Exchanging material
In this lesson, you will be looking at how living things interact with the
environment.
Living things take materials in from the environment as well as give
materials out. This is a characteristic of living things. Non-living things
do not interact with the environment in this way.
What sorts of materials are exchanged?
Living things do not all take the same materials out of the environment.
The same is true with the materials they put back into the environment.
However, what all living things have in common is that they all take
materials in from the environment and they all give materials back to the
environment.
Look at the materials that humans exchange with the environment – what
are they and why does it happen?
What sort of materials do you
need to survive?
__________________________________________________________
You've probably thought of things such as water, air, maybe even oxygen and
food.
Lesson 4/20 What are living things?
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drinking
breathing out
perspir
hing
ing
breat
air
g
n
ati
e
breath
urina
sweat
ting
eli
mi
na
tin
g
urine
faeces
Materials in and out of the human body
© State of New South Wales, Department of Education and Training, 2004
What sorts of materials are given out by your body?
__________________________________________________________
You may have thought of things such as perspiration, breath, urine and faeces.
Are the materials that go into our
bodies the same as the materials
that pass out of it?
Definitely not!
Why do living things take in materials?
It is essential for living things to take in materials from the environment.
Living things need water, food and gases from the air to carry out the
characteristics of life. That is, living things need these materials to grow,
develop, move, reproduce and respond.
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Living things
Why do we need water?
People drink lots of water. We
wouldn’t live very long without it!
Imagine getting stranded in the
desert without water to drink.
Humans, and all other living things,
need water.
But why?
Activity: Why do we need water?
Look carefully at the column graph following. It shows how much water
there is in the bodies of some organisms (living things).
Are the bodies of living things mainly made up of water? Use the graph
to find an answer.
100
90
80
Percentage of water
70
60
50
40
30
20
tomato
pineapple
jellyfish
earthworm
lobster
frog
chicken
kangaroo rat
human
0
herring
10
Percentage (%) of water in living things
Lesson 4/20 What are living things?
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You can see that the living things shown on the column graph are more
than 50% water. In fact, some living things are almost entirely made up
of water. You can see that jellyfish and tomatoes are approximately 98%
water!
1
Which organisms contain the smallest percentage of water?
_______________________________________________________
Humans and kangaroo rats contain the least water (but there is still more
than 50%).
2
Which organism contains more water than a lobster but less than an
earthworm?
_______________________________________________________
A frog is in between a lobster and an earthworm for water content.
Why then do you need water?
When you perspire, the water on your skin evaporates and cools you.
In the body, water surrounds the joints so the bones don't rub together.
Water is also important as a carrier. Blood is mainly water. It carries
nutrients and gases to all parts of the body. Urine is mainly water.
Urine carries away a waste called urea and other materials that are
produced by the body.
You also need water to digest your food. Many of the processes that
happen inside our bodies, like digestion (the breaking down of food),
need water for them to occur.
These are some of the reasons why living things need water.
Activity: Why then do you need water?
List some of the reasons why living things need water.
__________________________________________________________
__________________________________________________________
__________________________________________________________
Here are the reasons listed in the above text: water cools the body; water stops
the joints from rubbing; water carries substances around and out of the body;
water is needed for digestion.
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Living things
Did you find them all?
Why do you need to eat?
All living things need to take nutrients from the environment. These
nutrients are in the food you eat. You need nutrients such as proteins,
fats, sugars, vitamins and minerals.
What happens to the food you eat? How can our bodies get nutrients
from food?
When food is eaten, it is broken down into very small parts. This process
is called digestion. The digested food then goes into the bloodstream so
that it is carried to all parts of the body.
After food is digested, the nutrients are ready to be used. But what are
nutrients used for?
This depends on the type of nutrient. For example, proteins are used for
body building and repair to damaged parts of the body.
The simple substances produced by digestion are changed to more
complex substances when they are used for these purposes. This process
is called assimilation.
This is shown the following diagram.
hair
nail
egg
digestion
to simple
substances
bone
blood
muscle
What happens to the food you eat? Simple substances build and repair the body.
© State of New South Wales, Department of Education and Training, 2004
Lesson 4/20 What are living things?
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Fats and sugars are needed to provide energy. This energy enables you
to do all the things that living things do, such as respond to your
surroundings, grow and move.
How do body processes work together?
All the processes that occur in your body are linked. The different parts
of your body work together, or coordinate, to maintain the whole body.
In this way, breathing, digestion and providing energy are processes that
are linked.
Sugars are digested to produce a simple sugar called glucose. Oxygen
from the air and glucose react together to release energy. This process is
called respiration. Respiration occurs in all parts of the body because
every part of the body needs energy to work. This can happen since
blood carries oxygen and glucose throughout the body. This is an
example of how all the body's parts coordinate to make the whole body
work.
This idea is shown the following diagram.
•
•
•
•
Sugar is eaten, then digested to produce glucose.
Oxygen from the air is breathed in.
This oxygen reacts with glucose to release energy.
The waste materials are excreted (removed from the body) as urine,
breath and sweat.
sugar
digestion
glucose and oxygen
respiration
breathing
air
waste materials
energy
excretion
urine, breath, sweat
Linking the processes that release energy
© State of New South Wales, Department of Education and Training, 2004
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Living things
Activity: How do body processes work together?
Use the above diagram to answer the following questions.
1
List the four processes included in the diagram.
_______________________________________________________
2
What materials does your body need for respiration?
_______________________________________________________
3
Which process provides glucose for your body?
_______________________________________________________
4
What happens to waste materials made during respiration?
_______________________________________________________
Check your response by going to the suggested answers section.
Why do living things give out materials?
When respiration occurs, energy is released but so is carbon dioxide,
which is not useful to humans. Some of the waste materials that are
produced inside the body are harmful if they are not removed. This is
why there are parts of the body that work to get rid of these unwanted
materials. Getting rid of the unwanted materials that are produced by the
body is called excretion.
Lesson 4/20 What are living things?
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Preparing for the Exercise
Why do living things take in
and give out materials?
Go to the exercises section and complete Exercise – Exchanging
materials
What did you achieve?
Tick what you can do.
list some reasons why humans need to take in water and food
explain why living things need to exchange materials with the
environment
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Living things
Suggested answers
Check your responses against these suggested answers.
Activity: How do body processes work together
1
The four processes in the diagram are digestion, breathing, respiration and
excretion.
2
Your body needs glucose and oxygen for respiration.
3
Digestion provides glucose for your body.
4
The waste materials made during respiration are excreted in substances
such as urine, breath and sweat.
Lesson 4/20 What are living things?
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Living things
Exercises
Living things
Exercise
1
Name
___________________________
Teacher
___________________________
Exchanging materials
Living things need to take in materials such as food, water and air
because:
_______________________________________________________
_______________________________________________________
2
Living things need to get rid of wastes such as urine, breath and
sweat because:
_______________________________________________________
_______________________________________________________
Lesson 4/20 What are living things?
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