A2 Biology - Energy and Ecosystems

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PRODUCERS , DECOMPOSERS AND CONSUMERS

PRODUCERS - PHOTOSYNTHETIC ORGANISMS THAT GET THEIR ENERGY FROM THE SUN

CONSUMERS - OBTAIN ENERGY BY EATING OTHER ORGANISMS 

THOSE THAT EAT PRODUCERS - PRIMARY CONSUMERS 

THOSE ANIMALS EATING PRIMARY CONSUMERS - SECOINDARY CONSUMERS 

THOSE EATING SECONDARY - TERTIARY CONSUMERS 

DECOMPOSERS - WHEN PRODUCERS DIE THE ENERGY THEY CONTAIN IS BROKEN DOWN BY DECOMPOSERS  

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FOOD CHAINS AND WEBS

FOOD CHAINS - FEEDING RELATIONSHIPS IN WHICH THE PRODUCERS ARE EATEN BY PRIMARY ETC ETC.

EACH STAGE IN A CHAIN IS CALLED A TROPHIC LEVEL 

ARROWS REPRESENT THE DIRECTION OF ENERGY FLOW 

FOOD WEBS - IN REALITY MOST ANIMALS DO NOT RELY ON ONE FOOD SOURCE AND WITHIN A HABITAT MANY FOOD CHAINS LINKED TOGETHER FORM A FOOD WEB 




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ENERGY TRANSFER BETWEEN TROPHIC LEVELS

SUN IS SOURCE OF ENERGY FOR ECOSYSTEMS - ONLY 1% OF LIGHT ENERGY IS CAPTURED BY PLANTS

PLANTS NORMALLY CONVERT AROUND 1-3% OF SUNS ENERGY AVALIABLE INTO ORGANIC MATTER, MOST OF IT IS NOT CONVERTED BECASEU 

  • 90% IS REFLECTED BACK INTO SPACE BY CLOUDS AND ATMOSPHERE 
  • NOT ALL WAVE LENGTHS OF LIGHT CAN BE ABSORBED FOR PHOTOSYNTHSIS 
  • LIGHT MAY NOT FALL ON CHROROPHYLL
  • LIMITING FACTORS CAN LIMIT PHOTOSYNTHESIS 

TOTAL QUANTITY OF ENERGY THAT THE PLANTS IN A COMMUNITY CONVERT TO ORGANIC MATTER IS CALLLED - GROSS PRODUCTION 

THE AMOUNT OF ENERGY AVALIABLE IN NEXT TROPHIC LEVEL- NET PRODUCTION 

NET PRODUCTION = GROSS PRODUCTION - RESPIRATORY LOSSES 

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WHY IS SOME ENERGY NOT TRANSFERRED

  • SOME OF ORGANISM IS NOT EATEN 
  • SOME PARTS ARE EATEN BUT CANNOT BE DIGESTED AND ARE THEREFORE LOST IN FACES
  • SOME ENERGY IS LOST IN EXCRETORY PRODUCTS E.G URINE 
  • RESPIRATORY LOSSES - IN THE FORM OF HEAT
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EFFICENCY OF ENERGY TRANSFER

ENERGY TRANSFER = ENERGY AVALIABLE AFTER THE TRANSFER/ ENERGY AVALIABLE BEFORE TRANSFER X 100 

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ECOLOGICAL PYRAMIDS

FOOD WEBS AND CHAINS DONT SHOW QUANTATIVE INFORMATION 

SOMETIMES USEFUL TO BE KNOW THE NUMBER, MASS OR AMOUNT OF ENERGY STORED BY ORGANISMS AT EACH TROPHIC LEVEL - WE CAN USE ECOLOGICAL PYRAMIDS 

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PYRAMIDS OF NUMBER

USUALLY NUMBER OF ORGANISMS AT LOWER TROPHIC LEVELS ARE HIGHER THAN THE NUMBER AT HIGHER LEVELS E.G MORE GRASS THAN RABBITS 

The population of each organism in a food chain can be shown in a sort of bar chart called apyramid of numbers DRAWBACKS ; 

  • NO ACCOUNT IS TAKEN OF SIZE - ONE GIANT TREE IS TREATED THE SAME AS A GRASS PEICE - THIS MEANS SOMETIMES THE PYRAMID ISNT A PYRAMID AT ALL - ITS INVERTED 
  • THE SCALE OF OF INDIVIDUALS CAN BE SO GREAT ITS IMPOSSIBLE TO REPRESENT THEM ACCURATLEY 
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PYRAMID OF BIOMASS

BIOMASS IS THE TOTAL MASS OF THE PLANTS/ANIMALS IN A PARTICULAR AREA 

IT IS A MORE RELIABLE, QUANTATIVE DESCRIPTION OF A FOOD CHAIN.

DRY MASS -  A reliable measure of the biomass (as opposed to fresh mass).

