Unit 4 9B: Evolving and non-evolving populations

Question 1

Gene flow

Answer 1

The exchange of genetic information, specifically alleles between populations

Question 2

Genetic drift

Answer 2

A random change in allele frequency, occurring naturally in every population, due to chance events

Question 3

Bottleneck effect

Answer 3

When a population is drastically reduced to low numbers by a random or chance event and the allele frequencies of the surviving population do not reflect the genetic diversity of the original population

Question 4

Founder effect

Answer 4

When a small sample of a large population moves away to colonise a new area and becomes isolated; the allele frequencies of the founder population do not represent the genetic diversity of the larger original population

Question 5

Selection pressures

Answer 5

The conditions that influence allele frequencies in a population by contributing to the selection of which phenotypes survive in a given environment
e.g. Availability of resources, environmental conditions, predators and disease

Question 6

Natural selection

Answer 6

An evolutionary process whereby those individuals in a population that have a particular set of alleles are best suited to the environment and will survive, reproduce and pass on their genetic information to the next generation

Question 7

Selective advantage

Answer 7

A trait of phenotype that provides a survival advantage

Question 8

Selective breeding or artificial selection

Answer 8

A process whereby humans intervene in the breeding of a species to keep desired features in a population that are economically beneficial or aesthetically pleasing, by selecting which organisms are to reproduce

Question 9

Steps in allopatric speciation

Answer 9

1) Genetic variation exists in ancestral population
2)Geographical barrier splits population, causing them to become reproductively isolated
3)Different mutations arise in 2 populations
4)Selection pressures affecting each population may be different. Therefore, different phenotypes will be selected for as natural selection occurs over generations
5)Allele frequencies of 2 populations change as the 2 populations evolve in different ways
6) The accumulated genetic changes in the two gene pools prevents the formation of fertile and viable offspring. The 2 populations are now 2 distinct species

Question 10

Difference between Sympatric speciation and Allopatric speciation

Answer 10

Sympatric speciation is the result of reproductive isolation
Alloptric speciation is the result of geographic isolation