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Random Fun Facts

Clothes dried outside smell better because of a process called photolysis (sunlight breaks down compounds that cause odor).

A lions feed once every 3 to 4 days.

Cows can walk up stairs but not down them..

It is illegal in the United Kingdom to handle salmon in suspicious circumstances..

The Grand Canyon can hold around 900 trillion footballs.

A dragonfly can fly at 40kph (25mph).

Glaciers and ice sheets hold about 69 percent of the worlds freshwater..

The Eiffel Tower is repainted every 7 years.

Kangaroos can not walk backwards..

Shakespeare invented the words 'assassination' and 'bump'.

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What's a Biome?

To make sense of complexity, humans often need to categorize, or group, things. We have food groups, sexes, eye colors, ages, and movie genres, to name a few. We categorize all types of things, whether they are ideas or objects, and whether they are small or large. One of the largest things that we try to categorize may be the types of environments found on Earth.

The natural world is more varied than we can imagine, and one way to try to make this variation easier to handle is to put different environment types into groups. We can divide our surroundings many ways-by how much water there is, by how warm it is, or by the types of plants or animals we find there. Depending on what characteristics we choose to describe an environment, the groupings we end up selecting may be different.

Usually we group the different natural areas on Earth into categories based on plant and animal life and how they are able to survive in that part of the world. Making groups based on living organisms can be very complicated. We already know of over 1.7 million species of organism, and there are likely over 17 million that exist. But again, by grouping organisms with similar adaptations together, we can see through some of the complexity and have a chance to better understand the living Earth.

A biome is a type of environment that is defined by the types of organisms that live there. We can also think of these as life zones ("bio" means life). Dividing land up in this way lets us talk about areas that are similar, even if they're on different continents. But depending on whom you talk to, the way we divide up the world into separate biomes differs.

Biome vs. Biome

Biome categories can be broad or narrow. When we say forest, you may picture a cool, quiet area with pine trees, where bears, deer, and rabbits wander around. Or instead, you might imagine a wet, dark, and noisy rainforest, where you can see monkeys, parrots, and big cats.

According to some people, all forest types belong in one group - the forest biome. But others think that temperate forests (seasonally cold) with pine trees, are very different from tropical rainforests, with dense, leafy canopy and lots of rain. This difference of opinion means that the number of biomes can range anywhere from 5 to 20 biomes.

How Different is Different?

If we take a closer look at these temperate and rain forests, we see that they differ quite a bit in the amount of rain they get and in their temperatures. Tropical rainforests are warm and don't experience a winter season. But temperate forests have a defined winter, with snow and temperatures below zero.

With those cold temperatures, the plants and animals in temperate rainforests have to have adaptations to deal with cold weather. Do those groups seem different enough to you to be in a separate biome?

Don't worry, there is no right or wrong answer. This method of categorizing is one of convenience, and sometimes it just depends on why you're dividing the groups.

Biomes of the World

In order to give you a small taste of the huge diversity of the types of environments out there, we divide the world up into only nine biomes. Just remember that these groups could also be divided into nearly 20 biomes. That means that within each of these biomes there is a range of temperature and weather conditions, and we also find some organisms that are adapted to only part of the biome and others that are adapted to the full range of conditions within the boundaries we are defining.

You probably picture tropical rainforest as a jungle, where it stays warm all year. There are too many animals to count and the huge numbers of trees keep their leaves year-round. Many of these forests get so much rain that there isn't even much of a dry season - more like a rainy season and a rainier season.

This is the kind of forest where there are four relatively distinct seasons. Many of the trees shed their leaves in the fall and become inactive through the cold winter. In these forests, you find deer, woodpeckers, and bears, some of which hibernate through the winter.

Deserts make up the hottest biome, but can also get cold temperatures in winter. Such temperature swings make this an extreme environment, where many animals have to burrow underground to find more stable temperatures in order to survive. Plants and animals here must be able to withstand long periods without water.

