5.2.1 Selective Breeding

Question 1

Selective breeding or artificial selection means, what?

Answer 1

to select individuals with desirable characteristics and breed them together

• The process doesn’t stop there though because it’s likely that not all of the offspring will show the characteristics you want so offspring that do show the desired characteristics are selected and bred together

Question 2

This process has to be repeated for many, what?

Answer 2

successive generations before you can definitely say you have a ‘new breed’ that will reliably show those selected characteristics in all offspring

Question 3

When does artificial selection occur?

Answer 3

Only occurs when humans intervene

Question 4

When does natural selection occur?

Answer 4

Occurs naturally

Question 5

What features do natural selection populations have?

Answer 5

Results in development of populations with features that are better adapted to their environment and survival

Question 6

What features do artificial selection populations have?

Answer 6

Results in development of populations with features that are useful to humans and not necessarily to survival of the individual

Question 7

How long does natural selection take to occur

Answer 7

Usually takes a long time to occur

Question 8

How long does artificial selection take to occur

Answer 8

Takes less time as only individuals with the desired features are allowed to reproduce

Question 9

Offspring that show the desired characteristics are selected, and what?

Answer 9

bred together

Question 10

How many times is the process repeated?

Answer 10

for many successive generations

Question 11

Animals are commonly selectively bred for various characteristics, including:

Answer 11

1. Cows, goats and sheep that produce lots of milk or meat

Question 12

An example of an animal that has been selectively bred by humans in many ways to produce breeds with many different characteristics is the, what?

Answer 12

domestic dog, all breeds of which are descended from wolves

Question 13

Exam Tip

Answer 13

Make sure that you include the need to repeat the selective breeding process for many generations in any exam answer you give – selecting two parents with desired characteristics, breeding them and stopping there is not selective breeding and will not give rise to a new breed

Question 14

Selective breeding of plants takes place in the same way, as what?

Answer 14

selective breeding of animals

Question 15

Plants are selectively bred by humans for the development of many characteristics, including, what?

Answer 15

Disease resistance in food crops

Increased crop yield

Hardiness to weather conditions (eg. drought tolerance)

Better tasting fruits

Large or unusual flowers

Question 16

An example of a plant that has been selectively bred in multiple ways is wild, what?

Answer 16

brassica, which has given rise to cauliflower, cabbage, broccoli, brussel sprouts, kale and kohlrabi:

Question 17

What can Selective breeding lead to?

Answer 17

inbreeding

Question 18

When does inbreeding occur?

Answer 18

when only the ‘best’ animals or plants (which are closely related to each other) are bred together

Question 19

What is inbreeding cause?

Answer 19

This results in a reduction in the gene pool – this is a reduction in the number of alleles (different versions of genes) in a population

Question 20

As inbreeding limits the size of the gene pool, there is an increased chance of, what?

Answer 20

Organisms inheriting harmful genetic defects

Organisms being vulnerable to new diseases (there is less chance of resistant alleles being present in the reduced gene pool)