1. Interactions Within Ecosystems Chapter 2
Grade 7 Science Unit 1
Interactions Within Ecosystems
Chapter 2

2. Symbiosis Interactions between the biotic parts of the environment.
There are 3 types:
Parasitism
Mutualism
Commensalism

3. 1. Parasitism
One organism will benefit (the parasite) and the other is harmed (the host).

4. 2. Mutualism
Both organism benefit.
Lichen = algae + fungus

5. 3. Commensalism
One organism benefits while the other neither gains or loses.

6. Core Lab Activity 1-2B p. 22
Salty Seeds

7. Roles of Organisms in the Ecosystem
Producers
Consumers
Decomposers
Scavengers

8. 1. Producers
Plants can produce their own food from the abiotic environment. (photosynthesis)
Water + carbon dioxide + Sunlight
Food (sugar) + oxygen

9. 2. Consumers
Animals must consume, eat other organisms. (the biotic environment)
Can be classified as... herbivores, carnivores, or omnivores.

10. Herbivore:
Animals that eat ONLY plants (producers).

11. Omnivore:
Animals that eat both plants AND animals.

12. Carnivore:
Animals that eat ONLY other animals.

13. 3. Decomposers
Organisms that break down dead and waste materials into their basic parts.
They release chemicals that break apart dead tissues and cells and absorb the nutrients for their own use.

14. Examples include bacteria and other microorganisms, fungi and worms.

15. 4. Scavengers
Animals that eat decaying animals and waste materials.
Examples include vultures, dung beetle larvae, houseflies, crows and some gulls.

16. Microorganisms...
are found in a variety of habitats (air, soil, water)
play important roles in relation to human food supplies
have been studied to enhance food preservation techniques

17. Conditions that affect Microorganism Growth
Temperature
Moisture
Light
Acidity
Salinity

18. Food Preservation
Creates an environment which destroys existing decomposers and then prevents or slows down their growth rate.

19. Methods of Food Preservation
Pickling
Salting
Drying
Smoking
(the above started out of necessity )

20. (These are more modern and technology based.)
Refrigerating
Freeze-drying
Radiation
Canning
(These are more modern and technology based.)

21. Food Chains
The transfer of energy from organism to organism. Arrows show the direction of energy flow.
Green plants are the food (energy) source for all consumers and decomposers.

22. Producers
Primary Consumers
Secondary
Consumers

23. A Sample Food Chain

24. Food Webs
Interconnecting food chains.

25. A Marine Food Web

26. Energy Pyramids Describes the gradual loss of energy in food chains
About 10% is lost as you move from one level to the next and 10% of the new energy is lost as you move up and so on.

27. Note: Energy pyramids are not exact
Note: Energy pyramids are not exact. Energy is transferred to other types (eg. heat) as it moves from one level to the next. ie. Not all of the 10% is transferred.
Energy in hawk: 10 J
Energy in weasel: 100 J
Energy in mice: 1000 J
Energy in grass: J

28. Nutrient Cycles
Nutrients, such as nitrogen and carbon, are recycled in the environment.
All organisms are eventually recycled and their nutrients are returned to the soil by the action of decomposers.