AQA GCSE Biology Foundation (8461), Foundation tier · Ecology › Adaptations, interdependence and competition
Practise Abiotic factors. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Abiotic factors are the non-living conditions that affect a community, such as light intensity, temperature and soil pH. Expect recall of the list, then 2 to 4 mark questions asking you to explain how a change in one factor affects organisms, often using data from a table or graph.
Key facts
Abiotic = non-living
Light intensity → rate of photosynthesis → plant growth
Temperature → rate of enzyme-controlled reactions
Moisture: water for photosynthesis and to keep plant cells turgid
Soil pH and mineral content → which mineral ions plants can get → growth
Wind: increases water loss and can damage plants
Carbon dioxide level: can limit photosynthesis (plants)
Oxygen level in water: needed for aerobic respiration (aquatic animals); warm water holds less
Notes
The abiotic factors to learn
Abiotic factors are non-living factors that can affect a community.
They are: light intensity; temperature; moisture levels; soil pH and mineral content; wind intensity and direction; carbon dioxide levels for plants; oxygen levels for aquatic animals.
How each factor affects organisms
diagram
Light intensity: plants need light for photosynthesis. In shade, plants photosynthesise more slowly and grow less.
Temperature: affects the rate of enzyme-controlled reactions such as photosynthesis and respiration. Each species survives best within a certain range.
Moisture: plants need water for photosynthesis and to keep their cells firm (turgid); animals need water too. Waterlogged soil has little oxygen for roots.
Soil pH: affects which mineral ions plants can absorb, and the enzymes in plant cells work best at a particular pH.
Mineral content: plants need mineral ions for healthy growth, e.g. nitrate ions to make amino acids for proteins.
Wind: strong wind increases water loss from leaves and can damage plants. Trees in very windy places are often short and bent away from the main wind direction.
Carbon dioxide: plants need it for photosynthesis, so a low level can limit their growth.
Oxygen in water: aquatic animals need it for aerobic respiration. Warm water holds less dissolved oxygen than cold water, so some species cannot survive in warm water.
As water warms, it holds less dissolved oxygen, so animals that need a lot of oxygen cannot live there.
Effects on the whole community
A change in an abiotic factor often affects plants first. Animals that eat those plants, or shelter in them, are then affected.
Example: when the tree canopy of a wood comes into leaf, less light reaches the ground, so fewer small plants grow and there is less food for the insects that eat them.
In a field study, measure the abiotic factor (e.g. with a light meter, thermometer or pH probe) at the same places where you count the organisms.
How to answer each type of question
Recall: name abiotic factors
1 to 2 marksGrade 3
Choose from the list: light intensity, temperature, moisture, soil pH, soil mineral content, wind, carbon dioxide, oxygen.
Do not give biotic factors such as food, predators or disease.
Pick factors that fit the habitat in the question.
Example. Give two abiotic factors that could affect the plants growing on a sand dune.
Show the model answerHide the model answer
Any two from: wind intensity or direction (1); moisture level / amount of water (1); temperature (1); light intensity (1); soil mineral content (1); soil pH (1)
Describe the relationship shown by data
2 marksGrade 5
State the overall trend: as X increases, Y increases or decreases.
Look for a change in the pattern, such as levelling off.
Quote values from the data to support your description.
Example. A student placed quadrats at 2 m intervals along a line from the edge of a wood towards its middle. The table shows the results.
Distance from edge of wood in m
Light intensity in arbitrary units
Mean number of dandelions per quadrat
0
90
12
2
70
9
4
45
4
6
30
1
8
28
1
Describe how the number of dandelions changes with light intensity. (2 marks)Show the model answerHide the model answer
As light intensity decreases, the number of dandelions decreases (1). For example, there were 12 dandelions per quadrat at 90 units but only 1 per quadrat at 30 units or below (1).
Don’t lose marks
Giving biotic factors (food, predators, disease) when asked for abiotic ones.
Writing 'the weather' or 'the environment'. Name a specific factor such as temperature or light intensity.
Describing a trend without explaining it when the question says 'explain'. Link the factor to a life process.
Writing 'light affects photosynthesis' without saying how: less light means a slower rate, so less glucose for growth.
More tips
Memory tricks
Abiotic = 'a' (not) + 'bio' (life): not living.
Quick test: if the factor is an organism, or is caused by one (food, predators, pathogens, competitors), it is biotic. Physical and chemical conditions are abiotic.
Link each factor to a process: light → photosynthesis; temperature → enzymes; oxygen → respiration; water → photosynthesis and turgor.
Warm water holds less oxygen: think of a fizzy drink going flat faster when it is warm.
Exam technique
When data is given, quote values with units to support your description.
In 'explain' questions, use a chain: factor changes → process changes → growth or survival changes → population changes.
Remember that a correlation does not prove cause: other factors may change at the same time (light and temperature often change together).
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Define an abiotic factorA non-living factor in the environment that can affect a community.
Grade 4
List the abiotic factors in the specificationLight intensity, temperature, moisture level, soil pH and mineral content, wind intensity and direction, carbon dioxide (plants) and oxygen (aquatic animals).
Grade 5
Describe a trend in abiotic dataState how one variable changes as the other changes, quoting values from the table or graph.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
The oxygen level in water is an abiotic factor for aquatic animals. Why do aquatic animals need oxygen?
For aerobic respiration
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Abiotic factors are non-living factors that can affect a community.
(a) Which two of the following are abiotic factors? Tick (✓) two boxes.[2]
Availability of food
Light intensity
New pathogens
Soil pH
Predators
(b) Give two other abiotic factors that can affect a community.[2]
(c) The oxygen level in water is an abiotic factor for aquatic animals. Why do aquatic animals need oxygen?[1]
Show the answer and mark scheme
(a)Answer: Light intensity; Soil pH
(b)
temperature
moisture level / amount of water
soil mineral content
wind intensity / direction
carbon dioxide level (for plants)
oxygen level (for aquatic animals)
(c)Answer: For aerobic respiration
for (aerobic) respiration
Question 2Medium6 marks
A factory releases warm water into a river. Scientists measured the water temperature and the concentration of dissolved oxygen at different distances downstream from the factory. They also counted the mayfly nymphs in samples taken from the river bed. {table} shows the results.
[object Object]
(a) Describe the relationship between the concentration of dissolved oxygen and the number of mayfly nymphs.[1]
(b) Mayfly nymphs need water with a high concentration of dissolved oxygen. Use {table} to explain the distribution of mayfly nymphs in the river.[3]
(c) The scientists took several samples at each distance and calculated a mean. Give one reason why.[1]
(d) Suggest one other abiotic factor the scientists should measure before concluding that oxygen concentration affects the distribution of mayfly nymphs.[1]
Show the answer and mark scheme
(a)
as the concentration of dissolved oxygen increases, the number of mayfly nymphs increases / positive correlation
(b)
the water is warmest near the factory
warmer water contains less dissolved oxygen
near the factory, nymphs cannot get enough oxygen for (aerobic) respiration, so few survive
further downstream the water is cooler and contains more oxygen, so more nymphs survive
(c)
to reduce the effect of an unusual sample / anomaly / so the result is more representative / accurate
(d)
pH
speed of water flow
concentration of pollutants / chemicals from the factory