7.3 Speciation

Question 1

Define evolution

Answer 1

Change in allele frequencies in a population

Question 2

Regarding natural selection, and evolution, what are the primary and secondary causes of variation

Answer 2

• Mutations primary
• Meiosis secondary
• Random fertilisation of gametes secondary

Question 3

Effect on gene pools in a smaller population

Answer 3

Smaller populations have smaller gene pools

Question 4

What does genetic drift cause

Answer 4

Change in allele frequencies

Question 5

In what type of populations will genetic drift occur in

Answer 5

Small populations

Question 6

Describe disruptive selection

Answer 6

• Population experiances two different selection pressures
• Two phenotypes are advantageous and both become more common
• Speciation occurs

Question 6

Graph for disruptive selection

Answer 6

Question 7

What type of selection results in speciation

Answer 7

Disruptive

Question 8

Define allopatric speciation

Answer 8

Formation of new species from different populations, that are reproductivly isolated georgraphically

Question 9

Describe and explain the process of allopatric speciation

Answer 9

• Two populations become reproductivly isolated geographically
• No gene flow between populations
• Each population experiances different selection pressures
• Variation occurs in each population, due to mutation
• DIfferent alleles are advanatageous, so different alleles are passed on
• Change in frequency of alleles
• Disruptive selection
• Eventually, populations cannot interbreed to produce fertile offspring

Question 10

Describe and explain the process of sympatric speciation

Answer 10

• Two populations become reproductivly isolated in the same habitat
• No gene flow between populations
• Each population experiances different selection pressures
• Variation occurs in each population, due to mutation
• DIfferent alleles are advanatageous, so different alleles are passed on
• Change in frequency of alleles
• Disruptive selection
• Eventually, populations cannot interbreed to produce fertile offspring

Question 11

Define sympatric speciation

Answer 11

Formation of new species from a population that are reproductivly isolated, but not geographically isolated (in the same habitat)

Question 12

Explain stabilising selection

Answer 12

• Mean/intermediate phenotypes best adapted to survivie in unchanging enviroment
• Selection against extreme phenotypes in favour of mean/intermediate phenotypes
• Range and standard deviation reduced

Question 13

Example of stabilising selection

Answer 13

Birth weight in humans

Question 14

Explain directional selection and give an example

Answer 14

• Extreme phenotype is best adapted to survive in unchanging enviroment
• Selection against mean/intermediate phenotypes in favour of extreme phenotypes
• Range and standard deviation reduced

Question 15

Example of directional selection

Answer 15

Antibiotic resistance in rats