1 community ecology chapter 54. 2 biological communities a community consists of all the species...
TRANSCRIPT
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Community Ecology
Chapter 54
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Biological Communities
• A community consists of all the species that occur together at any particular locality.
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Fundamental and Realized Niches
• An organism’s niche is the total of all ways it utilizes the resources of its environment.
– fundamental - entire niche potentially available to an organism
– realized - actual niche utilized by an organism
• Habitat is the place where an organism lives.
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Realized Niche
• Interspecific competition - Occurs when different species attempt to utilize the same resource.
– interference - individuals fighting over the same resource
– exploitative - individuals utilizing shared resources
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Principle of Competitive Exclusion• The principle of competitive exclusion states
that no two species utilizing the same niche can coexist indefinitely.
– one will eventually eliminate the other Gause’s Paramecium experiments
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Detecting Interspecific Competition
• Negative effects of one species on another do not automatically indicate competition.
– Presence of one species may attract a predator that consumes both, causing one species to have a lower population size than the other.
must always look at underlying ecological mechanisms
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Predation and Prey Populations
• Predation occurs when one organism consumes another.
– provides strong selective pressure on prey populations
Any physiologic characteristic or behavior that would decrease the probability of capture should be strongly favored.
increased fitness
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Plant Defenses Against Herbivores
• Morphological – thorns, spines, etc.
• Chemical – secondary chemical compounds
• Evolutionary response of herbivores– Certain groups of herbivores are associated
with each group of plants protected by a particular secondary compound.
coevolution
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Animal Defenses Against Predators
• Some animals that feed on plants rich in secondary compounds receive an extra benefit.
– caterpillars that feed on members of the milkweed family
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Animal Defenses Against Predators
• Chemical defenses– poisons and stings
• Defensive coloration– aposematic coloration (warning coloration)
individuals advertise poisonous nature– cryptic coloration
camouflage (blending coloration)
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Mimicry
• Batesian mimicry– Palatable insects resemble brightly colored, distasteful species.
• Mullerian mimicry– Unrelated protected species resemble one another.
predators learn more quickly
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Coevolution and Symbiosis
• Coevolution involves long-term mutual evolution of two or more species.
– predator-prey interactions– symbiotic relationships
two or more kinds of organisms live together in permanent relationships
commensalism, mutualism, and parasitism
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Commensalism
• One species in symbiotic relationship benefits while the other is neither helped or hurt.
– tropical fish and sea anemones
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Mutualism
• Both species in relationship benefit.– mutual cooperation
ants and acacias
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Parasitism
• Parasite benefits while inflicting some form of harm to the prey.
– ectoparasites external parasites - lice
– endoparasites internal parasites
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Interactions Among Ecological Processes
• Keystone species– Species that have a particularly strong
effect on community composition. top predators
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Succession• Succession is the process of ecosystems
changing from a simple to a more complex structure.
– primary succession - occurs in bare areas– secondary succession - occurs following disturbance
• Succession occurs because species alter the habitat and available resources in ways that favor other species.
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An ecosystem includes all the organisms living in a particular place, and the abiotic environment in which they interact.
ProducersAutotrophs - capture light energy and manufacture own chemical energy
ConsumersHeterotrophs - must obtain organic molecules from autotrophs
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Trophic Levels - Food Chain
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Tertiaryconsumer
Primary consumer
Primary producer
Secondaryconsumer
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Trophic Levels
• Trophic level refers to the feeding level of an organism.• Organisms from each trophic level constitute a food chain.
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The Energy in Food Chains• Second Law of Thermodynamics
food chains are generally limited to 3 or 4 steps (trophic levels) ultimately determined by the amount of sunlight
• On average, 10% of the organic matter (energy) transfers from one trophic level to the next.
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Interactions Among Trophic Levels• Trophic cascading
effect of one trophic level flows down to lower levels. (top-down effects)
Bottom-up effectsproductivity of an ecosystem is low, herbivore populations will be too small to support any predators.
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Veg
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Her
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Productivity
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Interconnected food chains constitute a food web.