 Rain forests are the
most biologically diverse ecosystems in the world. They have
more plant and animal life than any other natural habitat on
Earth. Although rain forests represent less than 7 % of land
surface on the planet, they contain more than 60%, or maybe much
more, of the world's plant and animal species.
A typical
acre of forest in the Amazon may contain 250 or more tree species,
compared, for example, with perhaps a dozen in any acre of woods
in the northeastern United States. Because the crowns of these
forest giants form a virtually closed canopy, allowing only about
10% of the sunlight to filter through, there is little plant
or animal life on the ground below. However, the trees are festooned
with a wide variety of epiphytes, bromeliads and lianas while
their branches teem with animal life.
Lush
vegetation is the main characteristic of the rainforests, where
high temperature and rainfall occur throughout
the whole
year. The temperature is almost the same throught
the whole year. The average annual temperature is around 25°
C (77° F), being the average minimum around 18° C (64°
F). There are no dry seasons and if dry periods occur, they are
always short.
The Brazilian
Amazonian rainforest, in the north of Brazil, is the richest
ecosystem in the country with the most varied plant life on Earth,
a large number of different bird species and the largest variety
of monkeys in the whole world. It is one of the world's largest
woodland area, covering about 40% of the entire country.
 
 Some
1.400 bird species have been identified in the immediate vicinity
of the main stream of the Amazon river system. In this same area,
along the river banks, alligators, anacondas, boa constrictors,
"capivaras" (Hydrochareis hydrochaeris) - a
sub-aquatic animal and world's largest rodent - lizards, amphibians
and mammals can be found.
Among
the estimated 750 species of mammals identified in South  America,
394 are found in Brazil, such as pumas, jaguars, ocelots, armadillos,
anteaters and sloths among many others. Some like the ocelots
and the "onça", a type of jaguar, have been
hunted and are now among the endangered species.
In
the waters themselves there are manatees, freshwater dolphins,
and
some 1.500 identified fish species, with perhaps another 1.000
unidentified species; the variety includes many types of piranhas,
not all of them flesh-eating, electric eels, and some 450 species
of catfish.
The number
of invertebrates is estimated in more than 100,000 species, being
 70,000
of  these
a large variety of insects. The Amazon is also home to the world's
largest fresh-water turtle, of the genus Podocnemis, extinct
everywhere except there and on the island of Madagascar.
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