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Carbon and its compounds

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Revision Notes on Carbon and its Compounds Two or more elements combine to form compound. There are two types of compounds-  Organic Compound  and  Inorganic Compounds . Organic compounds are the one which are made up of carbon and hydrogen. Covalent Bond The bond formed by sharing a pair of electrons between two atoms are known as  Covalent   Bond . Carbon forms covalent bond. Carbon exists in two forms- as free state and as combined state. Free form of carbon is found in graphite, diamond and fullerene. In combined state, carbon exists as Carbon-dioxide, Glucose, Sugar etc. Allotropes of Carbon Different forms of an element that has same chemical properties but different physical properties are known as  Allotropes . There are three allotropes of carbon- diamond, graphite and fullerene. Diamond Diamond exits as three-dimensional network with strong carbon-carbon covalent bonds. Diamond is hard in nature with high melting point. It shines in presence of light and it is a bad c
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Heredity and variation very short answer questions

1. What is meant by characteristics? It is the detail of appearance or behaviour; in other words, a particular form or a particular function. Example: Four limbs of human beings is a characteristic and that plant can perform photosynthesis is also a characteristic. 2. Who is known as the father of genetics? Gregor Johann Mendel is known as the father of genetics. 3. Define chromosome. Chromosome is a thread-like structure that bears genes and are enclosed within a nucleus. It is composed of DNA and protein. 4. Define variation. The occurrence of differences among the individuals of a species is called variation. 5. Define a gene. Gene is a segment of a DNA molecule which carries the code for the synthesis of a specific protein. 6. Define alleles. Genes which code for a pair of contrasting traits are known as alleles, i.e., they are the different forms of the same gene. 7. Write the expanded form of DNA. Deoxyribonucleic acid 8. Where is DNA found in a cell? [CBSE (AI) 20
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Heredity and evolution HOTS

Why do all the gametes formed in human females have X chromosome?                    [NCERT Exemplar] Human females have two X chromosomes called sex chromosomes. During meiosis at the time of gamete formation, one X chromosome enters each gamete. Hence all the gametes possess an X chromosome. In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation. [NCERT Exemplar] The sex of an infant is determined by the type of sex chromosome contributed by the male gamete. Since the ratio of male gametes containing X chromosome and those containing Y chromosome is 50 : 50, the statistical probability of male or a female infant is also 50 : 50. Why did Mendel choose pea plant for his experiments?                                           [NCERT Exemplar] (a) Easy to grow (b) Short lifespan (c) Easily distinguishable characters (d) Larger size of flower (e) Self-pollinated Give reasons for the appearance of new combinat
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Heredity and evolution long answer question

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1. Explain with reason why giraffe has long neck. According to Lamarck’s theory of use and disuse, giraffes had to stretch their necks and forelimbs for feeding on leaves of tall trees because of which these organs were elongated. But this theory has been completely discarded. It is now proposed that, the giraffe’s neck evolved with time because of ‘necking’ battle with time and natural selection. only giraffes with long necks survived. 2. Give the basic features of the mechanism of inheritance.                                        [NCERT Exemplar] (i) Characters are controlled by genes. (ii) Each gene controls one character. (iii) There may be two or more forms of gene. (iv) One form may be dominant over the other. (v) Genes are present on chromosomes. (vi) An individual has two forms of gene whether similar or dissimilar. (vii) The two forms separate from each other at the time of gamete formation. (viii) The two forms are brought together in the zygote. 3. Answer the fo
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