1. Energy Flow Through Our Ecosystem
Science 10

2. The vast majority of life on Earth depends on sunlight as its source of energy.
Of all the solar energy that reaches the earth, some of it penetrates or passes through the earth's atmosphere to the Earth's surface, but only a small quantity is used to drive the process of photosynthesis.

3. Look at the picture!
About how much of the energy that reaches the earth is actually used in photosynthesis?

4. Albedo Effect:
The actual amount of energy that reaches the surface of the Earth is affected by the albedo effect of clouds and dust particles in the atmosphere.
Albedo is a measure of the amount of light reflected from an object (written as a decimal value) that shows the percentage of light reflected.

5. For example, clouds have an average albedo about
For example, clouds have an average albedo about .27 so about 27% of the sun’s energy is normally reflected by clouds back to space.
On a clear day, more light would be able to penetrate to the Earths surface and as a result a greater amount of photosynthesis should occur.

6. Photosynthesis
a biological process, uses the energy of sunlight to manufacture sugar, which serves as the universal food for life.
Oxygen produced as a product of photosynthesis is released into the environment.

7. Chemical Formula for Photosynthesis
6CO2 + 6H2O + sunlight energy → C6H12O6 + 6O2
Where:
CO2 represents carbon dioxide
H2O represents water
C6H12O6 represents the sugar molecules (carbohydrate)
O2 represents oxygen

8. To release the energy stored in the sugar, organisms carry out a metabolic process known as cellular respiration.
C6H12O6 + 6O2  →  6CO2 + 6H2O + energy
This equation is the reverse of our photosynthesis equation!

9. The energy released during cellular respiration is what allows organisms to carry on their life processes or metabolic processes such as movement, growth, and reproduction.
This process does transfer energy from the food to the organism for carrying life processes, but also releases heat which can not be used any further.
Heat energy is lost on a continuous basis from all living things.

10. Feeding Relationships in Our Ecosystem
Science 10

11. Food Chain or Trophic Structure
A food chain shows how each living thing gets its food. Some animals eat plants and some animals eat other animals.
Corn → Mouse → Snake → Hawk
Each link in this chain is food for the next link. A food chain usually starts with plant life and ends with an animal.

12. First Link in our Food Chain
1st link is plants.
Plants are called producers or autotrophs because they are able to “trap” solar energy from the Sun to produce oxygen and food (sugar) from carbon dioxide and water.

13. What about organisms that can’t make their own food?
Animals cannot make their own food so they must eat plants and/or other animals. They are called consumers or heterotrophs. There are three groups of consumers.

14. Heterotrophs or Consumers
Animals that eat ONLY PLANTS are called herbivores (or primary consumers).
Animals that eat OTHER ANIMALS are called carnivores.
carnivores that eat herbivores are called secondary consumers
carnivores that eat other carnivores are called tertiary consumers
Animals and people who eat BOTH animals and plants are called omnivores.

15. What comes next in the Food Chain?
Then there are decomposers or detritivores or saprobes (bacteria and fungi) which feed on decaying matter. These decomposers speed up the decaying process that releases mineral salts back into the food chain for absorption by plants as nutrients.

16. Why there are more herbivores than carnivores?
In a food chain, energy is passed from one link to another.
When a herbivore eats, only a small part of the energy (10%) that it gets from the plant food becomes new body mass.
The rest of the energy (90%) is lost as heat or used up by the herbivore to carry out its life processes (e.g., movement, digestion, reproduction).

17. Therefore, when a carnivore eats another animal, only a portion of the energy from the animal food is stored in its tissues.
In other words, organisms along a food chain pass on much less energy (in the form of body mass) than they receive.

18. Because of the large amount of energy that is lost at each link
Because of the large amount of energy that is lost at each link ... PYRAMID OF ENERGY
The further along the food chain you go, the less food (and less energy) remains available.
Note that as we go up, there are fewer giraffes than trees & shrubs and even fewer lions than giraffes.
In other words, a large mass of living things at the base is required to support a few at the top.

19. Why do most food chains have no more than four or five links?
There cannot be too many links in a single food chain because the animals at the end of the chain would not get enough food (or energy) to stay alive.
Most animals are part of more than one food chain and eat more than one kind of food in order to meet their food and energy requirements.
These inter-connected food chains form a food web.

20. Food Web

21. Australian Grassland Food Web

22. Antarctic Food Web

23. Marine Food Web

24. African Grassland Food Web