The dry matter of a sample or of an object when completely dried (lacks or excluding water).

BECAUSE ORGANISMS MUST BE KILLED TO MEASURE DRY MASS - ONLY SMALL SAMPLE TAKEN - MAY NOT BE REPRESENTATIVE 

NEARLY ALWAYS PYRAMID SHAPED 

MEASURED IN GRAMS PER CUBIC METRE 

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PYRAMIDS OF ENERGY

THIS IS THE MOST ACCURATE REPRESENTATION OF ENERGY FLOW 

COLLECTING THIS DATA CAN BE DIFFICULT AND COMPLEX 

THEY SHOW THE AMOUNT OF ENERGY AVALIABLE IN EACH TROPHIC LEVEL IN KILOJOULES PER SQUARE METRE PER YEAR 

ALWAYS PYRAMID SHAPED 

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AGRICULTURAL ECOSYSTEMS

MADE UP OF DOMESTICATED ANIMALS AND PLANTS USED TO PRODUCE FOOD FOR MANKIND 

HUMANS ARE OFTEN AT THE LAST FEW TROPHIC LEVELS OF A FOOD CHAIN MEANING WE ONLY RECIEVE A SMALL PROPORTION OF THE ENERGY AVALAIBLE FROM THE SUN 

AGRICULUTURE AIMS TO MAKE AS MUCH ENERGY FROM THE SUN AVALAIBLE AND TRANSFERRED TO HUMANS 

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DIFFERENCE BEWTEEN NATURAL AND AGRICULTURAL ECOSYS

NATRUAL ECOSYSTEM - SOLAR ENERGY ONLY, LOWER PRODUCTIVITY, MORE SPECIES DIVERSITY, MORE GENETIC DIVERSITY WITHN A SPECIES, NUTRIENTS RECYCLED NATURALLY, POPULATIONS ARE CONTROLLED BY NATRUAL MEANS, SUCH AS COMPETITION AND CLIMATE 

AGRICULTURAL ECOSYSTEM - SOLAR ENERGY PLUS ENERGY THROUGH LABOUR AND MACHINES, HIGHER PRODUCTIVITY, LESS SPECIES DIVERSITY, LESS GENETIC DIVERISTY WITHIN A SPECIES NATURAL RECYCLING MORE LIMITED AND SUPPLEMEMTED BY FERTILISERS, CONTROLLED BY NATURAL MEANS AND BY PESTICIDES ETC. 

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PESTS AND PESTICIDES

PEST - AN ORGANISM THAT COMPETES WITH HUMANS FOR FOOD OR SPACE 

PESTICIDE - POSINOUS CHEMICALS THAT KILL PESTS 

  • HERBICIDE
  • FUNGICIDIDES
  • INSECTICIDES 

AN EFFECTIVE PESTICIDE SHOULD;

  • BE SPECIFIC - ONLY TOXIC TO ORGANISM IT IS DIRECTED AT - HARMLESS TO HUMANS 
  • BIODEGRADE - SO IT BREASK DOWN TO HARMLESS SUBSTANCES IN THE SOIL 
  • BE COST EFFECTIVE 
  • NOT ACCUMULATE - SO THAT IT DOES NOT BUILD UP
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BIOLOGICAL CONTROLS

INTRODUCING A PREDATOR OF A PEST CAN HELP CONTROL THE INFLUENCE OF PESTS.

ADVANTAGES OF BIOLOGICAL CONTROL OVER USING CHEMICAL PESTICIDES 

  • VERY SPECIFIC - WHERE AS PESTICIDES ALWAYS HAVE AN EFFECT ON NON TARGET SPECIES 
  • ONCE INTRODUCED IT CAN REPRODUCE ITSELF - MUST BE REAPPLIED - EXPENSIVE 
  • PESTS DO NOT BECOME RESISTANT - PESTS DEVELOP GENETIC RESISTANCE TO PESTICIDES

DISADVANTAGES 

  • DO NOT ACT AS QUICKLY
  • CONTROL ORGANISM MAY ITSLEF BECOME A PEST 
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INTERGRATED PEST CONTROL

INTERGRATED PEST CONTROL AIM TO INTERGRATE ALL FORMS OF PEST CONTROL RATHER THAN BEING RELIANT ON ONE 

INTERGRATED CONTROL INVOLVES 

  • CHOOSING ANIMAL AND PLANT LIFE SUITED TO LOCAL AREA AND RESISTANT TO PESTS
  • MANAGEMENT OF HABITAT 
  • REGULAR MONITORING - FOR SIGNS OF PESTS 
  • REMOVING PESTS MECHANICALLY IF PESTS EXCEED AN ACCEPABLE POP LEVEL
  • USING BIOLOGICAL IF NECESSARY 
  • USING PESTICIDES AS LAST RESORT
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