“elephant is a big animal” “dinosaurs no more here on the earth” “snakes are poisonous” “beautiful birds fly in skies” “we would like to eat fishes” etc etc are a very simple statements made in our daily life and so many times we will go to zoo and enjoy them in their natural habitat. But friends do you know that there are plenty of animals which can’t be seen through necked eyes ! Yes lets look into them now in detail…
Animals can be distinguished from plants by their capacity of movement, presence of distinct organ systems. Its still very difficult to estimate the actual number of animals on the Earth, as because they are scattered in water, air and on land too. To learn them there is a branch of biology called zoology and can be defined as science of animals.
All animals in the world are broadly classified into 2 groups called INVERTEBRATES without backbone & VERTEBRATES with backbone and vertebral column.
Meanwhile animal kingdom is broadly classifies into two subkingdoms
- PROTOZOA – with single body cell, such as amoeba, euglena, paramecium etc and
- METAZOA – with numerous body cells, such as invertebrates and vertebrates.
7. 1. They do not have cell wall; some however, possess a flexible layer, a
pellicle, or a rigid shell of inorganic materials outside the cell membrane.
8. 2. They have the ability during their entire life cycle or part of it to move by
locomotor organelles or by a gliding mechanism.
9. 3. They have heterotrophic mode of nutrition, whereby the free-living
forms ingest particulates, such as bacteria, yeast and algae, while the
parasitic forms derive nutrients from the body fluids of their hosts.
10. 4. They reproduce primarily by asexual means, although in some groups
sexual modes also occur.