Tundra is flat and cold with low plants like grass and moss that only grow during the short summer. A thick layer of ice lies just below the shallow soil (permafrost) all year around, and trees cannot penetrate it to anchor their roots. Many birds visit the tundra in the summer to nest, but most escape the winter by migrating to warmer areas. Mice and other small mammals stay active during the winter in protected tunnels under the snow.

Taiga is the largest land (terrestrial) biome in the world. It is made up of mainly conical-shaped evergreen trees with needle-like leaves. These trees are called conifers because their seeds are clumped into cones. The taiga has long, cold winters when most mammals hibernate and birds migrate, or leave the area because the winters are too cold for them to stay. Animals like weasels, grouse and rabbits that do not migrate or hibernate grow dense feathers or fur and turn white to match the snow.

Sometimes called plains or prairie, grasslands are almost entirely short to tall grasses with no trees. This land type gets just enough rain to help grasses, flowers, and herbs grow, but stays dry enough that fires are frequent and trees cannot survive. Here we find large mammals that often travel together in huge herds.

These tree-studded grasslands receive enough seasonal rainfall so that trees can grow in open groups or singly throughout. The animals living here have long legs for escaping predators and usually are seen in herds. A combination of fire and grazing animals are important for maintaining the savannah.
Freshwater
This water biome is named for the low concentration of salt found in the water. This includes most ponds, streams, lakes, and rivers. Because salt is important to body function, the plants and animals here have many adaptations that help them save salt.
Marine
This water biome is the largest biome in the world, as it includes the five major oceans that cover 70% of the Earth. Marine water has high levels of salt, so animals and plants living here have adaptations that help them get rid of salt or take on water.
Virtual Biomes
Take a virtual look inside some of these biomes using a computer, smart phone, tablet, or Google Goggles. Our first two virtual biomes are the desert and rainforest. Compare how the two are different and how they are the similar. Write up your results in our biologist notebook.

Additional images from Wikimedia via Adrien Facélina and Pam Brophy.

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No two environments on Earth are the same. But with so many places to learn about, we often need to talk about some environments as a similar group rather than individually. For that, we have the brilliance of biomes.Also in: Français | Español

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Tell Me About Forests! - Science for Kids!

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Deserts of the World | Learn interesting facts about different deserts from around the world

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TUNDRA BIOME | What Is A Tundra Biome? | Tundra Region | The Dr Binocs Show | Peekaboo Kidz

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The grassland biome is made up of large open areas of grasses. They are maintained by grazing animals and frequent fires. Types of grasslands include savannas and temperate grasslands.

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Kids learn about the taiga forest biome. The largest of the land biomes is known for its evergreen trees.

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Kids learn about the desert biome. The dryest areas on Earth still have plant and animal life.

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For most of the year, the tundra biome is a cold, frozen landscape. This biome has a short growing season, followed by harsh conditions that the plants and animals in the region need special adaptations to survive.

Tundra form in two distinct cold and dry regions. Arctic tundra are found on high-latitude landmasses, above the Arctic Circle-in Alaska, Canada, Russia, Greenland, Iceland, and Scandinavia, for example-or on far southern regions, like Antarctica. Alpine tundra are located at very high elevations atop mountains, where overnight temperatures fall below freezing.

Tundra regions typically get less than 25 centimeters (10 inches) of precipitation annually, which means these areas are also considered deserts. They have long, cold winters with high winds and average temperatures below freezing for six to ten months of the year. On average, only six to ten weeks of the year have sufficiently warm temperatures and long days for plant growth. The soil in the Arctic is largely permafrost or soil that remains frozen year-round, leaving only a thin surface layer of thawed soil in summer for plant roots to grow in. Tundra soil is also scarce in many of the nutrients that plants need to grow.

These conditions lead to one of the tundra biome's most distinct features: They are largely treeless. (The word "tundra" derives from the Finnish word tunturia, meaning barren or treeless hill.) Instead, the tundra has patchy, low-to-ground vegetation consisting of small shrubs, grasses, mosses, sedges, and lichens, all of which are better adapted to withstand tundra conditions.

