Topic 4B - Diversity And Selection

Question 1

What is a mutation

Answer 1

A change in the base sequence
Usually occurs during DNA replication

Question 2

Why might mutation not lead to change in the amino acid sequence

Answer 2

Genetic code is degenerate so mutation may end up coding for same amino acid as the original triplet
Mutation may have occurred in intron

Question 3

What is a substitution mutation

Answer 3

When a nucleotide in the DNA sequence is replaced by another
More likely that no change occurs in amino acid sequence

Question 4

What is a deletion mutation

Answer 4

When a nucleotide in DNA sequence is lost. More likely to be harmful and significant, as it leads to frame shift which means the entire amino acid sequence will be different

Question 5

What is a mutagenic agent

Answer 5

Factors that increase the rate of gene mutation
X-rays, UV light

Question 6

What is a polyploidy chromosome mutation

Answer 6

Where an individual has three or more sets of chromosomes instead of two

Question 7

What is chromosomes non-disjunction

Answer 7

When chromosomes fail to seperate correctly in meiosis, resulting in gametes with one more or less chromosome than normal

Question 8

How does meiosis differ from mitosis

Answer 8

Produces 4 genetically different cells with half the number of chromosomes as the parent cell
Mitosis produces 2 genetically identical cells with the same number of chromosomes as the parent cell

Question 9

What is genetic diversity ?

Answer 9

Number of different alleles of genes in a species or population

Question 10

Why is genetic diversity important?

Answer 10

If a population has a low genetic diversity, it might not be able to adapt to a change in the environment and the whole population could be wiped out

Question 11

How can genetic diversity in a population be increased (2)

Answer 11

Mutations in a DNA forming new alleles
Different alleles being introduced into a population when individuals from another population migrate into it and reproduce - gene flow

Question 12

What is a genetic bottleneck?

Answer 12

An event that causes a big reduction in a population

Question 13

What are the effects of a genetic bottleneck?

Answer 13

Number of different alleles in a gene pool decreases, so it decreases genetic diversity.
The survivors reproduce and a larger population is created from a few individuals

Question 14

What is the founder effect?

Answer 14

Describes what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool.

Question 15

What can cause the founder effect to occur?

Answer 15

Result of migration leading to geographical seperation or if a new colony is separated from the original production

Question 16

Describe the process of natural selection (5)

Answer 16

1. Individuals with the advantageous allele increase their chances of survival, they survive and reproduce, passing on their advantageous allele - this means there are less individuals with the less advantageous allele
2. This means there is a greater proportion of the next generation inherits the beneficial allele
3. This in return means they are mire likely to survive, reproduce and pass on the genes
4. The advantageous allele increases in frequency from generation to generation
5. Over generations this leads to evolution as the advantageous allele become more common in the popualtion

Question 17

What are the 3 different types of adaptations?

Answer 17

Behavioural
Physiological
Anatomical

Question 18

What are behavioural adaptations?

Answer 18

Way an organism acts that increase its chances of survival

Question 19

What are physiological adaptations?

Answer 19

Processes inside an organisms body that increase its chances of survival

Question 20

What is the anatomical adaptations?

Answer 20

Structural features of an organisms body that increase its chance of survivcal

Question 21

What are the different types of selection (2)

Answer 21

Directional
Stabilising

Question 22

What is directional selection ?

Answer 22

Where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce. This could be in response to an environmental change

Question 23

What is stabilising selection?

Answer 23

Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce. It occurs when the environment isn’t changing, and it reduces the range of possible characteristics