1. Oxygen and Carbon dioxide
Oxygen comprises 21% of the earths atmosphere whereas carbon dioxide comprises less than 1%.
Oxygen and carbon dioxide are gases used and released by living organisms.
Both oxygen and carbon dioxide are exchanged between the atmosphere and life through the processes of photosynthesis and respiration.
The composition of the atmosphere depends on the balance between these processes.

2. Did you know plants can make their own food?

3. Plants do this in a process called:
PHOTOSYNTHESIS

4. So what is photosynthesis?
Photosynthesis describes how plants make food for themselves and the rest of living things on earth.
Plants have these special organelles in their cells called chloroplasts, inside of which photosynthesis happens.

5. First the chloroplasts absorb light energy
While the plant takes in carbon dioxide from the air
And water from the soil.

6. Through a series of chemical reactions the chloroplasts are able to take in the________, _________________and _____ and convert it into __________ and _______.
sunlight
Carbon dioxide gas
water
Oxygen gas
glucose

7. What does a plant need for photosynthesis?
Carbon dioxide
Water
Sun light + +

8. What are the products of photosynthesis?
Glucose
Oxygen +

9. Oxygen is the gas that people breathe in
Oxygen is the gas that people breathe in. So not only do plants make their own food, but they make the air that we breathe in!
Glucose is a type of sugar that plants use for food to them help them grow.

10. In other words, photosynthesis is:
Glucose is created in the green parts of a plant and every animal on earth depends on it. Without plants we would have no food to eat or oxygen to breath.
In other words, photosynthesis is:
sunlight + air people breath out (CO2) + water = plant food + air people breathe in (O2)

11. This is the reverse of photosynthesis
Respiration
This is the reverse of photosynthesis

12. In other words, respiration is:
In respiration, glucose is consumed, with energy, water and carbon dioxide produced. We breath in the oxygen produced by healthy growing plants and we breath out (respire) carbon dioxide and water.
In other words, respiration is:
Glucose + Oxygen (air we breathe in) = Carbon dioxide (air we breathe out) + Energy + Water

13. Oxygen produced during photosynthesis replenishes the oxygen that is used up by living things during respiration.
This cycle of photosynthesis and respiration maintains the balance of carbon dioxide and oxygen on earth.

14. Photosynthesis Respiration
Occurs in the presence of light (and chlorophyll in cells)
Occurs at all times in cells
Requires energy (light) to make sugar (glucose)
Releases energy from sugar
Glucose is a product of the process.
Glucose is used during the process.
Carbon dioxide and water are the raw materials.
Carbon dioxide and water are the waste products.
Oxygen is given out.
Oxygen is taken in.

15. Photosynthesis and Respiration
To summarize, photosynthesis and respiration are complimentary processes in the living world, because the waste products of one cycle provides the raw materials for the other cycle and vice versa.