Page 11 - The World About Us

Rainforest
2.1.2
1.1.1

What is the variety of life in the tropical rainforests?

Rainforests have the highest levels
of biodiversity on Earth. One square
kilometre of forest may contain over
1,000 different species of trees. These
trees will be draped with thousands of
species of mosses, epiphytes, orchids
and other flowing plants. These plants
provide food for insects and animals in
a vast and complex food web, up
through the trophic levels of the biome.
Rainforest may cover just 6% of the
Earth’s surface but contain an
es mated 50% to 75% of all the
world’s species. Some es mates
suggest that rainforests may contain 50
million species of plants and animals.
The trees grow tall in the rainforest
as they compete to access the energy
from the overhead Sun. The canopy of
fig.24 Rainforests have the highest biodiversity of any biome on the planet.
the forest, around 45m above the
ground, is a dense tangle of branches being eaten by numerous herbivores. means they must learn the different
covered in evergreen leaves. loca ons for each tree, of each frui ng
Trees have spines and thorns or
Over millions of years some trees, produce poisons to make the leaves species, in their territory.
such as the South American Olla de unpalatable. In turn, animals have
mono, have evolved to become evolved to display coping mechanisms,
emergents. These trees tower as high such as evolving a long gut to break
as 60m above the forest floor and down food slowly or descending to the
provide homes for eagles and other forest floor to eat mud which is able to
birds of prey. neutralise the poisons in the leaves.

The canopy is host to many species Trees have to synchronise flowering
of insects, amphibians, rep les, birds, so that there is sufficient pollen of the
and mammals. They all rely on the trees same species to pollinate their own
for food or prey upon other primary flowers. This means different species of
consumers of the canopy. In the canopy tree flower and then fruit at different fig.26 Orang utans and other
an 'arms race' has developed as trees mes of the year. For fruit ea ng birds, rainforest mammals and birds will
have tried to protect their leaves from or animals such as orangutans, this travel large distances in search of fruits.

Fig.25 The climate of Medan. KEY TERMS
400 40

350 35 Canopy: the layer of dense vegetation
at the top of most rainforest trees.
30
Mean monthly rainfall (mm) 250 25 Mean monthly temperature ( fig.27 Reptiles, such as the immediately north and south of the
300
Equatorial: relating to the region
Equator.
200
20
Rainforest: an area of dense
150
15
woodland which receives rainfall in
100
Tropical: relating to the land and sea
the rainforest. The warm temperatures
50 10 o Wagler’s Pit Viper (above), hunt in excess of 1500mm per year.
mean these cold-blooded reptiles can between the Tropic of Cancer (23 ⁄ N)
5 C)
0 0 be active both day and night. and Tropic of Capricorn (23 ⁄ S).
J F M A M J J A S O N D
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Ecosystems have distinct distributions and characteristics.