evolution + selection pressures

Question 1

What is continuous variation and how is it determined genetically? (3)

Answer 1

When individuals vary within a range with no distinct categories,

It is controlled by many genes (polygenic),

And often influenced by environmental factors (e.g. height, weight)

Question 2

What is discontinuous variation and how is it determined genetically? (2)

Answer 2

When there are distinct categories for a trait, and individuals fall into one of them,

It is controlled by a single gene (monogenic) and is not influenced by the environment (e.g. blood group)

Question 3

What is the definition of evolution? (1)

Answer 3

The change in allele frequency in a population over generations

Question 4

How does natural selection lead to evolution? (3)

Answer 4

Occurs when selection pressures (e.g. predation, disease) act on individuals with favorable alleles,

Allowing them to survive and reproduce, passing these alleles to the next generation,

Leading to evolution

Question 5

Why do some species have high reproductive rates? (3)

Answer 5

Ensure a sufficient population survives to reproduce,

Compensating for losses,

Due to predation, competition, and environmental factors

Question 6

What are the steps in the process of natural selection? (5)

Answer 6

1. Mutation creates new alleles,
2. Individuals with different alleles show variation,
3. Selection pressures act on the population,
4. Individuals with favorable traits survive and reproduce,
5. Over time, favorable alleles increase in frequency

Question 7

How does overproduction of offspring relate to natural selection? (4)

Answer 7

When there are too many offspring for the available resources,

There is intraspecific competition,

The best-adapted individuals are more likely to survive and pass on their favorable alleles, -

Driving evolution

Question 8

What is stabilising selection? (2)

Answer 8

Favours the average phenotype,

Reducing variation and maintaining the status quo in a population

Question 9

What is directional selection? (2)

Answer 9

Favours individuals with extreme phenotypes,

Leading to a shift in the population’s traits over time in response to environmental changes

Question 10

What is stabilising selection? (4)

Answer 10

Environment favours individuals with the most common characteristic,

Individuals with extreme traits die out,

The common characteristic becomes more frequent,

The range (standard deviation) of traits decreases

Question 11

What is directional selection? (3)

Answer 11

Environment favours individuals with traits at one extreme,

Extreme trait becomes more common over time,

Normal distribution of traits shifts in that direction