Lecture 20-Communities

Lecture 20-Communities - CommunitiesandEcosystems

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Communities and Ecosystems Biological community = the different species of plants and animals that interact with each other and share an ecosystem Interdependence Same geographic area Same habitat type 1
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Communities and Ecosystems Ecosystem = plants, animals, plus the physical environment e.g. water, soil, nutrients, biomass, temperature, rainfall 2
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Communities and Ecosystems Physical environment affects which plants and animals occur Physical environment affects how many organisms an area can support 3
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Communities and Ecosystems Natural processes affect the physical environment (soil, nutrients, biomass, temperature, rainfall) Photosynthesis Respiration Decomposition 4
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Communities and Ecosystems Energy moves through biological communities Analyze this by looking at food chains Each level of a food chain = trophic level 5
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Food Chains Producers = plants Make their own food from the sun’s energy Consumers = must eat other organisms 6
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Consumer Consumer Consumer Producer 7
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Types of Consumers Herbivores: eat plants Carnivores: eat other animals Omnivores: eat plants and animals Decomposers: eat dead stuff 8
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Carnivore Carnivore Herbivore Producer 9
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Food Webs Communities are usually made up of multiple food chains Food webs Many interactions between multiple species 10
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Energy Transfer Energy is neither created nor destroyed Energy can be transformed from one form to another Sun —> Plant tissue —> Animal tissue 12
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Trophic Levels Divisions within trophic levels: Primary producer = plant Primary consumer (1°) = eats plant Secondary consumer = eats 1° Tertiary consumer = eats 2° Quaternary consumer = eats 3° 13
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Trophic Levels Energy conversion is not perfectly efficient Heat Digestion 19
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Trophic Levels Energy is lost each time you go up the food chain! This is why top predators are less common than primary consumers Also why top predators need more space (to support their prey) 20
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Trophic Levels Biomass = mass of organisms within a given area unit Provides an estimate of total energy available in an ecosystem 21
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Community Population Control Bottom-up regulation of food web: species numbers are controlled by: Amount of primary productivity Nutrient levels Prey availability 22
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Community Population Control Bottom-up regulation of food web: species numbers are controlled by: Amount of primary productivity Nutrient levels Prey availability Affected by primarily by competition, not predation 23
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Community Population Control Bottom-up regulation = species numbers are controlled by amount of primary productivity E.g. when phytoplankton increases, so does zooplankton 24
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Community Population Control Top-down regulation of food webs: Abundance or number of species at lower trophic levels is controlled by effects of consumers at higher trophic levels Predator numbers control prey 25
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This note was uploaded on 08/30/2008 for the course BIOS 230 taught by Professor Gibbons during the Spring '08 term at Ill. Chicago.

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Lecture 20-Communities - CommunitiesandEcosystems

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