Energy Flow in Ecosystems

○ Sun ○ Provides energy to the earth in the form of heat and light ○ Major source of energy that drives the ecosystems on earth

○ Auto(self)trophic(feeding) producers use photosynthesis ○ Use the energy from the sun (photosynthesis) and simple inorganic substances to manufacture organic matter (food) ○ Energy is stored in the chemical bonds and is released when the chemical bonds are broken

○ Metabolic process of the chemical breakdown of organic matter to release energy ○ The process consumers use to extract energy from organic matter ○ Herbivores consume large amounts of plants material ○ Extract the energy stored in the chemical bonds by cellular respiration ○ Producers also perform cellular respiration

• Energy transfer from plant to consumer is not completely efficient - only 10% of the energy is transferred from producer to consumer □ Not all plant material is eaten and/or absorbed by the gut □ Energy is lost through movement and respiration

○ Food chains and food webs are qualitative models that allow ecologists to measure the sustainability of feeding relationships in an ecosystem ○ Each position of an organism has in a chain is referred to as a ‘trophic (feeding) level’ ○ Each organism feeds and obtains its energy and matter from the preceding one ○ Energy and matter are transferred progressively from one trophic level to the next

• Herbivore • Feed directly on producers • E.g. wombats, sheep

• Carnivore • Feed on primary consumers • E.g. dingoes, platypuses

• Apex predator • Feed on secondary consumers • E.g. wedgetail eagle, sharks

• Feed on both plants and animals • E.g. foxes, bandicoots

• Feed on dead remains of other organisms • E.g. foxes, ravens

• Feed on dead or decaying organic remains and wastes • Help speed up decay by breaking down larger pieces of detritus into smaller pieces (largen surface area for decomposers to work more efficiently) • E.g. dung beetles, maggots, earthworms

• Decompose/break down complex organic molecules into simpler inorganic forms and return nutrients to the soil or water • E.g. fungi, some bacteria

○ A food web is a group of food chains that are linked together showing the interactions between food chains in a community ○ Distinguishing feature is that an organism can occupy different trophic levels in different food chains ○ Members of populations can move in and out of food chains/food webs at different times - E.g. birds feeding off seeds in different ecosystems (depending on the seed)

• Diagrams that show the relative levels of one of three different factors present in an ecosystem at each trophic level • Three types: numbers, biomass, energy

• Number of organisms at each trophic level • Usually food chains have a drop in number of organisms as the trophic level rises • Inverted pyramid of number ◊ When more organisms occupy the trophic level above the preceding level ◊ E.g. producer - eucalyptus tree, primary consumer - wattlebirds, secondary consumer - parasites (on the bird)

• The biomass (amount of organic matter in terms of mass) present • Expressed as dry weight per unit (g/m2) ◊ Living biological matter contains water which is inorganic and cannot be used as an energy source Can be calculated ◊ At a given time ◊ Rates (e.g. measuring biomass in a given area the duration of a year (g/m2/year)) • At each successive trophic level, the biomass decreases ◊ Consumers must eat considerable amounts of food to fulfill energy needs • Inverted pyramid of biomass ◊ Occurs when the producer has a short life cycle and can reproduce at a fast rate, counteracting their biomass

• The amount of energy transferred from one trophic level to the next • Expressed in units of energy per area in a given time ◊ E.g. kilojoules per square metre per year (kJ/m-2/y-1) • The rate at which energy is transferred from one trophic level to another in a community • Ecologists can make predictions about whether a community can be sustained and what the impact changes in rates of energy transfer will have on the community • Only some of the energy stored in a trophic level goes to the next level (10% on average) • Can never be inverted • Drawing pyramids of energy ◊ Producer at the bottom ◊ Each level labelled (producer, primary consumer, secondary consumer, tertiary consumer) ◊ Draw to scale ◊ Use data is provided ◊ If no data, measure one tenth of preceding trophic level (average energy transfer efficiency rule of 10%) ◊ Labelled arrows to indicate energy leaving each trophic level in the form of heat