By Lauren Hauberg

Rainforest Layers

The tropical rainforest is made up of layers according to the growth of plants. The upper level, the emergent layer, is the point of the tallest trees. The canopy, directly under the emergent layer, are the growing trees and where many animals live. The understory is the top of other bushy plants and shrubs. The forest floor does not get much sunlight so the plants growing there must be able to survive without much sunlight. It is the least crowded layer of the rainforest.

Location of Tropical Rainforests

Map of tropical forests


Tropical rainforests are spread across the equator and are on every continent with the exception of Antarctica.


- The tropical rainforest is home to aproximately 5 million different species of animals, insects, and plants which is about half of the world's 10 million species.
- 25% of the world's prescription drugs are derived of plants from the tropical rainforest.
- One and a half acres of tropical rainforests are being destroyed every second.
- Tropical Rainforests cover about 5% of the Earth.
- Tropical rainforest produce about 40% of all oxygen on Earth.

Human Destruction of the Tropical Rainforest

Humans have caused much damage to tropical rainforests around the world. Deforestation is a wide spread problem in all parts of the world. The trees are valuable for wood and paper products and the cleared land is used for farming and cattle. The soil, that is already lacking in nutrients, soon becomes completely infertile, forcing the farmer to move. More of the forest is once again cleared and the process is repeated.

News Articles on Deforestation in Tropical Rainforests:

Invasive Species

The tropical ash tree is an invasive species in Hawaiian rainforests. This tree is taller than native trees, such as the ohia tree, therefore allowing it to get less sun. The native Hawaiian trees are dying out which is changing the rainforest. The tropical ash was introduced in the 1930's as a timber species to be used for wood products. It quickly spread and killed off many native trees.

Primary and Secondary Succession

Primary Succession:
In tropical rainforest, flooding happens quite often from the profuse rain. This strips the topsoil, so the environment must create new. 

Secondary Succession:
Farmers in the rainforest cut down large areas of trees to grow their crops and after a few years the soil becomes infertile. After the farmer moves, secondary succession sets in, fertilizing the soil and growing small plants and trees again until the forest, after hundreds of years, has grown back.

Food Web of Tropical Rainforest

Cycles of the Tropical Rainforest

Water Cycle:

Carbon Cycle:

Phosphorus Cycle:

Nitrogen Cycle

Limiting Factors of the Tropical Rainforest

Density-Dependent Factors:
A density-dependent factor affects a population size positively or negatively because of the size of that population. Examples of this are predators hunting more of a specific prey in an area due to increase in population or food supply of a species declining due to rapid growth of a population.

Density-Independent Factors:
A density-independent factor affects a population no matter the size. Human activity, such as deforestation affects many populations. Also, natural distasters and tropical storms are examples of density-independent limiting factors.

Coevolution in the Tropical Rainforest

Aposematic Coloration:
Aposematic coloration is abundant in tropical rainforests. One of the most popular examples of this are many types of colorful poison dart frogs. Their brightly colored bodies warn predators of their toxicity. Many variations in color and design are observed in these frogs.
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Sloths use camouflage to protect themselves in the rainforest. Due to their extremely slow movement, algae grows on their fur, which has adapted to make sure algae can thrive. The green tint of their algae coated fur allows them to blend into leave and other plants in the canopy layer of the rainforest.

Soil of Tropical Rainforest

The soil found in the tropical rainforest is very nutrient poor. This is due to the many decomposers and plants in need of any nutrients available, so they don't stay in the soil for long. The rain has left it acidic and lacking in minerals. The topsoil is very thin at only 1 to 2 inches deep. There are high concentrations of metals in the soil, creating mineral deposits.

Biotic and Abiotic Factors

Biotic factors are any living things in an envirnment. The tropical rainforest is full of life with apoximately 15 million different species of animals. A few examples of the many biotic feature are the rubber and bamboo trees, sloths, anteaters, poison dart frogs, lemurs, bromeliads, etc.

Abiotic factors of the rainforest include soil, water, rocks, light, and climate.

Predators of the Tropical Rainforest

Boa Constrictor:

Boa Constrictors eat mice, pigs, birds, frogs, and many other small to medium sized animals of the tropical rainforest.


The jaguars of the rainforest eat large mammals such as sloths, deer, and tapirs.

Sun Bear:

The sun bear, who dwells in Asain rainforests, eats small mammals, birds, and lizards along with plants and nuts.

Symbiotic Relationships in the Tropical Rainforest

Leaf cutter ants and fungus are an example of this relationship. The ants protect the fungi from pests and mold and also feed it with small pieces of leaves. The ants keep their larvae in the fungi which protects it and feeds it.

The strangler fig starts out life growing on a branch of a tree. It grows both downwards towards the ground and upwards to the sky, while also winding around the tree. The strangler fig kills the tree by stealing sunlight and root space after enveloping it.

Bromeliads, to get enough light, grow on high branches of trees. This does not do any damage to the tree itself, but it allows the brmeliad to survive.

In the dense tropical rainforests, there is fierce competition for sunlight. The taller, older trees that have established a spot in the forest shadow the ground. Due to that, new trees and other plants on the forest floor can't grow.