Topic 18

Question 1

Variation

Answer 1

The difference between individuals of the same species

Question 2

Mutation

Answer 2

Genetic change caused by ionising radiation/ chemicals called mutagens

Question 3

Gene mutation

Answer 3

A random change in the base sequence of DNA

Question 4

Adaptive features

Answer 4

Characteristics that an organism inherits which help it to survive and reproduce in its environment

Question 5

Xerophytes

Answer 5

• adapted to live in dry climates (marram grass)
• has stomata that are sunk in pits and surrounded by hairs slowing down transpiration to trap a layer of humid air close to leaf surface
• rolled leaves to trap humid air
• thick, waxy layer on epidermis to reduce water loss by evaporation

Question 6

Hydrophytes

Answer 6

• adapted to live in water (water lilies)
• leaves contain air spaces so they can float on top of the water and be exposed to most light
• stomata are usually present on the upper surface to maximise gas exchange
• stems are flexible to prevent damage from currents

Question 7

Adaptation

Answer 7

The process by which populations become more suited to their environment over several generations. It happens as a result of natural selection.

Question 8

selective breeding

Answer 8

When humans artificially select the plants or animals that are going to breed so the frequency of the alleles for desired characteristic increase in a population.

Question 9

artificial selection

Answer 9

1. desirable characteristics
2. faster than natural selection
3. may cause inbreeding - causing genetic disorders
4. if there is a new disease in the environment chances of survival are lower because there is no variation in population

Question 10

natural selection

Answer 10

1. surviving individuals have characteristics to suit their environment
2. long/slow process
3. all wild organisms
4. less likely to be inbred to are ‘healthier’
5. more variation = chances of survival increased