6.2 Inheritance, Variation and Evolution

Question 1

What is variation?

Answer 1

differences in the characteristics of individuals in a population

Question 2

What are the causes of variation within a species?

Answer 2

• Genetics
• Environment
• A mixture of both of the above

Question 3

What is genetic variation?

Answer 3

• variations in the genotype of organisms of the same species due to the presence of different alleles
• creates differences in phenotypes

Question 4

What creates genetic variation in a species?

Answer 4

• spontaneous mutations
• sexual reproduction

Question 5

What is a mutation?

Answer 5

A random change to the base sequence in DNA which results in genetic variants. They occur continuously

Question 6

State the three types of gene mutation

Answer 6

• insertion
• deletion
• substitution

Question 7

How may a gene mutation affect an organisms phenotype?

Answer 7

1. Neutral mutation does not change the sequence of amino acids. Protein structure and function same. No effect on phenotype
2. mutation may cause a minor change in an organism’s phenotype, e.g. change in eye colour
3. mutation may completely change the sequence of amino acid. This may result in a non-functional protein. Severe changes to the phenotype

Question 8

What is the consequence of a new phenotype caused by a mutation being suited to an environmental change?

Answer 8

there will be a rapid change in the species

Question 9

What is evolution?

Answer 9

• a gradual change in the inherited traits within a population overtime
• it occurs due to natural selection which may result in the formation of a new species

Question 10

What is the theory of natural selection?

Answer 10

All species of living things have evolved from simple life forms that first developed more than 3 billion years ago

Question 11

Outline the theory of natural selection

Answer 11

1. Genetic variation exists due to spontaneous mutations
2. Selection pressures exist
3. Random mutation gives an organism a selective advantage
4. Organism is better adapted to the environment and survives
5. organism reproduces, passing on its beneficial alleles
6. frequency of advantageous alleles increase

Question 12

What are examples of selection pressures?

Answer 12

competition or disease

Question 13

How do two populations become different species?

Answer 13

When their phenotypes become different to the extent that they can no longer interbreed to produce a fertile offspring

Question 14

What is selective breeding?

Answer 14

The process by which humans artificially select organisms with desirable characteristics and breed them to produce off springs with similar phenotypes

Question 15

Outline the main steps involved in selective breeding (4)

Answer 15

1. Identify a desired characteristic
2. select parent organisms that show the desired traits and breed them together
3. select offspring with the desired traits and breed them together
4. process repeated until all off springs have the desired traits

Question 16

Give examples of characteristics selected for in selective breeding

Answer 16

• disease resistance in crops
• higher milk or meat production in animals
• gentle nature in domestic dogs
• large flowers

Question 17

What is the main advantage of selective breeding?

Answer 17

it creates organisms with desirable features, e.g. plants produce larger fruit or domesticated animals

Question 18

Other than in agriculture, where else is selective breeding useful?

Answer 18

• In medical research
• In sports, eg. horse racing

Question 19

Outline the disadvantages of selective breeding (4)

Answer 19

• reduction in the gene pool
• inbreeding results in genetic disorders
• development of other physical problems, e.g. respiratory problems in bulldogs
• potential to unknowingly select harmful recessive alleles

Question 20

When can reduction in the gene pool become especially harmful?

Answer 20

If sudden environmental changes occur