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CHAPTER 6

ECOSYSTEM BALANCE

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Symbiosis Symbiosis is any relationship in which

two species live closely together. 3 types

◦ 1. Parasitism – a relationship in which one organisms feeds on the tissues or body fluids of another. One benefits and the other is harmed. Parasite feeds on another organism and benefits. Host – the organism on which a parasite feeds and is

harmed.

Section 6.1- Relationships in the Ecosystem

Tapeworm video

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Symbiosis 2. Commensalism – a relationship that

benefits one species and the other species is unaffected.

Section 6.1- Relationships in the Ecosystem

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Symbiosis 3. Mutualism – a relationship in which

both species benefit.

Section 6.1- Relationships in the Ecosystem

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Organisms affect the environment they live. An environment may change so much that

the species’ niche disappears. A species can be the cause of its own

destruction. Change is a fact of life in all ecosystems. Living things have evolved in response to

change. 4 types

◦ 1. Primary Succession – the sequence of communities forming in an originally lifeless habitat.

◦ Examples include – cooled lava field, bare rock exposed by a retreating glacier.

◦ The 1st step – colonization by new organisms and formation of soil from exposed rocks.

Section 6.2 – Ecological Succession

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Organisms affect the environment they live.

2nd Exposed rocks are first colonized by lichens.

Lichen – a fungus and an algae living in a mutualistic relationship.

They secrete acids which break down the rock and form organic material by photosynthesis which forms soil.

3rd Now grasses and other small plants grow from seeds carried by wind or animals.

Section 6.2 – Ecological Succession

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Organisms affect the environment they live. 4th The grass community provides for the

growth of trees and shrubs. In the absence of external disturbances, a

mature ecosystem will change very little over time.

5th Climax community - a community that does not undergo further succession. It is STABLE.◦ Highly diverse and often survive severe local

disturbances.

Section 6.2 – Ecological Succession

VIDEO

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Organisms affect the environment they live. 2. Secondary Succession – Succession

that occurs where a disturbance eliminates most organisms but does not destroy the soil.

Usually caused by fires, storms, and human activity.

Process is same as primary succession but already has the soil.

Section 6.2 – Ecological Succession

VIDEO

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Organisms affect the environment they live. 3. Aquatic Succession – can form from

retreating glaciers. 1st The water is low in nutrients and has few

organisms. 2nd As time passes, water plants begin to

grow near the shore of the lake, supporting other organisms.

3rd Water becomes richer in nutrients and more organisms can survive.

4th Eventually the lake becomes a marsh. Land plants begin to colonize the marsh.

5th Finally, the lake becomes a fertile meadow covered with land plants and may turn into a forest.

Section 6.2 – Ecological Succession

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Organisms affect the environment they live. 4. Island Succession – new island form quickly

by volcanic eruptions. Any organism found on an island must have

ancestors that were carried there by water, wind, or by other organisms.

Usually highly populated by birds. Many unfilled niches. Offspring of a few organisms can evolve to fill

several niches. This causes the development of new species. On some isolated islands some species of

birds have evolved that are unable to fly because there are no predators.

Section 6.2 – Ecological Succession

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VIDEO

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Stability Stability – is a measure of easily an

ecosystem is affected by a disturbance and how quickly it returns to its original condition after a disturbance.

When a disrupted ecosystem returns to a state of balance this is known as equilibrium.

When change is constant in an ecosystem, the ecosystem is said to be dynamic.

Chaos Theory – suggests that ecosystems may be sensitive to very small changes.◦ Which means one very small change can lead to

drastic results in an ecosystem.◦ Known as the butterfly effect.

Section 6.3 – Stability in the Ecosystem