A4.1 Evolution and Speciation

What is the definition of evolution?

Change in allele frequencies in a population over generations

On what type of variation does evolution act?

Heritable variation such as mutations

What is the main driver of evolution often associated with Darwinism?

Natural selection

Are acquired traits like muscle mass or learned languages inherited?

No they are not inherited

How does evolution leave signatures in biological sequences?

Through DNA/RNA bases and protein amino acids

What does having fewer sequence differences between two species indicate?

They are closer relatives

What does a high number of sequence differences between species suggest?

An older split from a common ancestor

Why do tan mice have lower survival on dark rocks in the natural selection example?

They are more visible to predators due to lack of camouflage

What is the result of dark mice having a higher survival rate in a dark habitat?

They leave more offspring and the next generation has a higher frequency of dark mice

What is artificial selection?

Human-directed natural selection through selective breeding

What have livestock and crops proven about the speed of evolution?

Evolution can be fast under strong selection (< 12,000 years)

What is the pentadactyl limb an example of?

A homologous structure

What does it mean when species have the same bones but different functions?

It is evidence of divergent evolution from a common ancestor; homologous structure

To earn full marks what must you link the pentadactyl limb to?

Divergent evolution from a common ancestor

What is the definition of homologous?

Common origin

What is the definition of analogous?

Same function but different origin

How does speciation occur from separated populations?

Independent selection leads to trait divergence

At what point do separated populations become two new species?

When they no longer interbreed on secondary contact

What is the process of speciation according to the note?

Isolation leads to divergence which leads to a reproductive barrier

What are the types of reproductive isolation barriers?

prezygotic isolation barrier and postzygotic isolation barrier

Is isolation alone enough for speciation?

No it must combine with selection

What is allopatric speciation?

Speciation occurring when a physical barrier separates populations

What is sympatric speciation?

divergence of species within the same geographical location (i.e. without a physical barrier)

What is adaptive radiation?

When one ancestor diversifies into many species in new niches

What are the benefits of adaptive radiation?

It reduces competition and allows for rapid divergence

What are classic examples of adaptive radiation?

Darwin's finches

What are prezygotic barriers?

Barriers before fertilisation can occur (no offspring are produced)

What are postzygotic barriers?

reproductive isolation mechanisms that prevent two populations from interbreeding + occurs after fertilisation (offspring are either not viable or infertile)

ye

Are all hybrids sterile?

No some such as certain plants and ducks are fertile

What are examples of pre zygotic barriers?

habitat/time/behavior/mechanical/gametic

What are examples of post zygotic barriers?

inviability, sterility, breakdown