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.

The Importance of Nitrogen

Why is nitrogen important to living things?

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.

The Importance of NitrogenWe and other animals need amino acids to

make the proteins to build our bodies our proteins from protein rich foods such as

EggsRed and white meatFishdairy productsbeanslentilspeas nuts

The Importance of NitrogenMost 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.

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.

Fertilisers contain nitrates to help with this.

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

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).

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.

ANIMAL PROTEIN

AMMONIA

DEAD ORGANISMS AND DUNG

NITRITES THEN INTO NITRATES

PLANT PROTEIN

Eating

Death and

excretion

Decay by fungi and bacteria

Conversion by

bacteria

Uptake by roots

Death

nitrogen fixing bacteriaOther 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.

ANIMAL PROTEIN

AMMONIA

DEAD ORGANISMS AND DUNG

NITRITESTHEN INTO NITRATES

PLANT PROTEIN

Eating

Death and

excretion

Decay by fungi and bacteria

Conversion by

bacteria

Uptake by roots

Death

NITROGEN GASIN THE AIR

Nitrogen fixing bacteriaDenitrifying

bacteria

In the roots of peas, beans and clover

(legumes) and free in soil.

A

F

G or E

E

F

D

B

C

Summary video- WARNING- This has some bad words in it

and so may not be suitable for your teacher!

snailgrass thrush

5.

grass

snail

thrush

A habitat is the place where an organism lives.

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.

oakwood mouse/ shrew/owl/foxfungi

squirrel/ caterpillar

6.

oak caterpillar shrew

leaf litter

earth wormwood mousefox

9.

41

32

nitrate

nitrifying bacterium

13.

• 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.

Learning Outcomes