unit 2, part 3 notes food chains, food webs, and the transfer of energy
TRANSCRIPT
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Unit 2, Part 3 NotesFood Chains, Food Webs, and
the Transfer of Energy
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Autotrophs
• A groups of organisms that can use the energy in sunlight to convert water and carbon dioxide into Glucose (food)
• Autotrophs are also called Producers because they produce all of the food that heterotrophs use
• Without autotrophs, there would be no life on this planet
• Ex. Plants and Algae
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Autotrophs
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Autotrophs• Chemotrophs
– Autotrophs that get their energy from inorganic substances, such as salt
– Live deep down in the ocean where there is no sunlight. Some bacteria use the sulphur to get energy and then use this to perform photosynthesis
– Ex. Bacteria and Deep Sea Worms
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Heterotrophs
• Organisms that do not make their own food
• Another term for Heterotroph is consumer because they consume other organisms in order to live
• Ex. Rabbits, Deer, Mushrooms
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Heterotrophs
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Heterotrophs
• Consumers– 1. Scavengers/Detritivores – feed on the
tissue of dead organisms (both plans and animals)
• Ex. – Vultures, Crows, and Shrimp
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Heterotrophs
• Consumers– 2. Herbivores – eat ONLY plants
• Ex. – Cows, Elephants, Giraffes
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Heterotrophs
• Consumers– 3. Carnivores – eat ONLY meat
• Ex. – Lions, Tigers, Sharks
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Heterotrophs
• Consumers– 4. Omnivores – eat BOTH plants and
animals • Ex. – Bears and Humans
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Heterotrophs
• Consumers– 5. Decomposers – absorb any dead material
and break it down into simple nutrients or fertilizers they do this by excreting an enzyme like substance, dissolving and absorbing the nutrients.
• Ex. – Bacteria and Mushrooms
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Transfer of Energy
• When a zebra eats the grass, it does not obtain all of the energy the grass has (much of it is not eaten)
• When a lion eats a zebra, it does not get all of the energy from the zebra (much of it is lost as heat)
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Transfer of Energy
• The two (2) previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate
• Only approximately 10% of the energy stored in the organic matter of one trophic level is used by the next level for growth.
• This is called the 10% law• The rest goes into heat, cellular
respiration and waste products
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When a bird eats a caterpillar, how much energy is available for the bird?
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Trophic Levels
• Energy moves from one organism to another when it is eaten
• Each step in this transfer of energy is know as a trophic level– The main trophic levels are producers,
consumers, and decomposers
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Food Chains• The energy flow from one trophic level to the
other is know as a food chain• A food chain is simple and direct• It involves one organism at each trophic level
– Primary Consumers – eat autotrophs (producers)– Secondary Consumers – eat the primary consumers– Tertiary Consumers – eat the secondary consumers– Decomposers – bacteria and fungi that break down
dead organisms and recycle the material back into the environment
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Food Chain
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Food Web
• Most organisms eat more the JUST one organism
• When more organism are involved it is know as a FOOD WEB
• Food webs are more complex and involve lots of organisms
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Food Web
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Food Web
• Notice that the direction the arrow points the arrow points in the direction of the energy transfer, NOT “what ate what”
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Food Web
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Biomass
• The total mass of the organic matter at each trophic level is called biomass
• This is always measured as dry weight because water has no useable energy.
• Biomass is often used as another term for potential energy – energy that is to be eaten and used.
• The transfer of energy from one level to another is very inefficient (10% Law)
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Productivity• Productivity: is the Rate at which
the biomass accumulates. It is usually written as grams per square metre of land per year
• A rainforest will produce 1000-3500g dry matter per m2 per year
• A dessert will produce from 10 up to 250g per m2 per year
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Energy transfer
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Ecological Pyramid
• Which level has the most energy?• Which level has the most organisms?• Which level has the least organisms?• Which level has the least energy?• Which level has the most biomass?
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Ecological Pyramids - Biomass
• An ecological pyramid shows the relationship between consumers and producers at different trophic levels in an ecosystem
• Shows the relative amounts of dry matter contained at each trophic level
• The Pyramid shows which level has the most dry matter for a given unit of time
• This can be inverted
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These can be inverted• In some ecosystems the pyramid can
look different. For example a simple marine system where:
• Phytoplankton grow and reproduce really quickly and then are eaten by the zoo plankton just as quickly.
• They never develop a large population size for a given period of time.
• Their rate of production, however is higher than the zooplankton that eat them or else the system would fail.
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• Biomass of some aquatic systems
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Pyramid of Energy
• Similar to the biomass pyramid • Shows the amount of energy
transferred to each level in a given area over a time period
• This can not be inverted.• The energy amounts at the bottom
must be more than the energy in the levels above. Why?
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Ecological Pyramid of Energy
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Ecological Pyramid of Energy
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Pyramid of Numbers
• This is when each box of the pyramid shows the numbers of individuals present in that level.
• These can be inverted• For example: If you have 3-4 rose
bushes only but hundreds of insects feeding off them.
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Biomass versus Numbers Pyramids
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Symbiosis
• A close and permanent association between organisms of different species– Commensalism – a relationship in which one
organism benefits and the other is not affected• Example: Barnacles on a whale
– Mutualism – a relationship in which both organisms benefit from each other
• Example: Birds eating pest off a rhino’s back
– Parasitism – A relationship in which one organism benefits and the other is harmed
• Example: Ticks on a dog
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Ecological Succession
• A change in the community in which new populations of organisms gradually replace existing ones
– 1. Primary Succession – occurs in an area where there is no existing communities and for some reason (s) a new community of organisms move into the area
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Ecological Succession
• A change in the community in which new populations of organisms gradually replace existing ones
– 2. Secondary Succession – occurs in an area where an existing community is partially damaged
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Ecological Succession
• A change in the community in which new populations of organisms gradually replace existing ones
– 3. Climax Community – a community that is stable and has a great diversity of organisms