotype


Disruptive Selection


Select against the most common phenotype which drives the evolution of 2 very different phenotypes


Stabilizing Selection


Select against both extremes (favor most common, intermediate phenotype)

-most common


Balancing Selection


Maintain multiple alleles, maintains 2 or more phenotypes at stable frequencies


Heterozygote Advantage


Individuals who are heterozygus for a certain trait have greater fitness than homozygus individuals


Frequency-Dependent Selection


The frequency of any 1 phenotype declines if it becomes too common

ex: predator prey interactions side blotched lizards (rock, paper, scissors)


Neutral Variation


Variation that has little or no affect on reproductive success---> it is not selected for or against

-while this variation may not have any effect today, it may have an impact in the future if the environment changes


Sexual Selection


Natural selection for mating success

-can lead to sexual dimorphism


Intrasexual


Within a sex

-competition for mates by individuals of the same se

ex: peacocks-best plumage Irish elk-biggest antlers


Why sex?


1 production of diploid cells2 meiosis-production of gametes (to eliminate errors of recombination)3 sex is good if its optional4 selection of sexiness5 maintained by the good, the bad and the ugly


Good


Maintainance of beneficial mutations

-the population can evolve faster


Bad


Weeding out the bad mutations


Ugly


Avoid boom/bust cycles caused by parasites

-the Red Queen Hypothesis


Macroevolution


The major changes in the history of life

ex: origin of new species origin of biological novelties (ex: wings) explosive diversification mass extinction


What is a species?


-produce fertile offspring-populations-behavioral interactions-morphological features


Biological Species Concept


A species is a population or group of populations whose members have the potential to interbreed in nature to produce fertile offspring

Alternatives:1 morphological - physical traits2 ecological3 genetic similarity


Prezygotic Reproductive Barriers


before fertilization

a mechaanical isolation-the parts dont fitb behavioral isolation-ex: distinctive odors, calls, mating ritualsc habitat isolationd temporal isolation-different breeding seasonse gametic isolation-no union of the male and female gametes


Postzygotic Reproductive Barriers


(after fertilization)

a hybrid inviabilityb hybrid sterilityc hybrid breakdown


Hybrid Inviability


Dies young and doesn't reach sexual maturity


Hybrid Sterility


No functional gametes produced by the hybrid

ex: mules


Hybrid Breakdown


Offspring are feeble/sterile


Allopatric Speciation


Geographic barrier that physically isolates a splinter population

-many splinter groups don't survive-the splinter population MUST be reproductively isolated


Sympatric Speciation


New species originates w/o geographic isolation w/in the parent population.-most common
a polyploidy-extra set of chromosomes (common in plants)b habitat differentiationc sexual selection