Interactions within Communities

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Interactions within Communities
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• Populations of different species interact in a
  community
• Some organisms rely on other organisms within the
  community for survival

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Ecological Niches

• An organisms ecological characteristics,
  including use of and interaction with abiotic and
  biotic resources within its environment
• Think of a habitat being ones address and its
  ecological niche as its occupation
• e.g. a lions niche includes what it eats, what
  eats it, the way it reproduces, the temperature
  range it tolerates, its habitat, behavioural
  responses, and all other factors that can
  describe its pattern of living

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Ecological Niches

• A Fundamental niche is the biological
  characteristics of the organism and the set of
  resources individuals in the population are
  theoretically capable of using under ideal
  conditions
• Realized niche the biological characteristics
  of the organism and the resources individuals in
  a population actually use under the prevailing
  environmental conditions

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Interspecific competition

• Interaction between individuals of different
  species for essential common resource(s) that are
  in limited supply
• serves to restrict population growth
• Can occur in two ways
• Interference competition involves aggression
  between individuals of different species who
  fight over the same resource(s)
• Exploitative competition involves consumption
  of shared resources by individuals of different
  species, where consumption by one limits the
  resource availability to the other species

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Interspecific competition

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• Gauses Principle
• competitive exclusion
• No two species with similar requirements could
  coexist in exactly the same niche indefinitely
• Population of weaker competitor can decline
• One species could change its behaviour to survive
  using different resources
• One population could migrate to another habitat
•  

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Resource partitioning

• Avoidance of/reduction in competition for similar
  resources by individuals of different species
  occupying different non-overlapping ecological
  niches

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Lake Malawi Cichlids

• 850 species from one ancestor!!

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Mimicry

• Batesian mimicry
• Palatable / harmless species mimics
  unpalatable/harmful organism
• Mullerian mimicry
• Several animal species resemble one another and
  are all poisonous or dangerous

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Predation

• interspecific interaction by which population
  density of one species (predator) increases while
  population density of other species (prey)
  declines
• time lags exist between responses to predator
  prey interactions and their population sizes
• sinusoidal curves exist in some predator-prey
  relationships

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Defence Mechanisms - Plants

• plants use both morphological defences
• thorns, hooks, spines, needles
• chemical defences
• the defensive systems in plants act as selective
  agents which initiate the evolution of
  counter-adaptations in herbivore populations
• these changes brought about by co-evolution
  between plants and insets can affect competition

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Defence Mechanisms - Animals

• sometimes employ passive defence mechanisms
• e.g. hiding
• others employ active defence mechanisms
• e.g. fleeing
• more costly to prey in terms of energy uses
• other effective behavioural defences exist
• e.g. alarm calls
• e.g. camouflage (cryptic colouration)
• e.g. visual warnings in terms of chemical
  defences

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Symbiosis

• Some organisms have obligatory mutualism
• neither organism could grow or reproduce without
  each other

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Mutualism

• Mutualism A symbiotic relationship in which
  both species benefit.

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Mutualism

• Examples
• Cowbirds and Large Animals
• Termites and Trichonympha
• Bees and Flowers

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Cowbirds and Large Animals
The cowbird benefits by eating the ticks and
mites off the large animal. The large animal
benefits from have the parasites removed from
them. The birds can also warn them of danger.
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Termites and Trichonympha

• You probably think termites eat wood they doin
  a way.
• Termites cant digest cellulose, which is the
  main component of wood.
• Therefore, they get help from a protozoan called
  trichonympha.
• This protozoan lives in the gut of the termite.
  It breaks down the cellulose for the termite.
  The trichonympha gets a free meal and shelter
  the termite is able to eat and receive nutrients
  from the wood.

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Termite and Trichonympha
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Trichonympha
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Bees and Pollen

• Bees receive nectar from the flowers in order to
  make honey. As the bees collect nectar, they
  collect pollen on their body. As they fly to
  another flower, they pollinate it by dusting the
  pollen on the flowers stamen.

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Commensalism

• Commensalism A symbiotic relationship in which
  one organism benefits and the other is not
  affected.

Examples Clown fish and sea anemones Shark and
remora
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Clown Fish and Sea Anemones
The clown fish is immune to the stings of the sea
anemones tentacles. The clown fish makes its
home in the tentacles for protection. The clown
fish gets shelter, but the sea anemone gets
nothing.
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Shark and Remora
The remora hangs around the shark picking up any
scraps it may leave. The remora gets food while
the shark gets nothing.
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Parasitism

• Parasitism A symbiotic relationship in which
  one organism benefits but the other is harmed.

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Parasitism

• one organism benefits at the expense of another
  organism which is usually harmed
• Parasites can be
• Microparasites microscopic in size with rapid
  reproduction rate (blood protozoans)
• Macroparasites larger organisms (tapeworms)
• Endoparasites live inside the body of their
  host
• Ectoparasites live and feed on the outside
  surface of their host (lice)
• Social parasites manipulate the social behaviour
  of another species so that they can complete
  their life cycle

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Parasitism

• Examples
• Tapeworm and Humans
• Cuckoo bird and warbler
• Ticks

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Tapeworm and Humans
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Tapeworms and Humans
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Tapeworms and Humans
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Tapeworms and Humans
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Cuckoo birds and warblers
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Cuckoo and Warbler
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Ticks
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Tick
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Even Athletes foot is a parasite
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Parasitism
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Parasitism
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Symbiosis
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Disruption of Community Equilibrium

• interspecific interactions help maintain
  necessary equilibrium within complex and dynamic
  natural systems that sustain communities
• A variety of disturbances affect this equilibrium
• natural disasters
• introduction of nonindigenous species
• human influences
• HOMEWORK P688 1-7