B2f - natural selection

Question 1

Describe Darwin’s theory of evolution by natural selection(4)

Answer 1

Presence of natural variation in a population caused by chance mutations in genes

There is competition for limited resource, and those better adapted will be able to out­compete others

Survival of the fittest - those who out­compete and are better suited to environment will survive, while others die

Inheritance of ‘successful’ adaptations via genes by the offspring from those who survive and reproduce

Question 2

What are adaptations controlled by

Answer 2

Genes which can be passed on to the next generation

Question 3

How are new species formed

Answer 3

over long periods of time the changes in the characteristics of organisms brought about by natural selection may result in the formation of new species

Question 4

What does speciation require

Answer 4

geographical or behavioural (reproductive) isolation of populations of a species

Question 5

Describe the process of speciation(5)

Answer 5

1. population of a species become geographically or behaviourally/reproductively isolated
2. different mutations create different features in the 2 populations
3. beneficial mutations will be different as the conditions are different
4. over time, each isolated group evolves differently; longer isolated means more different they become
5. 2 sub­populations changed so much that they can no longer interbreed, forming separate but closely related species

Question 6

Explain the reasons why the theory of evolution by natural selection met with an initially hostile response (3)

Answer 6

Against common religious beliefs about how life on Earth developed which was that God created all species

Darwin couldn’t explain why new, useful characteristics appeared or how they were inherited as genes were not discovered

Not enough evidence to back up his theory

Question 7

Why is the theory of natural selection now widely accepted? (2)

Answer 7

has been discussed and tested successfully by a wide range of scientists

explains a wide range of observations

Question 8

Describe Lamarck’s theory (3)

Answer 8

if a characteristic was used a lot by an animal, it would become more developed

these acquired characteristics are passed on to the offspring

different from Darwin’s theory as Darwin’s theory was based on mutations and genetic variation

Question 9

Explain why Lamarck’s theory was discredited

Answer 9

acquired characteristics don’t have a genetic basis so are unable to be inherited by next generation

Question 10

What has facilitated the development of the theory of natural selection?

Answer 10

making new discoveries, e.g. knowledge of genes and understanding of genetic inheritance