Flow of Energy

Energy in the ecosystem

• Energy comes into the living world as light energy from the sun

• Plants capture this light energy and change it to chemical energy (glucose) through the process of photosynthesis.

Carbon dioxide + Water Glucose + Oxygen + Water

CO2 + 12H2O C6H12O6 + 6O2 + 6H2O

SunlightChlorophyll

SunlightChlorophyll

Energy in the ecosystem

• Plants store glucose as starch, fats and proteins (by adding Nitrogen from the soil)

• The energy which is now locked up in a food molecule is passed from one organism to another through a food chain/food web

Energy in the ecosystem

• At each link in the food chain, energy is released by the process of respiration.

Glucose + Oxygen Carbon Dioxide + Water + Energy (ATP)

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

Enzymes

Enzymes

ATP

• ATP provides the energy for all the living processes in the body

• It is used to create– Mechanical energy when an organism moves– Chemical energy when an organism makes new

cells or molecules– Electrical energy when nerve cells fire– Light energy like in a glow worm– Energy of active transport

Energy in the ecosystem

• Eventually all energy changes to heat • Energy flows in one direction

Sunlight Food ATP HeatLightChemicalMechanicalElectricalActive transport

Photosynthesis Respiration

Energy flows

• There are two main ways energy flows through an ecosystem

1. In the grazing food chain – herbivores eat plants and carnivores eat the herbivores (what we have already looked at)

2. In the organic detritus food chain – dead material is broken down by bacteria and fungi

Energy flows

• Both systems are represented in food webs and have levels known as trophic levels

• The energy available at each trophic level equals the amount entering that trophic level minus total loses to that level

Energy flow through an ecosystem

• Energy can be lost at each trophic level as heat (due to metabolic activity) or as detritus (this stays in the ecosystem for other organisms to use)

• Only about 10% of energy is passed on to the next trophic level

• Energy is in kilojoules per square metre per year (kJ m-2 yr -1)

Energy flow in an ecosystem

Tertiary consumer

Secondary consumer

Detritus

ProducerPrimary

consumer

Heat loss

Sunlight

Energy flow through the ecosystem

Trophic level

100

Energy lostto detritus

Energy lostas heat through

metabolicactivity

Energy passed on tothe next trophic level

25

1065

Energy from previous trophic level

What can affect the energy flow?

• In silence think about this question for 1 min and jot down any ideas you have

• Turn to the person next to you and discuss your answer for 1 min

What can affect the energy flow?

• Block out light– E.g. Road works– E.g. Asteroid

• Remove a food source– Can happen due to pollution, drought, over fishing

and the removal of an organism

Activity

• Construct an energy flow diagram for a bull grazing in a paddock

Biozone

Pg 303-305