Food chains and food webs

1. Food chains and food webs WAL: About how energy moves through food chains and webs. Some • How is energy lost from the ecosystem? Most • What is meant by the terms: trophic level, food chain, food web, producer, consumer and decomposer? All • How does energy enter an ecosystem and become transferred between organisms?

2. Today we are covering from the specification: Pages 61-63 of the textbook.

3. How does energy enter an ecosystem and become transferred between organisms? • The ultimate source of energy for organisms found in an ecosystem is sunlight. • This is converted to chemical energy by photosynthesising organisms and passed as food between other organisms.

4. Radiation from the Sun (solar or light energy) is the main source of energy for all living things. The suns light energy is ‘captured’ and used by green plants and algae during photosynthesis, to make new biomass. 6CO2 + 6H20 C6H12O6 + 6O2 Light energy

5. Key words Producer Primary consumer Secondary consumer Tertiary consumer Quaternary consumer Herbivore Omnivore Carnivore Food chain Food web Trophic level Autotroph Heterotroph Decomposer TASK: try to write a definition for each of these terms.

6. What is a food chain? • Organisms need energy to live • They get this energy by eating other organisms • E.g. A rabbit gets energy from the carrots it eats • A food chain shows how energy is passed through a series of animals • E.g. Carrot  Rabbit  Fox

7. Methods of Obtaining Energy • Organisms may be autotrophs (like plants) or heterotrophs (like animals). • Autotrophs use energy from the sun to produce their own materials for growth etc. • Heterotrophs use organic substances from other organisms for growth etc. http://www.youtube.com/watch?v=O7eQKSf0LmY i.e. autotrophs are producers and heterotrophs are consumers.

8. Draw this diagram: Herbivores Carnivores Omnivores

9. What do they eat? Put these organisms into the correct categories: Grizzly bear Human Caterpillar Crow Fox Cat Grasshopper Pig Frog Slug Sparrowhawk Lion Horse Deer

10. What do they eat? Herbivore Omnivore Carnivore Caterpillar Grizzly bear Fox Grasshopper Human Frog Slug Crow Sparrowhawk Horse Pig Lion Deer Cat

11. Tertiary Consumer • Gains energy by eating secondary consumers. • Usually predators but may be scavengers or parasites 4th trophic level Stoat Toad Caterpillar Grass Secondary Consumer • Gains energy by eating primary consumers. • Usually carnivores but can be • omnivores Trophic level – position in the food chain. Primary Consumer • Gains energy by eating producers. • Usually herbivores Producer • Makes food from sun using photosynthesis 1st trophic level

12. Food chains • Food chains are diagrams that show what animals eat. • In habitats all animals and plants depend on each other. • If one animal or plant dies out it might affect the other animals .

13. Human Cow Grass What would happen to the cows if all the grass died out?

14. What are detritivores? Things that feed on detritus (dead or decaying material) giving it a bigger surface area for microorganisms to work on. LL 2008

15. Name some examples of detritivores LL 2008

16. Decomposers feed by releasing enzymes outside of their ‘body’, digesting the food externally and then absorbing the nutrients. Decay is caused by saprobionts. Bacteria & fungi are saprobionts. LL 2008

17. Constructing an ecosystem • A food chain is quite unrealistic – food webs are much better. • Within any ecosystem there are two main processes to consider: • The flow of energy through the ecosystem. • The cycling of elements through the ecosystem. • We are going to construct an ecosystem based on these two main principles.

18. Hedgehog Eats slugs and caterpillars. Caterpillar Eats lettuce. Lettuce Makes its own food using energy from the sun. Frog Eats grasshoppers. Grass Makes its own food using energy from the sun. Spider Eats aphids. Rabbit Eats lettuce and grass. Sparrowhawk Eats voles and thrushes. Aphid Eats grass. Thrush Eats slugs and spiders. Vole Eats grasshoppers. Slug Eats lettuce. Grass snake Eats frogs. Grasshopper Eats grass. Fox Eats hedgehogs, voles and rabbits.

19. Constructing an ecosystem • As well as the cards provided, you will also have to draw/add your own elements to the ecosystem as some are missing.

20. Constructing an ecosystem • Cut out all of the cards and try to arrange them in a logical ecosystem. • Once you’re happy, glue them down. • Draw arrows between organisms to show the flow of energy (and therefore feeding relationships) within the ecosystem. • Around the outside, list any abiotic factors which could affect the individuals in the ecosystem.

21. An example ecosystem

22. Food chains and food webs WAL: About how energy moves through food chains and webs. Some • How is energy lost from the ecosystem? Most • What is meant by the terms: trophic level, food chain, food web, producer, consumer and decomposer? All • How does energy enter an ecosystem and become transferred between organisms?

23. 5,4,3,2,1 go… can you talk about food chains and food webs for 60 seconds mentioning as many as the key words as possible? Food web Producer Consumer Decomposer Food chain Primary consumer Omnivore Detritivore Energy loss Quaternary consumer Secondary consumer Trophic level Tertiary consumer Habitat Heat Carnivore Herbivore Respiration

24. Ecology Bingo Draw a 2 x 3 grid and fill it with 6 key words from todays lesson...