Food Webs and Energy TransferAQA GCSE Biology: Flashcards

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What are producers, and what do they do?

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What are producers, and what do they do?: Photosynthetic organisms (plants and algae) that make glucose/biomass using light energy in photosynthesis; every food chain starts with one.
What eats producers in a food chain?: Primary consumers.
What eats primary consumers?: Secondary consumers.
What term describes an animal that kills and eats another animal?: A predator (the animal it eats is called prey).
What happens to predator and prey numbers in a stable community?: They rise and fall in cycles.
What organisms make up trophic level 1?: Producers (plants and algae).
What organisms make up trophic level 2?: Primary consumers (herbivores).
What is an apex predator?: An organism at the top of a food chain with no predators of its own.
What does a pyramid of biomass show?: The relative amount of biomass present at each trophic level.
Where is trophic level 1 positioned on a pyramid of biomass?: At the bottom.
Approximately what percentage of biomass is transferred from one trophic level to the next?: About 10%.
Give three reasons biomass is lost between trophic levels.: Any three of: not all food is absorbed (egested as faeces), material lost as CO2 and water in respiration, water and urea lost in urine, glucose used up in respiration.
How can the efficiency of biomass transfer be calculated?: As a percentage or fraction of the biomass passed from one trophic level to the next.
Why do food chains rarely have more than four or five trophic levels?: Because so much biomass and energy is lost at each level that there isn't enough left to support further levels of organisms.