Unit 5 - Energy transfers in and between organisms
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Summary Unit 5 - Energy transfers in and between organisms
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Unit 5 - Energy transfers in and between organisms
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AQA
Whole of Unit/Module 5 Energy transfer in and between organisms for AQA A level Biology based on class notes, specification, textbooks, websites, videos and revision sessions. Summarised into bullet point notes that are quick and to the point with just information you need for the exam.
Unit 5 - Energy transfers in and between organisms
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Module 5 (Energy) Revision Notes
What is the source of energy for an ecosystem? sunlight
What is the role of producers, consumers, decomposers in an ecosystem?
producers = plants, perform photosynthesis, use light energy to make biological
molecules
consumers = animals, cannot make their own biological molecules, need to eat plants
(primary consumers) or other animals
(secondary/tertiary consumers) to obtain biological
molecules
decomposers = bacteria and fungi, perform saprobiotic decomposition,
release enzyme onto dead plants/dead animals/animal
waste (organic matter) breaking them down to obtain
biological molecules
Why do producers (plants) need biological molecules?
Glucose = respiration, store as starch, make cellulose
Amino Acids = make proteins e.g. enzymes
Fatty Acid & Glycerol = make triglyceride as energy store, make phospholipid for
membranes
Why do consumers (animals) need biological molecules?
Glucose = respiration, store as glycogen
Amino Acids = make proteins e.g. enzymes
Fatty Acid & Glycerol = make triglyceride as energy store and insulation/protection,
make phospholipid for membranes
Why do decomposers (bacteria/fungi) need biological molecules?
Glucose = respiration
Amino Acids = make proteins e.g. enzymes
Fatty Acid & Glycerol = make phospholipid for membranes
How do organisms carry energy?
Main Source = Glucose
Stored as Starch in plants and Glycogen in animals
Alternative Source = Lipids/Fats/Triglycerides and Proteins
How does energy move through an ecosystem? by the food chain, begin with producer and then
moves onto primary consumer, then secondary consumer, then tertiary consumer – with
decomposers occurring at each stage (trophic level)
Why is all the light energy not utilised by plants in photosynthesis? only 2% is used in
photosynthesis – of the rest, a certain part misses the chloroplast, the other parts would be reflected
or the wrong wavelength
, Why is energy lost along a food chain?
not all the glucose made by producers is stored as starch or used to build biomass, as a
certain part is lost in respiration (as heat)
not all the stored energy in the plant is transferred to primary consumers as certain parts
of the plant are inedible and indigestible (available to decomposers)
of the energy the primary consumer obtains, a certain amount is used in respiration, the
rest is stored as glycogen and used to build biomass
not all this stored energy is transferred to secondary consumers due to inedible parts and
indigestible parts (available to decomposers)
only 10% of energy is transferred from producer to primary consumer
only 20% of energy is transferred from consumer to consumer
the losses are due to respiration, inedible parts, indigestible parts
higher proportion is transferred from consumer to consumer because consumers are
more edible and digestible, producers are made up of cellulose
the higher consumers have the highest respiratory losses as they have increased
movement (hunt for food)
Effect of energy loss on a food chain? places a limit on the length of a food chain, those at the
higher trophic levels (just quaternary consumers) would not obtain enough energy from the food it
consumes
What is Productivity?
Productivity = Amount of Glucose/Energy available to organism
Primary Productivity = Amount of Glucose/Energy available in Plants
Secondary Productivity = Amount of Glucose/Energy available in Animals
Net Productivity = Gross Productivity – Respiratory [and Faeces] Losses
Gross Primary Productivity is amount of glucose made by plant in photosynthesis,
Net Primary Productivity is amount of glucose stored as starch after respiration
Gross Secondary Productivity is amount of glucose consumed by animal,
Net Secondary Productivity is amount of glucose stored as glycogen after respiration
in all cases, net productivity is the glucose/energy available to organisms at next stage of
food chain
respiratory losses are higher in consumers then producers due to movement
and respiratory losses are higher in secondary/tertiary/quaternary consumers then
primary consumers as they move more to hunt for food
and respiratory losses are higher in consumers that have to maintain a constant body
temperature (endotherms)
What does a Pyramid of Number represent?
number of each type of organism at each trophic level – the numbers decrease as we
move up trophic levels due to the loss of energy (not as many individuals can be
supported)
can look inverted when it does not take into account mass (e.g. 1 oak tree or millions of
fleas)
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