An ecosystem brings together living things (animal and vegetable) and the environment in which they live and interact.

A food web (or trophic web) is the tying  together of several food chains within the same ecosystem. In this web, one living thing eats another to assure its own survival.

For this reason, one can also characterize a trophic web by the passage of energy (matter) from one living thing to another according to a particular hierarchy.  One thus makes the following distinctions:

Producers (plants) capable of producing their own energy (matter), principally by means of photosynthesis.

Consumers (aniimals) who eat another member of the web in order to obtain energy.The herbivores, the carnivores and the large carnivorous predators  belong to this consumers category.

Decomposers, not represented in this animation, complete the life cycle by degrading organic materail derived from the above categories (waste material, carrion).

The Greenhouse Effect is a natural phenomenon caused by the presence of certain molecules in the Earth's atmosphere (water vapor, Carbon Dioxide, Ozone, Methane...)

The Earth's surface is heated solely by solar energy (geothermal sources are 10,000 times less important).  Half of this solar energy is captured by the Earth, while the rest is absorbed by the atmosphere and, to a small extent, reflected back into space. The Earth, thus heated, itself emits radiation, but in the infrarouge.   The greenhouse gases in the atmosphere absorb  primarily these infrared wavelengths, and re-emit 80% of this energy back toward the Earth. It is this energy trap that we call the Greenhouse Effect.  It is responsible for permitting water in the liquid  state to exist on our planet, and so it favored the development of Life on Earth:  without the Greenhouse Effect, ground temperature would be around -18°C.

But human activities are beginning to disturb this equilibrium by increasing the atmospheric concentrations of several greenhouse gases, most notably Carbon Dioxide (CO₂ ) and Methane (CH₄).

An atmosphere is a layer of gas that surrounds a planet.

The Earth's atmosphere is divided by scientists into  5  theoretical layers:

• The Troposphere contains   80% of the 5 trillion tons of air!  In direct contact with and heated by the ground, this layer of air is where the important thermal exchanges responsible for meteorological  phenomena take place.
• In the Stratosphere, the temperature gets higher as altitude increases.  This temperature inversion acts as a limit for clouds. It is here that we fiind the Ozone Layer that filters out a large part of the ultraviolet radiation coming from the Sun.
• In the Mesosphere, the temperature once again begins to drop.
• Those rare particles still present in the Thermosphere interact with solar radiation.  In absorbing this energy, they increase in temperature and ionize. This is the ionosphere. This part of the Thermosphere has important electromagnetic properties.  The International Space Station (ISS) is in orbit in the thermosphere, beyond the ionosphere.
• Partcles are so rare in the Exosphere that the probability of collisions among them is negligible. Some even escape the gravitational attraction of the Earth. Although the boundary is not clearly defined, the exosphere marks the beinning of outer space.  The majority of satellites are   orbiting in the exosphere, at altitudes between 800 km and 36,000 km.

Will a child know how to find strategies for reducing  his or her CO₂  emissions,  and so aid in the fight against Global Warming caused by the Greenhouse Effect?

This little quiz provides the teacher with a pedagogical tool for sensitizing children to their own lifestyle and its consequences at the planetary scale.

This animation of the carbon cycle shows the exchanges of carbon dioxide between the planet’s 4 natural reservoirs ( atmosphere, biosphere, lithosphere, hydrosphere). Carbon dioxide is a greenhouse gas. The natural carbon cycle is balanced.
Human activities (industrialization, deforestation, combustion of fossil fuels) alter these exchanges and are at the origin of an excess of waste CO2 in our atmosphere. Only 50% of these wastes are absorbed by natural carbon wells (biomass and ocean).

This animation focuses on water pollution and its origins ( for both freshwater and salt  water).
Although natural phenomena not shown here cause water pollution (volcanism, mineral deposits), it is mostly a result of human activities.
Rivers, lakes and oceans are able to rid themselves of contamination by natural cleansing processes,  but only if  the pollutants don't exceed specific threshold values.
We have to preserve our drinking water supplies and  maintain biodiversity  in those ecosystems.

Remember that one third of the world's population do not have safe water to drink.

On the Earth’s surface, water is heated by the sun and evaporates into water vapour. As it rises into the atmosphere, the vapour condenses to form clouds which produce precipitation (rain, snow…). Some of this precipitation evaporates, while some seeps into the ground to supply the ground water table or to add to the volume of glaciers. The rest is carried back to the sea by steams and rivers.