Unit 2, Part 3 Notes

1. Unit 2, Part 3 Notes Food Chains, Food Webs, and the Transfer of Energy

2. Autotrophs • A groups of organisms that can use the energy in sunlight to convert water and carbon dioxide into Glucose (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

3. Autotrophs

4. Autotrophs • Chemotrophs • Autotrophs that get their energy from inorganic substances, such as salt • Live deep down in the ocean where there is no sunlight. Some bacteria use the sulphur to get energy and then use this to perform photosynthesis • Ex. Bacteria and Deep Sea Worms

5. 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

6. Heterotrophs

7. Heterotrophs • Consumers • 1. Scavengers/Detritivores – feed on the tissue of dead organisms (both plans and animals) • Ex. – Vultures, Crows, and Shrimp

8. Heterotrophs • Consumers • 2. Herbivores – eat ONLY plants • Ex. – Cows, Elephants, Giraffes

9. Heterotrophs • Consumers • 3. Carnivores – eat ONLY meat • Ex. – Lions, Tigers, Sharks

10. Heterotrophs • Consumers • 4. Omnivores – eat BOTH plants and animals • Ex. – Bears and Humans

11. Heterotrophs • Consumers • 5. Decomposers – absorb any dead material and break it down into simple nutrients or fertilizers they do this by excreting an enzyme like substance, dissolving and absorbing the nutrients. • Ex. – Bacteria and Mushrooms

12. Transfer of Energy • When a zebra eats the grass, it does not obtain all of the energy the grass has (much of it is not eaten) • When a lion eats a zebra, it does not get all of the energy from the zebra (much of it is lost as heat)

13. Transfer of Energy • The two (2) previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate • Only approximately 10% of the energy stored in the organic matter of one trophic level is used by the next level for growth. • This is called the 10% law • The rest goes into heat, cellular respiration and waste products

14. 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

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

16. Food Chain

17. Food Web • Most organisms eat more then JUST one organism • When more organism are involved it is known as a FOOD WEB • Food webs are more complex and involve lots of organisms

18. Food Web

19. Food Web • Notice that the direction the arrow points . The arrow points in the direction of the energy transfer, NOT “what ate what”

20. Food Web

21. Biomass • The total mass of the organic matter at each trophic level is called biomass • This is always measured as dry weight because water has no useable energy. • Biomass is often used as another term for potential energy – energy that is to be eaten and used. • The transfer of energy from one level to another is very inefficient (10% Law)

22. Productivity • Productivity: is the Rate at which the biomass accumulates. It is usually written as grams per square metre of land per year • A rainforest will produce 1000-3500g dry matter per m2 per year • A dessert will produce from 10 up to 250g per m2 per year

23. Energy transfer

24. Ecological Pyramids - Biomass • An ecological pyramid shows the relationship between consumers and producers at different trophic levels in an ecosystem • Shows the relative amounts of dry matter contained at each trophic level • The Pyramid shows which level has the most dry matter for a given unit of time • This can be inverted

25. Ecological Pyramid of Energy

26. Ecological Pyramid of Energy

27. Pyramid of Numbers • This is when each box of the pyramid shows the numbers of individuals present in that level. • These can be inverted • For example: If you have 3-4 rose bushes only but hundreds of insects feeding off them.

28. Biomass versus Numbers Pyramids

29. Symbiosis • A close and permanent association between organisms of different species • Commensalism – a relationship in which one organism benefits and the other is not affected • Example: Barnacles on a whale • Mutualism – a relationship in which both organisms benefit from each other • Example: Birds eating pests off a rhino’s back • Parasitism – A relationship in which one organism benefits and the other is harmed • Example: Ticks on a dog

30. Ecological Succession • A change in the community in which new populations of organisms gradually replace existing ones • 1. Primary Succession – occurs in an area where there is no existing communities and for some reason (s) a new community of organisms move into the area

31. Ecological Succession • A change in the community in which new populations of organisms gradually replace existing ones • 2. Secondary Succession – occurs in an area where an existing community is partially damaged

32. Ecological Succession • A change in the community in which new populations of organisms gradually replace existing ones • 3. Climax Community – a community that is stable and has a great diversity of organisms