A4.1 & D4.1 - Evolution & Natural Selection

Define evolution.

it is the cumulative change in heritable characteristics of a population over time.

What are 3 main ways of looking for evidence for evolution?

by fossil records, vestigal structures, and comparative DNA

What are homologous structures?

similar structures with different functions

What are analogous structures?

different structures with similar function

Explain divergent evolution.

Species with homologous structures (similar structure but different functions), imply a common ancestry, as structure adapt to different niches. An example would be the pentadactyl limb in vertebrates.

What does vestigal structures mean?

Functional structures that have remained the same in all ancestral species.

What does speciation not include?

gradual evolutionary changes

Explain how by comparing DNA, one can find evidence for evolution.

By comparing DNA or RNA sequences and amino acid sequences in proteins, which gives evidence of common ancestry.

Explain how isolation leads to speciation.

When there is a selection pressure due to different environmental conditions, different alleles are selected as a result of natural selection. Speciation then occurs when two populations can no longer interbreed and produce fertile offspring, as there is no gene flow between the two.

Give an example of a geographical isolation.

The separation of bonobos and common chimpanzee by the Congo River.

What is the isolation by the difference in mating behavior?

Behavioral isolation

What is the isolation by the difference in mating season?

temporal isolation

Explain what happens in natural selection.

Individuals with a fitter phenotype are more likely to survive and pass on their alleles to their offspring so that the advantegous alleles increase in frequency over time and generations.