Most of these species have adapted for life in the upper levels of the rainforest, where food is most plentiful. Insects, which can easily climb or fly from tree to tree, make up the largest group (ants are the most abundant animal in the rainforest). Insect species have a highly symbiotic relationship with the plant life in a rainforest. The insects move from plant to plant, enjoying the wealth of food provided there. As they travel, the insects may pick up the plants' seeds, dropping them some distance away. This helps to disperse the population of the plant species over a larger area。

　　The numerous birds of the rainforest also play a major part in seed dispersal. When they eat fruit from a plant, the seeds pass through their digestive system. By the time they excrete (排泄) the seeds, the birds may have flown many miles away from the fruit-bearing tree。

　　There are also a large number of reptiles and mammals in the rainforest. Since the weather is so hot and humid during the day, most rainforest mammals are active only at night, dusk or dawn. The many rainforest bat species are especially well adapted for this lifestyle. Using their sonar, bats navigate easily through the mass of trees in the rainforest, feeding on insects and fruit。

　　While most rainforest species spend their lives in the trees, there is also a lot of life on the forest floor. Great apes, wild pigs, big cats and even elephants can all be found in rainforests. There are a number of people who live in the rainforests, as well. These tribes--which, up until recently, numbered in the thousands--are being forced out of the rainforests at an alarming rate because of deforestation。

　　Deforestation

　　In the past hundred years, humans have begun destroying rainforests at an alarming rate. Today, roughly 1.5 acres of rainforest are destroyed every second. People are cutting down the rainforests in pursuit of three major resources:

　　· land for crops

　　· lumber for paper and other wood products

　　· land for livestock pastures

　　In the current economy, people obviously have a need for all of these resources. But almost all experts agree that, over time, we will suffer much more from the destruction of the rainforests than we will benefit。

　　The world's rainforests are an extremely valuable natural resource, to be sure, but not for their lumber or their land. They are the main cradle of life on Earth, and they hold millions of unique life forms that we have yet to discover. Destroying the rainforests is comparable to destroying an unknown planet we have no idea what we're losing. If deforestation continues at its current rate, the world's tropical rainforests will be wiped out within 40 years。

　1. Virtually all plant and animal species on Earth can be found in tropical rainforests。

　　2. There is not much change in the weather in the tropical rainforests all the year round。

　　3. The largest number of rainforests in the world are located on the African continent。