Ecosystems (Part 2) Notes

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.

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

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.

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.

Relationships in Food Webs

Relationships Between Populations

• Organisms interact with one another in a variety of ways.

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.

Symbiosis

• Symbiosis describes types of relationships and interactions between species.

–Mutualism (+/+)– Commensalism (+/0)– Parasitism (+/-)

Mutualism (+/+)• Two organisms live together and

interact and both benefit from thisEx: 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 (+)

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)

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) (-)

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).

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.