Topic 18

Question 1

What is variation?

Answer 1

The difference between organisms of the same species

Question 2

What is discontinuous variation?

Answer 2

Variation that produces distinct categories (e.g. eye colour or blood groups

Question 3

What is continuous variation?

Answer 3

Variation that cannot be placed into distinct categories and instead produces a spectrum (e.g. height, weight)

Question 4

What is a mutation?

Answer 4

A random change in the base sequence of the DNA of an organism

Question 5

State 2 things which may increase the rate of mutation

Answer 5

-Ionising radiation (x-rays / uv)
-Certain chemicals (mutagens & carciogens)

Question 6

Other than mutations, what else can give rise to variation?

Answer 6

Random fertilisation, meiosis, random mating

Question 7

What is an adaptive feature?

Answer 7

The inherited functional features of an organism that help it survive in its environment

Question 8

What are hydrophytes?

Answer 8

Plants which are adapted to live in aquatic conditions

Question 9

State 3 adaptations of hydrophytes

Answer 9

Wide and flat leaves/ Thin waxy cuticle
Stomata on only upper surface (maximise gas exchange)
Flexible stems (not damaged by currents)
Air spaces (float = more light exposure

Question 10

What are xerophytes?

Answer 10

Plants which are adapted to live in very arid and dry conditions

Question 11

State 3 adaptations of xerophytes

Answer 11

Rolled leaves (trap humid air)
Thick waxy cuticle (less water loss by evaporation)
Small needle shaped leaves
Fewer stomata + in sunken pits surrounded by hair (slows transpiration down)

Question 12

Describe the process of natural selection

Answer 12

“Populations are naturally varied due to random genetic mutations
Some of these mutations provide a selective advantage
These organisms survive and reproduce, passing on the successful genes”

Question 13

Define evolution

Answer 13

A change in the features of organisms over time due to natural selection

Question 14

What is the process of adaptation?

Answer 14

Populations become more suited to their environment over time due to natural selection

Question 15

What is the development of antibiotic resistance an example of?

Answer 15

Evolution by natural selection

Question 16

Describe how antibiotic resistance arises

Answer 16

“A random genetic mutation causes a bacterium to become resistant to the antibiotic
When the antibiotic is used, all the bacteria that do not have the mutation are killed
The population containing just the resistant bacteria then begins to grow”

Question 17

Describe how selective breeding is carried out

Answer 17

“Organisms with the desired traits are selected
These organisms are bred together
This process is repeated until the offspring have the desired characteristics”

Question 18

What is the difference between natural selection and artificial selection?

Answer 18

Natural selection occurs when the selection pressures are created by the environment whereas artificial selection is when humans deliberately create selection pressures