70 Nature
LIFE ON EARTH
Planet Earth is home to trillions of
organisms (living things), including
animals and plants. They are found
on land, in lakes, rivers, and oceans,
as well as in the air. Scientists
use. CLASSIFICATION to show
how different species, or types,
of organisms are related.
WHAT DO ALL LIVING THINGS HAVE IN COMMON?
All organisms need food for the energy required
to live and grow. They all excrete (get rid of) waste
products, and detect changes in their surroundings
and respond to them. All living organisms follow
a. LIFE CYCLE of growth and development,
reproduction, and death.CAN LIFE EXIST WITHOUT SUNLIGHT?
Sunlight is essential for most life forms on Earth to
exist. Plants use energy from sunlight to convert
water and carbon dioxide gas into food. This releases
essential, life-giving oxygen into the atmosphere.
Virtually all other organisms rely on plants for energy
to keep them alive. Even meat-eaters indirectly absorb
vegetation from their plant-eating prey.4 DOLPHIN FISH
These ocean-living dolphin fish,
or mahi mahi, swim in large
groups called shoals. They feed
on smaller fish and shrimps. Fish
are well adapted to life in water.
They have gills for absorbing
oxygen from water, and their
streamlined bodies dart easily
through rivers, lakes, and oceans.AFRICAN ELEPHANTS 3
The largest of all land animals is
the African elephant. Its massive
body is supported by four pillar-
like legs. Elephants have long,
bendy trunks that raise water and
food to the mouth and spray
water over their bodies. Long,
curved tusks are used for defence.HOW DOES THE MOVEMENT OF THE EARTH
AFFECT LIFE ON OUR PLANET?
The Earth’s rotation every 24 hours produces day and
night. Some animals are active in the daytime, others
at night. Without sunlight, plants cease making food
and releasing oxygen. The annual movement of the
Earth around the Sun creates the seasons. Living
things are more active in spring and summer.