Topic 3.2 Natural selection

Question 1

Why does natural selection occur?

Answer 1

1. Predation
2. Disease
3. Competition

All resulting in differential survival and reproduction.

Question 2

Explain how natural selection results in development of new charecterisitics

Answer 2

• Random mutations result in new alleles
• Some alleles give the possessor and advantage over the rest of the species, making them more likely to survive and reproduce
• Their offspring receive the new allele, and frequency continues to increase over many generations

Question 3

What are three types of adaptation? Give examples of each.

Answer 3

• Anatomical (changes to body structure) e.g. oily fur
• Physiological (changes to bodily processes) e.g. venom production
• Behavioral (changes to actions) e.g. hibernation

Question 4

Define a niche

Answer 4

The role of the species within its enviroment. Species sharing the same niche will compete with each other.

Question 5

Define speciation

Answer 5

Where a population is split and reproductively isolated, there are different selective preasure on the two groups. If the genetic makeup changes to the extent the two groups can no longer interbreed, they have become a separate species.

Question 6

What is meant by allopatric speciation?

Answer 6

Speciation resulting from a physical barrier e.g. river, mountain range. the enviroments occupied by the two groups are different , and therefore different alleles are favoured

Question 7

What is meant by sympatric speciation?

Answer 7

Speciation resulting from a non-physical barrier e.g. a mutation than no longer allows two organisms to produce fertile offspring. Any changes in anatomy or behavoir may also prevent breeding.

Question 8

How does evolution relate to bacterial antibiotic resistance?

Answer 8

Bacteria can develop mutations that make them resistant to antibiotics, which they will then pass on when the reproduce. This is an evolutionary ‘race’, meaning we always have to be developing new treatments.

Question 9

What is reproductive isolation?

Answer 9

When two or more parts of a population cannot interbreed, reproductive isolation occurs

Question 10

Give the six ways that reproductive isolation can occur

Answer 10

1. Geographical isolation
2. Habitat/ecological isolation
3. Seasonal/ temporal isolation
4. Mechanical isolation
5. Behavioral isolation
6. Gametic isolation

Question 11

What is geographical isolation?

Answer 11

Populations are divided by a physical barrier, e.g. a mountain range or river

Question 12

What is habitat/ecological isolation?

Answer 12

Populations occupy different habitats in the same area so don’t meet to breed

Question 13

What is seasonal/temporal isolation?

Answer 13

Species exist in the same area but are active for reproduction at different times

Question 14

What is mechanical isolation?

Answer 14

The reproductive organs no longer fit together

Question 15

What is behavioral isolation?

Answer 15

Populations don’t respond to each others reproductive displays

Question 16

What is gametic isolation?

Answer 16

Male and female gametes from two populations are incompatible with each other