Environmental science is a study of system. A system is a collection of parts that act together in some way. Think of a human body, the liver, heart, brain and stomach are all separate organs, yet none of them can act properly unless the entire system is functioning. The study in environmental science varies widely in form and function. Yet they all share similarities. Each one is far more than an independent collection of parts. Parts may be effected and change could take place on-the whole. For example, if the average temperature in a mountain stream rises a few degrees the types of plants and animals living in the stream may be altered.

Not all changes affect a system equally. Here we need to study how systems respond to changes. No system that involves living organisms is completely independent. A person must eat, drink, breathe and eliminate wastes. All these ,activities involve exchanges with environment. So an ecosystem is a system that includes plants and animals plus the physical environment in which they live. An ecosystem is regarded, for purposes of study, as it were an isolated unit, although this is an over simplification. Most matter is repeatedly recycled and only small quantities flow into and out of the ecosystem.

Ecology is the study of flow of energy and materials within an ecosystem and the interactions between the plants and animals that live there. Ecosystems differ widely with respect to size, location, whether patterns and the types of animals and plants that live in them. A watershed in New Hampshire, a Syrian desert, the Arctic ice cap, and lake Michigan are all distinct ecosystems.

Common to them all is a set of Processes

  1. On each there are plant  that use energy from the Sun to convert simple chemicals from the environment into complex, energy-rich tissues.
  2. Each houses various forms of plant eaters.
  3. Predators who eat the plant eaters.
  4. Predators who eat the predators, and organisms that cause decay.

Energy Relationships within an Ecosystem : Land, water and air are all the main components in this cycle. The vast machine is driven by the Sun because almost all of the energy available to us on Earth comes from the Sun. This process of energy relationship within an ecosystem can be treated or studied through the following steps:

Photosynthesis: Sunlight evaporates water that late falls as rain. The Sun heats the Earth unevenly causing winds to blow. Sunlight strikes the leaves or the neeles of green plants. Plants are fundamental to all life on Earth because they trap some of this solar energy and use it to build living tissues. This process called as photosynthesis is illustrated in following equations Sunlight = Carbon dioxide + Water → Sugar + Oxygen The sugar (glucose) then undergoes further chemical transformations to produce starch, so plants do not need to feed on other organisms. They are called autographs, meaning self-nourishes. Animal cannot use the sun in this manner. So they are dependent on plants as their fundamental source of food

Respiration : Plants and animals use the energy stored in sugar and other plant matter to maintain body functions. This process is called respiration. We can think of respiration as a slow, controlled burning. In fact, the equation is same.Respiration = Sugar + Oxygen ….. Carbon dioxide + Water + Energy

Animals cannot make their own food but must eat other organisms to obtain energy rich molecules needed for survival, therefore, they are called hetrotrophes. It is further divided into two categories. Those animals which eat the plants directly called the herbivores and those animals which eat flesh of other animals called carnivores like tiger etc. Third category is that who eat both plants or animals called omnivores i.e. rats etc.

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