Animals in the tundra are also adapted to extreme conditions, and they take advantage of the temporary explosion of plant and insect life in the short growing season. Tundra wildlife includes small mammals-such as Norway lemmings ( Lemmus lemmus), arctic hares ( Lepis arcticus), and arctic ground squirrels ( Spermophilus parryii)-and large mammals, such as caribou ( Rangifer tarandus). These animals build up stores of fat to sustain and insulate them through the winter. They also have thick coats of fur for further insulation. Some save energy by hibernating during the long winter months. Others migrate to warmer climes during winter. Many birds also migrate into the tundra during the growing season to feed, mate, and nest.

Atop the food chain are tundra carnivores, such as arctic foxes ( Vulpes lagopus), arctic wolves ( Canis lupus), snowy owls ( Bubo scandiaca), and polar bears ( Ursus maritimus), which move into the tundra during the summer when prey is plentiful and their usual hunting grounds on sea ice diminish. Many animals, both predator and prey, develop white fur or feathers in the winter months for camouflage in ice and snow.

Tundra insects have also developed adaptations for the cold; mosquitoes ( Aedes nigripes), for example, have a chemical compound that acts as antifreeze, lowering the freezing temperature in their bodily fluids.

Though the tundra is remote, it is increasingly threatened as people encroach on it to build or drill for oil, for example. Perhaps the greatest danger, however, comes from climate change. Warming temperatures could disrupt the cold tundra biome and the life in it, as well as thaw its underlying permafrost, releasing greenhouse gases that would further accelerate global warming.

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Tundras are cold, harsh environments with distinctive biodiversity adapted to these conditions.

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Kids learn about the tundra grasslands biome. This cold and dry ecosystem is located far to the north.

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Image

Photograph by James L. Amos

Marine ecosystems are aquatic environments with high levels of dissolved salt, such as those found in or near the ocean. Marine ecosystems are defined by their unique biotic (living) and abiotic (nonliving) factors. Biotic factors include plants, animals, and microbes; important abiotic factors include the amount of sunlight in the ecosystem, the amount of oxygen and nutrients dissolved in the water, proximity to land, depth, and temperature.

Sunlight is one of the most important abiotic factors for marine ecosystems. It's so important that scientists classify parts of marine ecosystems-up to three-by the amount of light they receive. The topmost part of a marine ecosystem is the euphotic zone, extending down as far as 200 meters (656 feet) below the surface. At this depth, there is sufficient light for regular photosynthetic activity. Most marine life inhabits this zone. Below the euphotic zone is the dysphotic zone, which can reach from 200 to as deep as 1,000 meters (656 to 3,280 feet) below the surface. At these depths, sunlight is still available, but only enough to facilitate some photosynthesis. Below the dysphotic zone lies the aphotic zone, which does not receive any sunlight.

Types of Marine Ecosystems

Scientists divide marine ecosystems into several broad categories, although there are discrepancies depending on the source about what qualifies as a marine ecosystem. The number of marine ecosystems is actively debated. Although there is some disagreement, several types of marine ecosystems are largely agreed on: estuaries, salt marshes, mangrove forests, coral reefs, the open ocean, and the deep-sea ocean.

An estuary is a coastal zone where oceans meet rivers. Here, nutrients and salts from the ocean mix with those from the river in regions sheltered from extreme weather. As a result, estuaries are among the most productive places on Earth and support many types of life. In addition, because they are located where rivers join the ocean, estuaries have traditionally supported many human communities and activities like fishing, shipping, and transportation.

While estuaries form where ocean meets rivers, salt marshes occur where oceans meet land. These places are rich in nutrients from sediment brought in by the ocean. Marshes are regularly flooded by high tides, making the surrounding ground wet and salty. As a result, the soil is low in oxygen and filled with decomposing matter. These ecosystems are dominated by low-growing shrubs and grasses.

