5.1: Communities5.1: Communities

Topic 5: Ecology & EvolutionTopic 5: Ecology & Evolution

Miss FriedmanMiss Friedman

5.1.1: Definitions5.1.1: Definitions

EcologyEcologyThe study of the relationship between living The study of the relationship between living

organisms and between those organisms and their organisms and between those organisms and their environmentenvironment

EcosystemEcosystemA community and its abiotic environmentA community and its abiotic environment

PopulationPopulationA group of organisms of the same species who live A group of organisms of the same species who live

in the same area at the same timein the same area at the same time

5.1.1: Definitions5.1.1: Definitions

CommunityCommunityPopulations of different species in the same area Populations of different species in the same area

which are interactingwhich are interacting

SpeciesSpeciesA group of organisms which can interbreed and A group of organisms which can interbreed and

produce fertile offspringproduce fertile offspring

HabitatHabitatLocation within which a species normally livesLocation within which a species normally lives

5.1.2: Autotrophs & 5.1.2: Autotrophs & heterotrophsheterotrophs

Obtains organic molecules from other organisms

consumerHeterotroph

An organism that synthesises its organic molecules from simple inorganic molecules

ProducerAutotroph

5.1.3: Consumers, detritivores, 5.1.3: Consumers, detritivores, saprophytessaprophytes

ConsumersConsumersAn organism that ingests other organic matter that is An organism that ingests other organic matter that is

living or recently deadliving or recently dead

DetritivoresDetritivoresAn organism that ingests non-living organic matterAn organism that ingests non-living organic matter

SaprophytesSaprophytesAn organism that lives on or in non-living organic An organism that lives on or in non-living organic

matter, secreting digestive enzymes into and matter, secreting digestive enzymes into and absorbing the products of digestionabsorbing the products of digestion

5.1.4: Food chains5.1.4: Food chains

►Food chains show a simple linear flow of Food chains show a simple linear flow of “who eats who” “who eats who”

►Therefore shows the energy flowing through Therefore shows the energy flowing through the links in the chainthe links in the chain

Questions to consider!Questions to consider!How is energy lost in the chain?How is energy lost in the chain?

Why are big, dangerous predators so rare?Why are big, dangerous predators so rare?

5.1.5: Food webs5.1.5: Food webs► A diagram that shows how food chains are linked A diagram that shows how food chains are linked

together into more complex feeding relationshipstogether into more complex feeding relationships

Advantages over food chainAdvantages over food chaino Shows much more complex interactions between species Shows much more complex interactions between species

within a community/ecosystemwithin a community/ecosystemo More than one producer supports a communityMore than one producer supports a communityo A single producer is a food source for many primary A single producer is a food source for many primary

consumersconsumerso A consumer might have a number of different food sources A consumer might have a number of different food sources

on the same/different trophic levelson the same/different trophic levelso A consumer can be an omnivore, feeding as a primary A consumer can be an omnivore, feeding as a primary

consumer but also as a consumer at higher tropic levelsconsumer but also as a consumer at higher tropic levels

5.1.6: Trophic level5.1.6: Trophic level► The tropic level of an organism defines the The tropic level of an organism defines the

feeding relationship of that organism to other feeding relationship of that organism to other organisms in a food weborganisms in a food web

Trophic level 4Tertiary consumerheterotroph

Trophic level 3Secondary consumerHetertroph

Tropic level 2Primary consumerHetertrophTropic level 1ProducerAutotraph

5.1.7: Determining tropic levels 5.1.7: Determining tropic levels in food chains/websin food chains/webs

►Assign tropic Assign tropic levels to the levels to the food web on food web on the right!the right!

5.1.8: Constructing a food web5.1.8: Constructing a food web

►Producers are usually shown at the bottomProducers are usually shown at the bottom►Use full name of organismsUse full name of organisms►Arrows show the movement of matter & Arrows show the movement of matter &

energyenergy

5.1.9:Light & food chains5.1.9:Light & food chains

►Sunlight is the source of energy for most Sunlight is the source of energy for most communities, both aquatic and terrestrialcommunities, both aquatic and terrestrial

►Very few communities deep in the ocean Very few communities deep in the ocean use geothermal energyuse geothermal energy

5.1.10: Energy flow in Food 5.1.10: Energy flow in Food chainchain

► a) a) Not all solar energy will come into Not all solar energy will come into contact with chlorophyll and will contact with chlorophyll and will therefore not be trapped in the therefore not be trapped in the synthesis of organic compoundssynthesis of organic compounds

► b)b) PhotosynthesisPhotosynthesis► c)c) Consumers feeding and passing on Consumers feeding and passing on

energy in the food energy in the food ► d)d) Loss of energy as heat from Loss of energy as heat from

respirationrespiration► e)e) death and the consumption of death and the consumption of

dead organisms by detritivores. Or as dead organisms by detritivores. Or as food not assimilated because of food not assimilated because of incomplete digestion.incomplete digestion.

Energy LossEnergy Loss► loss of energy in undigested food loss of energy in undigested food

which will then be used by which will then be used by saprophytes/ decomposerssaprophytes/ decomposers

► loss of heat energy in the reactions of loss of heat energy in the reactions of respirationrespiration

► ultimately all energy will be lost has ultimately all energy will be lost has heatheat

5.1.11: Efficiency of energy 5.1.11: Efficiency of energy transformationstransformations

► When energy is When energy is changed from one changed from one form into another, it form into another, it is never 100% is never 100% efficientefficient

► Approximately only Approximately only 10-20% of the 10-20% of the energy on one energy on one trophic level will be trophic level will be assimilated at the assimilated at the next higher trophic next higher trophic levellevel

5.1.12: Shape of energy 5.1.12: Shape of energy pyramidspyramids

►A A pyramid of energypyramid of energy is a graphical is a graphical representation of the amount of energy of representation of the amount of energy of each trophic level in a food chaineach trophic level in a food chain

►The units are kJ/mThe units are kJ/m22/yr/yr►The narrowing shape illustrates the gradual The narrowing shape illustrates the gradual

loss of energy processing along the links of a loss of energy processing along the links of a food chain to higher trophic levelsfood chain to higher trophic levels

5.1.13: Energy and matter in 5.1.13: Energy and matter in ecosystemsecosystems

► Energy is NOT recycled through the ecosystemEnergy is NOT recycled through the ecosystem► Energy is constantly received from the sun and Energy is constantly received from the sun and

constantly radiates out in the form of light & heatconstantly radiates out in the form of light & heat► Matter IS recycledMatter IS recycled► The process of recycling nutrients requires energyThe process of recycling nutrients requires energy

5.1.14: Decomposers5.1.14: Decomposers► Two main groups are Two main groups are detritivoresdetritivores (e.g. (e.g.

earthworms, dung beetles) and earthworms, dung beetles) and saprotrophssaprotrophs (e.g. (e.g. fungi, bacteria)fungi, bacteria)

► Decomposition is a complex process and serves Decomposition is a complex process and serves many functions; formation of soil, recycling of many functions; formation of soil, recycling of nutrients, reduction of high energy carbon nutrients, reduction of high energy carbon compoundscompounds

► Organic molecules are oxidized to release nitrogen Organic molecules are oxidized to release nitrogen in the form of nitrate, nitrite, and ammoniain the form of nitrate, nitrite, and ammonia

► Oxidation of organic compounds provides energy for Oxidation of organic compounds provides energy for saprophyte but returns matter to abiotic saprophyte but returns matter to abiotic environmentenvironment