4.1 The physical
environment
PAGES 78-79
Physical environment
The water in lakes , rivers, oceans, sand, rocks and pebbles are not
living things.
The physical environment is non – living , it is where organisms live.
To understand life, we must understand the physical environments
where life exists.
Abiotic factors
Microorganisms , plants and animals depend on a number of abiotic or
non living factors to survive.
For example:
The rocks, soil or sand making up a landscape affect the type of plants
and animals that survive there. The organisms that you see on a rocky
mountainside will be very different from the plants and animals in the
rich soil of a river valley.
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Temperature has a big impact on what can grow and survive.
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Water is needed for organisms to live, so the amount of water
available in an ecosystem affects all life.
Why is water so important?

About 71% of the surface of the Earth is covered in water. It fills our
oceans, rivers and lakes. It has carved out our landscapes. Almost
all of that water (96.5%) is in the oceans. Fresh water is rare and
precious.
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Water fills our cells. Up to 60% of an adult human being is water!
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All other animals rely on water too, both as part of their bodies and
as a place to live. Some animals, like jellyfish, are up to 90% water!
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Plants also depend on water. They need water to transport food
and minerals around their bodies, to make food in photosynthesis
and for support.
The properties of water

Water is a very good solvent. Many substances dissolve in it. Your
blood is water containing many dissolved food molecules, mineral
salts and chemical messengers, as well as your blood cells.
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It takes a lot of energy to heat water up, and it cools down very
slowly.
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When water freezes, the solid ice floats on top of the liquid water. It
makes an insulating layer that stops the water under the ice
freezing.
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