TN 10th Science Guide

19. Origin and Evolution of Life

I. Choose the Correct Answer.

1. Biogenetic law states that _____.

(a) Ontogeny and phylogeny go together.
(b) Ontogeny recapitulates phylogeny.
(c) Phylogeny recapitulates ontogeny.
(d) There is no relationship between phylogeny and ontogeny.

2. The ‘use and disuse theory’ was proposed by _____.

(a) Charles Darwin
(b) Ernst Haeckel
(c) Jean Baptiste Lamarck
(d) Gregor Mendel.

3. Paleontologists deal with _____.

(a) Embryological evidences
(b) Fossil evidences
(c) Vestigial organ evidences
(d) All the above.

4. The best way of direct dating fossils of recent origin is by _____.

(a) Radio – carbon method
(b) Uranium lead method
(c) Potassium – argon method
(d) Both (a) and (c).

5. The term Ethnobotany was coined by _____.

(a) Khorana
(b) J.W. Harshberger
(c) Ronald Ross
(d) Hugo de Vries.

II. Fill in the blanks.

1. The characters developed by the animals during their life time, in response to the environmental changes are called Acquired characters.

2. The degenerated and non-functional organs found in an organism are called Vestigial organ.

3. The forelimbs of bat and human are examples of Homologous organs.

4. The theory of natural selection for evolution was proposed by Charles Darwin.

III. State whether True or False. If false, write the correct statement.

1. ‘The use and disuse theory of organs’ was postulated by Charles Darwin?
Answer: False.
Correct statement: ‘The use and disuse theory of organs’ was postulated by Jean Baptiste Lamarck.

2. The homologous organs look similar and perform similar functions but they have different origin and developmental pattern?
Answer: False.
Correct statement: The homologous organs look dissimilar and perform dissimilar functions, but they have the same origin and developmental pattern.

3. Birds have evolved from reptiles.
Answer: True.

IV. Match the following:

Column A	Column B
1. Atavism	(c) rudimentary tail and thick hair on the body
2. Vestigial organs	(a) caudal vertebrae and vermiform appendix
3. Analogous organs	(d) a wing of a bat and a wing of an insect
4. Homologous organs	(b) a forelimb of a cat and a bat’s wing
5. Wood park	(f) Thiruvakkarai
6. W.F. Libby	(e) radiocarbon dating

V. Answer in a word or Sentence

1. A human hand, a front leg of a cat, a front flipper of a whale and a bat’s wing look dissimilar and adapted for different functions. What is the name given to these organs?

Homologous organs.

2. Which organism is considered to be the fossil bird?

Fossil bird Archaeopteryx.

3. What is the study of fossils called?

Palaeontology.

VI. Short Answers Questions

1. The degenerated wing of a kiwi is an acquired character. Why is it an acquired character?

Kiwi does not have the need to fly that is why they do not have wings. The characters developed by the animals during their life in response to environmental changes. The vestigial wings are so small (invisible) under the bristly, hair-like two-branched feathers. So the degenerated wing of a kiwi is an acquired character.

2. What is the study of fossils called?

Palaeontology is called as the study of fossils.

3. Define Ethnobotany and write its importance.

Ethnobotany is the study of a region’s plants and their practical uses through the traditional knowledge of the local culture of people.
Importance of Ethnobotany:

It provides traditional uses of the plant.
It gives information about certain unknown and known useful plants.
The ethnomedicinal data will serve as a useful source of information for the chemists, pharmacologists and practitioners of herbal medicine.
Tribal communities utilize ethnomedicinal plant parts like bark, stem, roots, leaves, flowers, flower bud, fruits, seeds, oils, resins, dyes and gum for the treatment of diseases like diarrhoea, fever, headache, diabetes, jaundice, snakebites and leprosy, etc.

4. How can you determine the age of the fossils?

The age of fossils is determined by radioactive elements present in it. They may be carbon, uranium, lead or potassium.

VII. Long Answer Questions

1. Natural selection is a driving force for evolution-How?

Darwin published his observations under the name “origin of species”. It elaborates on the theory of natural selection for evolutionary transformation.
The principles of Darwinism tells that natural selection is a driving force for evolution.

1. Overproduction: Living beings have the ability to reproduce and have the capacity to multiply in a geometrical manner.

2. Struggle for existence: Due to overproduction, a geometric ratio of increase in population occurs. The space to live and food available for the organisms remain the same. This creates a competition among the organisms, for food and space, leading to struggle.

The competition may be among the individuals of the same species (Intraspecific struggle).
Competition between the organisms of different species living together (Interspecific struggle).
Natural conditions like extreme heat or cold drought and floods can affect the existence of organisms (Environmental struggle).

3. Variations: Small variations are important for evolution. According to Darwin, favourable variations are useful to the organisms and unfavourable variations are harmful or useless to the organisms.

4. Survival of the fittest or Natural selection: During the struggle for existence, the organisms which can overcome the challenging situation, survive and adapt to the surrounding environment. Organisms, which are unable to face the challenges, are unfit to survive and disappear. The process of selection of organisms with favourable variation is called Natural selection.

5. Origin of species: According to Darwin, new species originates by the gradual accumulation of favourable variations for a number of generations.

2. How do you differentiate homologous organs from analogous organs?

Homologous organs	Analogous organs
1. The homologous organs have been inherited from common ancestors, with similar developmental pattern in embryos.	1. Analogous structures are shown in a batwing, a bird wing and an insect wing.
2. The forelimbs of a human hand, a front leg of a cat, the flipper of a whale and a bat’s, wing look dissimilar and adapted for different functions.	2. The analogous organs look similar but perform similar functions.
3. Their mode of development and the basic structure of bone are similar.	3. They have a different origin. Wings of insect are membranous extensions whereas wings of a bat is a bony structure. But performing the same function of flying.

3. How does fossilization occur in plants?

A plant fossil is any preserved part of a plant that has died long back. Fossils may be a prehistoric impression that may be hundred to millions of years old. Majority of the plant fossils are disarticulated parts of plants, it is rare to find plants to be preserved as whole.

VIII. Higher Order Thinking Skills (HOTS) Questions

1. Arun was playing in the garden. Suddenly he saw a dragonfly sitting on a plant. He observed the wings of it. He thought it looked similar to a wing of a crow. Is he correct? Give a reason for your answer.

No. He is not correct. Both crow and dragonfly have the same function of flying with wings. But it’s the origin (basic structure) is different. Dragonfly wing is the membranous extension. But the wing of the crow is the modification of forelimb.

2. Imprints of fossils tell us about evolution- How?

Fossil records show that evolution has taken a gradual process from simple to complex organisms. The study of fossils helps us to understand the link of evolution. The origin of modem birds is supported by the evidence of palaeontology.

3. Octopus, cockroach and frog all have eyes. Can we group these animals together to establish a common evolutionary origin? Justify your answer.

Convergent evolution is the process, by which the independently evolved features, may similar to each other, but can arise through different developmental pathways. So the octopus, cockroach and frog all have eyes. The independently evolved eye may similar in each other, but can arise through different developmental pathways.