Food Chains, Food Webs, and the Transfer of Energy CHAPTER 5

Photosynthesis Chemical reaction where green plants use water & carbon dioxide to store the sun’s energy Energy is stored in glucose Glucose is stored as starch in plants

6CO2 + 6H2O + sunlight & chlorophyll C6H12O6 + 6O2

Cellular respiration is the chemical reaction that releases the energy in glucose. 6O2 + C6H12O6 -->  6H2O + 6CO2 + energy

Review Questions Where does the energy used in photosynthesis come from? ____________________________________________ 2. How is the sun’s energy stored within plant cells? ____________________________________________________________________________________________________________________________________ 3. What is cellular respiration?

Autotrophs A group of organisms that can use the energy in sunlight to convert water and carbon dioxide into food. Autotrophs are also called producers because they produce all of the food that heterotrophs use. Without autotrophs, there would be no life on this planet Ex. Plants and Algae

Heterotrophs Organisms that do not make their own food Another term for heterotroph is consumer because they consume other organisms in order to live Ex. Rabbits, Deer, Mushrooms

Review Questions 4. What is another name for autotrophs? Why? ____________________________________________________________________________________________________________________________________ 5. What would happen if there were no autotrophs? ____________________________________________ 6. What is another name for heterotrophs? Why ____________________________________________________________________________________________________________________________________

Heterotrophs as Consumers 1. Scavengers – feed on the tissue of dead organisms (both plants and animals) Ex. – Vultures, Crows, and Shrimp

2. Herbivores – eat ONLY plants Ex. – Cows, Elephants, Giraffes

3. Carnivores – eat ONLY meat Ex. – Lions, Tigers, Sharks

4. Omnivores – eat BOTH plants and animals Ex. – Bears and Humans

5. Decomposers – absorb any dead material and break it down into simple nutrients or fertilizers Ex. – Bacteria and Fungi

Review Questions 7. Which type of consumer feeds on dead organisms? ____________________________________________ 8. Which type of consumer eats only plants? ____________________________________________ 9. Which type of consumer eats only animals? 10. Which type of consumer eats plants and animals? 11. Which type of consumer absorbs and breaks down dead organisms?

Transfer of Energy When a zebra eats the grass, it does not obtain all of the energy the grass has… When a lion eats a zebra, it does not get all of the energy from the zebra… The two (2) previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate.

Trophic Levels Energy moves from one organism to another when it is eaten. Each step in this transfer of energy is known as a trophic level. The main trophic levels are producers, consumers, and decomposers Only 10% of the energy from one trophic level is transferred to the next .

Review Questions 12. Does an organism receive all of the energy from what it eats? Why or why not? ________________________________________________________________________________________ 13. What is each step in the energy transfer as organisms eat and are eaten called? ____________________________________________ 14. What percentage of energy is passed along from one trophic level to the next? 15. What are the main trophic levels in an ecosystem?

Food Chains The energy flow from one trophic level to the other is known as a food chain. A food chain is simple. It involves one organism at each trophic level Primary Consumers – eat producers Secondary Consumers – eat primary consumers Tertiary Consumers – eat secondary consumers Decomposers – bacteria and fungi that break down dead organisms and recycle the material back into the environment

Review Questions 16. In the food chain below, label the producer, primary consumer, secondary consumer, tertiary consumer, and decomposer.

Food Web Most organisms eat more than one organism. When more organisms are involved it is known as a food web. Food webs are more complex and involve lots of organisms. Notice the direction the arrow points  the arrow points in the direction of the energy transfer, NOT “what ate what”.

Food Web

Review Questions 17. What are the producers in the previous food web? ________________________________________________________________________________________ 18. What are the primary consumers? 19. What are the secondary consumers? ____________________________________________ 20. What are the tertiary consumers?

Ecological Pyramid An ecological pyramid shows the relationship between consumers and producers at different trophic levels in an ecosystem Shows the relative amounts of energy or matter contained at each trophic level The pyramid shows which level has the most energy and the highest number of organisms

Ecological Pyramid

21. If you know that only 10% of the energy from one trophic level is passed to the next, fill in the boxes with the amount of energy at each level. 1% 100%

Review Questions 22. In which level of the ecological pyramid would the most energy be found? ____________________________________________23. In which level of the ecological pyramid would the least energy be found? ____________________________________________24. In which level of the ecological pyramid would the most organisms be found? ____________________________________________ 25. In which level of the ecological pyramid would the least organisms be found?