Biology - Ecosystems
Ecosystems:
A community of living things and their environment, and the way they are linked
together through the movement of nutrients and energy(as shown in food chains and food
webs). An ecosystem can be divided into many habitats.
1. The rainforest ecosystem
Rainforests are found on land around the middle of the planet. They are found in parts
of Central and South America, Africa, Australia and Asia. A rainforest is an ecosystem
in which a community of plants, animals and microorganisms live in a hot, wet
environment inside the forest. When you stand inside a rainforest, all you can see are
lots of plants. Ecologists have divided the plants into four layers:
Forest floor (undergrowth layer):
On the forest floor are many decomposing fallen trees and dead animals. Animals like wild pigs and
deer live in this layer. There may be leeches and ticks that are on the trees that are on the trees so that
they climb onto any any animal that passes to suck their blood. There may be insectivorous plants, like
pitcher plants, Venus flytrap, Cobra lily, Sundews etc.
Understory:
This layer is formed by small trees which may grow up into the higher levels. There might be pitcher
plants here, which feed on the insects that go in the trees. Birds may build their nests here and snakes
can hunt for their prey. Bigger animals like cheetahs will rest here and take their prey from the forest
floor.
Canopy:
This layer is made up of the branches of bigger trees. They will support other plants like ferns and
orchids. This is where monkeys like langur and macaque live. The canopy of some rainforests will have
gliding frogs pounce from branch to branch using their webbed feet like parachutes.
Emergent layer:
This layer is made of the most tallest trees. Eagles and vultures and hawks build their nest in this layer
and bats will settle here.
2. The desert ecosystem
A desert is an area of land which receives a very little amount of rain. There are hot and
cold deserts. Deserts are found in North and South America, Africa, Australia, Asia and
Antarctica. There are three main habitats in a hot desert. There are huge piles of
moving sand called sand dunes. There are areas of rocks and thin soil called desert
pavement, and places where water comes up from the ground to form a well or
pond-like structure called an oasis.
Sand dunes:
Sand dunes can change into different shapes and positions as they are whirled by the wind and they are
dry for long periods of time. The insects which are dead will fall on the sand and make food for lizards
and snakes that can dig into the sand and then come outside it and move over it. If it rains, seeds in the
sand will germinate and make plants with attractive flowers that will attract more organisms (insects).
Desert pavements:
Rocks and soil help more large and permanent plants grow, like cactus and agave. These plants make
home for animals like cactus wren ( a bird which requires spiny cacti for building a nest) and can be a
food source for camels.
Oasis:
Many plants grow in the wet region around the oasis, and are eaten by grasshoppers and butterflies,
which in turn are eaten by lizards and birds. Larger animals living the desert, such as foxes and
antelopes, come to the oases for water and food. The oases provide an important water source for
bigger animals.
3. The ecosystem of the oceans and seas
An ocean is a huge body of salty water that covers most of the Earth's surface. There
are five major oceans and around 50 seas in the world.
The ecosystem is divided into six major zones but there may be many habitats in each
zone.
Intertidal zone:
This is where the tide moves up and down in the sea-shore. There are two main kinds of habitat here:
the rock shore and the sandy shore. The plants and animals are adapted to live here and in the
sea-water for a few hours each day.
Coastal zone:
This zone is further away from the shore. It has deeper water and the tides do not form here. There are
wide ranges of seaweeds and animals like sea urchins and jellyfish.
Open sea:
This region is far away from the coast and is divided into three zones:
Sunlit zone:
There is enough light entering the water for microscopic plants to do photosynthesis in this zone.
These plants form part of a plankton which also includes very small organisms that feed on them.
Twilight zone:
In this layer there is not enough sunlight for the plants to make food. Some of the sea animals eat the
dead bodies that sink from the previous (sunlit) zone. The other animals here are only carnivores and
they have some organs that emit light that helps them to see, communicate with other animals and
hunt their prey.
Dark zone:
There is no light in this zone. The animals in this zone eat the dead bodies that sink from higher in the
water. Those bodies that are remaining uneaten are broken down into tiny particles by the
decomposers in the ocean floor. From the sea-shore to the ocean floor, there are decomposers on all
the surfaces in these zones, which release the nutrients back into the water as they eat.
By: Sheethala.S
Grade-7
