1. Energy flows - B2 3.1 Lesson objectives Where does biomass come from?
What is a pyramid of biomass?
How do we lose energy to the environment?
What is the effect of maintaining a constant body temeprature?

2. bierhover parroted recordup craveiron vinemoor comeruns
Solve these anagrams

3. Zooplankton Clown fish Sharks
Food chains show the feeding relationships between living things. They show us what eats what in a particular habitat.
What is meant by habitat?
The arrows between each item in the chain always point in the direction of energy flow.
The Sun is the ultimate source of energy for most communities of living things. Green plants absorb some of the Sun’s light energy to make their own food by photosynthesis. The other organisms in a food chain are consumers, because they all get their energy and biomass by consuming - eating - other organisms.
Ask them what each of the things in the food chain are?

4. Key terms
Producers - organisms which can make their own energy from carbon dioxide and water using sunlight for energy (plants)
Primary consumer - organisms which eat producers (herbivores)
Secondary consumers - organisms which eat primary consumers (carnivores)
Tertiary consumers - organisms which eat secondary consumers (carnivores)

5. Food chains Each level of a food chain is known as a trophic level.
Food chains always start with a producer.
Producers are always on the first trophic level.
Ask them to write an example of a food chain with four trophic levels in their books
e.g. Oak tree to bark beetle to woodmouse to barn owl

6. Food Web

7. 1. Write down two food chains from this food web.

8. Questions
1. What will happen to the number of clown fish if the sharks become vegetarian?
2. What effect will this have on the number of zooplankton?
3. What will happen to the Blue Regal fish if a disease wipes out the small invertebrates.

9. Pyramid of numbers clown fish zooplankton shark
When you look at a food chain there are normally more producers than primary consumers and usually more primary consumers than secondary consumers. If you count the number of organisms at each trophic level you can compare them. You can show this using pyramid of numbers. However, in many cases a pyramid of numbers does not accurately reflect what is happening. Can you think of an example where this might be the case? E.g. Oak tree to aphids to ladybirds
zooplankton

10. Biomass - the mass of living material in an animal or plant.
The biomass goes down as you go from one stage to the next.
To show what is happening more accurately we can use pyramids of biomass
Light energy pours out continuously onto the surface of the earth. Green plants capture a small part of this light energy using chlorophyll. It is then used in photosynthesis. So some of the energy from the sun is stored in substances which make up the cells of the plant. This new plant material adds to its biomass. Biomass is the mass of living material in an animal or plant. Ultimately all biomass is built up using energy from the sun. Biomass is often measured as the dry mass of biological material in grams.
The energy in the biomass made by plants is passed on through the food chain into the animals which eat the plants. It then passes on to othe animals which eat other animals

11. Pyramids of biomass Organism Number Biomass – dry mass in g Oak tree 1
aphids
10 000
1000
ladybirds
200 50
Ask the question: why is the biomass at each stage of a food chain less than it was at the previous stage?
A large amount of plant biomass supports a smaller amount of herbivore biomass. This in turn supports an even smaller amount of carnivore biomass. In general pyramids of biomass are drawn in proportion.
Pyramid of biomass
Pyramid of numbers

12. Biomass found at each stage of food chain is less than it was at the previous stage....
This is because:
Not all organisms at one stage are eaten by the stage above.
Some material taken in is passed out as waste.
Respiration to release energy for living.
At each stage of a food chain the amount of energy in biomass which is passed on gets less.
Students answer the questions on pyramids of biomass and pyramids of number.

13. Questions Why will they always be pyramid shaped?
Why do food chains not normally have more than 5 trophic levels in them?

14. Why does steak cost more than bread?
Discussion about where steak and bread come from and what has to be done to produce them. Tell students to draw a picture of themselves (or could print off class photos for them!) and label with where we get our energy from and what we do with it (10 mins)

15. Energy transfer
Energy is transferred along food chains from one stage to the next.
Not all of the energy available to organisms at one stage can be absorbed by organisms at the next one.
The amount of available energy decreases from one stage to the next.

16. Energy losses Biomass digested
Energy lost as heat from cellular respiration
Biomass turned into new horse biomass
Biomass digested
Biomass lost in faeces
Biomass in as food
Only between 2% and 10% of the biomass eaten by an animal such as a horse will get turned into new horse – the rest of the stored energy will be used or lost in other ways.
Biomass lost in urine
Biomass lost – used to provide energy for movement and growth

17. Energy losses Energy loss in waste Energy loss due to movement
Herbivores cannot digest all plant material they eat.
Some biomass always lost in faeces.
When an animal eats more protein than it needs, excess is broken down and passed out as urea in urine.
Energy loss due to movement
Movement uses a lot of energy.
Muscles produce heat as they contract.
Keeping a constant body temperature
Heat losses are very large in mammals because they are ‘warm-blooded’.
This means they keep their bodies at a constant temperature – use up energy to keep warm when its cold or to cool down when it is hot.

18. Complete energy through a food chain worksheet

19. Question
A 1 acre field produces 1000KJ of potatoes per day OR 100KJ of energy stored in cows.
A person requires 3000KJ of food per day.
How many acres do they need to survive if only eating potatoes? If only eating cows?
Class question - A 1 acre field produces 1000KJ of potatoes per day OR 100KJ of energy stored in cows. A person requires 3000KJ of food per day. How many acres do they need to survive if only eating potatoes? If only eating cows? (5 mins)
Discuss why it is more ecologically and energetically friendly to be a vegetarian than a meat eater – focus on area of grass needed to sustain small amount of cows as opposed to producing a large crop – make a list of pros and cons (15 mins)

20. Why is it more ecologically and energetically friendly to be vegetarian than a meat eater?
Discuss why it is more ecologically and energetically friendly to be a vegetarian than a meat eater – focus on area of grass needed to sustain small amount of cows as opposed to producing a large crop – make a list of pros and cons (15 mins)
Pyramids of biomass clearly show us that the organisms at each stage of a food chain contain less material and therefore less energy. In the developed world much of our diet consists of meat and other animal products such as eggs, cheese and milk. The cows, goats, pigs and sheep that we use to produce our food eat plants. By the time it reaches us, much of the energy from the plant has been used up.
In some cases we even feed animals to animals eg ground up fish which is often part of commercial pig and chicken feed. This means we have to put an extra layer into the food chain. What could have been biomass for us has been used up as energy by other animals in the food chain.
There is only a limited amount of earth’s surface that we can use to grow food. The most energy efficient way to use this food is to grow plants and eat them directly. If we only ate plants, then in theory at least, there would be more than enough food for every on eon earth. As much of the biomass produced by plants as possible would be used to feed people.
Every extra stage we add in the food chain, means less energy getting to us at the end of the chain. In turn this means less food to go round the human population.

21. Efficiency in food production
The efficiency of food production can be improved by reducing the amount of energy lost to the surroundings.
This can be done by:
preventing animals moving around too much
keeping their surroundings warm
Farmers apply these ideas to food production. People want meat, eggs, and milk but they want them as cheaply as possible. So farmers want to get the maximum possible increase in biomass from animals without feeding them anymore

22. Need to get the laptops.
Assign students to speak either for intensive farming or against it and for free-range farming. Students need to think carefully about the benefits t
You are going to take part in a debate on animal welfare and farming methods