Post on 29-Jan-2016
Interactions within Communities
Populations of different species interact in a community
Some organisms rely on other organisms within the community for survival
Ecological NichesAn organism’s ecological characteristics,
including use of and interaction with abiotic and biotic resources within its environment
Think of a habitat being one’s “address” and its ecological niche as its “occupation”e.g. a lion’s 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
Ecological NichesA 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
Interspecific competitionInteraction between individuals of different
species for essential common resource(s) that are in limited supplyserves to restrict population growthCan 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
Resource partitioningAvoidance
of/reduction in competition for similar resources by individuals of different species occupying different non-overlapping ecological niches
Lake Malawi Cichlids850 species from
one ancestor!!
Predationinterspecific 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
Defence Mechanisms - Plantsplants use both morphological defences
thorns, hooks, spines, needleschemical defences
the defensive systems in plants act as selective agents which initiate the evolution of counter-adaptations in herbivore populationsthese changes brought about by co-evolution
between plants and insets can affect competition
Defence Mechanisms - Animalssometimes employ passive defence
mechanismse.g. hiding
others employ active defence mechanismse.g. fleeingmore costly to prey in terms of energy uses
other effective behavioural defences existe.g. alarm callse.g. camouflage (cryptic colouration)e.g. visual warnings – in terms of chemical
defences
SymbiosisSome organisms
have obligatory mutualismneither organism
could grow or reproduce without each other
Mutualism
Mutualism – A symbiotic relationship in which both
species benefit.
Mutualism
Examples:Cowbirds and Large
AnimalsTermites and
TrichonymphaBees and Flowers
Cowbirds and Large AnimalsThe 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.
Termites and TrichonymphaYou probably think termites eat wood; they do…in a way. Termites can’t 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.
Termite and Trichonympha
Trichonympha
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.
Commensalism
Commensalism – A symbiotic relationship in which one organism benefits and the other is not affected.
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.
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.
Parasitism
Parasitism – A symbiotic relationship in which one
organism benefits but the other is harmed.
Parasitismone organism benefits at the expense of
another organism which is usually harmed.
Tapeworm and Humans
Tapeworms and Humans
Cuckoo and Warbler
Ticks
Tick
Parasitism
Disruption of Community Equilibriuminterspecific interactions help maintain
necessary equilibrium within complex and dynamic natural systems that sustain communities
A variety of disturbances affect this equilibriumnatural disastersintroduction of nonindigenous specieshuman influences