5.2 - Natural Selection

Question 1

Define variation

Answer 1

Any difference between organisms caused by genetic or environmental factors

Question 2

List the three sources of genetic variation

Answer 2

• mutation
• meiosis
• sexual reproduction

Question 3

Explain how mutation is a source of a genetic variation

Answer 3

New alleles are produced by gene mutation which enlarges the gene pool of a population.

Question 4

Explain how meiosis is a source of genetic variation

Answer 4

• It produces new combinations of alleles by breaking up the existing combination in a diploid cell.
• Every cell produced by meiosis in an individual is likely to carry a different combination of alleles, because of crossing over and the independent orientation of bivalents.

Question 5

Explain how sexual reproduction is a source of genetic variation*

Answer 5

Sexual reproduction involves interbreeding/genetic material from two parents
new combinations of paternal and maternal chromosomes leads to new genetic combinations.

Question 6

Explain how mutation is a source of genetic variation

Answer 6

New alleles are produced by gene mutation, which enlarges the gene pool of a population.

Question 7

Define adaptation

Answer 7

The process of change by which an organism or species becomes better suited to its environment.

Question 8

Speces tend to produce more offsping than the environment can support - what does this lead to?

Answer 8

More offspring - less resources - leads to competition for food, mates and space - survival of the fittest.

Question 9

Recall the three types of mutation and what they do.

Answer 9

Beneficial mutations - change the sequence of a gene in order to create new variations of a trait.
Detrimental mutations - truncate the gene sequence to abrogate the normal function of a trait.
Neutral mutations - have no effect on the functioning of the specific sequence.

Question 10

Explain how natural selection leads to changes in antibiotic resistance

Answer 10

Antibiotic resistance is due to genes in bacteria and so it can be inherited.
The bacteria mutates, allowing them to not be affected - the antibiotic will survive and reproduce.
They will then pass the trait on to their offspring, which wull be a fully resistant gene

Question 11

List reasons why evolution of antibiotic resistance has been rapid

Answer 11

1. Widespread use of antibiotics for treating diseases in animals, humans
2. Bacteria can reproduce very rapidly
3. Populations of bacteria are often huge - increases the chance of a gene for antibiotic resistance being formed by mutation.
4. Bacteria can pass genes on to other bacteria in several ways.