What Shapes an Ecosystem?

Review of Biotic and Abiotic Factors• Ecosystems are influenced by a

combination of biological and physical factors.

• Biotic factors – include all the living things with which an

organism might interact.• Abiotic Factors

– Physical, or nonliving, factors that shape ecosystems.

Habitat and Niche

• Habitat– all aspects of the area in which an

organism lives (includes both biotic and abiotic).

– Habitats may change or disappear due to natural causes or interference by man.

Habitat and Niche

• Niche – the role or place and position a species has in

its environment.• An ecological niche includes all of the

factors that a species needs to survive, stay healthy, and reproduce.– food– abiotic conditions– behavior

Habitat and Niche

• Why do you think no two species can share the same niche.• One species is better suited to the niche

and the other will either be pushed out or become extinct.

Community Interactions

• When organisms live together in ecological communities, they interact constantly.

• Community interactions include:– Competition– Predation– Symbiosis

Community Interactions

• Competition:– occurs when two organisms fight for the

same limited resource.– Direct competition in nature often results

in a winner and a loser—with the losing organism failing to survive.

How species avoid Competition

• The distribution of these warblers avoids direct competition, because each species feeds in a different part of the tree.

Community Interactions

• Predation:– occurs when one organism captures

and eats another.

Predator

Prey

Community Interactions

• Symbiosis:– Any relationship in which two species

live closely together– Includes:

– mutualism– commensalism – parasitism

Community Interactions • Mutualism:

– both species benefit from the relationship.

Community Interactions • Commensalism

– one member of the association benefits and the other is neither helped nor harmed.

Human Our eyelashes are home to tiny mitesthat feast on oil secretions and dead skin. Without harming us, up to 20 mites may be living in one eyelash follicle.

Demodicids Eyelash mites find all they need to survive in the tiny folliclesof eyelashes. Magnified here 225 times, these creatures measure 0.4 mm in length and can be seen only with a microscope.

+

Organism benefits+

Ø

Ø Organism is not affected

Commensalism

Community Interactions • Parasitism

– one organism lives on or inside another organism and harms it.

Organism benefits0

_

Organism is not affected

Hornworm caterpillarThe host hornworm will eventually die as its organs are consumedby wasp larvae.

Braconid waspBraconid larvae feed on their host and release themselves shortly before reachingthe pupae stage of development.

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Parasitism+0

Ecological Succession

• Succession occurs following a disturbance in an ecosystem and regenerates or creates a community after a disturbance.– a sequence of biotic changes– damaged communities are regenerated– new communities arise in previously

uninhabited areas

Ecological Succession

• There are two types of succession.• primary succession — started by pioneer

species

Ecological Succession

• There are two types of succession.– secondary succession — started by

remaining species