IB T5 1 Communities

7/27/2019 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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