Evolutionary Biology 4

Question 1

What are Hybrid zones

Answer 1

Areas where genetically distinct populations meet, mate and reproduce

• challenge our view of species

Question 2

why are hybrid zones good to study

Answer 2

• involve din nearly all speciation

- range of genotypes show various selection pressures

Question 3

CLINE

Answer 3

change in frequency of an allele from one geographic zone to another.

Question 4

What can happen in hybrid zones

Answer 4

• Remain indefinetly
• Reproductive isolation
• Species merge
• Third species

Question 5

CLINE Theory

Answer 5

If no gene flow (g=0) then CLINE will be very steep

High dispersal = wide CLINE

Question 6

CLINE shape

Answer 6

gene flow controls the steepness of the CLINE (low=steep)

dispersal controls the width of the CLINE (high=wide)

Question 7

an example of a wide shallow CLINE

Answer 7

Frequency of B allele in a East to west gradient (represents mongolian invasions)

Question 8

what is a tension zone

Answer 8

A hyrbid zone with a high selection against hybrids (heterozygote disadvantage)

Question 9

what is a CLINE like in a tension zone

Answer 9

usually steep as heterozygotes dont reproduce as much

Question 10

Types of Hybrid zone

Answer 10

Primary hybrid zone - where divergence is taking place between adjacent populations of a previously homogeneous species

Secondary hybrid zone - secondary contact between two previously allopatric populations that have expanded to meet.

Question 11

allopatric speciation

Answer 11

speciation that occurs when biological populations of the same species become isolated due to geographical changes

Question 12

Introgression

Answer 12

Transfer of genetic information from one species to another as a result of hybridisation between them and repeated back crossing