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 ecology chapter 56

Community EcologyChapter 56

Biological communities

Biological Communities

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

    • Evolve together

    • Forage together

    • Compete

    • Cooperate

Biological communities1

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

Ecological Niche

  • Niche: An Organism’s way of life

    • Habitat

    • Food

    • Temp. range

    • Reproduction

Ecological niche1

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 niche2

Ecological Niche

study of barnacles

Ecological niche3



Ecological Niche

  • causes of niche restriction

    • Competition

    • Predators

    • Absence of pollinators

    • Presence of herbivores

Ecological niche4

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

Community ecology chapter 56

Resource partitioning among sympatric lizard species

Ecological niche5

Ecological Niche

Character displacement in Darwin’s finches

Predator prey


  • 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

Community ecology chapter 56

  • Examples of prey adaptations:

  • Chemical defenses

  • Camouflage

  • Warning coloration

  • mimicry

Species interactions

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 interactions1

Species Interactions

  • Commensalism benefits one species and is neutral to the other

    • Spanish moss: an epiphyte hangs from trees

Community ecology chapter 56

Shark and Pilot Fish

Community ecology chapter 56

Barnacles and Whales

Species interactions2

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

Community ecology chapter 56

Human Intestine and E.Coli

Community ecology chapter 56

Zebra and Oxpecker Bird

Species interactions3

Species Interactions

  • Parasitism benefits one species at the expense of another

  • Can be external or internal parasites

Species interactions4

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

Community ecology chapter 56

Heartworm and Dogs

Community ecology chapter 56

Mistletoe and Mesquite Tree

Species interactions5

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 interactions6

Species Interactions

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

Species interactions7

Species Interactions

  • Keystone species: species whose effects are greater than expected

  • Examples:

    • Sea star predation on barnacles

    • Beaver ponds

    • Top predators

    • Krill

Species interactions8

Species Interactions

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

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