Variation and evolution

Question 1

What is heritable variation

Answer 1

Caused by different genes and so can be passed on from parent to child, eg hair colour, type of nose ect.

Question 2

What is environmental variation?

Answer 2

Is caused by the environment in which the organism has developed. It cannot be passed to the next generation. Eg scars, muscularity or dyed hair colours.

Question 3

What is continuous variation?

Answer 3

There is a continuous range with no ‘catergories’ for example height, people can be any height within a certain range.

Question 4

What is discontinuous variation?

Answer 4

There are distinct groups that don’t change (eg your fingerprints can either be an arch, whorl or loop, there are no ‘in-between’ fingerprints)

Question 5

What is a mutation?

Answer 5

A mutation is a random change in the structure of a gene.

Question 6

What can increase rates of mutation?

Answer 6

Ionising radiation or certain chemicals. (think sun radiation causing cells to mutate into cancerous cells)

Question 7

What mutations spread onto the next generation?

Answer 7

Mutations in gametes will be passed on, mutations in body cells will not.

Question 8

What does heterozygous mean?

Answer 8

Two different alleles (eg one dominant and one recessive)

Question 9

What does homozygous mean?

Answer 9

Two of the same alleles (eg both dominant)

Question 10

What is gene therapy?

Answer 10

It is the name given to a range of techniques that can be used to remove the effects of a harmful allele like the one causing cystic fibrosis.

Question 11

What 2 main ways is gene therapy completed?

Answer 11

• Introducing a healthy allele into a persons DNA (eg adding a dominant allele to counteract an unhealthy recessive)
• ‘Switching off’ the harmful allele

Question 12

Ethical rejections to gene therapy?

Answer 12

• Some religious groups believe that humans should never alter the genes of living organisms.
• The process is very expensive and could take funds from other types of healthcare which might help more people.

Question 13

What is evolution?

Answer 13

The process by which living species have gradually changed and developed from earlier forms over a long period of time.

Question 14

What does evolution result in?

Answer 14

Organisms becoming better adapted to their environments.

Question 15

The difference between the theory of evolution and the theory of natural selection?

Answer 15

The theory of evolution is that living things have evolved over a period of time. The theory of natural selection assumes that evolution has occurred and is a theory of how it has happened.

Question 16

Which theorist’s proposed natural selection?

Answer 16

Charles Darwin and Alfred Russel Wallace in 1958

Question 17

What is the process of natural selection?

Answer 17

• Most organisms over produce, there is competition in younger organisms.
• Some of the young have variations which help them survive better in their environment.
• The organisms that survive have a better chance of breeding and passing on the genes to the next generation.
• The next gen will have these variations, new competition arises and they adapt again. Process repeats, gen after gen.
• These changes will eventually spread to whole species, henceforth they have ‘evolved’ as the result from this.

Question 18

Reasons for animals to become extinct?

Answer 18

• Failed to adapt to its environment
• The organism has adapted, but cannot compete with other adapting species.
• Sudden changes in environment (usually human interference)

Question 19

Why is natural selection rapid in bacteria?

Answer 19

• They reproduce very quickly

- The level of exposure to antibiotics is very high

Question 20

What is a ‘genome’?

Answer 20

The name given to all genetic information in an organism.

Question 21

Why is mapping the human genome so important for medicine?

Answer 21

• Knowing about the existence of alleles that cause disease allows us with the possibility of altering them or counteracting their effects.
• Allows the possibility of creating drugs that attack only one gene, instead of jepodising all genes (eg chemotherapy does attack cancer mutations but also skin ells, hair cells ect)

Question 22

How many genes are there in a human being?

Answer 22

20500