ECOSYSTEM BALANCEChapter 6 (pgs. 88-107)

Mrs. Paul

6.1 RELATIONSHIPS IN THE ECOSYSTEM

All species interact and a change in the relationships may change a population and thus the food web.

Relationships: Predator/Prey Parasitism Symbiosis

Predators and Prey

Predators: consumers that actively hunt other organisms. Example: praying mantis (predator) eating a

dragon fly (prey) Prey: organisms that a predator feeds

upon Example: a snake (predator) eating a praying

mantis (prey). The size of both populations influence

each other

Example: snowshoe hare and lynx

Increases in the hare population increase the lynx population. More prey (food) can support more predators.

A decrease in the hare population leads to a decrease in the lynx population.

Parasitism

Parasitism: relationship in which one organism feeds on the tissues or body fluids on another.

Host: the organism on which the parasite feeds.

Parasites are harmful and have the potential to kill their host.

Depends on the host for many functions. Examples: fleas, ticks, lice, protists,

tapeworms.

Symbiosis

Symbiosis: relationship where two species live closely together. Parasitism-one harmed/one benefits Mutualism-both benefit Commensalism-one benefit/one not affected

Commensalism: relationship where one species benefits and the other is neither helped nor harmed. Examples:

barnicles living on the skin of whale.

Mutualism: relationship where both species benefits. Examples: ants

and acacia trees, flowers and insects that pollinate them, yucca plant and the yucca moth.

Check for Understanding:1. What processes link the sizes of predator

and prey populations?2. Why are herbivores not considered to be

parasites?3. How are the 3 types of symbiosis

different? How are they similar?

6.2 ECOLOGICAL SUCCESSION

Ecological Succession: gradual process of change and replacement of some or all of the species in a community. May take hundreds or thousands of years. Each new community makes it harder for the

previous community to survive. Two main types:

1. Primary Succession 2. Secondary Succession

Primary Succession

Primary Succession: sequence of communities forming in an originally lifeless habitat. Occurs in habitats without life. Examples: cooled lava field, bare rock after

retreating glacier.

Steps:1. Formation of soil from exposed rocks as lichen and

weather break them down.-Lichen: fungus and alga living in a mutualistic relationship. -Pioneer community: first community to colonize new habitat.

2. Grasses and small plants begin to grow from seeds carried by wind and animals.

3. Growth of non-woody plants with deep roots (shrub community).4. Growth of pine forest5. Growth of hardwood forest. -Climax community: community that does not undergo further succession.

Secondary Succession

Secondary succession: succession that occurs where a community has been cleared by a disturbance that does not destroy the soil. Examples: fires, storms, human disturbances. Frequently disturbed habitats may never

reach the climax community. Example: grassland frequently burned by fires.

Steps:1. Fast-growing grasses and non-woody

plants.

2. Larger shrubs grow.

3. Pine Forest

4. Hardwood Forest

Aquatic Succession Starts with a

body of water that is low in nutrients.

Leads to a fertile meadow as the lake fills in with vegetation over time.

Island Succession Populations of new

organisms can adapt quickly to fill new niches or to form new species.

Check for Understanding:1. How does primary succession differ from

secondary succession?2. What is a climax community?3. Suppose humans put out all the fires in a

large area of grassland over a period of 100 years. What would happen to the grassland community?

6.3 BALANCE IN THE ECOSYSTEM

If ecosystems are not balanced, they do not survive.

Disruptions are normal; they trigger change in the ecosystem.

Chaos Theory Suggests that ecosystems may be sensitive to

very small changes.

6.4 LAND BIOMES

We divide the ecosystems on Earth into several categories.

Biome: major type of ecosystem with distinctive temperature, rainfall, and organisms.

Terrestrial (land) biomes Type of biome depends on average temperature

and amount of precipitation the area receives. Aquatic (water) biomes

Determined by water depths, nutrients, and nearness to land.

8 Major Terrestrial Biomes: 1. Desert 2. Tundra 3. Coniferous Forest 4. Deciduous Forest 5. Rain Forest 6. Steppe 7. Prairie 8. Savanna