Food Chains And Food Webs
Visão Geral
Every meal is a transfer of energy. Trace your dinner backwards and you always arrive at the same place: a green plant capturing sunlight. Food chains and food webs are the maps biologists use to follow that energy as it passes from one living thing to the next, and they reveal something surprising, that most of the energy is lost at every step.
In this lesson you will name the feeding roles, build and read food chains and webs, draw the three kinds of ecological pyramid, and explain why energy leaks away so fast that food chains almost never have more than five links. You will also see why eating plants directly feeds far more people than feeding those plants to animals first.
Objetivos
- Describe a food chain as showing the transfer of energy from one organism to the next, beginning with a producer
- Construct and interpret simple food chains
- Describe a food web as a network of interconnected food chains and interpret food webs
- Describe a producer as an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis
- Describe a consumer as an organism that gets its energy by feeding on other organisms
- State that consumers may be classed as primary, secondary, tertiary and quaternary according to their position in a food chain
- Describe a herbivore as an animal that gets its energy by eating plants
- Describe a carnivore as an animal that gets its energy by eating other animals
- Describe a decomposer as an organism that gets its energy from dead or waste organic material
- Use food chains and food webs to describe the impact humans have through overharvesting of food species and through introducing foreign species to a habitat
- Draw, describe and interpret pyramids of numbers and pyramids of biomass
- Discuss the advantages of using a pyramid of biomass rather than a pyramid of numbers to represent a food chain
- Describe a trophic level as the position of an organism in a food chain, food web or ecological pyramid
- Identify the following as the trophic levels in food webs, food chains and ecological pyramids: producers, primary consumers, secondary consumers, tertiary consumers and quaternary consumers
- [Supplement] Draw, describe and interpret pyramids of energy
- [Supplement] Discuss the advantages of using a pyramid of energy rather than pyramids of numbers or biomass to represent a food chain
- [Supplement] Explain why the transfer of energy from one trophic level to another is often not efficient
- [Supplement] Explain, in terms of energy loss, why food chains usually have fewer than five trophic levels
- [Supplement] Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants
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- In a food chain the arrows show the direction of: A. movement of animals B. transfer of energy C. loss of water D. the breeding season Answer: B
- Which organism always begins a food chain? A. a herbivore B. a carnivore C. a producer D. a decomposer Answer: C
- In the chain grass -> rabbit -> fox, the rabbit is the: A. producer B. primary consumer C. secondary consumer D. decomposer Answer: B
- On average, the percentage of energy passed from one trophic level to the next is about: A. 1% B. 10% C. 50% D. 90% Answer: B
- Food chains rarely have more than five trophic levels because: A. animals stop breeding B. too much energy is lost at each level C. producers run out of sunlight D. decomposers eat the top predators Answer: B
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