10th Science - Book Back Answers - Biology Unit 19 - English Medium Guides

 

SSLC / 10th - Science - Book Back Answers - Biology Unit 19 - English Medium

Tamil Nadu Board 10th Standard  Science - Biology Unit 19: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Unit 19 – Biology from the Tamil Nadu State Board 10th Standard  Science textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Biology Unit 19 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 10 students! Prepare well and aim for top scores. Thank you!

Topic: 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
Answer Key:
(b) Ontogeny recapitulates phylogeny
 
2. The ‘use and disuse theory’ was proposed by:
(a) Charles Darwin
(b) Ernst Haeckel
(c) Jean Baptiste Lamarck
(d) Gregor Mendel
Answer Key:
(c) Jean Baptiste Lamarck
 
3. Paleontologists deal with:
(a) Embryological evidences
(b) Fossil evidences
(c) Vestigial organ evidences
(d) All the above
Answer Key:
(a) Embryological evidences
 
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)
Answer Key:
(a) Radio-carbon method
 
5. The term Ethnobotany was coined by:
(a) Khorana
(b) J.W. Harshberger
(c) Ronald Ross
(d) Hugo de Vries
Answer Key:
(b) J.W. Harshberger

II. Fill in the blanks

1. The characters developed by the animals during their life time, in response to the environmental changes are called ………..
2. The degenerated and non-functional organs found in an organism are called ……….
3. The forelimb of bat and human are examples of ………. organs.
4. The theory of natural selection for evolution was proposed by ………..
Answer Key:
1. acquired characters
2. vestigial organs
3. homologous
4. Charles Darwin

 

III. State true or false. correct the statement if it is false.

1. The use and disuse theory of organs’ was postulated by Charles Darwin.
2. The homologous organs look similar and perform similar functions but they have different origin and developmental pattern.
3. Birds have evolved from reptiles.
Answer Key:
1. False – The use and disuse theory of organs’ was postulated by Jean Baptiste Lamarck.
2. False – The analogous organs look similar and perform similar functions but they have different origin and developmental pattern.
3. True

IV.  Match the following  

 

Column I		Column II
1	Atavism	i	caudal vertebrae and vermiform appendix
2	Vestigial organs	ii	a forelimb of a cat and a organs bat’s wing
3	Analogous organs	iii	rudimentary tail and thick hair on the body
4	Homologous  organs	iv	a wing of a bat and a wing of an insect
5	Wood park	v	radiocarbon dating
6	W.F. Libby	vi	Thiruvakkarai

Answer Key:

Column I		Column II
1	Atavism	iii	rudimentary tail and thick hair on the body
2	Vestigial organs	i	caudal vertebrae and vermiform appendix
3	Analogous organs	iv	a wing of a bat and a wing of an insect
4	Homologous  organs	ii	a forelimb of a cat and a organs bat’s wing
5	Wood park	vi	Thiruvakkarai
6	W.F. Libby	v	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?
Answer Key:
Homologous organ – as they have inherited from common ancestors with similar developmental pattern in embryos.
 
2. Which organism is considered to be the fossil bird?
Answer Key:
Archaeopteryx is the fossil bird, found in the Jurassic period.
 
3. Why is Archaeopteryx considered to be a connecting link?
Answer Key:
Archaeopteryx is considered to be a connecting link between reptiles and birds as it had wings with feathers like a bird and had a long tail, clawed digits and conical teeth like a reptile.

VI. Short answer questions

1. The degenerated wing of a kiwi is an acquired character. Why is it an acquired character?
Answer Key:
The characters developed by the animals during their life time in response to the environmental changes are called acquired character. The acquired characters are transmitted to the offspring by the process of inheritance.

2. Why is Archaeopteryx considered to be a connecting link?
Answer Key:
Archaeopteryx is the oldest known fossil bird. It is considered to be a connecting link between reptiles and birds. It had wings with feathers, like a bird. It had a long tail, clawed digits and conical teeth, like a reptile.
 
3. Define Ethnobotany and write its importance.
Answer Key:
Ethnobotany is the study of a region’s plants and their practical uses through the traditional knowledge of the local culture of people.
 
4. How can you determine the age of the fossils?
Answer Key:
The age of fossils is determined by radioactive elements present in it. The elements may be carbon, uranium, lead or potassium. Carbon consumption of animals and plants stops after death, and the decaying process of C14 occurs continuously. The time passed since the death of a plant or animal can be calculated by measuring the amount of C14 present in their body.

 

VII. Long answer questions

1. Natural selection is a driving force for evolution-How?
Answer Key:
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 as natural selection.
 
2. How do you differentiate homologous organs from analogous organs?
Answer Key:

Homologous organs	Analogous organs
The homologous organs are those which have inherited from common ancestors with similar developmental pattern in Embryos.	The Analogous organs look similar and perform similar functions, but they have different origin and development pattern.
Their mode of development and basic structure are similar.	Their basic structures are different.
E.g: A human hand, flipper of a whale, Bat’s wing.	E.g: Wings of bat, wings of birds, wings of insects.

 
3. How does fossilization occur in plants?
Answer Key:
The process of formation of fossil in the rocks is called Fossilization. The common methods of fossilization include:
1. Petrifaction: Minerals like silica slowly penetrate in and replace the original organic tissue and forms a rock-like fossil. This method of fossilization can preserve hard and soft parts mostly bones and wood fossils are petrified.
2. Mould and cast: A replica of a plant or animal is preserved in sedimentary rocks. When the organism gets buried in sediment it is dissolved by underground water leaving a hollow depression called a mould. It shows the original shape but does not reveal the internal structure. Minerals or sediment fill the hollow depression and form a cast.
3. Preservation: Original remains can be preserved in ice or amber (tree sap). They protect the organisms from decay. The entire plant or animal is preserved.
4. Compression: When an organism dies, the hard parts of their bodies settle at the bottom of the sea bed and are covered by sediment. The process of sedimentation goes on continuously and fossils are formed.
5. Infiltration or Replacement: The precipitation of minerals takes place which later on infiltrates the cell wall. The process is brought about by several mineral elements such as silica, calcium carbonate and magnesium carbonate. Hard parts are dissolved and replaced by these minerals.

 

VIII. Higher Order Thinking Skills (HOTS)

1. Arun was playing in the garden. Suddenly he saw a dragon fly 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 reason for your Answer.

Answer Key:
No. Arun is not correct. It is called as Analogous organ. They look similar and perform similar functions, but they have different origin and developmental pattern.
 
2. Imprints of fossils tell us about evolution-How?
Answer Key:
Fossils provide solid evidence that organisms from the past are not the same as those found today. Fossils show a progression of evolution by comparing the anatomical record of fossils with modem and extinct species. Palaeontologist can infer the linkages of their species. For this the body parts such as shell bones or teeth are used. The resulting fossil record tells the story of the part and show the evolution of form over millions of years.
 
3. Octopus, cockroach and frog all have eyes. Can we group these animals together to establish a common evolutionary origin. Justify your Answer Key.
Answer Key:
No, we cannot group these animals together because development of eye is not a point utilised in classification as well as in evolution.