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Trophic levels in an ecosystem (biology only)
Students learn how biomass and energy move through food chains, why biomass is lost between trophic levels, and how to construct and interpret biomass pyramids.
24
Objectives
10
Flashcards
10
Questions
90 min
Study time
AqaGcseBiologyEcology
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Syllabus checklist
What you need to know
24 objective pages available
Trophic levels8 objectives
- Describe trophic levels as positions of organisms within a food chain or ecosystem (biology only).
- Identify producers as trophic level 1, including plants and algae that make their own food.
- Identify herbivores as primary consumers at trophic level 2.
- Identify carnivores that eat herbivores as secondary consumers at trophic level 3.
- Identify carnivores that eat other carnivores as tertiary consumers at trophic level 4.
- Define apex predators as carnivores with no predators.
- Describe decomposers as organisms that break down dead plant and animal matter.
- Explain that decomposers secrete enzymes into the environment and absorb small soluble food molecules.
Pyramids of biomass5 objectives
- Describe pyramids of biomass as diagrams showing relative biomass at each trophic level.
- Explain why trophic level 1 is shown at the bottom of a biomass pyramid.
- Construct accurate pyramids of biomass from appropriate data.
- Use data and scales correctly when drawing pyramids of biomass.
- Interpret biomass pyramids in relation to food chains and trophic levels.
Transfer of biomass11 objectives
- Describe how biomass is transferred from one trophic level to the next.
- Recall that producers transfer only a small proportion of incident light energy into biomass by photosynthesis.
- Recall that only about one tenth of biomass is transferred to the next trophic level.
- Explain how biomass is lost because not all ingested material is absorbed.
- Explain how biomass is lost in faeces through egestion.
- Explain how absorbed material is lost as waste, including carbon dioxide and water from respiration.
- Explain how absorbed material can be lost as urea in urine.
- Explain why large amounts of glucose used in respiration reduce biomass transfer.
- Calculate the efficiency of biomass transfer between trophic levels using percentages.
- Calculate the efficiency of biomass transfer between trophic levels using fractions of mass.
- Explain how biomass transfer efficiency affects the number of organisms at each trophic level.
Key terms
food chaintrophic levelproducerprimary consumersecondary consumertertiary consumerapex predatorDefinedecomposerDescribeenzymebiomass
Exam tips
- Trophic levels exam tip 1: Use precise biological vocabulary when you explain how to describe trophic levels as positions of organisms within a food chain or ecosystem (biology only)..
- Trophic levels exam tip 1: Use precise biological vocabulary when you explain how to identify producers as trophic level 1, including plants and algae that make their own food..
Common mistakes
- Trophic levels common mistake 1: Answer by clearly explaining how to describe trophic levels as positions of organisms within a food chain or ecosystem (biology only)..
- Trophic levels common mistake 1: Answer by clearly explaining how to identify producers as trophic level 1, including plants and algae that make their own food..
Practice preview
- Which option best matches the approved learning objective for Trophic levels (1)?
- Question 2: Which option best matches Trophic levels for this AQA GCSE Biology objective: Describe trophic levels as positions of organisms within a food chain or ecosystem (biology only)?
- Question 3: Which option best matches Trophic levels for this AQA GCSE Biology objective: Describe trophic levels as positions of organisms within a food chain or ecosystem (biology only)?
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