Unit 4 - Genetic Diveristy + Adaptation

Question 1

What is the definition of genetic diversity?

Answer 1

It is the number of different alleles of genes in a population. It is sometimes referred to as the gene pool.

Question 2

What does a large number of different alleles mean?

Answer 2

A large variety of different characteristics in the population and therefore a high genetic diversity.

Question 3

Definition of a gene?

Answer 3

A base sequence of DNA which codes for a polypeptide or functional RNA.

Question 4

Definition of an allele?

Answer 4

A different version of the same gene

Question 5

Definition of allele frequency?

Answer 5

The number of times an allele occurs in a population.

Question 6

Why is genetic diversity important?

Answer 6

A population with a low genetic diversity may not be able to adapt to a change in environment.

Question 7

Genetic diversity within a population is increased by?

Answer 7

1) Random mutation in DNA
2) Different alleles being introduced into the population when individuals from another population migrate into it and reproduce (gene flow).

Question 8

Definition of mutation?

Answer 8

A change in the base sequence of the DNA.

Question 9

What is the founder effect?

Answer 9

When a few organisms from a population start a new colony, as they may become geographically isolated from the rest of the population. This means that there are only a small number of different alleles from the original gene pool, decreasing genetic diversity. The frequency of each alleles in the new colony might be different to the frequencies in the original population - it may not be representative.

Question 10

What is a genetic bottleneck?

Answer 10

When an event which caused a big reduction in a population. This reduces the number of different alleles in a gene pool and so reduces genetic diversity. The survivors reproduce creating a larger population from a few individuals so there is reduced genetic diversity.

Question 11

How to answer natural selection exam questions?

Answer 11

1) A random mutation in an organism.
2) Forms an advantageous allele for X (name the allele).
3) Which gives them a selective advantage in the presence of the selection pressure (name it!).
4) The organism with the advantageous allele is more likely to survive and reproduce.
5) Some of the offspring of this organism will inherit the advantageous allele (name it!).
6) Over many generations, the allele frequency in the population increases.
7) This is an example of directional:stabilising selection (type of selection).

Question 12

What can natural selection lead to?

Answer 12

Evolution which is the gradual change in species over time. This has led to the huge variety of living organisms on earth.

Question 13

What are adaptations?

Answer 13

Features that can help organisms to survive in their environment.

Question 14

What are behavioural adaptations?

Answer 14

Organisms can change their behaviour in order to survive.

Question 15

What are physiological adaptations?

Answer 15

Chemical process inside an organisms body which increase chances of survival.

Question 16

What are anatomical adaptations?

Answer 16

Structural features of an organisms body which increase chances of survival.

Question 17

What is stabilising selection?

Answer 17

-Occurs in populations where environment is stable.
-The average is selected for.
-The extreme phenotypes are selected against.
-Reduces variability and the size of the range within population.
-Reduces opportunity for evolutionary change.
-Reduces the range of possible characteristics in the population.

Question 18

What is directional selection?

Answer 18

-The mean in population represents optimum for existing conditions.
-Environmental change may produce new selection pressure that favours an extreme characteristic.
-When conditions change, optimum characteristics necessary for survival also changes.
-Some organisms will possess the new optimum already due to mutation creating an allele which gives them an advantage in the new environment.
-Those with the advantageous allele will be selected for.
-Those that don’t have the favourable allele will be selected against.
-Over time selection means those with the advantageous allele will predominate and the mean will shift.

Question 19

How do antibiotic resistant bacteria develop resistance to multiple antiboiotics?

Answer 19

1) Due to random mutation.
2) An allele for resistance to penicillin may already exist in the population.
3) When penicillin is used this creates a selection pressure in the environment.
4) The allele for resistance to penicillin gives the bacteria a selective advantage in the presence of penicillin.
5) This bacteria is more likely to survive and reproduce, than bacteria without the allele. Those without the allele die.
6) Some of the offspring of this bacteria will inherit the allele for penicillin resistance.
7) The frequency of the penicillin resistance allele in the population increases over time eventually developing population which is resistant to penicillin.
8) This is an example of directional selection.
9) So a new antibiotic is used which creates a selection pressure.
10) This process is repeated, creating a bacterial population which have alleles giving resistance to penicillin and the new antibiotic.
11) This repeats to develop bacteria which are resistant to multiple antibiotics.