Another coastal ecosystem is the mangrove forest. Mangrove forests are found in tropical areas. These ecosystems frequently flood with ocean water, submerging the roots of mangrove trees. The root systems of mangroves filter out salt and sit above ground to access oxygen. These trees provide a home for a variety of species. Animals, such as fish, crabs, shrimp, reptiles, and amphibians, live among the mangrove's roots while its canopy provides a nesting site for birds.

A bit farther out into the tropical sea are coral reefs, euphotic-zone ecosystems built from the exoskeleton secreted by coral polyps. These exoskeletons form complex structures that shelter many different organisms. Coral reefs are extremely diverse ecosystems that host sponges, crustaceans, mollusks, fish, turtles, sharks, dolphins, and many more creatures. By some counts, coral reefs can account for a quarter of all ocean species.

Beyond the coral reefs lies the open ocean. Open ocean ecosystems vary widely as the depth of the ocean changes. At the surface of the ocean, the euphotic zone, the ecosystem receives plenty of light and oxygen, is fairly warm, and supports many photosynthetic organisms. Many of the organisms that we associate with marine ecosystems, such as whales, dolphins, octopi, and sharks, live in the open ocean.

As the depth of the ocean increases, it gets darker, colder, and with less available oxygen. Organisms living in deep-sea ecosystems within the dysphotic and aphotic zones have unusual adaptations that help them survive in these challenging environments. Some organisms have extremely large mouths that allow them to catch whatever nutrients fall from shallower ocean depths. Others have adapted to get their energy via chemosynthesis of chemicals from hydrothermal vents.

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Marine ecosystems are aquatic environments with high levels of dissolved salt. These include the open ocean, the deep-sea ocean, and coastal marine ecosystems, each of which has different physical and biological characteristics.

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Home | Online exhibits | The world's biomes

Freshwater is defined as having a low salt concentration — usually less than 1%. Plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration (i.e., ocean). There are different types of freshwater regions:

Ponds and lakes

These regions range in size from just a few square meters to thousands of square kilometers. Scattered throughout the earth, several are remnants from the Pleistocene glaciation. Many ponds are seasonal, lasting just a couple of months (such as sessile pools) while lakes may exist for hundreds of years or more. Ponds and lakes may have limited species diversity since they are often isolated from one another and from other water sources like rivers and oceans. Lakes and ponds are divided into three different "zones" which are usually determined by depth and distance from the shoreline.

The topmost zone near the shore of a lake or pond is the littoral zone. This zone is the warmest since it is shallow and can absorb more of the Sun's heat. It sustains a fairly diverse community, which can include several species of algae (like diatoms), rooted and floating aquatic plants, grazing snails, clams, insects, crustaceans, fishes, and amphibians. In the case of the insects, such as dragonflies and midges, only the egg and larvae stages are found in this zone. The vegetation and animals living in the littoral zone are food for other creatures such as turtles, snakes, and ducks.

The near-surface open water surrounded by the littoral zone is the limnetic zone. The limnetic zone is well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. Plankton are small organisms that play a crucial role in the food chain. Without aquatic plankton, there would be few living organisms in the world, and certainly no humans. A variety of freshwater fish also occupy this zone.

Plankton have short life spans — when they die, they fall into the deep-water part of the lake/pond, the profundal zone. This zone is much colder and denser than the other two. Little light penetrates all the way through the limnetic zone into the profundal zone. The fauna are heterotrophs, meaning that they eat dead organisms and use oxygen for cellular respiration.

Temperature varies in ponds and lakes seasonally. During the summer, the temperature can range from 4° C near the bottom to 22° C at the top. During the winter, the temperature at the bottom can be 4° C while the top is 0° C (ice). In between the two layers, there is a narrow zone called the thermocline where the temperature of the water changes rapidly. During the spring and fall seasons, there is a mixing of the top and bottom layers, usually due to winds, which results in a uniform water temperature of around 4° C. This mixing also circulates oxygen throughout the lake. Of course there are many lakes and ponds that do not freeze during the winter, thus the top layer would be a little warmer.

