World Of Living

Biology is the study of living organisms, that is, all plant and animal life, including man, and even the microbes.

There are well-defined characteristics that differentiate the living’ from the non-living’. Living organisms are characterised by the following features:

(i) Organization : Every organism has a definite biological organization. Every organismis composed of single cells. These single cells are organised to form multicellular organisation, which gives different size, shape and function to organisms.

(ii)Metabolism : The sum total of biochemical reactions involved in the release and utilization of energy within the organism is called metabolism. Metabolism consists of two broad patterns of chemical reactions that are inter-dependent and continuous. The anabolism consisting of chemical reactions that form complex substances from simpler substances resulting in the formation of more protoplasm and therefore growth; and the catabolism consisting of chemical reactions that break down complex substances in the release of energy.

(iii) Growth: Growth is defined as an irreversible increase in weight, size or volume of an organism.

(iv) Reproduction : Organisms tend to perpetuate their kind through reproduction. The living organisms are multiplied to form new individuals by sexual or asexual means. Responsiveness : All living organisms respond to physical or chemical stimuli like, temperature, light, chemicals, touch, etc. Some plants such as Mimosa leaves are sensitive to touch.

(vi)Adaptation : All living organisms (Plants and Animals) have a capacity to adapt themselves to changing environmental conditions. Plants and animals are adapted by changing their structure, physiology or behaviour.

(vii) Movement : Living organisms have the capacity to move from one place to another.

(viii) Respiration : Al1 living organism takes Oxygen and release Co. This process is called

The earth shows a remarkable variety of living organisms. Some sort of classification is needed when dealing with such diversity if we are to understand living things. Aristotle and other ancient Greeks (4th and 3rd century B.C.), possibly made the earliest serious efforts to classify living things in the world they knew as plants and animals. They identified a few thousands types. Charaka (first century A.D.) the father of Ayurveda listed the names of over 200 kinds of animals and about 340 kinds of plants in his book *Charaka Samhita”.

In the modern classification system, each living thing belongs to a species, genus, family, order, class, phylum (or division, in plants), and kingdom. These groups are sometimes divided into subgroups.

The five kingdoms are Monera, Protista, Fungi. Plantae (plants) and Animalia (animals).