1. Ecosystems (Part 2) Notes

2. Food Chain Food Chain: Shows the pathway of energy as one organism eats another. The arrow shows the direction in which the energy is traveling.

3. Food Web Food Web: A diagram that shows the feeding relationships between organisms in an ecosystem. The arrow still shows the direction in which energy is moving

4. Food Chain vs. Food Web Food webs are more realistic than food chains because most organisms eat more than one kind of food to survive.

5. Relationships in Food Webs If the predator population increases, the prey population(s) may decrease. If the prey population increases, the predator population(s) may increase. If the population of plant eaters increases, the population of plants may decrease.

6. Relationships in Food Webs

7. Relationships Between Populations Organisms interact with one another in a variety of ways.

8. Competition Populations of similar organisms have similar needs –They compete directly for resources (food, water, shelter, etc.) Ex: Two populations of squirrels compete more directly for resources than a population of squirrels and rabbits.

9. Symbiosis Symbiosis describes types of relationships and interactions between species. –Mutualism (+/+) –Commensalism (+/0) –Parasitism (+/-)

10. Mutualism (+/+) Two organisms live together and interact and both benefit from this Ex: Lichen is an organism that comes from algae and fungi having a mutualistic relationship. Algae lives in the fungi. Algae has somewhere safe to live. Fungi is protected from drying out. Algae benefits (+) Fungi benefits (+)

11. Commensalism (+/0) Two organisms live together and interact and one benefits while the other is unaffected. Ex: Cattle egrets (birds) eat organisms that livestock stir up in the ground when they walk. Cattle egret (bird) benefits (+) Livestock is unaffected (0)

12. Parasitism (+/7) Two organisms live together and interact and one benefits from living on or within its host while the other is harmed. The host is not always killed. Ex: A flea lives on a dog. The flea feeds on blood from the dog. Flea benefits (+) Dog is harmed (itching) (-)

13. Mutually Beneficial Relationships Two populations may develop a mutually beneficial relationship. –This means that both organisms benefit (+/+) This can lead to the organisms depending on one another to survive (interdependency).

14. Mutually Beneficial Relationships Example: –Flowers of a particular plant population may come to depend on bees to pollinate their plant, while the bees depend on the flower population for the pollen. –These organisms are interdependent upon one another They need one another to survive.