Streams and rivers

These are bodies of flowing water moving in one direction. Streams and rivers can be found everywhere — they get their starts at headwaters, which may be springs, snowmelt or even lakes, and then travel all the way to their mouths, usually another water channel or the ocean. The characteristics of a river or stream change during the journey from the source to the mouth. The temperature is cooler at the source than it is at the mouth. The water is also clearer, has higher oxygen levels, and freshwater fish such as trout and heterotrophs can be found there. Towards the middle part of the stream/river, the width increases, as does species diversity — numerous aquatic green plants and algae can be found. Toward the mouth of the river/stream, the water becomes murky from all the sediments that it has picked up upstream, decreasing the amount of light that can penetrate through the water. Since there is less light, there is less diversity of flora, and because of the lower oxygen levels, fish that require less oxygen, such as catfish and carp, can be found.

Wetlands

Wetlands are areas of standing water that support aquatic plants. Marshes, swamps, and bogs are all considered wetlands. Plant species adapted to the very moist and humid conditions are called hydrophytes. These include pond lilies, cattails, sedges, tamarack, and black spruce. Marsh flora also include such species as cypress and gum. Wetlands have the highest species diversity of all ecosystems. Many species of amphibians, reptiles, birds (such as ducks and waders), and furbearers can be found in the wetlands. Wetlands are not considered freshwater ecosystems as there are some, such as salt marshes, that have high salt concentrations — these support different species of animals, such as shrimp, shellfish, and various grasses.

Visit our gallery of wetlands images, which illustrate the amazing diversity of wetland ecosystems.

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Home | Online exhibits | The world's biomes Freshwater is defined as having a low salt concentration - usually less than 1%. Plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration (i.e., ocean).

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, also spelled savannah, vegetation type that grows under hot, seasonally dry climatic conditions and is characterized by an open tree canopy (i.e., scattered trees) above a continuous tall grass understory (the vegetation layer between the forest canopy and the ground). The largest areas of savanna are found in Africa, South America, Australia, India, the Myanmar (Burma)- Thailand region in Asia, and Madagascar.

Origin

Savannas arose as rainfall progressively lessened in the edges of the tropics during the Cenozoic Era (66 million years ago to the present)-in particular, during the past 25 million years. Grasses, the dominant plants of savannas, appeared only about 50 million years ago, although it is possible that some savanna-like vegetation lacking grasses occurred earlier. The South American fossil record provides evidence of a well-developed vegetation, rich in grass and thought to be equivalent to modern savanna, being established by the early Miocene Epoch, about 20 million years ago.

Climates across the world became steadily cooler during that period. Lower ocean surface temperatures reduced water evaporation, which slowed the whole hydrologic cycle, with less cloud formation and precipitation. The vegetation of midlatitude regions, lying between the wet equatorial areas and the moist cool temperate zones, was affected substantially.

The main regions in which savannas emerged in response to that long-term climatic change-tropical America, Africa, South Asia, and Australia-were already separated from each other by ocean barriers by that time. Plant migration across those barriers was inhibited, and the details of the emergence of savannas on each continent varied. In each region different plant and animal species evolved to occupy the new seasonally dry habitats.

In temperate regions, savannas became much more widespread, at the expense of forests, during the long, cool, dry intervals-contemporaneous with the ice ages, or glacial intervals, of the Pleistocene Epoch (2.6 million to 11,700 years ago). Studies of fossilized pollen in sediments from sites in South America, Africa, and Australia provide strong support for this view.

When human beings (Homo sapiens) first appeared, in Africa, they initially occupied the savanna. Later, as they became more adept at modifying the environment to suit their needs, they spread to Asia, Australia, and the Americas. There their impact on the nature and development of savanna vegetation was superimposed on the natural pattern, adding to the variation seen among savanna types. The savannas of the world currently are undergoing another phase of change as modern expansion of the human population impinges on the vegetation and fauna.

