Topic 6 - Speciation

Question 1

What is speciation?

Answer 1

The process by which one species splits into two or more species

Question 2

What are reproductive barriers?

Answer 2

Can be distinguished by whether they occur before or after fertilization

Question 3

What is reproductive isolation?

Answer 3

The inability of a species to breed successfully with related species due to geographical, behavioural, physiological or genetic barriers

Question 4

What are the different species concepts and their advantages / disadvantages?

Answer 4

Biological
- Species that can interbreed and still remain fertile

Morphological
- Species with morphology similarities

Ecological
- Species with similar ecological niches

Advantages
- Straightforward
- Evolving independently

Disadvantages
- Hard to assay barriers
- Can’t be applies asexually

Question 5

What are pre zygotic and post zygotic barriers?

Answer 5

Prezygotic
- Block fertilization by reducing likelihood of mating

Postzygotic
- Reduce the survival / reproductive success of hybrids

Question 6

Allopatric vs. Sympatric

Answer 6

Allopatric
- Occurring in separate non overlapping geographic areas

Sympatric
- Occurring in the same, overlapping geographical area

Question 7

Explain the different mechanisms of speciation

Answer 7

Ecological
- Reproductive isolation increases as a product of different environments or niches

Polyploidization
- Increased number of whole sets of chromosomes
- Instantaneous
- Autopolyploid (an individual with >2 chromosomes taken from a single species) or allopolyploid (and individual with >2 chromosomes taken from different species)

Reinforcement
- Strengthening of pre zygotic barrier by natural selection to reduce hybrid fitness

Question 8

Summarize the technique of experimental evolution and how the labs provide insight into speciation

Answer 8

Experimental Evolution
- Technique where multiple replicate populations derived from a common ancestor have their evolution tracked under different conditions

Insight from labs
- Tests ecological speciation

Question 9

How does the existence of ecologically dependent post zygotic isolation provide evidence for ecological speciation?

Answer 9

Hybrids only have low fitness in the parent’s different environments, showing that ecological differences are what drive reproductive isolation