B6.2 Variation and evolution

Question 1

Genes determine the phenotype of an organism – true or false?

Answer 1

False – the environment also plays a role.

Question 2

What is variation within a population?

Answer 2

Differences in the characteristics of individuals in a population.

Question 3

State three causes of variation in a population.

Answer 3

“1. Genes

2. The environment
3. A combination of both”

Question 4

Within a population, there is normally very little genetic variation – true or false?

Answer 4

False – just look around you at humans!

Question 5

What causes variation within a population?

Answer 5

Mutations.

Question 6

How often does a mutation result in a new phenotype?

Answer 6

Very rarely.

Question 7

What is evolution?

Answer 7

A change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species.

Question 8

True or false – does the theory of evolution by natural selection state that all living things evolved from simple life forms more than three billion years ago?

Answer 8

True.

Question 9

“Would the best organism within a species to survive and reproduce be:

a) the strongest?
b) the one which reproduces the fastest?
c) the best adapted to the environment?”

Answer 9

c)

Question 10

What is the definition of a species?

Answer 10

Organisms that can interbreed to produce fertile offspring.

Question 11

What is selective breeding?

Answer 11

The process by which humans breed plants and animals for particular genetic characteristics.

Question 12

Name two historic examples of selective breeding.

Answer 12

“1. Breeding food crops from wild plants

2. Domesticating animals”

Question 13

How many generations of selective breeding does it take to obtain an organism with a desired characteristic?

Answer 13

Many!

Question 14

State four modern examples of selective breeding.

Answer 14

“1. Disease resistance in food crops

2. Animals which produce more meat or milk
3. Domestic dogs with a gentle nature
4. Large or unusual flowers”

Question 15

State a drawback to selective breeding.

Answer 15

Inbreeding – some breeds are prone to disease or inherited defects (e.g. some pugs have breathing problems).

Question 16

What is genetic engineering?

Answer 16

The process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.

Question 17

State three ways plants might be genetically engineered.

Answer 17

“1. Resistant to insect attack

2. Resistant to herbicides
3. Increased yields”

Question 18

Give one example of how bacterial cells have been genetically engineered.

Answer 18

To produce useful substances such as human insulin to treat diabetes.

Question 19

How is a gene “cut out” from the genome of one species and inserted the genome of another?

Answer 19

Using enzymes.

Question 20

Into what is the gene inserted?

Answer 20

A vector

Question 21

Give two examples of vectors used in genetic engineering

Answer 21

A bacterial plasmid, a virus

Question 22

When should a gene be transferred to another organism by genetic engineering?

Answer 22

At an early stage in their development

Question 23

Why should a gene be transferred between organisms at an early stage of development?

Answer 23

So that they develop with desired characteristics.

Question 24

State three concerns around genetically engineering plants.

Answer 24

“1. Unknown effects on populations of wild flowers

2. Unknown effects on populations of insects
3. Some people feel the effects of eating GM crops on human health have not been fully explored”

Question 25

What is plant tissue culture?

Answer 25

Using small groups of cells from part of a plant to grow identical new plants.

Question 26

What are “plant cuttings”?

Answer 26

An older, but simple, method used by gardeners to produce many identical new plants from a parent plant.

Question 27

Where might these techniques be useful?

Answer 27

Horticulture and agriculture.

Question 28

Describe the two steps involved in embryo transplanting.

Answer 28

Splitting apart cells from a developing animal embryo before they become specialised transplanting the identical embryos into host mothers.

Question 29

Describe the steps involved in adult cell cloning or SCNT (somatic cell nuclear transfer) (5 steps)

Answer 29

“1. The nucleus is removed from an unfertilised egg cell

2. The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell
3. An electric shock stimulates the egg cell to divide to form an embryo
4. These embryo cells contain the same genetic information as the adult skin cell
5. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development”

Question 30

State a disadvantage to cloning plants and animals.

Answer 30

Reduces genetic variation, so makes populations more susceptible to disease.