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Savanna | African Grasslands, Wildlife & Climate

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Savanna, vegetation type that grows under hot, seasonally dry climatic conditions and is characterized by an open tree canopy (i.e., scattered trees) above a continuous tall grass understory (the vegetation layer between the forest canopy and the ground). The largest areas of savanna are found in

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The tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches (125 to 660 cm.) of rain falls yearly.

Rain forests belong to the tropical wet climate group. The temperature in a rain forest rarely gets higher than 93 °F (34 °C) or drops below 68 °F (20 °C); average humidity is between 77 and 88%; rainfall is often more than 100 inches a year. There is usually a brief season of less rain. In monsoonal areas, there is a real dry season. Almost all rain forests lie near the equator.

Rainforests now cover less than 6% of Earth's land surface. Scientists estimate that more than half of all the world's plant and animal species live in tropical rain forests. Tropical rainforests produce 40% of Earth's oxygen.

A tropical rain forest has more kinds of trees than any other area in the world. Scientists have counted about 100 to 300 species in one 2 1/2-acre (1-hectare) area in South America. Seventy percent of the plants in the rainforest are trees.

About 1/4 of all the medicines we use come from rainforest plants. Curare comes from a tropical vine, and is used as an anesthetic and to relax muscles during surgery. Quinine, from the cinchona tree, is used to treat malaria. A person with lymphocytic leukemia has a 99% chance that the disease will go into remission because of the rosy periwinkle. More than 1,400 varieties of tropical plants are thought to be potential cures for cancer.

All tropical rain forests resemble one another in some ways. Many of the trees have straight trunks that don't branch out for 100 feet or more. There is no sense in growing branches below the canopy where there is little light. The majority of the trees have smooth, thin bark because there is no need to protect the them from water loss and freezing temperatures. It also makes it difficult for epiphytes and plant parasites to get a hold on the trunks. The bark of different species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by their flowers.

Despite these differences, each of the three largest rainforests--the American, the African, and the Asian--has a different group of animal and plant species. Each rain forest has many species of monkeys, all of which differ from the species of the other two rain forests. In addition, different areas of the same rain forest may have different species. Many kinds of trees that grow in the mountains of the Amazon rain forest do not grow in the lowlands of that same forest.
Layers of the Rainforest
There are four very distinct layers of trees in a tropical rain forest. These layers have been identified as the emergent, upper canopy, understory, and forest floor.

Emergent trees are spaced wide apart, and are 100 to 240 feet tall with umbrella-shaped canopies that grow above the forest. Because emergent trees are exposed to drying winds, they tend to have small, pointed leaves. Some species lose their leaves during the brief dry season in monsoon rainforests. These giant trees have straight, smooth trunks with few branches. Their root system is very shallow, and to support their size they grow buttresses that can spread out to a distance of 30 feet.

The upper canopy of 60 to 130 foot trees allows light to be easily available at the top of this layer, but greatly reduced any light below it. Most of the rainforest's animals live in the upper canopy. There is so much food available at this level that some animals never go down to the forest floor. The leaves have "drip spouts" that allows rain to run off. This keeps them dry and prevents mold and mildew from forming in the humid environment.

The understory, or lower canopy, consists of 60 foot trees. This layer is made up of the trunks of canopy trees, shrubs, plants and small trees. There is little air movement. As a result the humidity is constantly high. This level is in constant shade.

The forest floor is usually completely shaded, except where a canopy tree has fallen and created an opening. Most areas of the forest floor receive so little light that few bushes or herbs can grow there. As a result, a person can easily walk through most parts of a tropical rain forest. Less than 1 % of the light that strikes the top of the forest penetrates to the forest floor. The top soil is very thin and of poor quality. A lot of litter falls to the ground where it is quickly broken down by decomposers like termites, earthworms and fungi. The heat and humidity further help to break down the litter. This organic matter is then just as quickly absorbed by the trees' shallow roots.

