WBBSE Solutions For Class 10 Life Science And Environment Chapter 4 Evidence For The Theory Of Evolution

Chapter 4 Evidence For The Theory Of Evolution Summary

WBBSE Class 10 Evidence for Evolution Overview

• There are various compelling evidences of evolution and one of them is fossil. Fossils provide solid evidence for the fact that the ancestors of an organism were not the same as those found today. Fossils show the progression of the evolution of an organism.
• Highly detailed fossil records have been discovered that depict the evolution of modern horses. The actual sequence of species in the evolution of horses is-Eohippus (first ancestor)→ Mesohippus (intermediate horse) → Merychippus → Pliohippus → Equus (Modern horse).
• In the course of evolution, horses developed larger bodies, longer limbs, longer necks and longer and slimmer heads. Reduction in the number of toes and development of a third toe, reduction in the number of teeth and concentration on incisor and molar teeth are a few other features observed in the line of evolution of horses.

Life Science Class 10 Wbbse

• The organs with the same basic structural design and origin but with different functions are called homologous organs.
• Example: Flipper of a whale, the hand of a human, patagium of the bat. Homologous organs are the result of divergent evolution.
• Divergent evolution refers to the process by which interbreeding species diverge into two or more evolutionary groups mainly because of adaptation to different environmental conditions.
• The organs with different origins but the same functions are called analogous organs.
• Example: Wings of a bird and insect. Analogous organs develop because of convergent evolution. Convergent evolution is the process by which organisms, not closely related, independently evolve similar traits in order to adapt to similar environments.
• The organ having no apparent functions within an organism, but was active in the ancestors of that organism, is called a vestigial organ.
• Example: vermiform appendix and coccyx of human, wings of ostriches, pistinode of Cassia, etc.
• Structures of hearts of vertebrates show gradual complexity and thus point out towards evolution. Embryos of all the vertebrates shows pharyngeal gill cleft and myotome muscle indicating their interrelationship.

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Chapter 4 Evidence For The Theory Of Evolution LAQs

Question 1. Explain the importance of fossils in finding the evolutionary lineage of horse.

Answer:

Importance of fossils in finding the evolutionary lineage of horse

Fossils play very important role in finding the evolutionary lineage of any group of organisms. In case of horse’s evolution also, fossils played a very important role.

Palaeontologists have discovered the fossils of all the ancestors of horse, which helped the scientists to draw a complete evolutionary line of the modern horse from its earliest ancestor.

Life Science Class 10 Wbbse

It is now known that the earliest ancestor of horse, Eohippus, emerged about 55 million years ago. It was adapted in forest environment with its shorter legs consisting multiple digits.

Gradually, grassland developed and horses were adapted in the new environment by gradually acquiring changes in their physical structure. The evolutionary lineage of horse is-

Eohippus → Mesohippus → Merychippus → Pliohippus → Equus

By comparative analysis of fossil structures, scientists found the following features-

1. Only 11 inches tall Eohippus has evolved into 60 inches tall modern horse, Equus.
2. The hind legs have become more muscular to facilitate fast running.
3. The number of digits in both limbs has reduced gradually and hoofs have developed.
4. The length of the neck has increased.
5. Sizes of cranium and cerebrum have increased significantly.
6. The crowns of teeth have become higher to help in chewing of grass.

From this fossil study, the scientists have revealed almost all the adaptive features of the ancestral horses with the changing environment and presented the evolutionary lineage of modern horse from its ancestors.

Question 2. Briefly describe the evolution of horse.

Answer:

Evolution of horse:

The evolutionary lineage of horses has become clear today because palaeontologists have discovered fossils of all the ancestors of the modern horses.

The oldest ancestor of a horse was Eohippus, from which the modern horse, Equus, has come into being after crossing three other stages of evolution. Descriptions of the fossils of all ancestors of horses are mentioned below.

Homologous Chromosomes Definition

Fossil Evidence for Evolution

Question 3. How do homologous organs support organic evolution?

Answer:

Homologous organs in support of organic evolution:

Homologous organs support organic evolution to a great extent. This is explained as below.

1. Homologous organs of animals:

The basic skeletal structures of forelimbs of whale, bat, bird, cat. and man are same. All possess humerus, radius-ulna, carpals, metacarpals and phalanges.

However, these animals use their forelimbs in different ways to adapt to separate environments. Whale uses its forelimbs for swimming, but birds and bats use it for flying. Cat walks and captures prey with its forelimb and man uses it for grasping and eating.

