AP bio unit 7

What did darwin propose about the finches

proposed that each bird was descended from the mainland species

common descent

Who had similar ideas to darwin

Alfred Wallace

Artificial selection

the selective breeding of domesticated plants and animals to encourage the occurance of desirable traits

What is the difference between natural and artificial selection

Natural: Nature “selects” traits that are better suited for survival and reproduction

Artificial: Humans select traits that are desirable

Both lead to evolutionary change in an organism, but natural selection occurs in nature without the influence of humans

Descent with modification

each generation will have more individuals with the traits than the previous generation

modern species can be traced to a common ancestor

Evolution

the change in allele frequencies or a change in the gene pool of a population

You don’t need to see an animal change physically, you only need to measure changes at the DNA level

a change in allele frequency over time

Important Points about natural selection

individuals do not evolve, they either live or die → populations evolved

evolution does not have a direction → organisms aren’t trying to be anything

Individuals differ in Fitness (relative fitness) → fitness measure reproductive success

Fossil evidence

the remains and traces of past life or any other direct evidence of past life

anatomical evidence

homologous structures

analogous structures

vestigal structures

homologous structures

“same parts, different functions.”

Example: Vertebrate forelimbs have the same set of bones.

Indicates more recent common ancestry.

Analogus structures

“same function, different parts.”

Example: Bird wings vs. Insect wings

More distance common ancestry.

Vestigal structures

anatomical features that are fully developed in one group of organisms but are reduced and may have no function in related groups.

Example: Pelvic girdle and hindlimbs in some snakes and whales.

Inherited from ancestors.

Biochemical/developmental evidence

All living species have DNA, RNA, ATP, etc.

Use triplet code for amino acids.

-Cytochrome-C protein

What are hox genes

orchestrate development of the body plan in all animals.

•All animals share Hox ancestor, but the number and type of hox genes amongst animals varies.

embryological evidence

•Homologies shared by vertebrates are observable during their embryological development.

•Vertebrates inherit the same developmental pattern from their common ancestry.

population

a group of organisms of a single species living together in the same geographic area

Gene pool

the alleles of all genes in all individuals of a population

allele frequency

the percent of each allele in a populations gene pool

if allele frequencies don’t change over generations, the population has not evolved

Hardy Weinberg equilibrium

a stable non-evolving state

a mathematical model to estimate genotype frequencies of a population at genetic equilibrium

never achieved in wild populations

Hardy Weinberg equilibrium equations

p² + 2pq + q²

p+q=1

p²

DD

2pq

Dd

q²

dd

p

D

q

d

under what conditions does the harvey weinberg equilibrium apply

no mutation

no migration

large gene pool

random mating

no selection

mutation

source of variation but may not affect genetic equilibrium of a pop

must be passed to next gene to alter the gene pool

gene flow

movement of alleles between pops

depends on distance, gamete movement, and behavior

if migration doesn’t occur, can lead to speciation

genetic drift

changes in alleles due to change events

affect smaller pops

inbreeding increases small pops but does not affect allele frequency

large pops can become small suddenly bc of

bottleneck

founder effect

variation is lost when individuals break away to form new pops

non-random mating

affect how alleles in gene pools assort into genotype

assortative mating

when individuals chose a mate with a preferred trait

natural selection and harvey weinberg

in nature some phenotypes can have reproductive advantage

This can lead to an increase in the frequency of the alleles associate with that trait, while other alleles decrease

Allopatric Speciation

geographic barrier population

River or mountain

populations can have significant genetic differences

microevolution can occur -> can lead to reproductive isolation

Sympatric speciation

same area but still isolated

pre-zygotic and post-zygotic

pre-zygotic barriers

habitat

Temporal

behavioral

mechanical

gamete

habitat isolation

species at the same locale occupy different habitats

Ex: Land frog v. water frog

Temporal isolation

species reproduce at different times of the year or times of the day

Ex: eastern and western spotted skunk

behavioral isolation

in animals, courtship rituals differ OR individuals respond to different songs, calls, pheromones, etc

ex: fireflies and frogs

mechanical isolation

genitalia between species are unsuitable for one another

Ex: great dane and chihuahua

gamete isolation

sperm can’t reach or fertilize egg

Ex: different types of coral gametes

Postzygotic barriers

hybird inviability

hybrid breakdown

hybrid sterility

hybrid inviability

fertilization occurs, but the zygote does not survive

ex: sheep and goats

hybrid breakdown

hybrid is fertile but F2 (gen 2) has reduced fitness

Ex: ligers (lions and tigers)

hybrid sterility

hybrid surives, but it is sterile and it cannot reproduce

ex: Horse and Donkey → Mule

Stabilizing Selection

Both of the extremes are selected against → extremes die out

over time, only going to see individuals that are average

average selected for

Disruptive selection

both of the extremes are selected for

average are selected against

Direction selection

One of the extreme phenotypes is favored, shifting the population all together

phylogenetic tree

a tool used to classify organisms

taxon

a groups of organisms that share common traits

What can scientists use to classify organisms into taxa

Cladogram (phenotype) or phylogenetic trees (genotype)

microevolution

allele frequency changes over generation

macroevolution

evolution on a large scale

involves speciation

natural selection, genetic drift, mutations

Ways in which microevolution occurs

gradualism

punctuated equilibrium

gradualism

continuing evolution slowly

punctuated equilibrium

rapid speciation followed by a period of stagnancy, extinction, evolution again

Adaptive radiaiton

when a single ancestral species rapidly gives rise to a variety of new species

Convergent evolution

when a trait evolves in 2 unrelated species as a result of similar environments