Variation And Natural Selection

Question 1

What is variation?

Answer 1

Differences in the characteristics of individuals in a species

Question 2

What is continuous variation?

Answer 2

The type of variation categorised by gradual change in a characteristic across a population

Question 3

What is discontinuous variation?

Answer 3

The type of variation in which all the individuals can be clearly divided into two or more groups and there are no intermediate (in between) states

Question 4

Give an example of continuous variation

Answer 4

An organism’s height or weight

both are numerical

Question 5

Give an example of discontinuous variation

Answer 5

An animal’s fur colour / human’s blood type / shoe size / rolling tongues etc.

All can be categorised into distinct groups

Question 6

How is continuous variation usually represented?

Answer 6

Histograms

Question 7

How is discontinuous variation usually represented?

Answer 7

Bar charts

Question 8

What are the 2/3 causes of variation?

Answer 8

• environment
• genetic mutations

(Or both)

Question 9

What are genetic mutations?

Answer 9

A random change in number of chromosomes or type of gene

Question 10

Give an example of variation caused by mutations

Answer 10

• genetic disorders like Down syndrome
• blood type
• skin / fur colour at birth
• eye colour

Etc

Question 11

Give an example of variation caused by environment

Answer 11

• scars
• language

Etc.

Question 12

How does meiosis cause variation?

How is this increased by reproduction?

Answer 12

• chromosome arrangements are mixed up during meiosis - independent assortment
• When gametes fuse, they will have unique genes (two different zygotes)

Question 13

Give an example of variation caused by environment and genetics

Answer 13

• weight
• height
• skin colour
• hair colour

Etc.

Question 14

How often do mutations occur?

Are they visible?

Answer 14

• Continuously
• not always, don’t change phenotype usually

Question 15

What is meant by an adaptive phenotype?

Answer 15

a phenotype suited to environmental change

Question 16

What are genetic variants?

Answer 16

Changes in DNA as a result of mutation

Question 17

Explain Darwin’s ’survival of the fittest’ principal

Answer 17

Individuals with genes and characteristics most suited to the environment are more likely to survive and breed successfully

Question 18

Why do are characteristics inherited (natural selection)?

Answer 18

The genes and characteristics that have enabled the species to survive are then passed on

Question 19

Explain natural selection (2)

Answer 19

• A process where individuals in a population display variations that put them at a biological advantage,
• increasing the chances that these individuals will successfully reproduce and pass on their adaptive traits

Question 20

What is evolution (3)

Answer 20

• A change in the inherited characteristics of a population over a long period of time
• due to changes in environment
• through the process of natural selection, can result in speciation

Question 21

What is speciation

Answer 21

An outcome of evolution and isolation, where two populations of a species become so distinct they can no longer interbreed to produce fertile offspring

Question 22

What is a modern day example of natural selection

Answer 22

Antibiotic resistance in bacteria

Question 23

How does extinction occur?

Answer 23

When natural selection is too slow for organisms to adapt to new conditions

Question 24

What are fossils?

Answer 24

The remains of organisms from millions of years ago that are found in rocks, peat, ice or amber

Question 25

How are fossils formed?

Answer 25

From parts of organisms that have not decayed, when parts of organisms are replaced by minerals, as trace fossils

Question 26

What is decay?

Answer 26

The breakdown of dead organic matter by microbes (such as bacteria) and detritivores e.g. worms

decay may not occur if there aren’t these conditions

Question 27

Give examples of trace fossils?

Answer 27

Footprints, burrows, shell impressions, rootlet traces that are preserved as fossils

Question 28

What are the issues with the fossil record

Answer 28

Not all organisms fossilise and many early forms of life were soft-bodied, so very few traces of these organisms have been left behind

Question 29

Why is there difficulty in determining the origin of life

Answer 29

Geological activity has destroyed most traces of early life forms

Question 30

Why is interpreting the fossil record useful?

Answer 30

We can learn how much or how little
organisms have changed as life developed on Earth

Question 31

what do fossils prove? (2)

Answer 31

• That fossils are very similar to existing organisms
• suggesting modern organisms may have evolved from or share a common ancestor with ancient organisms

Question 32

How can natural selection lead to evolution? (2)

Answer 32

• it causes gradual changes
• over a long period, can lead to the development of a new species