Homologous

These evidences strongly indicate that all vertebrates have evolved from the same ancestor but separated from each other to adapt in separate environments.

2. Homologous organs in plants:

The thorn of the wood apple tree, stem tendril of the passion flower plant, phylloclade of cactus, etc. are modifications of the same organ but these perform different functions.

The above-mentioned examples prove that these organisms evolved from the same ancestor but with time, their organs have changed their shapes and functions to adapt in separate environments.

 

Question 4. How do analogous organs support organic evolution?

Answer:

Analogous organs in support of organic evolution:

Analogous organs support organic evolution. This is explained below.

1. Analogous organs in animals:

Wings of birds and wings of insects are used for flying. However, structurally these two are different. Wings of birds are modifications of the forelimbs but the wings of insects are lateral folds of the cuticle of the thorax.

The sting of a scorpion and the sting of a honeybee are functionally identical, however, the sting of a scorpion is the modification of a telson and the sting of a honeybee is a modified ovipositor.

2. Analogous organs in plants:

The leaf tendril of the pea plant and the stem tendril of the passion flower plant are functionally similar. However, the former one is the modification of terminal leaflets and the latter one is the modified branch of the stem.

Homologous

Analogous organs indicate the adaptation of distantly related organisms in identical environments. Therefore, analogous organs provide strong support in favour of organic evolution.

Question 5. Distinguish between homologous and analogous organs. Mention differences between amphibian and reptilian hearts.

Answer:

Distinguishing features between homologous organs and analogous organs

Life Science Class 10 Wbbse

Differences between amphibian and reptilian heart

Question 6. How do vestigial organs favour organic evolution?

Answer:

Vestigial organs as evidence for organic evolution:

1. In many herbivores, like rabbits, guinea pigs, etc. a big saccular caecum is present at the junction of the large and small intestine. It gives shelter to symbiotic bacteria to facilitate their cellulose digestion. However, human food contains less cellulose. Therefore, this organ remains as a functionless, tiny worm-like projection in a man called a vermiform appendix.
2. The tail of the monkey acts as a balancing organ in arboreal locomotion. In humans, tail is of no need, hence it is present as a tiny coccyx bone at the end of the spine.
3. The nictitating membrane is active in amphibians but non-functional in humans. Muscles of pinnae are useless in humans but functional in cattle. Transverse abdominal muscles are essential for cheetahs but of no use in human beings.
4. Wings of birds are essential organs but in flightless birds (ostrich, kiwi, emu, etc.), wings become vestigial.
5. Scale leaves of the rhizome of ginger and turmeric, and staminodes of Cassia are examples of vestigial organs in plants.

 

Homologous and Analogous Structures Explained

The presence of vestigial organs in certain organisms proves that in the course of evolution, those have become functionless and reduced but in ancestral forms, they were prominent and active. Therefore, vestigial organs can be treated as good evidence in favour of organic evolution.

Question 7. Explain the comparative anatomical evidence in support of organic evolution.
Or,
Explain the comparative anatomy of vertebrate hearts and forelimbs in support of organic evolution. Part question, How the comparative anatomy of hearts act as proof in favour of evolutionary theory?

Answer:

Comparative anatomical evidence in support of organic evolution:

A comparative study on related groups of organisms, clearly reveals the basic structural similarity among few of their organs. It also indicates the evolutionary trend of those organisms.

Here, comparative studies on some organs of different groups of vertebrates are mentioned below.

Homologous

1. Heart of vertebrates:

The basic structure of the hearts of fishes, amphibians, reptiles, birds and mammals is similar. All of them have an auricle as the blood-receiving chamber and a ventricle as the chamber that expels blood from the heart. However, in the course of evolution, the hearts of different vertebrates encountered some changes.

The heart of fish has one auricle and one ventricle and thus carries only deoxygenated blood along a single circuit. Amphibians have two auricles and one ventricle in their heart. Here, oxygenated and deoxygenated blood get mixed in the ventricle.

Apart from two auricles, the reptilian heart has a partially divided ventricle, in which partial mixing of oxygenated and deoxygenated blood occurs (exception-crocodile has a four-chambered, double-circuit heart).

Hearts of birds and mammals have two auricles and two ventricles. Therefore oxygenated and deoxygenated blood flow through separate circuits.

