Biology

Origin and Evolution of Life and Introduction to Classification

NIOS Class 12 Biology Intext Solutions Chapter 1

INTEXT QUESTIONS 1.1

1. Approximately how many years ago was the Earth formed?

5 billion years.

2. Who gave the Chemosynthetic Theory for the origin of life?

A.I. Oparin.

3. Name the four gases present in the primitive atmosphere of the Earth.

NH3, CH4, CO2, water vapour

4. Name one source of energy which was used for chemical combination in the primitive atmosphere.

Lightening/geothermal energy/UV rays (any one)

5. Where did life originate in water or on land?

Water.

6. What are ‘coacervates’?

aggregates of (life-like) molecules

7. In the origin of life, the first large molecules were formed from inorganic compounds. Name any two such large molecules.

amino acids, fatty acids, sugars (any two)

8. Name the two scientists who experimentally tried to verify Oparin’s hypothesis.

Miller and Urey

INTEXT QUESTIONS 1.2

1. Define organic evolution.

The process of slow and gradual change as a result of descent with modification, from a common ancestor.

2. Name one fossil animal which forms a connecting link between reptiles and aves.

Archaeopteryx

3. Which organ of man is homologous to the wings of birds?.

Fore-limb/arm

4. Define vestigial organ.

Functionless organs of the body

5. Give one example of a connecting link among the living beings.

(i) Lungfish between fish and amphibians
(ii) Egg-laying mammals between reptiles and mammals.

6. Give two examples from molecular biology which support organic evolution.

All organisms have a cell as the basic unit of life. The cell is made of biomolecules common to all organisms.
Ribosomes, the cellular organelles, are of universal occurrence in organisms.
DNA is the hereditary material of all organisms, except for some viruses.
ATP is the molecule that stores and releases energy for biological processes.
The same 22 amino acids form the constituents of proteins of almost all organisms.
The genetic code is universal (exceptions are very few).
The central dogma, which deals with the transfer of genetic information in cells, is the same.
The basic steps of transcription and translation for protein synthesis are similar in all organisms.
The sequence of nucleotides, such as that for the promoter gene (TATA box) is common to all organisms.

INTEXT QUESTIONS 1.3

1. Who gave the theory of natural selection?

Charles Darwin

2. What is the modern interpretation of Darwin’s theory of evolution called?

Neo-Darwinism/synthetic theory

3. What are the two major contributions of Charles Darwin regarding evolution?

All organisms are related through ancestry, and he suggested natural selection as the probable mechanism for evolution.

4. Give two main features of Neo-Darwinism.

(i) Variation in population forms the basis of evolution
(ii) Differential reproduction

5. What do you mean by “differential reproduction”?

Randomly mating population.

INTEXT QUESTIONS 1.4

1. List the sources of organic variation.

Mutation, Recombination, gene flow, and genetic drift,

2. What is ‘industrial melanism’ about? Answer in one or two sentences.

It is about the evolution of a variety of peppered moths during the Industrial Revolution, through mutation and Natural Selection.

3. State one point of difference between (a) allopatric & sympatric speciation (b)

Ecological and Ethological Isolation

Allopatric speciation leads to differences in the population of a species due to physical isolating barriers. Reproductive barriers separate sympatric species that may live in the same geographical area.
Both are isolating mechanisms: Ecological Isolation by barriers of season or habitat, and Ethological Isolation by barriers of behavioural differences.

4. What is a panmictic population?

A population of sexually reproducing organisms in which genes combine at random due to random mating is called panmictic. In other words, a panmictic population is one in which mating partners are not specifically selected.

5. According to the Hardy-Weinberg Principle, (p + q)2 = 1. Explain this mathematical Expression.

The Hardy-Weinberg Principle states that in a panmictic population, if there is no pressure of mutation, selection, genetic drift, etc., then the relative frequency of any pair of genes remains constant, generation after generation.

For example, a gene has two alleles, p and q, in the population, and no mutation or selection, etc. takes place, then the frequency of these two alleles will remain constant generation after

generation. This can be mathematically represented as:

(p + q)2 = 1. It means frequencies of allelic genes p + q remain the same for generation after generation if there is no force of evolution like variation, natural selection, etc.

INTEXT QUESTIONS 1.5

1. Name the scientists who proposed :

(a) Binomial nomenclature ….

(b) Five Kingdom Classification.

(a) Carolus Linnaeus (b) R.H. Whittaker

2. Which were the first organisms to appear on Earth?

Bacteria

3. Name the taxonomic categories which come before and after the family.

Kingdom, phylum, class, order, family, genus, Genus

4. Name the categories above the order level in a correct sequence.

Kingdom, phylum, class, order

5. Rewrite the following in the correct form –

(a) Mangifera Indica

(b) Homo Sapiens

(c) Felis leo

(i) Mangifera indica (ii) Homo sapiens (iii) Felis leo

6. Place the following in their respective kingdoms

(a) Bacteria which curdle the milk…

(b) Cow

(c) Grass

(d) Amoeba

(e) Bread mould

(i) Monera (ii) Animalae (iii) Plantae (iv) Protoctista (v) Fungi

INTEXT QUESTIONS 1.6

1. With reference to viruses, fill in the blanks (1, 2, and 3) in the following table :

1. …	Tobacco	Tobacco Mosaic Disease
HIV	2. …	AIDS
Herpes	Human	3. …

1. Tobacco mosaic virus, 2. humans, 3. Herpes.

2. Give one feature because of which viruses are considered non-living.

They cannot reproduce on their own / they can be crystallised (any one)

3. Name one chemical common to viruses and all other organisms.

Nucleic acid/protein (any one)

4. Complete the following :

(a) Core particle of virus contains …

(b) Coat of virus is made of …

(a) DNA or RNA (b) Protein

5. In what way is a viroid structurally different from a virus?

A virus has a DNA or RNA molecule surrounded by a protein coat, whereas Viroids are circular RNA molecules, consisting of several hundred nucleotides..

6. Why are viroids considered a menace to plants that they attack?

They infect plants and, when inside the plant cells, use the host plants’ enzymes to replicate & increase in number, resulting in stunted and abnormal growth of the plant.