Plant Life
Besides these four layers, a shrub/sapling layer receives about 3 % of the light that filters in through the canopies. These stunted trees are capable of a sudden growth surge when a gap in the canopy opens above them.

The air beneath the lower canopy is almost always humid. The trees themselves give off water through the pores (stomata) of their leaves. This process, called transpiration, can account for as much as half of the precipitation in the rain forest.

Rainforest plants have made many adaptations to their environment. With over 80 inches of rain per year, plants have made adaptations that helps them shed water off their leaves quickly so the branches don't get weighed down and break. Many plants have drip tips and grooved leaves, and some leaves have oily coatings to shed water. To absorb as much sunlight as possible on the dark understory, leaves are very large. Some trees have leaf stalks that turn with the movement of the sun so they always absorb the maximum amount of light. Leaves in the upper canopy are dark green, small and leathery to reduce water loss in the strong sunlight. Some trees will grow large leaves at the lower canopy level and small leaves in the upper canopy. Other plants grow in the upper canopy on larger trees to get sunlight. These are the epiphytes such as orchids and bromeliads. Many trees have buttress and stilt roots for extra support in the shallow, wet soil of the rainforests.

Over 2,500 species of vines grow in the rainforest. Lianas start off as small shrubs that grow on the forest floor. To reach the sunlight in the upper canopy it sends out tendrils to grab sapling trees. The liana and the tree grow towards the canopy together. The vines grow from one tree to another and make up 40% of the canopy leaves. The rattan vine has spikes on the underside of its leaves that point backwards to grab onto sapling trees. Other "strangler" vines will use trees as support and grow thicker and thicker as they reach the canopy, strangling its host tree. They look like trees whose centers have been hollowed out.

Dominant species do not exist in tropical rainforests. Lowland dipterocarp forest can consist of many different species of Dipterocarpaceae, but not all of the same species. Trees of the same species are very seldom found growing close together. This bio diversity and separation of the species prevents mass contamination and die-off from disease or insect infestation. Bio diversity also insures that there will be enough pollinators to take care of each species' needs. Animals depend on the staggered blooming and fruiting of rainforest plants to supply them with a year-round source of food.
Animal Life
Many species of animal life can be found in the rain forest. Common characteristics found among mammals and birds (and reptiles and amphibians, too) include adaptations to a life in the trees, such as the prehensile tails of New World monkeys. Other characteristics are bright colors and sharp patterns, loud vocalizations, and diets heavy on fruits.

Insects make up the largest single group of animals that live in tropical forests. They include brightly colored butterflies, mosquitoes, camouflaged stick insects, and huge colonies of ants.

The Amazon river basin rainforest contains a wider variety of plant and animal life than any other biome in the world. The second largest population of plant and animal life can be found in scattered locations and islands of Southeast Asia. The lowest variety can be found in Africa. There may be 40 to 100 different species in 2.5 acres ( 1 hectare) of a tropical rain forest.

When early explorers first discovered the rainforests of Africa, Southeast Asia and South America, they They were amazed by the dense growth, trees with giant buttresses, vines and epiphytes . The tropical vegetation grew so dense that it was difficult to cut one's way through it. It was thought at the time that the soil of a rainforest must be very fertile, filled with nutrients, enabling it to support the immense trees and other vegetation they found.

Today we know that the soil of the tropical rainforests is shallow, very poor in nutrients and almost without soluble minerals. Thousands of years of heavy rains have washed away the nutrients in the soil obtained from weathered rocks. The rainforest has a very short nutrient cycle. Nutrients generally stay in an ecosystem by being recycled and in a rainforest are mainly found in the living plants and the layers of decomposing leaf litter. Various species of decomposers like insects, bacteria, and fungi make quick work of turning dead plant and animal matter into nutrients. Plants take up these nutrients the moment they are released.

A study in the Amazon rainforest found that 99% of nutrients are held in root mats. When a rainforest is burned or cut down the nutrients are removed from the ecosystem. The soil can only be used for a very short time before it becomes completely depleted of all nutrients.
Where the Rainforests Are Found
The tropical rain forest can be found in three major geographical areas around the world.