Conclusion:

The above-mentioned evidence proves that advanced and complex forms of animals have evolved from primitive and simple forms. The gradual development of the heart and circulatory system of different vertebrates point towards the evolutionary trend as mentioned below.

Fishes → Amphibians → Reptiles → Birds and mammals

Life Science Class 10 Wbbse

2. Forelimbs of different vertebrates:

The basic skeletal structures of the forelimbs of whales, bats, birds, horses and men are all alike. All possess humerus, radius-ulna, carpals, metacarpals and phalanges.

However, these animals use their forelimbs in different ways to adapt in different environments. As whale uses its forelimbs for swimming, birds and bats use them for flying. The horse runs with the help of their forelimbs and man use them for grasping.

Conclusion:

This evidence strongly indicates that all vertebrates have evolved from a single ancestor but diverged from each other to adapt in separate environments.

Question 8. Briefly describe the embryological evidence in favour of organic evolution.

Answer:

Embryological evidence in favour of organic evolution:

Comparative and chronological study of the embryos of fishes, amphibians, reptiles, birds and mammals reveals that all these groups of vertebrate organisms have many similarities in the shape and structure of the embryos for a period of time.

This observation directly indicates that all these different groups of organisms have evolved from a single ancestor.

Vestigial Organs and Evolution

The similarities are-

1. Embryos of all these forms have developed from a unicellular zygote.
2. The zygotes of these organisms have divided mitotically to form blastocysts.
3. In the next phase of development, these blastocysts transform into gastrula.
4. All these forms are triploblastic.

A comparative study of these vertebrates reveals two main structural similarities among them.

Homologous

1. Presence of pharyngeal gill clefts and internal gill pouches:

All these groups of animals have pharyngeal gill clefts at the lateral sides of their heads in their initial embryonic states. The endothelium of the pharynx infolds to form two laterally placed gill pouches in all these embryos.

The gill clefts and gill pouches jointly form the pharyngeal organ. In the course of maturity, fishes develop gills from this pharyngeal organ, but in other terrestrial organisms, the pouches either give rise to other structures or disappear.

In humans, the clefts develop into thyroid, parathyroid and thymus glands.

2. Tail-like structure and myotome muscles:

Embryos of all these classes have a tail-like structure and laterally placed myotome muscles. For example, a frog bears a tail in its larval stages but not in its adult stage.

Similarly, in human beings, the tail becomes vestigial in the form of a coccyx after embryonic development. Further, in addition to fishes, myotome muscles are also found in human beings, in a specific segment of the spinal cord where the spinal nerve innervates.

These above-mentioned similarities indicate towards same ancestral lineage of these vertebrate classes and also support the concept of organic evolution.

Chapter 4 Evidence For The Theory Of Evolution SAQs

Question 1. Furnish some evidence in favour of Darwinism.
Answer:

The pieces of evidence in favour of Darwinism is as follows-

1. Stick insects and leaf insects take the shape of dry branches and dry leaves respectively to camouflage in the plants to avoid predation. These typical shapes are naturally selected to help them survive on the earth.
2. The length of the suckers of nectar-eating insects is so adjusted that can reach the nectar glands of their favourite flowers. This typical length of the sucker is naturally selected to let the insects get their food easily.

Question 2. What are fossils?
Answer:

Fossils:

Fossils are the petrified remains, impressions traces of extinct primitive organisms, preserved via natural processes within the layers of ancient sedimentary rocks.

Example-Fossils of dinosaurs, Archaeopteryx, etc.

Question 3. What are living fossils?
Answer:

Living fossils:

Certain primitive plants and animals are still surviving in the recent world without any significant characteristic change throughout the course of evolution. These organisms are called living fossils.

Example-Limulus (animal), Ginkgo biloba (plant), etc.

Embryological Evidence for Evolution

Question 4. What are missing links?
Answer:

Missing links:

While drawing the evolutionary lineage of any group of organisms, it is often noticed that there are certain gaps in it due to the extinction of certain connecting species.

These extinct species are called missing links. Fossil of Archaeopteryx, for instance, is the missing link between reptiles and birds.

Question 5. Mention the importance of fossils as evidence of organic evolution.
Answer:

Fossils provide strong evidence in favour of organic evolution in the following ways-

1. Fossils provide the idea about the size, shape, food habit and approximate age of a fossilised organism.
2. By studying fossils, scientists can acquire knowledge about the nature of flora and fauna present in the environment of that time.
3. Fossils can trace the ancestral history of any modern species, thus depicting the evolutionary lineage.

