Patterns in evolution

Question 1

1. Homologous structures

Answer 1

Preadaptation- same structure performs new function.
existing structures modified
eg.) pentadactyl condition- all vertebrates are related and have homologous structures for locomotion- they did not evolve independently (same bones in each fn part)
character may be homologous but character state may differ (loss/fusion of bones)
this can be examined in embryos which retain the ancestral condition

Question 2

2. Homoplasy is wide-spread.

Answer 2

Independent evolution of a character state in unrelated taxa- either due to convergent evo or trait reversal.
eg.) eyes of cephalopods and humans have retina + lens but are vastly diff in how they fn, therefore independent evo

Question 3

3. Parallel Evolution

Answer 3

Structure with very similar fn evolves in 2 taxa bc they are closely related and had similar structures to begin with.
eg.) 3 pairs maxllipeds on 1st 3 thoracic segments in add to normal mandibles

Question 4

4. Evolution is often gradual

Answer 4

Sometimes intermediate forms evident, other times in higher taxa (insects) there are no distinguishable intermediates

Question 5

5. Change in form=change in fn

Answer 5

Even structures that were homologous can change with time.