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Life Processes and Living Things - Food Chains and Food Webs

Grade 5Cambridge (IGCSE)

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Producers: These are organisms, mainly green plants and algae, that produce their own food using light energy from the SunSun. This process is called photosynthesis.

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Consumers: Organisms that cannot make their own food and must eat other organisms. They are classified as Primary Consumers (herbivoresherbivores), Secondary Consumers (carnivorescarnivores or omnivoresomnivores), and Tertiary Consumers.

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Decomposers: Organisms like bacteriabacteria and fungifungi that break down dead organic matter, recycling nutrients back into the soil.

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Food Chain: A linear sequence that shows how energy is transferred from one organism to another. The arrows always point in the direction of energy flow (from the eaten to the eater).

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Food Web: A complex network of interconnected food chains within an ecosystem, showing that most organisms eat more than one type of food.

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Predator and Prey: A predator is an animal that hunts and eats other animals. The prey is the animal that is being hunted.

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Energy Loss: Only about 10%10\% of the energy from one level of a food chain is passed on to the next level; the rest is used for life processes like movement and growth or lost as heat.

📐Formulae

Carbon Dioxide+Water→Sunlight+ChlorophyllGlucose+OxygenCarbon\ Dioxide + Water \xrightarrow{Sunlight + Chlorophyll} Glucose + Oxygen

Sun→Producer→Primary Consumer→Secondary ConsumerSun \rightarrow Producer \rightarrow Primary\ Consumer \rightarrow Secondary\ Consumer

Energy Transferred≈10%×Energy Consumed\text{Energy Transferred} \approx 10\% \times \text{Energy Consumed}

💡Examples

Problem 1:

Given the food chain: Grass→Grasshopper→Frog→SnakeGrass \rightarrow Grasshopper \rightarrow Frog \rightarrow Snake. Identify the role of each organism and explain what the arrows represent.

Solution:

  1. GrassGrass: Producer
  2. GrasshopperGrasshopper: Primary Consumer (HerbivoreHerbivore)
  3. FrogFrog: Secondary Consumer (CarnivoreCarnivore)
  4. SnakeSnake: Tertiary Consumer (Apex PredatorApex\ Predator) The arrows represent the flow of energy from the GrassGrass to the SnakeSnake.

Explanation:

In science, the arrow in a food chain means 'is eaten by' or 'energy transfers to'. The GrassGrass gets energy from the SunSun, which is then passed through the chain.

Problem 2:

In a pond food web, if the population of Small FishSmall\ Fish (which eat AlgaeAlgae) decreases significantly due to pollution, what might happen to the AlgaeAlgae and the HeronsHerons (which eat the fish)?

Solution:

The population of AlgaeAlgae will likely increase (Algae↑Algae \uparrow) because there are fewer fish to eat them. The population of HeronsHerons will likely decrease (Herons↓Herons \downarrow) because their food source has disappeared.

Explanation:

This demonstrates the interdependence of organisms in a food web. Removing one link affects both the organisms 'below' it (the prey) and 'above' it (the predators).

Problem 3:

If a producer captures 10001000 units of energy from the SunSun, approximately how much energy is available to the secondary consumer in a chain: Plant→Rabbit→FoxPlant \rightarrow Rabbit \rightarrow Fox?

Solution:

1000 units (Plant)→100 units (Rabbit)→10 units (Fox)1000 \text{ units (Plant)} \rightarrow 100 \text{ units (Rabbit)} \rightarrow 10 \text{ units (Fox)} Answer: 1010 units.

Explanation:

Applying the 10%10\% rule: The RabbitRabbit (primary consumer) gets 10%10\% of 10001000 (100100 units). The FoxFox (secondary consumer) gets 10%10\% of 100100 (1010 units).