Simiar functions w/o close relationship

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


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


Adaptations that evolved originally for a different function

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


-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


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


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


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


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


Maintainance of beneficial mutations

-the population can evolve faster


Weeding out the bad mutations


Avoid boom/bust cycles caused by parasites

-the Red Queen Hypothesis


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