Chapter 6 (pgs. 88-107)
Mrs. Paul
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
All species interact and a change in the
relationships may change a population and
thus the food web.
Relationships:
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
Predator/Prey
Parasitism
Symbiosis
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Predators: consumers that actively hunt other
organisms.


Prey: organisms that a predator feeds upon


Example: praying mantis (predator) eating a dragon
fly (prey)
Example: a snake (predator) eating a praying mantis
(prey).
The size of both populations influence each
other

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.
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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: 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.
1.
2.
3.
What processes link the sizes of predator and prey
populations?
Why are herbivores not considered to be parasites?
How are the 3 types of symbiosis different? How
are they similar?

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:
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
1. Primary Succession
2. Secondary 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.
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 forest
5. Growth of hardwood forest.
-Climax community: community that does not undergo
further 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.
1. Fast-growing grasses and non-woody plants.
2. Larger shrubs grow.
3. Pine Forest
4. Hardwood Forest


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.

Populations of
new organisms
can adapt quickly
to fill new niches
or to form new
species.
1.
2.
3.
How does primary succession differ from secondary
succession?
What is a climax community?
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?
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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.
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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
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