Wbbse Class 10 Life Science Solutions

Question 6. Distinguish between fossil and living fossil
Answer:

The distinguishing features between fossil and living fossils are-

Question 7. What is palaeontology?
Answer:

Palaeontology:

Palaeontology is a branch of biology, in which fossils are studied to gain knowledge about the characteristic features of ancient animals. Palaeontology helps to draw the evolutionary trend of the related organisms.

Moreover, study of palaeontology helps the scientists to find out the lineage of emergence of a new species from it’s ancestors.

Question 8. Write in chronological sequence the names of four main fossil ancestors during the course of evolution of the horse.
Answer:

In chronological sequence, the four main fossil ancestors during the course of evolution of the horse are-Eohippus → Mesohippus → Merychippus → Pliohippus → Equus (modern horse)

Question 9. Write four important features modified in the evolution of horse.
Answer:

Four important features modified in the evolution of horse are-

1. Gradual increase in height,
2. Decrease in number of digits in both forelimbs and hindlimbs and formation of hoof,
3. Increase in the size of crown of molar and pre- molar teeth,
4. Increase in volume of cerebral hemisphere.

Question 10. Distinguish between Eohippus and Equus.
Answer:

The distinguishing features between Eohippus and Equus are-

Wbbse Class 10 Life Science Solutions

Molecular Evidence Supporting Evolution

Question 11. What are homologous organs?
Answer:

Homologous organs:

The organs of different organisms, having similar origin and fundamental structures but with differences in appearance and functions, are called homologous organs.

Example: Hands of humans and wings of birds.

Question 12. Which anatomical feature proves forelimbs of amphibians and wings of birds as homologous organs?
Answer:

Both the forelimbs of amphibians and wings of birds have same skeletal elements, i.e. humerus, radius-ulna, carpal, metacarpal and phalanges. This anatomical similarity proves that these two organs are homologous in nature.

Question 13. Mention two features of internal structures on the basis of which ‘flippers of whales and ‘wings of birds’ are considered homologous organ.
Answer:

Two features of internal structures on the basis of which ‘flippers of whale’ and ‘wings of birds’ are considered homologous organ are-

1. The basic skeletal structures of flipper of whales and wings of birds are same. Both possess humerus, radius- ulna, carpals, metacarpals and phalanges.
2. Well developed flexor and extensor muscles are present in flipper of whale and also in wings of birds.

Question 14. What is divergent evolution?
Answer:

Divergent evolution:

To adapt in dissimilar environments, certain organs, having same origin and structure, may take different shapes to perform separate functions in descendants coming from a common ancestral form. This type of adaptive evolution is called divergent evolution.

Example:

Homologous organs like forelimbs of horse, paddle of whale and hands of man are structurally similar but functionally different, which indicates divergent evolution.

Wbbse Class 10 Life Science Solutions

Question 15. What are analogous organs?
Answer:

Analogous organs:

The organs of different organisms having different origin and fundamental structures, but with somewhat similar appearances and identical functions are called analogous organs.

Example: Patagium of bats and wings of insects.

Question 16. Give examples of analogous organs in animals.
Answer:

Examples of analogous organs in animals

The wings of birds and insects are examples of analogous organs in animals. Both these animals use the wings for flight, but structurally these are completely different.

Question 17.

1. Structure and function
2. Indicating the nature of evolution

Based on the above two features, establish the concept of analogous organs with the help of proper example.
Answer:

Analogous organs are those organs which are different in structure and origin but perform similar functions.

Analogous organs indicate convergent evolution. For example, wings of bird, wings of insect and patagium of bat perform same function, i.e., they help the organisms to fly but they have different structures.

Wings of birds are modification of forelimbs, wings of insects are outgrowth of insects’ exoskeleton and patagium of bat is actually fold of skin between forelimbs and hind limbs.

All these structures point towards the fact that in same environment, different structures may evolve to perform same function. This further points toward convergent evolution.

Question 18. What is meant by convergent evolution?
Answer:

Convergent evolution:

Distantly related groups of animals or plants, inhabiting in identical surroundings for a long period, may develop analogous organs to adapt themselves in that particular environment.

This adaptive evolution is known as convergent evolution. Example-The terminal leaflets of pea plants and some branches of pumpkin plants are modified into tendrils.

