1. Lesson 2 – Energy Flow in Ecosystems

2. The Source of Energy
The Sun is the source of almost all the energy living things need to survive
Most of the Sun’s energy is radiant energy, which travels through empty space
About 30 % of the Sun’s energy is reflected by clouds or Earth’s surface

3. The Source of Energy
About 70 % is absorbed by the atmosphere, water, and land, and is converted into thermal energy
A very small amount is absorbed by living organisms ~ %

4. The Source of Energy 30 % reflected
19 % absorbed by clouds and atmosphere
70 % absorbed
0.023 % absorbed by plants
51 % absorbed by land and oceans

5. Photosynthesis Some organisms use light to make their own food
An organism that makes its own food is called a producer – plants are producers
The process of converting light energy into chemical energy is called photosynthesis
Plants are green because they contain chlorophyll, the chemical that absorbs light energy

6. Photosynthesis
Light energy is used to convert two chemicals (carbon dioxide and water) to a different chemical (sugar) which is stored in the plant
During photosynthesis, plants release oxygen
We use a word equation to describe photosynthesis:
carbon dioxide + water sugar + oxygen
light energy
Photosynthesis Video

7. Cellular Respiration
Many organisms do not produce their own food and must obtain energy from other sources
These organisms are called consumers, e.g. humans
Consumers obtain energy by eating other organisms that contain stored energy
As food is digested, the energy is released through a process called cellular respiration

8. Cellular Respiration
In cellular respiration, the sugar and oxygen are changed into carbon dioxide and water
As this occurs, energy is released
We use a word equation to describe cellular respiration:
sugar + oxygen carbon dioxide + water + energy

9. Complementary Processes
Photosynthesis and cellular respiration are opposite reactions
Both processes need to happen in order to sustain life