Communities and Ecosystems

1. Communities and Ecosystems Topic 5.1

2. Assessment Statements • 5.1.1 Define species, habitat, population, community, ecosystem and ecology. • 5.1.2 Distinguish between autotroph and heterotroph. • 5.1.3 Distinguish between consumers, detritivores and saprotrophs. • 5.1.4 Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms). • 5.1.5 Describe what is meant by a food web. • 5.1.6 Define trophic level. • 5.1.7 Deduce the trophic level of organisms in a food chain and a food web. • 5.1.8 Construct a food web containing up to 10 organisms, using appropriate information. • 5.1.9 State that light is the initial energy source for almost all communities. • 5.1.10 Explain the energy flow in a food chain. • 5.1.11 State that energy transformations are never 100% efficient. • 5.1.12 Explain reasons for the shape of pyramids of energy. • 5.1.13 Explain that energy enters and leaves ecosystems, but nutrients must be recycled. • 5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients.

3. Species – a group of organisms that can interbreed and produce fertile offspring

4. Habitat – the environment in which a species normally lives or the location of a living organism

5. Population – a group of organisms of the same species which live in the same area at the same time

6. Community – a group of populations living and interacting with each other in an area

7. Ecosystem – a community and its abiotic environment

8. Ecology – the study of relationships between living organisms and between organisms and their environment

9. What is meant by ‘environment’? • Hydrosphere • Atmosphere • Lithosphere • Biosphere • What is the difference between abiotic components of the environment and the biotic components?

10. Distinguish between autotroph and heterotroph. • Autotrophsare capable of making their own organic molecules from inorganic molecules as a food source (a.k.a. producers); Examples? • Heterotrophs – cannot make their own food and must obtain organic molecules from other organisms (a.k.a. consumers); Examples?

11. Distinguish between consumers, detritivores and saprotrophs. • Detritivores – eat non-living organic matter; Examples? • Saprophytes – live on or in non-living organic matter secreting digestive enzymes into it and absorbing the products of digestion; Examples?

13. Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms). • A sequence showing the feeding relationships and energy flow between species • The direction of each arrow shows which way the energy flows • grass→grasshoppers→toad→snake→hawk

14. Describe what is meant by a food web. • An interconnecting series of food chains

15. An organism’s position in a food chain Classifies organisms’ feeding relationships with each other within the same ecosystem T5 – quaternary consumer T4 – tertiary consumer T3 – secondary consumer T2 – primary consumer T1 – producer Which group would you expect to have the most number of organisms? Define trophic level.

17. Find the producer Determine what eats the producer (primary consumer) Determine what eats the primary consumer (secondary consumer) Etc. Deduce the trophic level of organisms from the following list: Juvenile trout Kingfisher Algae Mayfly larva Deduce the trophic level of organisms in a food chain and a food web.

18. Construct a food web containing up to 10 organisms, using appropriate information. • Put producer at bottom of diagram (algae or plants) • Above producers include all the primary consumers • Continue until you get to the top predator

19. State that light is the initial energy source for almost all communities. • Example: • Milk gets its energy from the cow which produced it • The cow got its energy from grass, which got its energy from sunlight • Name a food chain that can start without sunlight.

20. Explain the energy flow in a food chain. • Light energy absorbed by producers • Chemical energy obtained by photosynthesis is stored as carbohydrates • Energy is transferred from one organism to the next when carbohydrates, lipids, or proteins are digested • During cellular respiration energy is lost as heat to the environment

21. State that energy transformations are never 100% efficient. • Only chemical energy can be used by the next trophic level • Only a small amount of the energy which an organism absorbs is converted into chemical energy • No organism can use 100% of the energy present in the organic molecules of the food it eats • Only 10-20% of the energy is used from the previous step in the food chain

22. Reasons for non-absorption • Not all of the organism is consumed • Not all the food can be absorbed • Some organisms die before being eaten • Considerable heat loss due to cellular respiration at all levels

23. Explain reasons for the shape of pyramids of energy. • Energy pyramid used to show how much and how fast energy flows from on trophic level to the next in a community • Units used are energy per unit area per unit time (kJm-2y-1) • Because energy is lost each level is always smaller than the one before it • Organisms cannot create energy

24. Explain that energy enters and leaves ecosystems, but nutrients must be recycled. • Once energy has been radiated into the environment, it cannot be collected back and used as an energy source by the ecosystem • Energy enters as light, exits as heat • Nutrients, however, must be recycled • Minerals and compounds are used to build cells which are locked within the organism until eaten or decomposed

25. State that saprotrophic bacteria and fungi (decomposers) recycle nutrients. • Decomposers unlock nutrients stored in cells of plants and animals through decay • Digestive enzymes convert the organic matter into a more usable form for themselves and for other organisms