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Chapter summary

  • A rainforest is a complex ecosystem that has developed and evolved over thousands of years.
  • A rainforest is a natural environment. It cannot be created, which is why it is so delicate.
  • A rainforest works through interdependence. This is where the plants and animals depend on each other for survival.
  • One of the cycles that contributes to the running of the rainforest is one that recycles water through a process that helps provide some plants with necessary nutrients.
  • Another cycle that also provides plants with nutrients is one that removes carbon dioxide from the air and releases oxygen.
  • The water and oxygen cycles are part of photosynthesis.


A rainforest is a natural environment. This means that it has evolved and developed independent of construction or control by people. As a natural environment, a rainforest cannot be controlled by people. We can, however, help to maintain the rainforests. If we destroy them, it is beyond our ability to recreate them. All of the processes and functions that make a rainforest work are natural and have existed or developed as part of its unique needs.

A rainforest is an ecosystem. An ecosystem is a complex balance of plants and animals (see image 1). The ecosystem of a rainforest relies on interdependence.

Interdependence means that the plants and animals of a specific environmental system depend on each other for survival. This means that if a plant or animal dies then another plant or animal that depended on it may also die. If the web of interdependence is broken, the rainforest will never grow back. There is no way to rebuild such a complex system, which has developed and evolved over thousands, even millions, of years.

One of the ways that a rainforest works is by reusing everything. All of the dead matter that falls to the ground is absorbed as nutrients. Rainforests even recycle their own water, which they need large amounts of in order to grow. Another important cycle in a rainforest is one which converts carbon dioxide into oxygen. Both the water and air processes are important because they are a part of photosynthesis, a scientific process that helps plants to grow.


As the name would suggest, the rain plays a hugely important part in the life of a rainforest. Three-quarters of the rain falling on the canopy is absorbed. Plants absorb water through their roots and animals absorb it directly, by drinking it. Animals also absorb water indirectly by eating plants and animals. Water, both that which is consumed and that which remains on the ground, can become water vapour (mist).

Evaporation happens when the water from rivers, streams, ponds, puddles and other wet areas is heated by the sun and turns into vapour. See image 2
Transpiration: Water that is absorbed by plants is transpired into the air again as vapour. Respiration, perspiration and decomposition also release water into the air as vapour. In the rainforest, when this vapour is released through different processes, it hangs over the rainforest as mist or cloud. This shields the rainforest from the sun's rays, which could possibly dry it out.
Condensation: When the moist air cools down, it condenses. This means that it joins together and becomes heavier. When the condensing droplets are heavy enough, they fall again as rain.
The cycle: The water that originally fell has now gone through an entire process. It fell to the ground and was either absorbed or entered a larger body of water. It was then turned into vapour by one of the processes above. In the final step the vapour condensed and fell again as rain. See image 3
See animation 1


Carbon dioxide is taken from the air through the surface of leaves. The roots take in water from the soil. The carbon dioxide and water are combined. This process is made possible using energy from sunlight. The plant produces chemicals called carbohydrates, which are the food it uses for growth, and releases oxygen into the atmosphere.

Photosynthesis: These air and water cycles combined are called photosynthesis. It is this process that makes the trees of the rainforest so important. They remove carbon dioxide from the atmosphere and turn it into the gas that we breathe. The trees also contribute to the recycling of water. See image 4


Sunlight is the main source of energy in a rainforest, and all life forms depend on it.

See animation 2

Chapters: Balance and cycles Food chains

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Question 1/5

1. How much of the rain that falls on the rainforest canopy is absorbed?



One quarter



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