ib t5 1 communities
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5.1: Communities
Topic 5: Ecology & Evolution
Miss Friedman
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5.1.1: Definitions
EcologyThe study of the relationship between living
organisms and between those organisms and theirenvironment
Ecosystem A community and its abiotic environment
Population A group of organisms of the same species who live
in the same area at the same time
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5.1.1: Definitions
CommunityPopulations of different species in the same area
which are interacting
Species A group of organisms which can interbreed and
produce fertile offspring
HabitatLocation within which a species normally lives
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5.1.2: Autotrophs & heterotrophs
Autotroph Producer An organism thatsynthesises its organicmolecules from simpleinorganic molecules
Heterotroph consumer
Obtains organicmolecules from otherorganisms
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5.1.3: Consumers, detritivores,saprophytes
Consumers An organism that ingests other organic matter that is
living or recently dead
Detritivores An organism that ingests non-living organic matter
Saprophytes An organism that lives on or in non-living organicmatter, secreting digestive enzymes into andabsorbing the products of digestion
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5.1.4: Food chains
Food chains show a simple linear flow of who eats who
Therefore shows the energy flowing throughthe links in the chain
Questions to consider!How is energy lost in the chain?Why are big, dangerous predators so rare?
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5.1.5: Food webs A diagram that shows how food chains are linkedtogether into more complex feeding relationships
Advantages over food chain
o Shows much more complex interactions between specieswithin a community/ecosystemo More than one producer supports a communityo A single producer is a food source for many primary
consumerso A consumer might have a number of different food sources
on the same/different trophic levelso A consumer can be an omnivore, feeding as a primary
consumer but also as a consumer at higher tropic levels
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5.1.6: Trophic level The tropic level of an organism defines thefeeding relationship of that organism to other
organisms in a food web
Autotraph Producer Tropic level 1Hetertroph Primary consumer Tropic level 2
Hetertroph Secondary consumer Trophic level 3
heterotroph Tertiary consumer Trophic level 4
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5.1.7: Determining tropic levelsin food chains/webs
Assign tropiclevels to the
food web onthe right!
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5.1.8: Constructing a food web
Producers are usually shown at the bottom Use full name of organisms
Arrows show the movement of matter & energy
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5.1.9:Light & food chains
Sunlight is the source of energy for mostcommunities, both aquatic and terrestrial
Very few communities deep in the oceanuse geothermal energy
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5.1.10: Energy flow in Foodchain
a) Not all solar energy will come intocontact with chlorophyll and willtherefore not be trapped in thesynthesis of organic compounds
b) Photosynthesis c) Consumers feeding and passing on
energy in the food d) Loss of energy as heat from
respiration e) death and the consumption of dead organisms by detritivores. Or asfood not assimilated because of incomplete digestion.
Energy Loss loss of energy in undigested food
which will then be used bysaprophytes/ decomposers
loss of heat energy in the reactions of respiration
ultimately all energy will be lost hasheat
http://click4biology.info/c4b/3/Chem3.8.htmhttp://click4biology.info/c4b/3/Chem3.8.htm -
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5.1.11: Efficiency of energytransformations
When energy ischanged from oneform into another, itis never 100%efficient
Approximately only10-20% of theenergy on onetrophic level will beassimilated at thenext higher trophiclevel
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5.1.12: Shape of energypyramids
A pyramid of energy is a graphicalrepresentation of the amount of energy of each trophic level in a food chain
The units are kJ/m2
/yr The narrowing shape illustrates the gradual
loss of energy processing along the links of a
food chain to higher trophic levels
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5.1.13: Energy and matter inecosystems
Energy is NOT recycled through the ecosystem Energy is constantly received from the sun and
constantly radiates out in the form of light & heat Matter IS recycled The process of recycling nutrients requires energy
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5.1.14: Decomposers Two main groups are detritivores (e.g.
earthworms, dung beetles) and saprotrophs (e.g.fungi, bacteria)
Decomposition is a complex process and servesmany functions; formation of soil, recycling of nutrients, reduction of high energy carboncompounds
Organic molecules are oxidized to release nitrogenin the form of nitrate, nitrite, and ammonia
Oxidation of organic compounds provides energy forsaprophyte but returns matter to abioticenvironment
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