The Invisible Living World

 Air

CHAPTER 6-Water

Transportation Of Materials

AIl living organisms need to transport substances from one part Lof the body to the other for their growth and development. The substances that are transported may be nutrients, waste products, messenger molecules, heat, etc.

This movement of substances within the body becomes more and more important as the size and complexity of the organism increases. Therefore, the mechanisms of transport also advance from simple diffusion to more specialised methods. In unicellular and some lower multicellular organisms, the distribution of substances can be achieved easily by means of diffusion. The cells of these organisms exchange materials directly with the environment. In higher organisms, a separate well-organised system, known as circulatory system is employed for the efficient transport of materials.

Respiration In Plants And Animals

Energy is the basic requirement of all living organisms. It is required for the ongoing life processes inside the body and for the activities performed by an organism. Energy is obtained from the food consumed. Respiration is the process through which energy from food is released for use by the body.

Respiration can be defined as Inhalation of oxygen and exhalation of carbon dioxide coupled with the chemical reactions that release energy from digested food.

 4.Our Changing Earth-II

 Acids, Bases And Salts-Class-VII