Energy and ecosystems

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What is an ecosystem?
All the biotic (living) and abiotic (non-living) factors in an area
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What is a population?
A group of organisms of the same species living in a particular area and interbreeding
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What is a niche?
An organism's place within an ecosystem. Unique. Concerns its habitat, how it feeds, its response to predation etc.
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What is a microhabitat?
A small specialised habitat within a larger habitat
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What is an autotroph?
An organism that synthesises complex organic molecules from simple inorganic compounds such as CO2 and water
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What is a heterotroph?
Organism that consumes complex organic molecules derived from other living organisms
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What is a food web?
A diagram that represents the flow of energy through an ecosystem
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Describe the 4 main components of a food chain
Energy source (sunlight), primary producers (autotrophs, convert light energy to chemical energy), primary consumers (feed on primary producers/herbivores), secondary consumers (feed on primary consumers/carnivores), decomposers (saprophytes)
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What are decomposers and why are they important?
They are saprophytes that feed extracellularly on dead organisms or non living organic compounds. Have an important role in recycling nutrients in the ecosystem.
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Why is energy transfer along a food chain inefficient, and how does this effect the food chain?
Energy is lost as heat in respiration, inedible material e.g. fur, through excretion. Prevents chain having more than 4/5 trophic levels.
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Why isnt all of the light that falls on a leaf utilised in photosynthesis?
Wrong wavelength of light absorbed by photosynthetic pigments, some of the light is reflected or transmitted through the leaf, so not absorbed by pigments
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What is photosynthetic efficiency?
A meaure of how much of the light energy falling on a plant is incorporated into the biochemical products of photosynthesis. Plants rarely above 5%
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How is photosynthetic efficiency calculated?
(energy incorporated into photosynthetic products)/(total light falling on plant) x100
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What is the difference between gross primary productivity and net primary production?
GPP: rate at which producers make photosynthetic products. NPP = GPP - energy used in plant respiration. Represents potential food available to primary consumers.
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Why do herbivores have a lower efficiency of energy conversion compared to carnivores?
Herbivore diet contains higher amount of difficult-to-digest molecules like cellulose, so digestion is quite inefficient. Carnivore digestion is more efficient as protein is much easier to digest than plant material
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What is gross ecological efficiency and how is it calculated?
A measure of how much energy is transferred from one trophic level to the next. (energy in trophic level)/(energy in previous level) x 100
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Describe, it and the advantages and disadvantages of a pyramid of numbers?
Shows number of organisms at each trophic level. Easy to collect, can easily be inverted due to size differences between organisms
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Describe it and the advantages and disadvantages of a pyramid of biomass
Biomass of the organisms at each trophic level. Harder to collect, less easily inverted - only really due to temporal population variations
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Describe it and the advantages and disadvantages of a pyramid of energy
Shows the energy in each trophic level per unit are per unit times. Energy is always lost, only one source, so never can invert. Very difficult to collect data.
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Define succesion
The change in the composition of the community of organisms in an ecosystem over time
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Define primary succession
the introduction of plants/animals into an area that has not previously been colonised
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Define secondary succesion
The reintroduction of organisms into a bare habitat previously occupied by plants and animals
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Describe primary succession of bare rock
Algae and lichens (pioneer species) colonise bare rock. Erosion, death and decay develops simple soil, suitable for moss growth. Further decay improves soil, grasses grow, then shrubs then trees. Trees form a wood: climax community, stable end sere.
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Other cards in this set

Card 2

Front

What is a population?

Back

A group of organisms of the same species living in a particular area and interbreeding

Card 3

Front

What is a niche?

Back

Preview of the front of card 3

Card 4

Front

What is a microhabitat?

Back

Preview of the front of card 4

Card 5

Front

What is an autotroph?

Back

Preview of the front of card 5
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