Speciation and genetic drift Flashcards Preview

Y13 A2 Biology > Speciation and genetic drift > Flashcards

Flashcards in Speciation and genetic drift Deck (22)
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1
Q

What is speciation?

A

The development of a new species from an existing species

2
Q

When does speciation occur?

A

When populations of the same species become reproductively isolated

3
Q

What does reproductively isolated mean?

A

Changes in allele frequency causes changes in phenotype which means they can no longer interbreed to produce fertile offspring

4
Q

When can reproductive isolation occur?

A

Physical barriers which cause geographical isolation

Without physical barriers

5
Q

What are the two types of speciation?

A

Allopatric

Sympatric

6
Q

What is allopatric speciation?

A

Populations that are geographically isolated and will experiences slightly different conditions

7
Q

When two populations become geographically isolated, how does this change allele frequencies?

A
  • Different alleles will be more advantageous in different populations so natural selection occurs
  • Allele frequencies will also change as mutations occur independently in each population
  • Genetic drift may also affect the allele frequencies in one or both populations
8
Q

How do changes in allele frequency cause allopatric speciation?

A

The changes in allele frequency will lead to differences accumulating in the gene pools of the separated populations, causing changes in phenotype frequencies
Over time, individuals from different populations will have changed so much that they wont be able to breed with one another to produce fertile offspring and they have become reproductively isolated.

9
Q

What is sympatric speciation?

A

Occurs when random mutations within a population prevents individuals that carry the mutation from breeding with other members of the population that don’t carry the mutation

10
Q

What does sympatric speciation not include?

A

Geographical isolation

11
Q

Which type of speciation is rare?

A

Sympatric

12
Q

What is an example of sympatric speciation?

A

Sometimes a mutation can occur in individuals, known as polyploidy, causing them to have more chromosomes than the diploid population. This means they cant reproduce sexually to give fertile offspring

13
Q

What are the mechanisms of reproductive isolation?

A
  • Seasonal changes
  • Mechanical changes
  • Behavioural changes
14
Q

What are seasonal changes?

A

Individuals develop different flowering or mating seasons or become sexually active at different times of the year. They cant breed as they aren’t reproductively active at the same time

15
Q

What are mechanical changes?

A

Changes in the shape, size or function of the genitalia can prevent successful mating

16
Q

What are behavioural changes?

A

Courtship behaviour may change and therefore they wont be seen as attractive anymore, prevents breeding even if they could do it successfully

17
Q

What is the effect of selection pressures?

A

They can change the allele frequency of a population over time

18
Q

What two ways can evolution occur?

A

Natural selection

Genetic drift

19
Q

What is genetic drift?

A

Instead of environmental factors affecting which individuals survive, breed and pass on their alleles, chance dictates which alleles are passed on

20
Q

How does genetic drift work?

A

1) Individuals within a population show variation in their genotypes
2) By chance, the allele for one genotype is passed on to more offspring than the others so the number of individuals with the allele increases
3) If by chance the same allele is passed on more often again and again, it can lead to evolution as the allele becomes more common in the population

21
Q

What might happen if enough differences in allele frequencies build up due to genetic drift?

A

Leads to reproductive isolation and speciation

22
Q

Out of evolution and genetic drift, which has a greater effect in smaller populations?

A

Genetic drift