Biodiversity, Species Interactions, and Population Control

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Biodiversity, Species Interactions, and
Population Control

• Chapter 5

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5-1 How Do Species Interact?

• Concept 5-1 Five types of species interactions
  competition, predation, parasitism, mutualism,
  and commensalism affect the resource use and
  population sizes of the species in an ecosystem.

3

• Species
• Interactions

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COMPETITION

• Organisms compete for shared or limited resources
  such as food, water, space, and habitats.
• Competitive exclusion principle No two species
  can occupy the exact same niche for very long
• More in Section 5-2

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COMPETITION

• Interspecific competition is the competition
  between member of two different species. The
  result is that neither species can obtain as many
  resources as they could in the absence of the
  other species.
• Intraspecific competition is the competition
  between member of the same species.
• This also includes the competition
  for mates.

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PREDATION

• Species called predators feed on other species
  called prey.
• Organisms use their senses to locate objects and
  their prey.
• Some predators are fast enough to catch their
  prey, some hide and lie in wait, and some inject
  chemicals to paralyze their prey.

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PREDATION

• Some prey may escape their predators by
• Camouflage
• Outer protection
• Chemical warfare
• Warning coloration
• Mimicry
• Deceptive looks
• Deceptive behavior

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Predator and Prey Species Can Drive Each Others
Evolution

• Intense natural selection pressures exist between
  predator and prey populations
• Coevolution changes in the gene pool of one
  species can lead to changes in another species
• Evolution in the predator population improved
  abilities to capture prey
• Evolutionary response the prey improves its
  abilities to avoid capture
• The evolution of improved escape abilities should
  result in increased capture abilities.
• Evolutionary arms race
• The levels of defense and counter-defense will
  continue to escalate.

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Parasitism

• Parasitism occurs when one species feeds on part
  of another organism.
• Although parasites can harm their hosts, they can
  promote community biodiversity.
• Some parasites live inside the host
  (micororganisms, tapeworms).
• Some parasites live outside the host (fleas,
  ticks, mistletoe plants, sea lampreys).
• Some have little contact with host (cowbirds
  lay eggs in anothers nestlet them take care of
  young.)

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Parasitism
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Mutualism

• In mutualism, two species interact in a way that
  benefits both of them.
• Most organisms benefit through mutualistic
  interactions by gaining nutrition or protection.

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Commensalism

• Commensalism is an interaction that benefits one
  species but has little, if any, effect on the
  other species.

• Epiphytes

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5-2 How Can Natural Selection Reduce Competition
between Species?

• Concept 5-2 Some species develop adaptations
  that allow them to reduce or avoid competition
  with other species for resources.

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5-2 How Can Natural Selection Reduce Competition
between Species?

• Niches (way of life) become separated to avoid
  competition for resources.
• Reduce niche overlap
• This is also the basis of natural selection the
  pressure that drives the evolution of new
  species.
• Chapter 4

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5-2 How Can Natural Selection Reduce Competition
between Species?

• Some species evolve adaptations that allow them
  to reduce or avoid competition for resources with
  other species (resource partitioning).
• Each species minimizes competition with the
  others for food by spending at least half its
  feeding time in a distinct portion of the spruce
  tree and by consuming somewhat different insect
  species.

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5-2 How Can Natural Selection Reduce Competition
between Species?

• Genetic variation and specialized feeding niches
  can lead to evolutionary divergence.
• Use shared resources at different
• Times
• Places
• Ways
• Each species has a beak specialized to take
  advantage of certain types of food resource.