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Unit 4: Ecosystems

GRADE 7 – Unit 4: Ecosystems — HIA International - Grade 7 Revision Notes & Topical Questions

5 min read 9 parts Lesson 1 of 5 1 quiz

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Lesson summary

GRADE 7 - Unit 4: Ecosystems — HIA INTERNATIONAL notes: Describe ecosystems and habitats, introduced species, and bioaccumulation and biomagnification.Ecosystem = a network of interactions between living organisms and the non-living things around them.Habitat = the place where an…

  • Not all natural
  • Non-living factors
  • Other links
  • Adaptations
  • Safety and care
  • Pitfall trap

Part 1 of 7Ecosystems and habitats

Ecosystems and habitats
Ecosystem
Ecosystem a network of interactions between living organisms and the non-living things around them.
Habitat
Habitat the place where an organism naturally lives.
Ecology
Ecology the study of ecosystems.
Examples
  • Examples desert, mangrove forest, Arctic sea ice and rice paddy.
Not all natural
  • Not all natural a rice paddy is farmed by people.

Part 2 of 7Interactions in the Sonoran Desert

Non-living factors
  • Non-living factors light, temperature, soil, water and air all affect organisms.
Feeding
  • Feeding producers such as cacti make food and energy passes along the food web.
Other links
  • Other links nesting, pollination, seed spreading and holding soil in place.
Adaptations
  • Adaptations nocturnal habits, burrowing and water storage help survival.

Part 3 of 7Studying a local ecosystem

1
Describe or draw the whole area.
2
Find the habitats within it.
3
Sample organisms using pitfall traps, sweep nets and hand lenses.
4
Record organisms found and visit at different times.
5
Draw a diagram of interactions.
  • Safety and care
    • stay with a partner and release animals where they were found.

Part 4 of 7Pitfall trap and sampling

Pitfall trap
  • Pitfall trap a plastic cup set into the ground with its rim level with the soil.
Catch
  • Catch small animals that crawl over the ground fall in.
Checking
  • Checking traps must be checked regularly.

Part 5 of 7Introduced and invasive species

Native species
  • Native species naturally live in an area.
Introduced species
  • Introduced species brought into a new place by human action.
Invasive species
  • Invasive species spread and harm the ecosystem, for example stoats and rats in New Zealand.
Reasons for success
  • Reasons for success no predators or diseases, fast breeding and competition.
Eradication
  • Eradication very difficult once a species has settled.

Part 6 of 7Persistent chemicals

DDT
  • DDT an insecticide that is persistent and toxic, so it is not broken down by decomposers.
Thin eggshells
  • DDT makes the shells of birds' eggs thin so they break.
Silent Spring
  • Rachel Carson's 1962 book showed how DDT harmed birds.

Part 7 of 7Bioaccumulation and biomagnification

1Bioaccumulation
  • Bioaccumulation build-up of a chemical in an organism over its life.
2Biomagnification
  • Biomagnification concentration increases at each level up a food chain.
3Top consumers
  • Top consumers such as cormorants have the highest concentrations.
4Biodegradable insecticides
  • Biodegradable insecticides break down and do not build up.

Key terms

TermMeaning
EcosystemA network of interactions between organisms and their environment.
HabitatThe place where an organism lives.
Invasive speciesAn introduced species that harms an ecosystem.
Native speciesA species that naturally lives in an area.
BioaccumulationBuild-up of a substance in an organism.
BiomagnificationConcentration rising up a food chain.
PersistentNot broken down.
Pitfall trapA buried cup that catches small animals.

Avoid these mistakes

1
Saying an ecosystem is only a place.
2
Saying all introduced species cause harm — only invasive ones do.
3
Mixing up bioaccumulation and biomagnification.
4
Saying DDT breaks down quickly.
5
Taking pitfall trap animals away from their habitat.

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