Central America in the Amazon river basin.

Africa - Zaire basin, with a small area in West Africa; also eastern Madagascar.

Indo-Malaysia - west coast of India, Assam, Southeast Asia, New Guinea and Queensland, Australia.

Rainforests
In an average year the climate in a tropical rain forest is very humid because of all the rainfall. A tropical rainforest gets about 150 cm of rain per year. It gets lots of rain because it is very hot and wet in rain forests. The hotter the air, the more water vapor it can hold. It rains usually about 1/8 of an inch per day.

This climate is found near the equator. That means that there is more direct sunlight hitting the land and sea there than anywhere else. The sun warms the land and sea and the water evaporates into the air. The warm air can hold a lot of water vapor. As the air rises, it cools. That means it can hold less water vapor. Then as warm meets cold, condensation takes place and the vapor forms droplets and clouds form. The clouds then produce rain. It rains more than ninety days a year and the strong sun usually shines between the storms. The water cycle repeats often along the equator.

The main plants in this biome are trees. This is important because in the rain forest, some rain never gets past the trees and to the smaller plants and ground below. Trees in this climate reach a height of more than 164 feet. They form a canopy. The forest floor is called understory. The canopy also keeps sunlight from reaching the plants in the understory. Between the canopy and understory is a lower canopy made up of smaller trees. These plants do receive some filtered sunlight.

The tropical rain forest is classified under the Köppen Classification system as Af, meaning tropical forest. The A is given to tropical climates that are moist for all months and which have average temperatures above 18 degrees Celsius. The f stands for sufficient precipitation for all months. The latitude range for my climate is 15° to 25° North and South of the equator.

The annual precipitation of a rain forest is greater than 150 cm. In a rain forest there is a short dry season. In only a month the rainforest receives 4 inches of rain. The rain forest climate is different from a lot of other climates. In other climates, the evaporation is carried away to fall as rain in far off areas, but in the rain forests, 50 percent of the precipitation comes from its own evaporation. A lot of the rain that falls on the rain forest never reaches the ground, instead it stays on the trees because the leaves act as a shield.

The average temperature of a rain forest is about 77° Fahrenheit. The rain forest is about the same temperature year round. The temperature never drops below 64° Fahrenheit. Rain forests are so hot because they are found near the equator. The closer to the equator you are, the more solar radiation there is. The more solar radiation there is, the hotter it is. Rain forest are never found in climates which have temperatures 32° Fahrenheit and below because the plant life will not be able to live in the frost. All the plants will die out if the rain forest is cooler.

The plants that make up the understory of a rain forest have adapted to the small amount of sunlight that they receive. Ferns and mosses do well, along with epiphytes. These are plants that grow on other plants. They can be found growing on branches of tall trees. There are many different plant species found in the rain forest.

by Michael G. 2001
Bibliography:
"Introduction", http://www.hqlist.demon.nl/gvg/ctkoppen.htm (Nov 2000)

"Köppen Biomes", http://www.tesarta.com/www/resources/library/biomes.html (Dec 2000)

"Rainfall", http://encarta.msn.com/find/print.asp?&pg=8&ti=00531000&sc=29&pt=1 (Dec.2000)

"Temperature", http://encarta.msn.com/find/print.asp?&pg=8&ti=00531000&sc=29&pt=1 (Dec.2000)

Allaby, Michael, Biomes of the world volume 7 Oxford: Anndromedia Limited1999

Kellert, Stephen R. Macmillion Encyclopedia of the Environment. Simon and Schuster and Prentice Hall International. 1997

"Rainforest Climate", http://passporttoknowledge.com/rainforest/GEOsystem/Rainforests/climate.html (March 2001)

Stralhler, Arthur N. Strahler, Alan H. Elements of Physical Geography . John Wiley & Sons. 1997.

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The tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches (125 to 660 cm.) of rain falls yearly. Rain forests belong to the tropical wet climate group.