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Community
Collection of interacting organisms of different species within an ecosystem.
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Diversity
- The variety of different kinds of organisms.
- 1. Species richness
- 2. Relative abundance
- 3. Species diversity
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Species richness
Total number of different spp in the community
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Relative abundance
Size of populations of different spp in the community
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Species diversity
The number and relative abundance of spp in a community.
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Other Properties of a Community
- 1. Prevalent Form of Vegetation.
- 2. Stability.
- 3. Trophic Structure.
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Interspecific Interactions
Encounters be-tween members of different species. Three main types of interspecific interactions: Competition, Predation, Symbiosis
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Competitive Exclusion Principle
Populations of two spp cannot coexist in a community if their niches are nearly identical. Usually results in one spp dying out, moving out, or adapting to occupy another niche. Possible mechanism for natural selection.
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Interspecific Competition
- When populations of two or more spp in a community rely on similar limiting resources.
- 1. Niche
- 2. Resource partitioning
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Niche
Sum total of spp use of biotic and abiotic resources in the environment (eco-logical role in nature - job). Example: birds of prey - diurnal v. nocturnal.
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Resource partitioning
Differentiation of niches that enables similar spp to co-exist in a community (Darwin’s finches).
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Predation
- Predator: Organism that eats another.
- Prey: Organism that gets eaten by another (food).
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Predator Adaptations
- 1. Acute senses
- 2. Ability to catch and subdue prey.
- 3. Fast and agile (pursuit).
- 4. Camouflage (ambush).
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Plant Defenses v.
Herbivores
- 1. Chemical weapons: Poisonous (nicotine) or distasteful (peppermint).
- 2. Mechanical weapons: Spines or thorns.
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Animal Defenses v. Predators
- 1. Hiding, fleeing (passive).
- 2. Alarm calls distraction (active).
- 3. Cryptic coloration (camouflage).
- 4. Mechanical, chemical defenses.
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Specialized Animal
Defenses v. Predators
- 1. Aposematic coloration: Bright-color warning. Frog.
- 2. Batesian mimicry: Copy a harmful spp. Camouflage.
- 3. Mullerian mimicry: Shared copies of distasting spp. Monarch taste bad so Bisoroy (spelling) must taste bad because they look similar.
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Symbiotic Relationships
- Interaction between two or more spp that live in close contact.
- 1. Parasitism: Parasite, Host
- 2. Mutualism
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Parasite
Organism that lives on or in another organism – usually smaller; benefits.
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Host
Organism supporting another organism living on or in it –usually bigger; harmed.
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Mutualism
Interaction between two or more species in which both benefit. Methanogens & N-fixing bacteria, Acacia trees and ants, Coevolution usually occurs between mutualistic spp.
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Disturbance
Episodes that damage biological communities temporarily or long term by destroying organisms and affecting the availability of resources. Examples: storms, fires, floods, droughts, & humans.
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Ecological Succession
Transition in spp composition of a community following an ecological disturbance.
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Primary succession
Occurs in a virtually lifeless area where no original organisms exist; no soil is present.
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Secondary succession
Occurs where an existing community has been cleared by a disturbance, but the soil is left in tact.
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Trophic Levels and
Food Chains
- 1. Trophic level
- 2. Food chain
- 3. Producers
- 4. Consumers
- 5. Omnivores
- 6. Decomposers
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Trophic level
Feeding relationship.
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Food chain
Logical sequence of food transfer from one trophic level to another.
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Producers
Organisms that use sunlight for photosynthesis and produce organic molecules from inorganic molecules. Examples: cyanobacteria, algae, & plants.
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Consumers
- Organisms that obtain energy as organic material from other organisms. Examples: herbivores (plant eaters - primary) & carnivores (meat eaters - secondary).
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Omnivores
Organisms which feed on both plants and animals.
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Decomposers
Organisms which feed on dead and decaying material.
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Food Web:
A system of interwoven food chains creating a more stable community.
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Pyramids
- 1. Pyramid Base; Producers.
- 2. 1st Level: 1° Consumers.
- 3. 2nd Level: 2° Consumers
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Biomass
Dry weight of all organisms at a specific trophic level.
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Chemical Cycles
- Include carbon, nitrogen, phosphorous, and water.
- 1. All cycles have an abiotic reservoir and can bypass the biotic components.
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Chemical Cycles –
Nitrogen
- 1. Certain cycles (N) require microorganisms in order to enter biotic components.
- a)80% of atmosphere is N, but plants cannot utilize N directly (N-fixing bacteria).
- b)Animals obtain N from their diet.
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Biomes
Large regional communities primarily determined by climate (temperatures & rainfall as well as altitude and latitude (terrestrial).
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Aquatic Biomes –
Freshwater
- 1. Standing bodies of water (lakes & ponds).
- 2. Flowing water (rivers & streams).
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Estuaries
Where freshwater merges with salt. Marine life distributed according to depth, degree of light penetration, distance from shore & surface, and temperature.
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