5.2 Natural selection

Question 1

Conditions to which natural selection responds

Answer 1

1. Inherited variation - genetic variation in a population
2. Competition - overproduction and limited resources
3. Selection - environmental pressures lead to differential reproduction
4. Adaptations - more adapted survive - reproduce
5. Evolution - over time allele frequencies change

Question 2

Define natural selection

Answer 2

NATURAL SELECTION - a process which favours the survival of organisms which are better adapted to survive in the given conditions and produce more offspring

Question 3

What causes genetic variation in populations?

Answer 3

• mutations in germline: random changes in genes - new alleles - beneficial/neutral/detrimental
• sexual reproduction - random individuals mate + random fertilisation
• meiosis - crossing over (prophase I - non sister chromatids exchange), independent allele assortment (metaphase I - homologous chromosomes move) in gametes

Question 4

Why does competition emerge?

Answer 4

Species produce more offsping than the environment can support - competition for resources and survival

Question 5

Types of adaptations of an organism

Answer 5

PS BBD

Physiological: better adapted organs

Structural: neck length in giraffe

Biochemical: bllod groups, lactose tolerance

Behavioural: patterns in activity

Developmental: patterns of ageing

Question 6

When can a change in allele favouring change?

Answer 6

If environmental conditions change - favouring of different alleles also changes - detrimental may become beneficail and vice versa

Question 7

Examples of natural selection

Answer 7

• antibiotic resistance
• Galapagos finches