Practise 35 exam-style questions on Levels of organisation for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
35 questions
3–5 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
3 marks
Describe how quadrat sampling and transect sampling differ and give one situation where each method is preferable.
Model answer
Quadrat sampling estimates abundance/density by counting within repeated square plots; preferable for patchy or even distributions. Transect sampling records species along a line, showing changes with distance; preferable for environmental gradients (shoreline to inland).
Explanation
Quadrats give quantitative abundance measures where species are distributed across an area. Transects are ideal to detect zonation or gradients where conditions change along a line, e.g., from sea to dunes.
Mark scheme
1 mark
Quadrat: repeated area samples (counts in squares) to estimate abundance/density
1 mark
Transect: sampling along a line to study distribution changes with distance (gradient)
1 mark
Use quadrat for estimating abundance in patchy areas; use transect for studying environmental gradients
Question 2
4 marks
Draw a simple food chain of four organisms typical of a pond ecosystem and state which organism is the producer, a primary consumer and a secondary consumer.
Model answer
Algae ? Daphnia ? Small fish ? Heron. Producer: Algae. Primary consumer: Daphnia. Secondary consumer: Small fish.
Explanation
A food chain shows energy flow from producers (make biomass by photosynthesis) to consumers (herbivores then carnivores). In a pond, algae (producer) are eaten by Daphnia (primary consumer), which are eaten by small fish (secondary consumer), sometimes eaten by a heron (tertiary consumer).
Award 2 marks for correct sequence of four organisms, order matters
1 mark
Identify producer correctly
1 mark
Identify primary and secondary consumers correctly
Can be split as 0.5 + 0.5 if needed
Question 3
4 marks
Explain the concept of biomagnification and give one real-world example.
Model answer
Biomagnification is the increase in concentration of persistent toxins up trophic levels because predators accumulate the toxin from their prey. Example: DDT or mercury concentrations increase in fish and are highest in top predators like tuna or eagles.
Explanation
Small organisms pick up toxins; predators eat many contaminated prey, concentrating toxins in their tissues. This can harm top predators and humans consuming contaminated animals.
Mark scheme
1 mark
Definition: toxins increase in concentration up the food chain / trophic levels
1 mark
Reason: persistent toxins are not metabolised and accumulate in consumers that eat contaminated prey
1 mark
Example: DDT, mercury (in aquatic food chains)
Accept any correct real example
1 mark
Consequence: top predators suffer high toxin effects (eg eggshell thinning, poisoning)
Question 4
5 marks
Describe how you would estimate the population size of a mobile animal (e.g., rabbits) in a field using mark–release–recapture. Include formula and two assumptions of the method.
Model answer
Capture and mark a sample M, release and allow mixing, recapture a sample n and count marked recaptures m. Population N ˜ (M × n) / m. Assumptions: marked animals mix randomly and marking does not affect survival or behaviour; no births/deaths/immigration/emigration between samples.
Explanation
Mark–release–recapture uses proportions of marked animals in a second sample to estimate total population, assuming marked individuals represent the whole population and conditions are stable between samplings.
Mark scheme
1 mark
Capture and mark first sample (M) and release
1 mark
Recapture sample (n) and count marked animals (m)
1 mark
Use formula N = (M × n) / m to estimate population
1 mark
Assumption 1: marked and unmarked mix randomly and marking does not affect behaviour/survival
1 mark
Assumption 2: closed population (no births, deaths, immigration or emigration) between samples
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