TNPSC Exam MaanavaN Time Table October Month Day 3 09.Oct.2017

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TNPSC Exam MaanavaN Time Table October Month Day 3 09.Oct.2017

How does life evolved on earth? What is the major classification adopted by biologists to understand this? This tutorial is devised to enable students to review the basic biological concepts that they may need in preparing for Competitive Exams. The aim of this material on biology is to support students on introductory and essential topics in a pointwise and systematic manner.

The planet earth came into existence between 4 and 5 billion years ago. Life evolved on planet earth about 3.5 billion years ago. Since then approximately 15 million different species of organisms have evolved. But only about two million have been identified so for. In this lesson we will learn how life first originated on earth and how such a vast variety of organisms, popularly known as biodiversity, evolved through variation and natural selection. The study of such a wide variety becomes convenient only when organisms are grouped according to similarities and differences among them, named, and their evolutionary relationships established. We will learn about the importance and method of classification of organisms in this lesson too.

The kingdoms Monera which includes all the bacteria and the protoctista which includes the protoza, the diatoms and some algae are in a way the lowest among the living world. All bacteria, majority of Protoctists and many fungi are microscopic and generally referred to as microorganisms. You will learn about the three kingdoms in this lesson.

You have just learnt that cell is the fundamental structural and functional unit of organisms and that bodies of organisms are made of cells of various shapes and sizes. Groups of similar cells aggregate to collectively perform a particular function. Such groups of cells are termed “tissues”. This lesson deals with the various kinds of tissues of plants and animals.

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