NATURE AND ORIGIN OF LIFE
You know what nature is. We live in nature. We have soil, water, air different plants, animals, insects and worms etc. all around us. All these together constitute nature. Millions of years ago nature was not as we see it today. Nor will it remain the same after millions of years. This indicates that nature is always changing. Nature undergoes changes due to various natural forces such as river-currents, earthquakes, volcanic eruptions etc. Different human activities, such as destruction of forests, construction of dams etc. also bring about changes in nature.
Scientists have been thinking about the origin of nature. There are different theories about the origin of the Earth. Among these the commonly acceptable theory explains that a part of the Sun or a similar star got detached as a result of the attraction of another star. The planets including the Earth and then satellites have been created from the detached part of the sun.
According to this theory at the beginning the Earth was in a hot, gaseous state Subsequently the Earth gradually cooled and condensed to form the Earth as it is now. The core of the Earth is still in an extremely hot liquid and gaseous state. Nature of the Earth at the primary stage was not at all suitable for inhabitation of life. Gradually it became favourable for the existence of living forms. Now a question may arise in your mind as to how life originates in nature. Did plants and animals exist in nature from the very beginning?
There are different theories regarding the origin of life on the Earth. In the beginning of this chapter we have described an old concept of the origin of life But the theory presented by Oparin, a Russian scientist, about the origin of life is still accepted.
According to the theory of Oparin nature was quite hot when life was created Different gases such as ammonia (NH3), hydrogen (H2), methane (CH4) hydrogen cyanine (HCN) etc. were present in the atmosphere. During that period there was heavy rainfall and thunderstorm. Under such environmental condition amino acids were formed by the interaction of various gases and these amino acids are considered by scientists to be the first molecule of life The first cell or life came into being through incorporation of amino acids. It is also believed that life was created first in the primitive aquatic environment.
According to the Oparin's theory and established scientific reasons which one of the following is correct if arranged chronologically from origin of life to the recent?
a. Amino acid ® Unicellular Algae ®Bacteria ®Unicellular Amoeba.
b. Amino acid ® Unicellular Amoeba®Bacteria ®Unicellular Algae.
c. Amino acid ® Bacteria ® Unicellular Algae ® Unicellular Amoeba.
d. Amino acid ® Bacteria ® Unicellular Algae ® Unicellular Amoeba.
According to the Oparin's theory and established scientific reasons which one of the following animals came into being at the last in the terrestrial environment?
a. Bird b. Man
c. Buffalo d. Banyan tree
1. Kalidas became curious about plants and animals when he was studying at Shingua High School. Seeing his curiosity the teachers of that school advised him to study biology when he will be grown up. According to that advise Kalidash studied on Botany in the University. The subjects he studied included both pure and applied branches of Biology. But afterwards he started working on applied branch and invented many high yielding fruits & crops. He is still engaged in this works.
a) What is Biology?
b) Why is physiology called the pure branch of Biology?
c) Explain that why is the works of Kalidash included in the applied branch of Biology.
d) Analyse the importance of pure branch in the success of Kalidash.
The first cell had protoplasm, amino acid and later on DNA molecules are formed by union of amino acid molecules, But the cells did not have any nucleus. This non-nucleated cell successively gave rise to nucleated cell and multicultural organism.
Copyright © 2018-2021 BrainKart.com; All Rights Reserved. (BS) Developed by Therithal info, Chennai.