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Biology Chapter 3
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3.1 – What is Ecology? Interactions and Interdependence Ecology – the study of interactions among organisms and their environment Oikos (ec) – Greek word meaning house Ology – means study of
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Levels of Organization
The levels of organization that ecologists study include: Individuals Species – group of similar organisms that can breed and produce fertile offspring Populations – group of individuals of the same species that live in the same area and interbreed Communities – different populations that live together in a defined area
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Ecosystem – The interaction of all the organisms and the environment in a given area
Biome – a group of ecosystems that have the same climate Biosphere – part of Earth in which life exists including land, water and atmosphere It extends about 8km above the Earth’s surface to about 11km below If you could shrink earth to the size of an apple, the biosphere would be thinner than the apple’s peel
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Biotic and Abiotic Factors
Biotic Factors – all the living organisms in an ecosystem Example: tree, bird, bacteria, fungi Abiotic Factors – nonliving factors in an ecosystems Example: temperature, precipitation, wind, soil, sunlight, humidity Habitat – area where an organism lives Includes both biotic and abiotic factors Niche – the role and position a species has in its environment No two species can share the same niche in the same habitat
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3.2 – Energy Flow Sunlight is the main energy source for life Autotrophs Make their own energy Convert sun energy into chemical energy Also called a producer Plants are the main autotrophs on land Algae are the main autotrophs in water
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Some autotrophs can produce food in the absence of light
Chemoautotrophs – organisms use chemical energy to produce carbohydrates Performed by several types of bacteria Live in… Volcanic vents Deep ocean Hot springs Marshes
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Heterotrophs Get energy from other organisms Unable to make its own energy Also called consumers Types of Heterotrophs Herbivores Eats only plants Example: cows, deer, rabbits, bees, elephants, squirrels
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Carnivores Eats only animals Example: snakes, dogs, lions, crocodiles Omnivores Eats plants and animals Example: humans, bears, crows
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Detrivores Eat decomposing bits of organic matter Example: mites, earthworms, snails, crabs Decomposers Break down organic matter Example: bacteria and fungi Scavenger Ingest nonliving plants and animals Example: vulture, termite, beetle
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Feeding Relationships
Food Chain – a straight line series of steps by which energy is stored and passed on to higher trophic levels
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Food Web – a network of crossing interlinked food chains that shows all the possible feeding relationships at each trophic level
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Energy is passed through no more than four or five trophic levels
Trophic Levels – step in a food chain or food wed Plants and other producers are 1st trophic level Consumers make up the 2nd, 3rd, or higher trophic levels Each consumer depends on the trophic level below it for energy Energy is transferred from one trophic level to another and is never 100% At each trophic level only 10% of the energy taken in by the organism is stored. The rest is used up during metabolism to process the energy
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Ecological Pyramids Ecological Pyramid – a diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or food web Example: Ecological Pyramids
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Community Interactions
Competition – occurs when organisms of the same or different species attempt to use the same resources Predator – eat other animals Prey – the animal a predator eats Symbiosis – relationship in which two species live closely together
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Three Types of Symbiosis
Mutualism Both species benefit from the relationship Example: plants and bacteria on roots Shark and fish
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Commensalism One organism benefits and the other is neither helped nor harmed Example: tree and bird nest
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Parasitism One organism lives on or inside another organism and harms it Example: tick, ringworm
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Fig , p. 862
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3-3 Cycles of Matter Biogeochemical Cycles – process in which elements, chemical, and other forms of matter are passed from one organism to another and from one part of the biosphere to another
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The Water Cycle Evaporation – process by which water changes from a liquid to a gas Transpiration – loss of water from plants by the process of evaporation Condensation – water vapor changes to a liquid Precipitation – water returns to the earth (rain, snow, hail)
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The Carbon Cycle Carbon is released into the atmosphere by… Respiration Burning fossil fuels Volcanic activity Burning trees Carbon is taken out of the atmosphere by… Photosynthesis performed by plants Carbon is released into the ground by… Decomposition Carbon is taken out of the ground by… Mining oil and coal Roots of plants
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Photosynthesis Volcanic Activity Burning Trees Respiration
CO2 Photosynthesis Volcanic Activity Burning Trees Burning Fossil Fuels Respiration Organism eats plants C6H12O6 Decomposition Coal Root Uptake Oil
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Nitrogen Cycle Gaseous nitrogen (N2)makes up 80% of the atmosphere Nitrogen Fixation Bacteria convert N2 to ammonia (NH3) This dissolves forming ammonium (NH4) Ammonification Bacteria degrade nitrogenous wastes and remains of organisms. Convert NH3 to NH4
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Nitrification Bacteria convert NH4 to nitrite (NO2) to nitrate (NO3) Denitrification Bacteria convert extra nitrates or nitrites (NO3, NO2) to N2 N2 is released back into the atmosphere
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Bacteria in the soil convert N2 → NH3 → NH4 Ammonification
Gaseous Nitrogen N2 Nitrogen Fixation Bacteria in the soil convert N2 → NH3 → NH4 Ammonification Bacteria convert wastes and decomposing organics to NH3 → NH4 Denitrification Bacteria convert NO3 → N2 Autotrophs can take up NH4 and NO3 Nitrification Bacteria convert NH4 → NO2 → NO3
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Humans are harming the nitrogen cycle by:
Deforestation Conversion of grasslands for agriculture Sewage enters waterways Fossil fuel burning Vehicles having combustion engines releases NO2
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4-2 What Shapes an Ecosystem?
Ecological Succession Succession – changes that occurs in a community over time Pioneer Species – first species to populate the area Climax Community – a stable mature community that undergoes little or no change in species
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Two Types of Succession
1. Primary Succession Succession that occurs on surfaces where no soil exists Example: rock surfaces formed after volcanoes erupt
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Secondary Succession Succession following a disturbance that destroys a community without destroying the soil Because soil already exists, secondary succession usually takes less time than primary succession Example: fires, floods, farming, construction, hurricanes, tornadoes
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