Category Physics

Insects have the largest number of species among animals on the Earth. Out of ten different animal species, eight are of insects. They can survive in almost all types of habitats regardless of temperature. Many can survive only in specific environmental conditions, while others are found in all parts of the world. The reason for this difference within the species is not known. Insects have six legs and a body divided into three parts with a solid outer covering called the armour. Many insects are useful (bees which pollinate fruit tree flowers), while others are harmful (plant louse on indoor plants). 

‘Mammal’ is derived from the word ‘mammary’. The young ones of mammals suckle milk from the teats of the mother. This milk contains all the essential nutrients for growth. Except for the monotremes, all mammals are born as young ones and are not hatched from eggs. Contrary to almost all other animal species, mammals nurture and train their young ones for a considerable time. Mammals have a constant body temperature of 36-40°C, so they need a hide (like an elephant) or a thick layer of fat (like a whale) as protection against extreme heat or cold.

Biologists have classified the animals according to their common features. Animals that share a lot of common features are known as species. For instance, all members of the dog species have similar body structures and group behaviour. Similar species are grouped together in one family, similar families are grouped in orders, and orders are further combined to form classes. The fox, wolf, and dog species combine to make one ‘family’ of canine predators. Together with the cat and bear families, they belong to the ‘order’ of predators in the ‘classes of mammals, which in turn belong to the vertebrates in the ‘kingdom’ of animals. 

There are more than 1.5 million animal species. Ranging from simple animals like sponges and jellyfish, the invertebrates include the arthropod phylum with over 1 million species of insects. The higher- level vertebrates include fish with about 35,000 species. Around 350 million years ago, when aquatic animals moved to land, they adapted to the new environment and amphibians were born. They adapted some more and became reptiles. From reptiles came the birds and around 4000 known species of mammals.