Ecosystems, Food Chains & Webs
An ecosystem is the interaction of a community of living organisms (biotic factors) with the non-living parts of their environment (abiotic factors). Energy enters ecosystems via photosynthetic producers and flows through trophic levels in food chains, while decomposers recycle carbon, water, and mineral ions.
- Population
- All the organisms of one species living in a habitat.
- Community
- The populations of different species living in a habitat.
- Biotic factor
- A living factor that affects a community (e.g., food availability, predators).
Ecosystems, Food Chains & Webs: Enzyme Collision, Active Site & Rate Curve Lab
Drag the temperature, pH, and substrate sliders to watch how kinetic collisions, active-site binding, and denaturation change the reaction rate in real time.
Key Concepts & Exam Definitions (6)
- Population
- All the organisms of one species living in a habitat.
- Community
- The populations of different species living in a habitat.
- Biotic factor
- A living factor that affects a community (e.g., food availability, predators).
- Abiotic factor
- A non-living factor that affects a community (e.g., light intensity, soil pH).
- Trophic level
- A stage in a food chain or food web.
- Biomass
- The mass of living material in an organism or population.
Quick-Fire Flashcards (5)
Click any card to check the answer, then mark it as Known to track your progress.
What do all food chains start with?
What is a primary consumer?
What do the arrows in a food chain represent?
Give two examples of abiotic factors.
What is a predator?
Exam-Style Questions & Mark Schemes (3)
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- Q1
Explain why food chains rarely have more than four or five trophic levels.
Click “Check Mark Scheme” to compare your answer, Energy is lost at each trophic level (e.g., through respiration, movement, faeces). After four or five stages, there is not enough energy left to support another level.
- Q2
Describe how a new predator could affect a community.
Click “Check Mark Scheme” to compare your answer, A new predator could reduce the population of its prey. This might lead to an increase in the prey's food source, and could also create competition with existing predators.
- Q3
What is meant by a stable community?
Click “Check Mark Scheme” to compare your answer, A community where all the species and environmental factors are in balance so that population sizes remain fairly constant.
Common Exam Questions (3)
What is an ecosystem?
An ecosystem consists of all the living organisms (the community) in a given area interacting with each other and with their non-living physical environment.
What is a producer?
A producer is a photosynthetic organism, such as a green plant or alga, that synthesises glucose using light energy from the Sun and forms the first trophic level of every food chain.
What is the difference between biotic and abiotic factors?
Biotic factors are living components of an ecosystem that affect populations, such as predation, competition, food availability, and new pathogens. Abiotic factors are non-living physical conditions, such as light intensity, temperature, moisture levels, and soil pH.
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