Energy in Ecosystems

The Flow of Energy

•The energy in ecosystems does not flow in cycles like matter does -such as nitrogen, water, carbon - but flows in a straight line.

•If energy is not passed on it is lost (such as heat).

•This means that there must be a constant supply of energy to sustain the ecosystem.

The Flow of Energy

Herbivore Omnivore Carnivore

H2O

O2

CO2 C6H12O6

Photosynthesis in the chloroplast converts light energy into chemical energy:

6CO2 + 6H2O 6O2 + C6H12O6

90% lost

20%lost

20% of energy lost

10%lost

90% of energy is lost

Energy lost through cellular Respiration + Heat

Cellular respiration takes place in the mitochondria of all cells and is responsible for releasing the energy stored in

glucose to make ATP which breaks down to ADP

6O2 + C6H12O6 6CO2 + 6H2O + Energy

Detritus: energy lost as waste products and ‘dead’ material

Decomposers such as bacteria and fungi recycle nutrients such

as nitrogen and carbon

Photosynthesis & Respiration

•These two complex reactions appear to be the reverse of each other, but in actual fact they are not.

•The plants convert the light energy into chemical energy, which is stored in organic compounds such as glucose.

•The glucose is passed from the plants to the animals when they eat them, and then on to other animals the same way.

•The breakdown of glucose releases energy into the organism which releases energy into the ecosystem.

Respiration•All living cells need a constant supply of energy all the time to stay alive.

•They need this energy to synthesize new molecules, to grow, to reproduce, to repair and maintain themselves, to transport various materials and to undergo various generalised and specialised functions.

•Respiration itself is a series of about 50 different chemical reactions, each one using a different enzyme to catalyse it.

•The chemical energy held in the bonds of glucose release energy when they are broken.

•This energy is transferred to ATP (adenosine tri phosphate) where is can then be used by the cell.

•About 40% of the energy in glucose is converted to ATP.

Respiration

•This is an over simplified diagram of how the reactants and products in respiration balance each other out.

Respiration

glucose + oxygen carbon dioxide + water + energy

ADP + P +glucose +oxygen carbon dioxide + water + ATP

ADP + P ATP

Energy out

Energy in

Respiration•The stages of respiration can be thought of as occurring in two stages.

•The first stage occurs in the cytoplasm, produces 2 ATP’s and does not require oxygen. This is known as glycolysis or anaerobic respiration.

•The second stage occurs in the mitochondria of the cell, produces 36 ATP’s and is called aerobic respiration.

When I undergo anaerobic respiration I produce lactic acid

When I undergo anaerobic respiration I produce alcohol

Sugar Lactic acid + carbon dioxide + 2ATP

Sugar Ethanol + carbon dioxide + 2ATP

Photosynthesis & Respiration

The role of Photosynthesis in the ecosystem:•To provide oxygen for all living things in order to undergo respiration

•To provide food for herbivorous animals in the form of glucose

•To trap the sunlight energy so that it can actually enter the ecosystemThe role of Respiration in the ecosystem:•To provide carbon dioxide for plants to use during photosynthesis

•To release the energy in glucose so it can be used in the ecosystem

Food Chains•A food chain represents the flow of energy from one living thing to another

•Producer•1o Consumer

•Herbivore

•2o Consumer

•1 o Carnivore

•3o Consumer

•2o Carnivore

..or if we want to look at trophic levels…..

1st trophic level

2nd trophic level

3rd trophic level

4th trophic level

Food Webs•A food web is a set of food chains interacting

1st trophic level2nd trophic level

3rd trophic level

4th trophic level

Producer

Primary consumer

Secondary consumer

Tertiary consumer

Top order consumer

Pyramids of Energy

Producers

Primary consumers

Secondary consumersTertiary consumers

•Each step represents the amount of energy available.

•At each tropic level the amount of energy is reduced.

•Greater tropic efficiency gives a pyramid with much steeper sides compared to a food chain with poor tropic efficiency.

Pyramids of Numbers

•Pyramids of numbers are essentially population pyramids.

•They need not always take the step progression of energy pyramids. So often they don’t even appear pyramidal in shape. Here are a few examples:

Plants

Kangaroos

Parasites

Producers

Biomass Pyramids

•The total amount of mass in a community, or a given tropic level is called the biomass.

•They are time consuming to make and are nearly always pyramidal.

Producers

The End!