The Living World

Spermatogenesis is the formation of sperm from a germ cell. Four spermatozoa are produced from a primary spermatocyte, therefore, 16 spermatozoa will be formed from four primary spermatocytes.

Taxonomy or systematics is the branch of biology that deals with the classification of biological world of living organisms. The classification is the grouping of organisms in an orderly manner. This grouping is based upon similarities and dissimilarities.

Process of ageing is called senescence.

 In humans, aging is associated with degenerative changes in the skin, bones, heart, blood vessels, lungs, nerves, and other organs and tissues. It is genetically controlled programme regulated by regulatory genes. Example, the great range of lifespans among different animal species from a few days in the fruit fly to more than 100 years in some tortoises. Scientists have recently learned how to double the lifespans of such laboratory organisms as roundworms and fruit flies through genetic manipulation, and mutant genes in mice have been observed to have a comparable effect in postponing ageing.

The advancement in the field of biology has reached to such an extent that it requires the basic knowledge of chemistry, physics and other basic sciences. It is a fact that living organisms are made up of atoms and molecules which follow chemical and physical laws. Therefore, knowledge of chemistry and physics is essential for studying biology.

Kaziranga National Park is famous for one horned Rhinoceros. It is situated at Sibsagar district in Assam.

Periyar sanctuary is located in Kerala. Important animals found here are elephant, tiger, wild bear, sloth bear, grey hornbill etc.

Virus is without necessary metabolic enzymes, hence, free virus are inert particles incapable of any vital activities and uses host machinery. Virus is regarded as obligate parasite and have characteristic of both living and non-livings.

In meroblastic cleavage, division occurs only in small amount of metabolically active cytoplasm, confined to the animal pole or peripheral region of egg. The yolk remains undivided. It is found in macrolecithal eggs. e.g. birds

Living organisms are regarded as open systems as they can lose or gain the mass or energy from the surrounding environment. All living organisms restore their lost energy either from the sunlight or indirectly from the food material.

Death is regarded as the most important regulatory process on earth. It reduces the number of individuals in a population and avoids overcrowding caused by continuous reproduction.

Overcrowding due to reproduction is countered by death as the ultimate termination of functional life.