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Interspecific Interactions andthe Ecology of Communities

Chapter 57

Biological Communities• Community

– “all the living organisms and the environment they live in”

– Communities are characterized by:• Species diversity

–“Number of different species present”• Species composition

–“Number of individuals in each species”• Primary productivity

–“Amount of energy produced”

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Functional Roles of Living Organisms

• Two types:– Autotrophs– Heterotrophs

Functional Roles of Living Organisms

• Organisms are categorized by what they eat:

• Primary consumers• Secondary consumers• Tertiary consumers

Roles Outside the Trophic Pyramid

• Scavengers

• Detritivores– Feed off detritus

• There are 2 types of detritivores– Detritus feeders

– Decomposers

Trophic Level Pyramid

Ecological Niche

• Niche: “A species’ way of life or functional role in the ecosystem”

• There are two types of ‘niches’– Fundamental niche– Realized niche

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Niches - Competition

• Because of competition, realized niches are much smaller than fundamental niches.

• 2 Types of competition:– Intraspecific competition– Interspecific competition

• Exploitative competition

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• Resource partitioning

– Morphological

– Temporal

– Spatial

Morphological Temporal Spatial

Ways to Avoid Competition

Predator–Prey• Predation and Coevolution

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Predator–Prey• Morphological and Chemical defenses:

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PreyProtect themselves both offensively

and defensively.

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Moth

Flower Fly

Wasp

Honey bee

BatesIan

Mimicry

14Mullerian Mimicry

Species Interactions• Commensalism: “One species benefits. The other is neither hurt nor helped”

• Mutualism: “both species benefit”

• Parasitism: “one species benefits at the expense of another”

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Commensalism Mutualism

Parasitism

Ecological Succession and Disturbance

• Primary succession

• Secondary succession

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Mt. St. Helen’s Succession

After eruption 1980 1st plant - Lupines

Shrubs Today

Succession and Disturbance• Animal species in a disturbed

community also change over time– As vegetation changes, animal

habitat changes– Plants that need animals for

pollination or to spread their seed take longer to return.

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