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The Ecology of a Rain Forest


     In 1980, the estimated amount of rain forests in the world was 40,000
square miles.  This number decreases each year by roughly 1,000 square
miles due to construction and the resources being used for profit.  It is
too bad, because the rain forest is one of the most beautiful places on
earth.  It is the most diverse, containing the most species of living
things, much more than anywhere else, and most have yet to be identified.
All rain forests are located on earth's "green belt", that is, the area
roughly around the equator that covers all the area from Mexico and the
northern area of South America, to Africa, to India, streching out to
Indonesia, the northern tip of Australia and all the way to New Guinea.
This area is heavily covered with flora and fauna, and it abounds with life.
 In a rain forest, it is very wet and it rains every day or every other day
very heavily.  There is a high and steady level of heat and moisture. 
There are some general layers to the rain forest.  It starts 135 feet up in
the air, with the lofty crowns of the tallest trees in the jungle.  They
take the most light, heat, rain and the most punishment from the winds. 
Woodpeckers hunt insects in this layer, and also the black and white
Colobus monkey can be found here, ready to lauch into the air, using his
specially developed tail as a rudder to guide his flight.  Beneath this is
the second layer of trees, whose crowns form a forest canopy.  Rain filters
through this canopy, and the top sides of the crowns hold a large amount of
ferns and other small plants whose roots never touch soil.  They live off
the water and nutrients held in the small pockets of the leaves and
branches.  Tree frogs and chimpanzees live here, burrowing holes to live in
the vast vegetation.  The third layer is called the "understory". This
grows beneath the canopy.  The gorilla makes this his regular hangout, also
pythons lie here waiting for prey.  The dim forest floor teems with life. 
Termites and ants feed on all the decomposing matter on the ground, and
elephants make their way down a path of moss.  Butterflies move silently by,
and the air is still and very humid.  These are the layers that make up the
rain forest's complex ecology.  In the rest of the essay I will describe
some of the life forms found in the rain forest, and ways they affect the
environment.  In the rain forest, plants develop poisonous alkaloids to
protect against insects, and insects develop complex digestive chemistry to
overcome these poisons.  Some of these plant alkaloids give native indians
great poisons for darts, and to cancer researchers hope for a new medicine.
The rain forest root systems are so efficient that almost all of the
nutrients in decaying plants are recycled into new ones.  Most roots are
found within three inches of the surface in heavy clay or at the surface in
sandy soils.  Tiny rootlets grow up and attach themsleves to leaves.  When
the leaf decays, miniscule fungi on the rootlets take over and send
threadlike projections into the leaf which absorbs all of the leaf's
nutrient material.  The phosphorous that the fungi produces is taken by the
root, and in turn gives the fungus sugars from the tree.  Also, termites
and ants break down the forest litter.  In a small lake in the middle of
the rain forest, a small lizard skims across the water away from danagerous
prey and attacks its own victim by suprise, yet another marvel of the
tropical rain forest.  Mutualism occurs in the jungle with a specialized
ant and a swollen-thorn acacia.  The acacia provides budlike leaflet tips
which are called Beltian bodies, which the ants give to their young for
food.  The insects hollow out the tree's thorns when soft and green and
raise their young inside.  The acacia doesn't have chemical defenses to
repel dangerous and damaging insects and demands pure sunlight for proper
growth.  The ants patrol the tree day and night.  If any insect lands on
the tree, they bite it with a poisonous sting.  They also attack plants
that grow onto the tree, such as a vine.  In this case, they would attack
the vine at it's base and pull it off the tree.  There are also small leaf-
cutting ants in the jungle that cut a portion of a leaf, bring it to their
home, and chew it to a pulp and inject a body fluid to create a wet mulch. 
On this mulch grows the only food of this particular ant -- a fungus that
has only one species.  The mysterious part about this is that any spores
that could develop on the mulch and contaminate it don't develop.  Paper
wasps in the rain forest have to bail out their home after a heavy shower. 
They lap up a mouthful of water from the colony, and then spit it out onto
the forest floor.  They also coat the small stalk that attaches the nest to
the branch of a tree with a sticky black sectretion that repels some ants. 
But there are still some predators, such as jungle katydids which eat the
leaves, and some species of ants that are not repelled by the black
secretion.  In one rain forest, there is a kind of toad that is voiceless. 
So for the male to attract a mate, nature gave it a very noticeable
characteristic -- a flourescent orange color, which is unmistakable.  The
females are blackish green with scarlet spots on them. In April and May,
mating takes place.  Where pools are formed on the forest floor by water
trickling down trees, females lay around 200 eggs.  After the males
fertilize them, the embryos live in their aquatic world for about two weeks,
then after that they hatch and mature.  This species was discovered in 1964
and it helped win government protection for Monteverde, which is the place
where these frogs can be found.  Biologist Jay M. Savage, amazed by the
frogs, once wrote "I must confess. . .my. . .disbelief and suspicion that
someone had dipped the examples in enamel paint."  There are other species
of frogs, such as the green leaf frog, whose green body and glowing red
eyes is an incredible sight.  They extrude and fertilize their eggs on a
leaf over water.  Young that are ready to leave their embryo drop into the
water below.  Also the poison-arrow frog is an interesting variety.  The
males battle for dominance and mates.  Two can struggle for hours until one
give up and croaks "uncle".  Their color warns predators of their
composition which could prove toxic for snakes and other such beasties. 
The Dendrobates Granuliferus frog doesn't have young that develop in water.
Instead, the tadpoles cling to the mother's wet back.  She transports them
this way from place to place, usually depositing them in a cup of rainwater
in a high branch safe from predators.  She immerses herself in the water at
first until the young let go of her body and swim into the water.  A rare
bird found only in rain forests, the quetzal, is a beautiful sight.  They
have long colorful tails which have long been worn by royalty of the
Colombian Indians, who called the birds sacred.  It is beautiful animals
like these that might start spur nations into preserving more of their rain
forests, in hopes of keeping one of the most complex and interesting
ecologies on earth.