Question 19. Distinguish between homologous and analogous organs.
Answer:

The distinguishing features between homologous and analogous organs are-

 

Question 20. What is parallel evolution?
Answer:

Parallel evolution:

Two or more descendants from the same ancestor, inhabiting in identical surroundings may develop similar traits to adapt themselves in that particular environment. This adaptive evolution is known as parallel evolution.

Example:

Deer and antelopes have same ancestors, they thrive in similar environments and both have split hoofs for fast running.

Wbbse Class 10 Life Science Solutions

Question 21. What are vestigial organs?
Answer:

Vestigial organs:

Vestigial organs are the organs which have become reduced and non-functional due to prolonged disuse. These organs were previously functional and well-built in ancestral forms.

The muscles of the pinnae, vermiform appendix, and nictitating membrane of the eye are some vestigial organs in humans.

Question 22. Write the names of one each vestigial organ present in the vertebral column and alimentary canal in the human body.
Answer:

In the human body, the vestigial organ present in the vertebral column is the coccyx and that present in the alimentary canal is the appendix.

Question 23. Distinguish between the amphibian heart and the mammalian heart.
Answer:

The distinguishing features between the amphibian heart and the mammalian heart are-

 

Question 24. Mention the biogenetic theory of organic evolution.
Answer:

The biogenetic theory of organic evolution:

Biogenetic theory of evolution or the theory of recapitulation, proposed by scientist Ernst Haeckel, states that ontogeny repeats phylogeny. It means the embryonic phases of a species resemble its evolutionary trend.

Question 25. Briefly mention the role of Ernst Haeckel in the field of comparative embryology.
Answer:

German scientist Ernst Haeckel explained the organic evolution under the light of comparative embryology and thus confirmed Darwinian concept on evolution.

He compared three embryonic stages of eight different vertebrates and reached to a conclusion that ontogeny repeats phylogeny. This means, the embryonic stages of animals resemble their evolutionary trend.

 

Natural Selection as Evidence of Evolution

Question 26. How do principles of Von Baer, on comparative embryology, support the organic evolution?
Answer:

To support the organic evolution in 1828, German scientist Von Baer had put forward certain principles on embryology. According to him-

1. General species characters appear first in its early embryonic stages.
2. With advance- ment of embryonic development, typical and specific characters of species appear in the embryos.

Question 27. What are pharyngeal gill clefts?
Answer:

Pharyngeal gill clefts:

In any of the stages of their life, chordates. possess several parallel clefts at two lateral sides of the pharynx. In aquatic forms, these clefts transform into gills.

In terrestrial forms, these ridges develop certain glands, which are known as pharyngeal gill clefts.

 

Chapter 4 Evidence For The Theory Of Evolution MCQs

Question 1. The stings of honeybees and wasps are—

1. Homologous organs
2. Analogous organs
3. Vestigial organs
4. Both 1 and 2

Answer: 2. Analogous organs

Question 2. The branch of science, dealing with the study of fossils, is called—

1. Palaeontology
2. Palaeogeography
3. Herpetology
4. Embryology

Answer: 1. Palaeontology

Question 3. Organs with similar structure and origin but different functions are called—

1. Homologous organs
2. Analogous organs
3. Vestigial organs
4. Connecting organs

Answer: 1. Homologous organs

Question 4. The feature of analogous organs is—

1. Different in origin and functions are also different
2. Different in origin but functions are the same
3. Indicates divergent evolution
4. Identical in origin and structure

Answer: 2. Different in origin but functions are the same

Question 5. A vestigial structure in the human body is—

1. Humerus
2. Caecum
3. Vermiform appendix
4. Trachea

Answer: 3. Vermiform appendix

Question 6. Which of the following is not vestigial in humans?

1. Tail bone
2. Appendix
3. Nail
4. Nictitating membrane

Answer: 3. Nail

Question 7. The connecting link between reptiles and mammals is—

1. Archaeopteryx
2. Platypus
3. Peripatus
4. Octopus

Answer: 2. Platypus

Question 8. The fossilised animal, Archaeopteryx, is treated as the missing link between which of the following two groups?

