ap bio unit 7

natural selection was developed by _____________.

charles darwin

natural selection is established due to __________ in the population and competition for ____________

variation, resources

What is evolutionary fitness?

Reproductive success (ability to pass on genes)

organisms with more favorable traits are more likely to survive and produce more offspring to pass on their traits to the next generation

What happens to organisms with favorable traits?

More likely to survive and reproduce → traits increase in population

Give two examples of natural selection

Peppered moths, antibiotic resistance

What is a Lamarckian idea (and why is it wrong)?

Traits acquired during life are inherited (incorrect—traits must be genetic)

What is disruptive selection?

Favors extreme phenotypes, selects against intermediate

What is stabilizing selection?

Favors intermediate phenotype, selects against extremes

What is directional selection?

Favors one extreme phenotype

What is artificial selection?

Organisms with certain traits are bred until population has that trait. Humans breed organisms for specific traits. Humans affect variation in the population.

Examples of artificial selection

Dog breeds, corn from maize, wild mustard → broccoli/cabbage/etc.

Natural selection can only act on..

existing features

What creates new genetic variation?

Mutations

Migration

gene flow (addition or removal of alleles from a population)

What is genetic drift?

Nonselective process in small population changes allele frequency

• Random change in allele frequencies

• Ex) bottleneck and founder effect

Mechanisms of Genetic Variation / Drivers of Evolution

• Mutations – new genetic variation
  • Migration – gene flow (addition/removal of alleles from population)
  • Genetic drift – nonselective process in small populations changes allele frequencies
  • Bottleneck effect – population size reduced to small number of individuals
  • Founder effect – population separated from other members of population

Types of genetic drift are

bottleneck effect and founder effect

What is the bottleneck effect?

Population drastically reduced → less genetic diversity

What is the founder effect?

Small group starts new population → different allele frequencies

• population separated from other members of population

Why is genetic diversity important?

Increases survival under environmental change

What happens to populations with low diversity?

Higher risk of extinction

Can an allele be both beneficial and harmful?

Yes, depends on environment

Alleles that are adaptive in one environmental condition may be _________ in another because of different ________ __________.

deleterious, selective pressures

What is Hardy-Weinberg equilibrium?

a principle stating that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. It serves as a null model for non-evolving populations, assuming random mating, no mutation, no migration, no selection, and a large population size.

Five conditions (Five Fingers of Evolution)

• Large population

• Random mating

• No mutations

• No gene flow (migration / emigration)

• No natural selection

The Hardy-Weinberg equilibrium is never met but serves as a ____ ______________ for non-evolving populations, assuming random mating, no mutation, no migration, no selection, and a large population size.

null hypothesis

Equation for allele frequency

p + q = 1

Equation for genotype frequency

p² + 2pq + q² = 1

Any change in allele frequencies between generations is called

microevolution

Evolution (is / is not) occurring if p and q change!

is

What is 2pq?

Heterozygous genotype frequency

Hardy-weinberg is a valuable tool for predicting frequencies if allele frequencies (are/are not) changing! This means it will be correct if the 5 criteria are met.

are not

Null hypothesis

hypothesis which the researcher tries to disprove. Assumption that there is not relationship between the independant and dependant variable in a study.

The conditions of HWE are never met, but in experimental studies, they provide a null hypothesis for determining which factors are changing allele frequencies.

what is gene flow

movement of alleles between populations

p²

proportion of individuals that show the homozygous dominant phenotype (AA)

2pq

proportion of individuals with heterozygous genotype (Aa)

q²

proportion of individuals with the homozygous recessive genotype

How are fossils dated?

1) the age of the rocks where a fossil is found

2) the rate of decay of isotopes (incl.carbon-14)

3) geographical data.

What is biochemical evidence for evolution?

DNA or protein

Comparison of the number of differences

What is biogeography?

distribution of species and ecosystems in

geographic space & through geological time

Structural and functional evidence indicates

common ancestry of all ________________.

eukaryotes

Evidence that all eukaryotes share common ancestry

i. Membrane-bound organelles

ii. Linear chromosomes

iii. Genes that contain introns

What are homologous structures?

Similar structures from common ancestry

What are analogous structures?

Similar function, different ancestry (convergent evolution)

Ancestral/Derived Traits:

characteristics derived

from ancestor or from descendants

Analogous structures are due to __________ evolution. similar selective pressures result in similar phenotypic adaptations in different populations or species.

convergent

What is a phylogenetic tree?

show the amount of change over time calibrated by fossils or a molecular clock

What is a cladogram?

Shows relationships but NOT time or amount of change

What is an outgroup?

Least related lineage

nodes

represent the most recent common ancestor of any two groups or lineages.

the biological species concept provides a commonly used definition of a species for sexually reproducing organisms. it states that…

defined as a group capable of interbreeding and exchanging genetic information to produce viable, fertile offspring.

What is speciation?

Formation of new species, two populations become reproductively isolated from each other

What is allopatric speciation?

Occurs when biological populations of the same

species become isolated due to geographical

changes

What is sympatric speciation?

New species form in same location

Examples of sympatric mechanisms?

• Behavioral isolation

• Habitat isolation

• Polyploidy

• Sexual Selection

prezygotic barrier

occurs before fertilization

behavioral reproductive isolation

different mating rituals

habitat / ecological reproductive isolation

mate in different ecological environments

mechanical reproductive isolation

incompatible anatomically

temporal reproductive isolation

mate at different times of day

geographic reproductive isolation

two organisms are separated by geographical barrier

gametic reproductive isolation

gametes are unable to fuse

name the 3 postzygotic reproductive barriers

after fertilization :

• Reduced hybrid viability

• Reduced hybrid fertility

• Hybrid breakdown

reduced hybrid viability

hybrid is not healthy / viable

reduced hybrid fertility

hybrid not fertile

hybrid breakdown

subsequent hybrid starts decreasing viability and fertility (F2)

the ______ the population, the more chance for ____________ drift.

smaller, genetic