1. What are we going to learn about today?
Today we’re going to look at nutrient cycling in the environment particularly at the nitrogen cycle.

3. Why is nitrogen important to living things?
The Importance of Nitrogen
Why is nitrogen important to living things?

4. Proteins contain the elements carbon, hydrogen, oxygen and nitrogen
The Importance of Nitrogen
Proteins contain the elements carbon, hydrogen, oxygen and nitrogen
Proteins are made of units called amino acids.
etc
Amino Acids
Proteins are essential for growth and repair of body tissues in all living things.

5. The Importance of Nitrogen
We and other animals need amino acids to make the proteins to build our bodies our proteins from protein rich foods such as
Eggs
Red and white meat
Fish
dairy products
beans
lentils
peas
nuts

6. The Importance of Nitrogen
Most plants make their own proteins using nitrogen. But not from the air as they can’t absorb gaseous nitrogen. instead they absorb it through their roots as nitrates from the soil that they grow in.
Fertilisers contain nitrates to help with this.
Animals then eat plants digest the protein and absorb the amino acids that they are made from into their blood to be carried to where they are needed to make protein for growth and repair.

7. If all this nitrogen ends up in living things
why doesn’t it run out?

8. Not all of the protein in plants or prey eaten by animals end up being absorbed. A lot of it comes out in faeces (dung).
In the bodies of animals excess amino acids not needed for making protein for growth and repair are broken down into urea- a nitrogenous waste (meaning it contains nitrogen).

9. The proteins in dead bodies and dung and nitrogenous wastes are broken down by bacteria and fungi (decomposers) into ammonia. This ammonia is then made into nitrates by bacteria.
Let’s summarise
all of this.

10. Conversion by bacteria
ANIMAL PROTEIN
Death and excretion
Eating
Death
DEAD ORGANISMS
AND DUNG
PLANT PROTEIN
Decay by fungi and bacteria
Uptake by roots
AMMONIA
NITRITES
THEN INTO
NITRATES
Conversion by bacteria

11. nitrogen fixing bacteria
Other bacteria take nitrogen from the air and convert it to a form that plants can use some live free in the soil and others such as Rhizobium live in a special relationship with legumes- plants such as peas, beans and clover.
Here is a clover plant showing the “root nodules” in which the Rhizobium lives.

12. Nitrogen fixing bacteria
NITROGEN GAS
IN THE AIR
Nitrogen fixing bacteria
Denitrifying
bacteria
ANIMAL PROTEIN
In the roots of peas, beans and clover (legumes) and free in soil.
Death and excretion
Eating
Death
DEAD ORGANISMS
AND DUNG
PLANT PROTEIN
Decay by fungi and bacteria
Uptake by roots
AMMONIA
NITRITES
THEN INTO
NITRATES
Conversion by bacteria

13. A F
G or E

14. E F D B C

15. WARNING- This has some bad words in it
Summary video-
WARNING- This has some bad words in it
and so may not be suitable for your teacher!

16. 5.
snail
grass
thrush
thrush
snail
grass
A habitat is the place where an organism lives.

17. Bacteria or fungi.
Decomposers break down organic matter by respiration. In the nitrogen cycle they convert protein and nitrogenous wastes into ammonium and nitrates that may be used by plants to build protein.

18. 6.
oak
wood mouse/ shrew/owl/fox
fungi
squirrel/ caterpillar

19. oak
caterpillar
shrew
fox
wood mouse
earth worm
leaf litter

20. 9.

22. 13. 4
nitrate 1 3 2
nitrifying bacterium

23. Learning Outcomes
Animal and plant proteins are made up of amino acids that contain the element nitrogen.
Plants and animals cannot absorb nitrogen from the air.
Plants gain their nitrogen in the form of nitrates through their roots in a process known as uptake.
Nitrifying bacteria convert ammonia into nitrates.
Denitrifying bacteria convert nitrates into nitrogen gas.
Nitrogen fixing bacteria convert nitrogen from the air to a form that plants can use. Some are found free in the soil and others in the root nodules of legumes (peas beans and clover).
Decomposers (bacteria and fungi) convert proteins and nitrogenous waste in urine and faeces (pee and poo) into ammonia.