1. Reptiles and mammals
2. Birds arid mammals
3. Amphibians and mammals
4. Reptiles and birds

Answer: 4. Reptiles and birds

Question 9. The heart, carrying deoxygenated blood, is present in—

1. Toad
2. Fish
3. Snake
4. Crocodile

Answer: 2. Fish

Question 10. The tendril of pea and passion flower plants are—

1. Homologous organs
2. Vestigial organs
3. Analogous organs
4. Growth organs

Answer: 3. Analogous organs

Question 11. Horses evolved on earth approximately—

1. 40 million years ago
2. 65 million years ago
3. 100 million years ago
4. 55 million years ago

Answer: 4. 55 million years ago

Question 12. An example of a missing link is—

1. Equus
2. Archaeopteryx
3. Eohippus
4. Ostrich

Answer: 2. Archaeopteryx

Question 13. The modern horse evolved approximately—

1. 5 million years ago
2. 1 million years ago
3. 15 million years ago
4. 20 million years ago

Answer: 2. 1 million years ago

Question 14. Name an animal which is a living fossil.

1. Earthworm
2. Rohu fish
3. Limulus
4. Garden lizard

Answer: 3. Limulus

Question 15. The height of Eohippus was—

1. 11-12 inches
2. 51-52 inches
3. 71-72 inches
4. 81-82 inches

Answer: 1. 11-12 inches

Question 16. Name a plant which is a living fossil.

1. Cooksonia
2. Rhynia
3. Pinus
4. Ginkgo biloba

Answer: 4. Ginkgo biloba

Question 17. Dawn horse is more commonly called as

1. Eohippus
2. Merychippus
3. Mesohippus
4. Pliohippus

Answer: 1. Eohippus

Question 18. Which is known as a ‘ruminating horse’?

1. Eohippus
2. Pliohippus
3. Mesohippus
4. Merychippus

Answer: 4. Merychippus

Question 19. The intermediate horse is—

1. Pliohippus
2. Mesohippus
3. Merychippus
4. Equus

Answer: 2. Mesohippus

Question 20. The horse with a single digit is—

1. Mesohippus
2. Merychippus
3. Pliohippus
4. Equus

Answer: 4. Equus

Question 21. The oldest ancestor of the horse was seen in—

1. Eocene era
2. Miocene era
3. Pliocene era
4. Oligocene era

Answer: 1. Eocene era

Question 22. The 24 inches tall ancestor of the modern horse, which was seen in the Oligocene era, is—

1. Eohippus
2. Mesohippus
3. Pliohippus
4. Merychippus

Answer: 2. Mesohippus

Question 23. The horse of the Miocene era, having three digits in both the fore and hindlimbs, is—

1. Merychippus
2. Mesohippus
3. Eohippus
4. Pliohippus

Answer: 1. Merychippus

Question 24. The height of Merychippus was—

1. 100 cm
2. 60 cm
3. 28 cm
4. 160 cm

Answer: 1. 100 cm

Question 25. The reptilian heart has two auricles and a partly divided ventricle. An exception is seen in—

1. Snake
2. Garden lizard
3. Tortoise
4. Crocodile

Answer: 4. Crocodile

Question 26. The modern horse is called—

1. Eohippus
2. Mesohippus
3. Pliohippus
4. Equus

Answer: 4. Equus

Question 27. Who discovered the fossils showing the evolution of horse?

1. Darwin
2. Lamarck
3. Wales
4. Charles Marsh

Answer: 4. Charles Marsh

Question 28. Which of the following denotes a vestigial organ of plants?

1. Stamen
2. Leaf
3. Staminode
4. None of the above

Answer: 3. Staminode

Question 29. Which of the following has vestigial wings?

1. Pigeon
2. Hornbill
3. Vulture
4. Kiwi bird

Answer: 4. Kiwi bird

Question 30. “Ontogeny repeats phytogeny”—Who proposed this?

1. Mendal
2. Lamarck
3. Darwin
4. Haeckel

Answer: 4. Haeckel

Question 31. Number of chambers in the heart of reptiles—

1. Two
2. Three
3. Incompletely four
4. Four

Answer: 3. Incompletely four

Question 32. Which of the following sequence is right?

1. Pishes → Amphibians → Birds and mammals → Reptiles
2. Amphibians → Fishes → Reptiles → Birds and mammals
3. Birds and mammals → Fishes → Amphibians → Reptiles
4. Fishes → Amphibians → Reptiles → Birds and mammals

Answer: 4. Fishes → Amphibians → Reptiles → Birds and mammals

Question 33. Which of the following changes did not occur during the course of the evolution of the horse?

1. Lengthening of limbs
2. Increase in the length and thickness of all digits in limbs
3. Increase in the length and thickness of only the third digit in limbs
4. Increase in size of the whole body.

