population interactions ch. 51
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Population InteractionsCh. 51
Ecological Community • Interactions between all living
things in an area• Coevolution changes encourages
by interactions between two or more species– Predator vs. Prey– Herbivore vs. Plant
• Food Availability creates complex interactions:– Optimal Foraging Theory animal
must balance the energy spent to get food with the energy they get from eating it; determines diet
– Specialist eat one or few types– Generalist eat almost anything
Arms Race• Prey must adapt methods to
protect themselves if they are to survive– Hiding places; physical defenses;
poisons– Aposematic coloration bright,
contrasting color patterns that act as a warning of poison
• Predators must learn to over come these methods too– Recognize poisonous prey;
hunting skills; immunity to poisons
• Cryptic coloration camouflage to help hide predators and prey
Copy Cat• Mimicry resembling the
appearance of a another species to gain an advantage
• Batesian harmless species mimics a dangerous species – Mimic gains protection but
does not commit energy like the model does
• Mullerian dangerous species have similarities; predators learn of danger much faster
Fight for the Right to Survive• Interspecific competition competing
between different species– IntRAspecific competition inside a
population of one species1) Interference species directly limit
access to resources– Lions chase away hyenas
2) Exploitative species lower amount of resources so they are harder to find– Birds eat seeds so it is harder for
squirrels to find them• Competitive Exclusion Principle if
two population require the same limited resources in the same way, one will destroy the other
You Need a Niche• Niche specific way a species
interacts with its environment– All successful businesses need a
market in order to survive• Ecological niche the food
type, amount, and space required for a species to survive– Fundamental all possible
resources that CAN be used– Realized all possible resources
ACTUALLY used• Competition can occur when
fundamental niches overlap
Cant We All Just Get Along• Not all overlapping parts of niches
lead to competition– All animals breath air but rarely have to
compete for it• Resource partitioning different
species can use the same resources but can get them or use them in different ways– Birds species can feed on the same
insects but get them different parts of the tree
• Character Displacement– Sympatric species living in the same
area are more morphologically different• Darwin’s Finches
– Allopatric species living in different areas are less morphologically different
Symbiotic Interactions• Symbiosis physical ecological
interactions1) Commensalism one species benefits
and one species is not affected– Grass eaters stir up insects that birds will eat
2) Mutualism both species benefit– E. coli in your intestine gets nutrients from
us and gives us vitamins 3) Parasitism one species benefits
(parasite) and one species is negatively affected (host) – Tapeworm takes nutrition from our intestine
and decreases our health• Endoparasites live inside the body• Ectoparasites live outside the body
Defining A Community• Some see communities as “super-
organisms”; species in the community are so well connected they require each other to exist and to exist in certain amounts– Species composition could reach equilibrium
and shifts with major changes• Others think communities constantly
change and have no strict boundaries or composition
• Some biomes do have clear boundaries though; Water vs. Land, Aerobic vs. Anaerobic
• Ecotones edges where communities meet; full of biodiversity
• ESSAY!!!• Explain which of these ideas you most
agree with; support with reference material
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