Ecosystems and Communities

Chapter 4

1. Biotic and abiotic factors.2. The niche3. Community interactions4. Ecological succession

What Shapes an Ecosystem?

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…

Biotic and Abiotic factors

How an organism interacts within its environment is called its niche.◦ 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.

The Niche

Bay-Breasted WarblerFeeds in the middlepart of the tree

Yellow-Rumped WarblerFeeds in the lower part of the tree andat the bases of the middle branches

Cape May WarblerFeeds at the tips of branchesnear the top of the tree

Spruce tree

Section 4-2

Figure 4-5 Three Species of Warblers and Their Niches

Organisms interact constantly in their community and help shape the ecosystem.◦ Competition◦ Predation◦ Symbiosis

Community Interactions

Competition◦ Organisms compete for the same resources.

Water, food, shelter, mates…

Community Interactions

Predation◦ The interaction when a predator captures and

feeds on a prey.

Community Interactions

Symbiosis◦ Two different species live in close association with

each other and at least one benefits.

Community Interactions

Mutualism – both benefit; lichens

Symbiosis

Commensalism – one benefits; shark and remora

Symbiosis

Parasitism- one benefits; one is harmed

Symbiosis

Ecosystems change over time until a climax community is established. ◦ This is called ecological succession.

Ecological Succession

Primary succession◦ Occurs on surfaces where no soil exists.◦ Bare rock◦ Lichens and moss.

Ecological Succession

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.

Secondary Succession

Secondary Succession