Communities: How Do Species Interact?

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Communities How Do Species Interact?

• Chapter 27

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• Succession the predictable change in the
  numbers and kinds of organisms in a particular
  area over time.
• Habitation of a completely new environment is
  called primary succession.
• Reestablishment of life after serious damage is
  called secondary succession.

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• Pioneer community the first community in a
  succession.
• Climax community the long-lived community at
  the end of a succession.
• successional communities the intermediate
  communities between the pioneer and climax
  communities
• Pioneer and successional communities change over
  periods of 1 to 500 years.
• Climax communities last for more than 500 years.

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Successional communities

• We tend to think primarily of plants since they
  are the producers.
• A deer carcass or a pile of dung can also have
  successional communities

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Why does succession occur?

• Non-climax communities may degrade their
  environments
• Species in early successional stages can
• Facilitate succession
• Tolerate succession
• Inhibit succession
• Pioneer communities always facilitate succession

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• The character of a climax community depends on
  abiotic factors such as climate, soil and
  terrain.
• May depend on the history of the region
• Sequoia forests and fires

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Are communities integrated or individualistic?

• Integrated communities consist of characteristic
  species that always interact with each other in
  predictable ways
• Individualistic communities are separate
  populations that merely inhabit the same habitat.
  Every community is unique.

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• Competition between trees?
• Mycorrhizae soil fungus that supports the
  growth of certain plants
• Replanting issues

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The First Law of Ecology

• Every species affects every other species.
• Predator prey interactions
• Herbivore-plant interactions
• Parasite host interactions

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• A parasite consumes only part of its host, and
  does not necessarily kill the host.
• A good parasite would harm its host as little
  as possible so it would have a place to live.
• A predator usually kills its prey and consumes
  most of the preys body.
• Use swiftness, intelligence, acute senses and
  sharp teeth to obtain food
• Herbivores use patience and a good digestive
  system.

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How does one keep from being eaten?

• Camouflage or crypsis blending into your
  surroundings

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Plant defenses

• Mechanical defenses
• Waxy cuticle keeps bacteria and fungi out
• Hairy or sticky leaves discourage tiny herbivores
• Spines, thorns and prickles fend off larger
  predators

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Plant defenses

• Chemical defenses secondary plant compounds
• Terpenes lipids- such as pyrethriods, essential
  oils, saponins, and gossypol
• Phenolic compounds carbon ring compounds -repel
  herbivores and pathogens or attract pollinators
  and fruit dispersers. Also lignin and tannins
• Alkaloids nitrogen containing compounds
  nicotine, atropine, cocaine, morphine, strychnine
  and caffeine
• Mustard oil glycosides cabbage family

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Animal chemical defenses

• Bees and wasps inject a powerful acid
• Skunk uses noxious chemicals
• Poison dart frog and the pitohui bird have deadly
  toxins in their skin

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Warning coloration

• Keeps animals from being attacked repeatedly by
  warning off attackers
• These organisms have bright colors and memorable
  designs
• Harmless organisms can use mimicry
• Batesian mimicry when something harmless (and
  tasty) mimics something harmful
• Mullerian mimicry two equally harmful organisms
  develop the same warning patterns
• Protects both predator and prey

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How do organisms live together?

• Symbiosis living together.
• Parasitism one species benefits and the other
  is harmed
• Predation - one species benefits and the other is
  harmed
• Mutualism lichen algae and fungus
• Commensalism one species benefits, and the
  other is neither helped nor harmed.

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Coevolution

• The acacia and the ants
• Bacteria and plants
• mycorrhizae

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Competition

• One organism uses a resource that is in limited
  supply, negatively affecting another species
  ability to survive and reproduce.
• Organisms can compete for
• Territory
• Prey
• Other resources

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• Habitat the place where an organism lives,
  along with the set of environmental conditions
  characterize that place.
• Address
• Niche the way an organism uses its environment
• occupation

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• When there is a limiting resource and two
  different species compete directly for the same
  resource, the more efficient species will
  eliminate the other. the competitive exclusion
  principle
• No two species can occupy the exact same niche in
  the same habitat indefinitely.

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How can competing species coexist?

• Resource partitioning dividing up the niche

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