Topic 10.3 - Gene pool and speciation

Question 1

Gene pool

Answer 1

All genes and their different alleles that are present in an interbreeding population.

Species may be geographically separated and have different gene pools so a species may have many pools.

Question 2

Genetic equilibrium

Answer 2

Exists when all members of a population have an equal chance of passing on their genes to future gene pools.

Question 3

Allele frequency and evolution

Answer 3

Evolution -> cumulative change in heritable characteristics over time.
requires that allele frequencies change over time with populations

May occur due to :
Selection pressures (certain characteristics favoured)
Mutations

Question 4

Patterns of natural selection

Answer 4

Fitness of a genotype/phenotype is the likelihood of it being found in the next generation.

Three types of natural selection:
Stabilising, disruptive, and directional

Question 5

Stabilising selection

Answer 5

Selection pressures act to reduce extremities of a population (normal weight babies favoured over high or low weight)

Question 6

Disruptive selection

Answer 6

Extremes favoured, intermediates removed. Different types of red crossbill have different shaped bills that allow for vastly different seeds to be gathered.

Question 7

Directional selection

Answer 7

The population changes as one extreme of a range of variation are favoured

Question 8

Reproductive isolation

Answer 8

Three types of reproductive isolation:

geographical, temporal, or behavioural

Question 9

Geographical isolation

Answer 9

Called allopatric speciation

ie - differing water levels across the year separate species, potentially causing speciation

Question 10

Temporal isolation

Answer 10

Temporal isolation occurs when two populations reproduce at different times of the day or in different seasons, causing speciation to occur.

(ie - different plants flowering at different times)

Question 11

Behavioural isolation

Answer 11

Sympatric speciation

ie - differing courtship behaviours may lead to reproduction with only those with similar behaviours

Question 12

Speciation

Answer 12

Formation of a new species due to the splitting of a population. Occurs as gene pools of populations are separated.

Question 13

Gradualism in speciation

Answer 13

Speciation is often gradual

Gradualism is a dominant framework in palaeontology. However, it is criticised as there are lacking of intermediates in fossil records. Absence is however explained by just having incomplete fossil records.

Question 14

Punctuated equilibrium

Answer 14

Speciation can also act gradually

Punctuated equilibrium -> Long periods of stability are punctuated by rapid evolution.
Suggests that missing fossil intermediates are not missing, evolution just occurred rapidly.
Could be caused by allopatric speciation for example
Occurs more frequently in organisms with short generational times (ie insects and prokaryotes)

Question 15

Polyploidy

Answer 15

More than 2 sets of chromosomes

Unable to reproduce with those who have a normal amount of chromosomes but can with other polyploidy or do asexual repro. Can be caused by total non-disjunction.

Polyploidy organisms are often plants, ie garlic.

May also therefore cause speciation.