Variation and Selection

Question 1

What continuous variation?

Answer 1

This is a gradual change in the characteristics of a population due to genetic and environmental factors

Question 2

What is discontinuous variation

Answer 2

This is a discrete change in characteristics due to genetic variation

Question 3

Give 2 examples of continuous variation

Answer 3

height, mass & length

Question 4

Give 2 examples of discontinuous variation

Answer 4

Blood type, right or left handed & ability to roll your tongue

Question 5

What type of chart should you draw for continuous variation?

Answer 5

histogram (no gaps between the bars)

Question 6

Give 2 examples of discontinuous variation?

Answer 6

Bar chart (gaps between the bars)

Question 7

What is genetic variation caused by?

Answer 7

can be caused by a mutation in the number of chromosomes or the type of gene

Question 8

Explain natural selection

Answer 8

Organisms may compete for resources e.g. nutrients, light, shelter,
mates and space
* Organisms adapt (by mutating) over a long period of time
* This mutation has made them better adapted to their environment and will allow them to survive, reproduce and pass on their genes to their offspring

Question 9

What did Scientists use as evidence for evolution and why?

Answer 9

Scientists use fossils as evidence for
evolution. Fossils are the remains of living organisms that have been preserved and show what they may have looked like millions of years ago and how they have changed over that time.

Question 10

What is extinction?

Answer 10

This occurs when there are no living examples left e.g. Dodo bird
and Dinosaurs. This happens because these animals did not
adapt to the changing environment.

Question 11

Give 3 reasons for extinction

Answer 11

*CLIMATE CHANGE OR NATURAL DISASTERS
* HUNTING BY HUMANS
* SPREAD OF DISEASES
* LOSS OF HABITAT e.g., deforestation

Question 12

How do we reduce extinction?

Answer 12

• Legislation preventing the hunting of endangered species
• International agreements (plans to reduce climate change)
• Creating nature reserves to protect habitats
• Educating people to do their part in protecting the environment

Question 13

What is selective breeding?

Answer 13

The selection and breeding of organisms chosen by MAN for their desirable characteristics

Question 14

What is the difference between natural selection and selective breeding?

Answer 14

The difference between selective breeding and natural selection is that
selective breeding happens much quicker

Question 15

Explain how humans selectively breed animals

Answer 15

*Individuals with the characteristics you want are bred together
* Offspring that show the desired characteristics are selected and bred
together
* This process is repeated for many successive generations

Question 16

Give some examples of animals that are selectively bred and the reason why

Answer 16

*Cows that produce lots of milk (high yield of milk) or excellent quality of meat
*chickens that lay large eggs
* domestic dogs that have a gentle nature, do not shed
(hypoallergenic)
* sheep with good quality wool
* horses with fine features and a very fast pace

Question 17

Give some examples why plants that are selectively bred

Answer 17

*Disease resistance in food crops
* Increased crop yield
* Hardiness to weather conditions (eg. drought tolerance)
*Better tasting fruits
* Large or unusual flowers