The Theory of Evolution

Question 1

What were Darwin’s 4 key observations about the world around him?

Answer 1

• organisms produce more offspring than survive
• there’s variation in the characteristics of members of the same species
• some of these characteristics can be passed on from one generation to the next
• individuals that are best adapted to their environment are more likely to survive

Question 2

What is Darwin‘s theory of evolution by natural selection?

Answer 2

• individuals within a population show variation in the phenotypes
• Selection pressures create a struggle for survival
• individuals with better adaptations are more likely to survive and reproduce success passing on their advantageous adaptations to their offspring
• Over time the proportion of the population possessing the advantageous adaptations increases
• over generations this leads to evolution as the favourable adaptations become more common in the population

Question 3

What evidence did Wallace find to support the theory of evolution by natural selection?

Answer 3

He realised that warning colours are used by some species (e.g butterflies) to deter predators from eating them and that this was an example of an advantageous adaptation that had evolved by natural selection

Question 4

Explain how fossil record evidence supports the theory of evolution. Give an example

Answer 4

• Fossils are the remains of organisms preserved in rocks. By arranging fossils in chronological order, gradual changes in organisms can be observed and provide evidence of evolution
• e.g the fossil record of the horse shows a gradual change in characteristics, including increasing size and hoof development

Question 5

Explain how DNA evidence can be used to support the theory of evolution. Give an example

Answer 5

• The theory of evolution suggests that all organisms have evolved from shared common ancestors
• closely related species diverged more recently
•  Evolution is caused by gradual changes in the base sequence of an organisms DNA
• organisms that diverged away from each other more recently should have more similar DNA as less time has passed for changes in the DNA sequence to occur

-e.g Humans, chimps and mice all evolved from a common ancestor. Humans and mice diverged a long time ago, but humans and chimps more recently. The DNA base sequence of humans and chimps is 94% the same, but human and mouse DNA is only 85% the same

Question 6

Explain how molecular evidence supports the theory of evolution. 

Answer 6

-scientist compare the sequence of amino acids in proteins and compare antibodies
Organisms that diverged away from each other more recently have more similar molecules, as less time has passed for changes in proteins and other molecules to occur

Question 7

What are pesticides?

Answer 7

Chemicals that kill pests (e.g insects that damage crops) 

Question 8

Explain how the evolution of pesticide resistance can be explained by natural selection

Answer 8

• there is variation in a population of insects. Genetic mutations create alleles that make some insects naturally resistant to a pesticide
• if the population of insects is exposed to that pesticide only the individuals with resistance will survive to reproduce
• the alleles which cause the pesticide resistance will be passed on to the next generation and so the population will evolve, meaning more individuals will carry the allele than in previous generations

Question 9

Explain the implications for humans that the evolution of pesticide resistance can cause

Answer 9

-crop infestations of pesticide resistant insects are harder to control – if some insects are resistant to lots of different pesticides it takes farmers a while to figure out which of the pesticides will kill the insect and then by that time all the crops could be destroyed

-if disease carrying insects become pesticide resistance the spread of disease could increase


Question 10

Explain the implications that the evolution of drug resistance can cause to humans

Answer 10

• infections caused by drug resistant microorganisms are harder to treat- it can take doctors a while to figure out which drug will get rid of the infection and then that time the patient could become very ill or die
• that could be a point where a pathogen has become resistant to all the drugs we currently use against it. To prevent this new drugs need to be developed which takes time and costs a lot of money

Question 11

Explain the acronym used to explain the process of natural selection

Answer 11

M = mutation
A = adaptation
S = selection pressures
S = survive
R = reproduce
C = change in allele frequency
A = allele frequency increases