AQA GCSE Combined Science Foundation (8464), Foundation tier · Biology › Inheritance, variation and evolution › The development of understanding of genetics and evolution
Practise Evidence for evolution. 6 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Why the theory of evolution by natural selection is now widely accepted: we know that characteristics are passed on in genes, and there is evidence from the fossil record and from bacteria becoming resistant to antibiotics. Usually short 'give the evidence' or 'explain how this supports evolution' questions.
Key facts
Evolution by natural selection is now widely accepted
Evidence: characteristics are passed on to offspring in genes
Evidence: the fossil record shows how organisms changed over time
Evidence: the evolution of antibiotic resistance in bacteria
Bacteria reproduce quickly, so evolution can be seen in years, not millions of years
Notes
Why the theory is accepted now
The theory of evolution by natural selection is now widely accepted.
Evidence for Darwin's theory is now available, because it has been shown that characteristics are passed on to offspring in genes. This explains how variation is inherited, which was unknown when Darwin published.
There is further evidence in the fossil record and from how resistance to antibiotics evolves in bacteria.
Evidence from fossils
diagram
Fossils are the remains of organisms from millions of years ago, found in rocks.
Comparing fossils from rocks of different ages shows how much or how little organisms have changed as life developed on Earth.
Older rocks generally contain simpler organisms, and more complex organisms appear in younger rocks.
Some groups have a series of fossils showing gradual changes over millions of years, such as changes in the size of the body or the shape of the limbs.
Fossils in rock layers show how organisms have changed over time.
Evidence from resistant bacteria
Bacteria reproduce very quickly, so natural selection can be seen happening over a short time.
A mutation can make a bacterium resistant to an antibiotic. When the antibiotic is used, non-resistant bacteria are killed, but resistant bacteria survive and reproduce.
The population of the resistant strain rises. This is evolution by natural selection that we can actually observe.
How to answer each type of question
Give evidence for evolution
1 to 2 marksGrade 4
Name the fossil record and antibiotic resistance in bacteria.
You can also say that characteristics have been shown to be passed on in genes.
Example. Give two types of evidence that support the theory of evolution by natural selection. [2 marks]
Show the model answerHide the model answer
The fossil record (1). The evolution of antibiotic resistance in bacteria (1). Also allow: characteristics are passed on to offspring in genes.
Don’t lose marks
Saying bacteria become resistant because they 'get used to' the antibiotic. Resistance comes from a random mutation, which is then selected.
Saying the antibiotic causes the mutation. The mutation happens by chance; the antibiotic kills the bacteria that are not resistant.
Saying fossils show every stage of evolution. The fossil record is incomplete.
More tips
Memory tricks
Evidence for evolution: bones, bugs and genes (fossils, resistant bacteria, inheritance in genes).
Bacteria are evolution you can watch: many generations in a few days.
Exam technique
In 'explain' questions, go through natural selection step by step: mutation → survive → reproduce → resistant population rises.
Say why bacteria are useful evidence: they reproduce quickly, so change can be seen in a short time.
Describe the theory as 'widely accepted' or 'supported by evidence', not 'proved'.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
State that evolution is widely acceptedThe theory of evolution by natural selection is now widely accepted.
Grade 4
Name two types of evidence for evolutionThe fossil record and the evolution of antibiotic resistance in bacteria.
Grade 5
Explain why genes support Darwin's theoryIt has been shown that characteristics are passed on to offspring in genes, which explains how they are inherited.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Complete the sentence. We now know that characteristics are passed on from parents to offspring in ..................... .
genes
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
The theory of evolution by natural selection is now widely accepted.
(a) Which two of the following provide evidence for evolution by natural selection? Tick (✓) two boxes.[2]
Antibiotic resistance in bacteria
The fossil record
The inheritance of characteristics gained during an organism’s life
The naming of organisms using the binomial system
The use of a fungus to make mycoprotein
(b) Complete the sentence. We now know that characteristics are passed on from parents to offspring in ..................... .[1]
(c) Bacteria can evolve rapidly. Give the reason why.[1]
Show the answer and mark scheme
(a)Answer: Antibiotic resistance in bacteria; The fossil record
(b)Answer: genes
genes
(c)
they reproduce at a fast rate / very quickly (so there are many generations in a short time)
Question 2Medium6 marks
An antibiotic was first used widely in 1995. {fig} shows the percentage of samples of one species of bacterium that were resistant to this antibiotic between 2000 and 2020.
[object Object]
(a) Describe the trend shown in {fig}.[2]
(b) Explain why antibiotic resistance in bacteria provides good evidence for evolution by natural selection.[3]
(c) The fossil record is another source of evidence for evolution. Give one reason why the fossil record is incomplete.[1]
Show the answer and mark scheme
(a)
the percentage of resistant bacteria increased
use of data, e.g. from 2% in 2000 to 48% in 2020
(b)
bacteria reproduce very quickly / have a short generation time
(so) changes in a population can be observed within a few years
mutations produce (new) resistant strains
resistant bacteria survive the antibiotic and reproduce, while non-resistant bacteria are killed
(so) the proportion of resistant bacteria increases, showing natural selection happening
(c)
many organisms decayed completely / were soft-bodied, so did not form fossils
many fossils have been destroyed by geological activity