Geoscience Reference
In-Depth Information
forest floor. Frogs must always keep their skin moist since most of their respiration
is carried out through the skin. The high humidity of the rainforest and frequent
rainstorms give tropical frogs infinitely more freedom to move into the trees and
escape the many predators of rainforest waters. The majority of rainforest frogs
place eggs in vegetation or lay them on the ground. By leaving the water, frogs
avoid egg-predators like fish, shrimp, aquatic insects, and insect larvae. Frogs have
evolved to take advantage of the many layers of the tropical rainforest, some live
and breed high in the canopy in bromeliads, others have developed toe pads to
climb and hang onto vegetation. Many toads and frogs, such as the poison dart frog
of the Amazon, have developed toxicity to discourage predation.
Humans play a role in tropical species presence and distribution. Regions
where humans have been present for millions of years seem to have fared better in
terms of the presence of larger animals. Populations of terrestrial vertebrates in
those areas more recently inhabited, such as the Neotropics, Madagascar, and
New Guinea, have decreased or gone extinct. In their travels and migrations,
humans have transported (both intentionally and unintentionally) species foreign
to the new area. These newcomers often adapt and do well in their new environ-
ment to the detriment of native species of the region.
Tropical Invertebrates
By far the most abundant and successful animals of the tropical rainforest are
insects, as demonstrated by their tremendous diversity. In the rainforest canopy,
insects abound. A study of the rainforest canopy in Peru found more than 50 spe-
cies of ants, 1,000 beetles species, and 1,700 other species of arthropods, including
more than 100,000 individuals in a plot measuring 30 in 3 (500 cm 3 ). A rainforest
tree alone can have some 1,200 species of beetles, while a 2.4 ac (1 ha) plot of rain-
forest canopy is projected to have more than 10 times that number.
Additionally, many insects and other organisms not typically found in the
trees make their home in the canopy of the tropical rainforest. Several species of
crab have been found hundreds of feet above the ground in bromeliads of Neo-
tropical rainforests. Similarly, earthworms and giant planarians (flatworms) are
also part of the canopy system. Earthworms play an important role in the process-
ing of canopy soils and mulch that supports epiphytic growth. Even leeches are
found in the forest canopy. Mosquitoes are abundant in the canopy with fewer on
the ground. Many insects like stick and leaf insects, katydids, leaf hoppers, and
mantids have developed incredible behavior, body structure, or color to adapt to
their surroundings.
Products and Services from the Rainforest
Hundreds of items used in the world today come from tropical rainforests. They
include fruits, vegetables, spices, cocoa, coffee and tea, oils, cosmetics and
perfumes, houseplants, fibers, building material, and medicines (see Table 2.1).
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