Chapter 4
1.
2.
3.
4.
Biotic and abiotic factors.
The niche
Community interactions
Ecological succession

Living factors that influence an ecosystem are
called biotic factors.
◦ All the organisms and their interactions.

Nonliving factors that influence an ecosystem
are called abiotic factors.
◦ Sunlight, temperature, humidity, average rainfall,
soil composition, rock structure…

How an organism interacts within its
environment is called its niche.
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◦
◦
◦
◦

What it eats
How it obtains food
When and how it reproduces
If and how it cares for its young
How it modifies its environment
No two species can occupy the same niche.
Figure 4-5 Three Species of Warblers and Their Niches
Section 4-2
Cape May Warbler
Feeds at the tips of branches
near the top of the tree
Bay-Breasted Warbler
Feeds in the middle
part of the tree
Spruce tree
Yellow-Rumped Warbler
Feeds in the lower part of the tree and
at the bases of the middle branches

Organisms interact constantly in their
community and help shape the ecosystem.
◦ Competition
◦ Predation
◦ Symbiosis

Competition
◦ Organisms compete for the same resources.
 Water, food, shelter, mates…

Predation
◦ The interaction when a predator captures and feeds
on a prey.

Symbiosis
◦ Two different species live in close association with
each other and at least one benefits.

Mutualism – both benefit; lichens

Commensalism – one benefits; shark and
remora

Parasitism- one benefits; one is harmed

Ecosystems change over time until a climax
community is established.
◦ This is called ecological succession.

Primary succession
◦ Occurs on surfaces where no soil exists.
◦ Bare rock
◦ Lichens and moss.

Secondary succession occurs when a disaster
(natural or man-made) destroys an original
community.
◦ Ecosystems tend to return to their climax
community unless human activity prohibits this.