IB Diploma · Biology C4.2
IB Biology C4.2: Tran. of En. & Mat. — Practice Questions & Answers
IB Biology C4.2 study notes: trophic levels, energy flow and the 10 percent rule, food chains and webs, and nutrient cycling in ecosystems.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
What are ecosystems composed of?
- Multiple communities interacting with their abiotic environment.
- Only living organisms.
- Only non-living components.
- Individual organisms.
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WhyEcosystems consist of interacting communities together with their non-living, abiotic environment.
2
Multiple choice
What does matter refer to in the context of ecosystems?
- Nutrients, gases, and other substances essential for living organisms.
- Energy used for biological processes.
- Heat dissipated from organisms.
- Sunlight.
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WhyMatter refers to the nutrients, gases and substances that organisms require and recycle.
3
Multiple choice
What does energy refer to in ecosystems?
- The ability to perform work or cause change.
- Nutrients and gases.
- Dead organic matter.
- Inorganic compounds.
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WhyEnergy is the capacity to do work or drive change, flowing one way through an ecosystem.
4
Multiple choice
What is the primary source of energy for most ecosystems?
- Sunlight.
- Inorganic compounds.
- Heat from the Earth.
- Chemical energy from minerals.
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WhySunlight is the primary energy source, captured by producers through photosynthesis.
5
Multiple choice
What is the role of chemosynthetic organisms?
- Extracting energy from inorganic compounds.
- Converting sunlight into chemical energy.
- Decomposing dead organic matter.
- Consuming other organisms.
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WhyChemosynthetic organisms obtain energy by oxidising inorganic compounds rather than using light.
6
Multiple choice
What do food chains illustrate?
- The transfer of energy through a sequence of organisms.
- The cycling of nutrients.
- The flow of water.
- The distribution of minerals.
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WhyFood chains show the one-way transfer of energy from producers through successive consumers.
7
Multiple choice
What do food webs represent?
- Interconnected food chains.
- Single food chains.
- Decomposers and detritivores.
- Autotrophs and heterotrophs.
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WhyFood webs depict multiple interconnected food chains showing complex feeding relationships.
8
Multiple choice
What is the role of decomposers in ecosystems?
- Breaking down dead organisms and organic matter.
- Producing organic compounds.
- Consuming living organisms.
- Converting sunlight into energy.
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WhyDecomposers break down dead organisms and waste, recycling nutrients back into the ecosystem.
9
Multiple choice
What are saprotrophs?
- Decomposers that obtain organic nutrients from dead organisms through external digestion.
- Organisms that consume living plants.
- Organisms that consume living animals.
- Organisms that produce their own food.
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WhySaprotrophs feed on dead matter by secreting enzymes and absorbing the products (external digestion).
10
Multiple choice
What are detritivores?
- Decomposers that obtain nutrients from detritus by internal digestion.
- Organisms that consume living plants.
- Organisms that consume living animals.
- Organisms that produce their own food.
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WhyDetritivores ingest detritus and digest it internally to obtain their nutrients.
Key terms in Tran. of En. & Mat.
Trophic level: The position an organism occupies in a food chain, defined by how it obtains energy.
Producer (autotroph): An organism that synthesises its own organic molecules from inorganic sources, usually by photosynthesis.
Consumer (heterotroph): An organism that obtains energy and carbon by feeding on other organisms.
Food web: An interconnected set of food chains showing the feeding relationships in a community.
Decomposer: An organism, such as a bacterium or fungus, that feeds on dead organic matter and releases nutrients back to the environment.
Energy flow: The one-way movement of energy through an ecosystem, entering as light and leaving as heat; energy is not recycled.
Ten percent rule: The generalisation that only about 10% of the energy at one trophic level is passed on to the next.
Carbon sink: A long-term store of carbon, such as fossil fuels, limestone or peat, that holds carbon out of the atmosphere.
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