Evolution May Lead To Speciation

Question 1

What is the primary source of variation?

Answer 1

Mutations producing different alleles

Question 2

What are some other sources of variation?

Answer 2

• random fertilisation of gametes
• independent segregation
• crossing over

Question 3

What is the effect of selection on allele frequencies?

Answer 3

• not all individuals can survive + reproduce due to factors such as disease, predation + competition
• organism with phenotypes with a selective advantage are more likely to survive and reproduce + pass on their advantageous alleles
• allele frequencies change over time due to evolution

Question 4

What is disruptive selection?

Answer 4

• favours both extreme phenotypes at different times due to environmental factors

Question 5

What is speciation?

Answer 5

The evolution of new species from existing ones

Question 6

When do new species arise?

Answer 6

When genetic differences due to selection lead to an inability of members of the populations to interbreed or produce fertile offspring

Question 7

What are the 2 types of speciation?

Answer 7

Allopatric speciation - geographically separated

Sympatric speciation - reproductively isolated

Question 8

What is the process of allopatric speciation?

Answer 8

• population becomes geographically separated e.g river formation or mountain range
• separated population cannot reproduce due to physical barrier
• separate populations have different selection pressure so they will accumulate different beneficial mutations over time
• differential reproductive success so changes in allele frequency
• 2 populations eventually become so genetically different that they can no longer reproduce to produce fertile offspring and are now different species

Question 9

What is the process of sympatric speciation?

Answer 9

• become reproductively isolated due to differences in behaviour
• random mutation could influence reproductive behaviour e.g fertile at different time of the year/different courtship behaviours
• individuals will not reproduce together
• overtime their DNA changes so much they can no longer reproduce together to produce fertile offspring so 2 different species

Question 10

What is a genetic drift?

Answer 10

• change in allele frequency within a population between generations
• continual genetic drift leads to evolution
• larger effect on small populations since allele frequency changes have a larger impact -> evolution occurs quicker