Oswaal Tamilnadu SSLC Question Bank With Complete Solution For Samacheer Kalvi Class 10th Science

Oswaal Tamilnadu SSLC Question Bank With Complete Solution For Samacheer Kalvi Class 10th Science
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Oswaal Tamilnadu SSLC Question Bank With Complete Solution For Samacheer Kalvi Class 10th Science

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Publisher: Oswaal Books
ISBN: 9789351276272
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CHAPTER
1
Heredity and Evolution QUICK REVIEW The inheritance of characteristics through generations is called heredity. The inheritable characteristics may be morphological anatomical physiological reproductive and are known as traits. Gregor Johann mendel carried out several experiments on heredity. Mendel concluded that out of any pair of contrasting characters, one is dominant and the other is recessive. The homozygous dominant trait is denoted by two capital letters whereas the homozygous recessive trait is denoted by two small letters. The expression of morphological characters is called phenotype. The expression of gene of an individual for a particular trait is called genotype. The genotype of a character is influenced by genes. Genes are the factors which form the physical basis for inheritance of characters. The alternate expression of the same gene are called alleles. The contrasting pair of alleles make up an allelomorph. Organisms differ in expressing phenotype which leads to variation. Changes occurring in the DNA of germ cells are heritable whereas changes taking place in the non-reproductive tissues are not inherited. Charles Darwin proposed that evolution of species is influenced by natural selection, but he did not know the underlying mechanism. Evolution is a slow process and has occurred over millions of years, as revealed by fossil evidences. The age of fossils can be determined by using the relative method or the isotope dating method. Evolution has resulted in the diversity of organisms. All human beings, whether fair skinned or dark skinned, belong to the same species i.e., Homo sapiens that originated in Africa. The human ancestors gradually migrated from Africa to various parts of the world such as Asia, Europe, Australia and America. Thus they spread to different parts of the earth and adapted as best as they could to their environmental conditions. Genetic engineering is the modification of the genetic information of living organisms by manipulation of DNA by adding, removing or repairing part of genetic material DNA and changing the phenotype of the organism. It is also known as gene manipulation or recombinant DNA Technology r-DNA Technology Bio-technology has contributed towards exploitation of biological organisms or biological processes through modern techniques which could be profitably used in medicine, agriculture, animal husbandry and environmental cleaning.