Populations and Evolution- Variation and Selection

Question 1

What is variation?

Answer 1

The differences that exist between individuals

Question 2

What does variation within a species mean?

Answer 2

Individuals in a population can show a wide range of phenotypes

Question 3

What causes genetic variation within a species?

Answer 3

Individuals have different alleles even though they have the same genes

Question 4

What is the main source of genetic variation?

Answer 4

Mutation

Question 5

How can genetic variation be brought about from meiosis?

Answer 5

Crossing over of chromatids and the independent segregation of chromosomes

Question 6

What is the third way that genetic variation can be brought about?

Answer 6

Through random fertilisation of gametes during sexual reproduction

Question 7

What changes in the environment can cause variation within a species?

Answer 7

Climate, food, lifestyle…

Question 8

How is most variation within a species caused?

Answer 8

By a combination of genetic and environmental factors

Question 9

What does most genetic variation result in?

Answer 9

Evolution

Question 10

Why do individuals of the same species vary?

Answer 10

Because they have different alleles

Question 11

What creates a struggle for survival?

Answer 11

Selection pressures

Question 12

What are 3 examples of selection pressures?

Answer 12

Predation, disease and competition

Question 13

Why are some individuals better adapted to selection pressures than others?

Answer 13

Because individuals vary

Question 14

Which individuals are more likely to survive, reproduce and pass on their genes?

Answer 14

The individuals with a phenotype that increases their chance of survival

Question 15

How does the frequency of beneficial alleles increase from generation to generation?

Answer 15

Those better adapted pass on their alleles to their offspring

Question 16

What is stabilising selection?

Answer 16

Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce

Question 17

When does stabilising selection occur?

Answer 17

When the environment isn’t changing, and it reduces the range of possible phenotypes

Question 18

What is an example of stabilising selection?

Answer 18

Human birth weight, average sized babies are more likely to survive

Question 19

What is directional selection?

Answer 19

Where individuals with alleles for a single extreme phenotype are more likely to survive and reproduce

Question 20

When does directional selection occur?

Answer 20

In response to an environmental change

Question 21

What is an example of directional selection?

Answer 21

Antibiotic resistance

Question 22

What is disruptive selection?

Answer 22

Where individuals with alleles for extreme phenotypes at either end of the range are more likely to survive and reproduce

Question 23

How is disruptive selection opposite to stabilising selection?

Answer 23

Because characteristics towards the middle of the range are lost

Question 24

When does disruptive selection occur?

Answer 24

When the environment favours more than one phenotype