Human body has two lines of defence against pathogens :

Non Specific Mechanism: This mechanism is used against most of the infections. It is of two types.

External defence or First line of defence.
Internal defence or second line of defence.

Some useful bacteria living on the skin release acids and metabolic wastes which check the growth of micro–organism.

Lysozyme of tears prevents eye infections.

(b) Biomedical Engineering: Biomedical engineering is a discipline that combines the design and problem solving skills of engineering with medical and biological science to improve healthcare, diagnosis, and therapy.

ii. Stem cells are those cells that have the ablity to renew themselves through mitotic cell division and differentiate into a diverse range of specialized cell types. The two main types of mammalian stem cells are embryonic stem cells that are found in blastocysts and adult stem cells that are found in adults tissue.

iii. Cryopreservation : The preservation of germplasm at ultra low temperature (like 196°C ) is termed cryopreservation. In such kind of preservation the biological activity ceases and there is no genetic change occurs.

(c) Darwin studied the climate conditions, fauna and flora of Galapagos island.  He noticed nearly 20 related varieties of small birds in these islands which differed mainly in the shape and size of the their beak and in the colour of their plumage. These birds are now called Darwin’s finches. Finches are, in fact, a group of small birds found in these islands. The general bird fauna of these islands shows affinty with the American species but the Darwin’s finches differ considerably from American finches. However, a related species of Darwin’s finches was reported from South American mainland. Therefore, Darwin concluded that the American mainland species was the original one from which different forms migrated to the different island of Galapagos and adapted to the different environmental conditions of these island. These adapted forms are considered to be the new species. Thus, Darwin’s finches provide a beautiful example of adaptive radiation supporting the concept of evolution.