Community ecology chapter 56
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Community Ecology Chapter 56. Biological Communities. Community: all the organisms that live together in a specific place Evolve together Forage together Compete Cooperate. Biological Communities.

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Community Ecology Chapter 56

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Community EcologyChapter 56

Biological Communities

  • Community: all the organisms that live together in a specific place

    • Evolve together

    • Forage together

    • Compete

    • Cooperate

Biological Communities

  • Individualistic concept: a community is a group of species that happen to occur together at one place

    • species respond independently to changing environmental conditions

    • The composition of a Community can change

Ecological Niche

  • Niche: An Organism’s way of life

    • Habitat

    • Food

    • Temp. range

    • Reproduction

Ecological Niche

  • Fundamental niche: the entire niche that a species is capable of using.

  • Realized niche: actual niche in which the species can establish a stable population

Ecological Niche

study of barnacles



Ecological Niche

  • causes of niche restriction

    • Competition

    • Predators

    • Absence of pollinators

    • Presence of herbivores

Ecological Niche

  • Principle of competitive exclusion: no two species can occupy the same niche when resources are limited

    • Species may divide up the resources, (resource partitioning)

    • natural selection can then lead to adaptive radiation

Resource partitioning among sympatric lizard species

Ecological Niche

Character displacement in Darwin’s finches


  • Predation and coevolution

    • Predation provides strong selective pressure on the prey population

    • Features that decrease the probability of capture are strongly favored

    • Predator populations counteradapt to continue eating the prey

      Coevolution race

  • Examples of prey adaptations:

  • Chemical defenses

  • Camouflage

  • Warning coloration

  • mimicry

Species Interactions

  • Symbiosis: two or more kinds of organisms interact in more-or-less permanent relationships

  • All symbiotic relationships carry the potential for coevolution

  • Three major types of symbiosis

    • Commensalism (Win-Neutral)

    • Mutualism(Win-Win)

    • Parasitism(Win-Lose)

Species Interactions

  • Commensalism benefits one species and is neutral to the other

    • Spanish moss: an epiphyte hangs from trees

Shark and Pilot Fish

Barnacles and Whales

Species Interactions

  • Mutualism benefits both species

  • Coevolution: flowering plants and insects

    Ants and acacias

    • Acacias provide hollow thorns and food

    • Ants provide protection from herbivores

Human Intestine and E.Coli

Zebra and Oxpecker Bird

Species Interactions

  • Parasitism benefits one species at the expense of another

  • Can be external or internal parasites

Species Interactions

External parasite: the yellow vines are the flowering plant dodder, it is a parasite that obtains its food from the host plant it grows on

Heartworm and Dogs

Mistletoe and Mesquite Tree

Species Interactions

  • Ecological processes can interact

    • Predation reduces competition

      • Superior competitors become more numerous and attract predators

      • This allows other species to survive when they could have been out competed

Species Interactions

Starfish eat barnacles, allowing other species to thrive instead of being crowded out by the explosive population of barnacles

Species Interactions

  • Keystone species: species whose effects are greater than expected

  • Examples:

    • Sea star predation on barnacles

    • Beaver ponds

    • Top predators

    • Krill

Species Interactions

Beavers construct dams and transform flowing streams into ponds, creating new habitats for many plants and animals

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