AQA GCSE Biology Foundation (8461), Foundation tier · Inheritance, variation and evolution › Variation and evolution
Practise Evolution. 8 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.
Evolution is a change in the inherited characteristics of a population over time through natural selection, which may result in a new species. The classic 4 to 6 mark question asks you to explain how a feature evolved by natural selection, using the details in the question.
Key facts
Evolution = change in the inherited characteristics of a population over time, through natural selection
All species evolved from simple life forms that first developed more than 3 billion years ago
Natural selection: variation → competition → best suited survive and reproduce → pass on alleles → alleles more common over many generations
Variation comes from mutations
New species: populations can no longer interbreed to produce fertile offspring
Notes
What evolution is
Evolution is a change in the inherited characteristics of a population over time through a process of natural selection. It may result in the formation of a new species.
The theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed more than three billion years ago.
How natural selection works
diagram
There is variation in a population, because of mutations. Some variants give phenotypes that are better suited to the environment.
Individuals compete for limited resources such as food, water and mates, and face predators and disease.
Individuals with phenotypes best suited to their environment are more likely to survive and reproduce.
They pass on the alleles for these characteristics to their offspring.
Over many generations, these alleles become more common in the population.
Natural selection: the best-suited individuals survive and breed, so their alleles become more common.
Individuals do not change during their lives to suit the environment. The population changes because some individuals survive and breed more than others.
New species
A species is a group of organisms that can interbreed to produce fertile offspring.
If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring, they have formed two new species.
How to answer each type of question
Define evolution or species
1 to 3 marksGrade 4
Evolution: a change in the inherited characteristics of a population over time, through natural selection.
Species: organisms that can interbreed to produce fertile offspring.
Example. (a) What is meant by evolution? (b) Horses and donkeys can breed together to produce mules, but mules are infertile. Explain why horses and donkeys are different species. [3 marks]
Show the model answerHide the model answer
(a) A change in the inherited characteristics of a population over time (1) through natural selection (1) (b) They cannot interbreed to produce fertile offspring (1)
Don’t lose marks
Saying an organism 'adapted because it needed to' or 'decided to change'. Mutations happen randomly, and selection acts on the variation that already exists.
Saying the organism survives but forgetting that it reproduces and passes on its alleles.
Saying that characteristics developed during an organism's life are passed on. Only inherited (genetic) characteristics are passed on.
Writing 'survival of the fittest' without explaining what makes an individual better suited to that environment.
Using 'species' when you mean 'population'.
More tips
Memory tricks
Natural selection in five words: variation, competition, survival, reproduction, inheritance ('Very Clever Squirrels Reproduce Intelligently').
Each step in the chain is usually a mark: don't skip 'reproduce' or 'pass on alleles'.
Populations evolve; individuals don't.
Exam technique
Use the context: name the predator, food or climate from the question in your answer.
Write 'more likely to survive', not 'will survive'.
Finish with 'over many generations' and 'the allele becomes more common in the population'.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Define evolutionA change in the inherited characteristics of a population over time through natural selection.
Grade 4
State when simple life first developedAll species evolved from simple life forms that first developed more than three billion years ago.
Grade 5
List the steps of natural selectionVariation, competition, the best suited survive and reproduce, alleles passed on, alleles become more common.
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. Individuals with the characteristics best suited to their environment are more likely to .......... and ..........
survive and reproduce (breed)
A population of rabbits lives in a cold area. The sentences below describe how natural selection could make thick fur more common in the population, but they are in the wrong order. A Rabbits with thicker fur are more likely to survive a cold winter. B There is variation in fur thickness in the population. C The allele for thick fur becomes more common over many generations. D The surviving rabbits breed and pass on the allele for thick fur. Write the letters in the correct order.
B, A, D, C
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy6 marks
The theory of evolution by natural selection explains how living things have changed over time.
(a) What is evolution? Tick (✓) one box.[1]
A change in the inherited characteristics of a population over time through natural selection
The changes that happen to an individual during its lifetime
The process by which a species becomes extinct
The production of offspring from one parent
(b) All species of living things have evolved from simple life forms. When did these simple life forms first develop? Tick (✓) one box.[1]
More than three thousand years ago
More than three million years ago
More than three billion years ago
More than three trillion years ago
(c) Complete the sentence. Individuals with the characteristics best suited to their environment are more likely to .......... and ..........[2]
(d) Two populations of one species can become so different in phenotype that they form two new species. How can you tell when this has happened?[2]
Show the answer and mark scheme
(a)Answer: A change in the inherited characteristics of a population over time through natural selection
(b)Answer: More than three billion years ago
(c)Answer: survive and reproduce (breed)
survive
reproduce / breed
(d)Answer: They can no longer interbreed to produce fertile offspring
they can no longer interbreed
to produce fertile offspring
Question 2Medium6 marks
A population of frogs was split into two when a river changed its course. After many thousands of years, scientists put frogs from the two populations together.
(a) Describe how the scientists could find out whether the two populations had become different species.[2]
(b) Horses and donkeys can mate and produce offspring called mules. Mules are infertile. Are horses and donkeys the same species? Explain your answer.[2]
(c) Suggest how natural selection could have made the two populations of frogs different from each other.[2]
Show the answer and mark scheme
(a)Answer: See whether frogs from the two populations can interbreed, and whether any offspring are fertile
see whether they can interbreed / mate and produce offspring
see whether the offspring are fertile / can themselves reproduce
(b)Answer: No: although they can interbreed, their offspring are not fertile
no / different species
because their offspring (mules) are not fertile
(c)Answer: Conditions on each side of the river were different, so different variants were best suited and survived to reproduce in each population
the environment / conditions were different on each side of the river
so different variants survived and reproduced in each population (and the populations could not interbreed)