Unit 18 - Variation & Selection

Question 1

Variation

Answer 1

The differences between individuals of the same species.

Question 2

Phenotypic Variation

Answer 2

The difference in features between individuals of the same species.

Question 3

What causes variation?

Answer 3

Genes and the environment

Question 4

What are the two types of phenotypic variation?

Answer 4

Continuous variation, Discontinuous variation

Question 5

Continuous Variation

Answer 5

When there are many small degrees of difference for a particular characteristic. (Can usually be measured)

Question 6

Discontinuous Variation

Answer 6

When there are distinct differences for a characteristic.

Question 7

Continuous Variation Graph

Answer 7

Smooth bell curves.

Question 8

Discontinuous Variation Graph

Answer 8

Step-shaped.

Question 9

What causes phenotypic variation?

Answer 9

Genetic and Environmental

Question 10

Which type of variation is affected by both genes and the environment?

Answer 10

Continuous Variation

Question 11

Which type of variation is only affected genetically?

Answer 11

Discontinuous Variation

Question 12

Mutation

Answer 12

Genetic changes.

Question 13

Mutations happen continuously and spontaneously, but their frequency can be increased by…

Answer 13

• Gamma rays
• X-rays
• Ultraviolet rays
• Certain types of chemicals.

Question 14

What happens to cells with increased rates of mutation?

Answer 14

They become cancerous.

Question 15

Sources of Genetic Variation in Populations

Answer 15

• Mutations
• Meiosis
• Random mating
• Random fertilization

Question 16

Adaptive Features

Answer 16

The inherited functional features of an organism that increases its fitness.

Question 17

Fitness

Answer 17

The probability of an organism surviving and reproducing in the environment in which it’s found.

Question 18

Hydrophytes

Answer 18

Plants adapted to live in extremely wet conditions.

Question 19

What are the adaptations of hydrophytes?

Answer 19

• Large air spaces in leaves to keep them close to the water surface (where there’s more light for photosynthesis).
• Small roots for extracting nutrients from surrounding water.
• Stomata concentrated on the upper epidermis for easier gas exchange.

Question 20

Xerophytes

Answer 20

Plants adapted to live in extremely dry conditions.

Question 21

What are the adaptations of xerophytes?

Answer 21

• Thick waxy cuticle to cut down water loss.
• Small leaves that reduce surface area and hence evaporating area.
• Extensive shallow roots for quick absorption of lots of water when it rains.

Question 22

What causes natural selection?

Answer 22

How, in any environment, individuals that have the best adaptive features are the most likely to survive and reproduce.

Question 23

Natural Selection

Answer 23

Survival of the fittest.

Question 24

When some individuals develop a phenotype (or mutation) they may get a survival advantage and will therefore…

Answer 24

• Live longer
• Breed more
• Be more likely to pass on their genes

Question 25

Evolution

Answer 25

The change in the adaptive features of a population over time as a result of natural selection.

Question 26

Selective Breeding

Answer 26

To select individuals with desirable characteristics and breed them together.