(i) Plants, animals and human beings depend on their immediate surroundings. They are often interdependent on each other as well. These relations of dependence and interdependence together constitute an ecosystem.
In other words, an ecosystem is the system formed as a result of the interactions of all living organisms with each other, and with the physical and chemical factors of the environment in which they live.
(ii) The environment that consists of all objects created by nature is called natural environment. The natural environment comprises land, water, air, plants and animals.
(iii) The major components of environment are natural environment (consists of all objects created by nature), human environment (consists of human beings) and human-made environment (consists of objects created by human beings).
(iv) Parks, buildings, roads and industries are some examples of human-made environment.
(v) Lithosphere (or the domain of land) is the solid crust or the hard top layer of the Earth. It is made up of rocks and minerals, and is covered by a thin layer of soil. It is an irregular surface with various landforms such as mountains, plateaus, plains and valleys.
(vi) The two major components of biotic environment are plants and animals.
(vii) Biosphere is the narrow zone of the Earth where land, water and air interact with each other to support life.