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Unit 7: Microorganisms and food webs

Food chains and webs — HIA International - Grade 6 Revision Notes & Topical Questions

5 min read 10 parts Lesson 3 of 6 3 quizzes

📚 HIA International - Grade 6 Hub / Topical Revision
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Lesson summary

7.2 Food chains and webs — HIA INTERNATIONAL notes: Construct food chains and food webs using arrows for energy transfer and the correct terms for each organism.Source — the energy in food begins in the Sun and reaches the Earth in sunlight.Plants — use energy from sunlight to ma…

  • Primary, secondary and tertiary consumers
  • Decomposers
  • Why needed
  • Tracing energy
  • African plains example
  • Energy loss

Section 1 of 10Energy in food chains

Source
  • Source the energy in food begins in the Sun and reaches the Earth in sunlight.
Plants
  • Plants use energy from sunlight to make their own food and store some in roots, stems, fruits and leaves.
Energy transfer
Energy transfer energy passing from one organism to the next when it is eaten.
Food chain
Food chain a diagram that shows how energy is passed from one organism to another through feeding.
Arrows
  • Arrows point from the organism that is eaten to the organism that eats it, showing the direction of energy transfer.

Section 2 of 10Producers and consumers

1Producer
  • Producer the first organism in a food chain;
    • a green plant or alga that uses energy from the Sun to make food.
2Consumer
  • Consumer every other organism in the chain; animals must eat ready-made food.
3Primary, secondary and tertiary consumers
  • Primary, secondary and tertiary consumers eat producers, primary consumers and secondary consumers in turn.
4Decomposers
  • Decomposers bacteria and fungi that break down dead organisms and waste and recycle nutrients into the soil.

Section 3 of 10Types of consumer

TermMeaning
HerbivoreA consumer that eats only plants
CarnivoreA consumer that eats other animals
OmnivoreA consumer that eats both plants and animals
PredatorAn animal that catches, kills and eats other animals
PreyAn animal that is caught and eaten by a predator
Top predatorA predator with no natural predators in that food web

Section 4 of 10Food webs

Food web
Food web a set of linked food chains showing the feeding relationships in a habitat.
Why needed
  • Why needed most animals eat, and are eaten by, more than one kind of organism.
Tracing energy
  • Tracing energy follow the arrows from a producer to a consumer to see each chain.
African plains example
  • African plains example two chains are acacia tree to springbok to cheetah, and grass to termite to aardvark to leopard.
  • Together with other animals such as zebra and hyena they form a food web.

Section 5 of 10Building a food web

1
List the organisms in the habitat.
2
Identify the producers and place them at the bottom.
3
Place herbivores above the plants they eat and draw arrows from the plant to the herbivore.
4
Add carnivores above their prey with arrows pointing towards the carnivore.
5
Check that every arrow points in the direction of energy flow.

Section 6 of 10Energy and numbers along a chain

Energy loss
  • Energy loss energy is lost at each step as heat from respiration, movement and waste.
Chain length
  • Chain length food chains are therefore usually short, rarely more than 4 or 5 links.
Numbers
  • Numbers there are usually most producers, then fewer consumers at each higher level.

Section 7 of 10Changes in a food web

Linked populations
  • Linked populations if one population changes, others are affected.
Predator removed
  • Predator removed its prey may increase and then eat more of their own food, which then decreases.
Toxic chemicals
  • Toxic chemicals some pesticides build up along a food chain and harm top predators most.

Section 8 of 10Food webs as models

Useful
  • Useful they show how plants and animals in a place depend on each other for food.
Limitations
  • Limitations they are never totally complete, because real feeding relationships are more complicated than those drawn.

Section 9 of 10Key terms

TermMeaning
ProducerAn organism that makes its own food using energy from sunlight.
ConsumerAn organism that eats other organisms for energy.
HerbivoreA consumer that eats only plants.
CarnivoreA consumer that eats only animals.
PredatorAn animal that hunts, kills and eats other animals.
PreyAn animal eaten by a predator.
Food chainA diagram showing energy passing from organism to organism.
Food webLinked food chains in one habitat.

Section 10 of 10Exam technique

1
Drawing arrows from the eater to the food — arrows show energy moving from the food to the eater.
2
Starting a chain with an animal — every food chain starts with a producer.
3
Saying herbivores are predators — predators kill and eat animals, herbivores eat plants.
4
Forgetting that removing one organism affects the others — populations in a web are linked.

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