Speciation

Question 1

what is speciation? what happens to frequencies of alleles?

Answer 1

-Occurs when one species splits into two or more
lineages with their own independent evolutionary
trajectories
-Frequencies of alleles in these lineages change
independently of one another

Question 2

why does speciation typically begin? what happens over time?

Answer 2

• some sort of barrier to gene flow
• Reduces the amount of gene flow among populations

-Over time populations diverge due to evolutionary mechanisms that occur in each population independently

Question 3

what are the 2 main categories of barriers to gene flow that occur in sexually reproducing species?

Answer 3

1. Pre-zygotic = barriers occur before fertilization

2. Post-zygotic = barriers occur after fertilization

Question 4

what are pre-zygotic barriers to gene flow?

Answer 4

1. Geographical (spatial) Barriers
   -Prevent reproduction because populations live in
   non-overlapping areas
2. Reproductive Barriers
   -Prevent reproduction because mating between
   populations doesn’t result in successful fertilization
   -Can be due to differences between populations in
   (i) breeding timing and/or behaviour
   (ii) incompatibility between reproductive structures
   and/or gametes

Question 5

what are post-zygotic barriers to gene flow associated with?

Answer 5

Associated with reduced fitness of hybrid offspring

• Hybrid offspring not viable
• Hybrid offspring survive but don’t produce functional gametes = sterile

Question 6

what does reduction of gene flow between populations lead to?

Answer 6

-reproductive isolation and possibly speciation

Question 7

what is Allopatric Speciation?

Answer 7

occurs when populations are geographically isolated

Question 8

what is Sympatric Speciation?

Answer 8

occurs when species overlap in the same geographical area
-is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region