Answer: 2. Increase in the length and thickness of all digits in limbs

 

Chapter 4 Evidence For The Theory Of Evolution Answer In A Single Word Or Sentence

Question 1. What type of organs are the flippers of whales, the forelimbs of horses and the hands of man?
Answer: Homologous organs

Question 2. What type of organs are the wings of birds and wings of insects?
Answer: Analogous organs

Question 3. Which type of evolution is indicated by homologous organs?
Answer: Divergent evolution

Question 4. Which reptile has a four-chambered heart?
Answer: Crocodile

Question 5. Which group of animals has a venous heart?
Answer: Fish

Question 6. What is the scientific name of the modern horse?
Answer: Equus caballus

Question 7. Give an example of a vertebrate living fossil.
Answer: Tuatara (Sphenodon sp.)

Question 8. From the point of view of origin, which organ of the horse shows similarity with the wings of birds?
Answer: Forelimbs

Question 9. Certain organisms possess characteristics of two different groups of organisms. What are these organisms called?
Answer: Connecting link

Question 10. Certain organs have become non-functional in the course of evolution. What are these called?
Answer: Vestigial organs

Question 11. Which digit of a horse is modified into a hoof?
Answer: The third digit

Question 12. Which is the vestigial organ of an ostrich?
Answer: Wings

Question 13. Name an egg-laying mammal.
Answer: Duck-billed platypus

Question 14. Name the oldest ancestor in the evolutionary path of the horse.
Answer: Eohippus

Artificial Selection and Its Role in Evolution

Question 15. How many digits were there in the fore and the hindlimbs of an Eohippus?
Answer: The forelimbs and the hindlimbs of an Eohippus had four and three functional digits respectively.

Question 16. Which type of fossils are examined under the microscope?
Answer: Microfossils

Question 17. Name the connecting link between gymnosperms and angiosperms.
Answer: Gnetum

Question 18. On attaining maturity, what happens to the embryonic gill pouches and gill clefts in mammals?
Answer: On attaining maturity, the embryonic gill pouches and gill clefts in mammals transform into thyroid, parathyroid and thymus glands.

Question 19. Who proposed the concept, ‘ontogeny repeats phylogeny’?
Answer: Scientist Ernst Haeckel

Question 20. What is Archaeopteryx?
Answer: Archaeopteryx is the missing link between reptiles and birds.

Question 21. Which digit of the horse is transformed into a hoof?
Answer: The third digit

Question 22. Which is the vestigial organ of the kiwi?
Answer: Wings

Question 23. Which teeth of a human is vestigial?
Answer: The third molar teeth

Question 24. When was Merychippus originated?
Answer: Miocene

Question 25. How many chambers are there in a bird’s heart?
Answer: Four

Question 26. Write down the names of two vestigial organs of plants.
Answer: Staminode of Cassia and scale leaf present in the rhizome of ginger.

Question 27. What is the alternative name of biogenetic law?
Answer: Recapitulation theory

 

Chapter 4 Evidence For The Theory Of Evolution Fill In The Blanks

Question 1. The petrified remains or impression of any organism, kept for ages in the layers of sedimentary rocks are called ________.
Answer: Fossils

Question 2. Coccyx is a ________ organ of the human body.
Answer: Vestigial

Question 3. Among the ancestors of the horse, hoofs developed first in ________.
Answer: Merychippus

Question 4. The hoof of modern horse is the transformation of the digit number ________ of their ancestors.
Answer: Three

Question 5. Homologous organs evolve due to ________ evolution.
Answer: Divergent

Question 6. Analogous organs in different types of organisms, provide evidence of ________ evolution.
Answer: Convergent

Question 7. Phylloclade of cactus and tuber of potato are examples of two ________ organs.
Answer: Homologous

Question 8. The leaf tendril of pea plant and stem tendril of the passion plant are examples of ________ organs.
Answer: Analogous

Question 9. The appendix is a ________ organ of the human body.
Answer: Vestigial

Question 10. The heart of fish carries deoxygenated blood only, therefore, it is known as ________ heat.
Answer: Venous

Question 11. Hearts of birds and mammals have ________ chambers.
Answer: Four

Question 12. One living fossil animal is ________.
Answer: Limuliis

Question 13. The number of digits on the forelegs of Merychippus were ________.
Answer: 3

Question 14. The heart of fish is ________ chambered.
Answer: Two

Question 15. According to Haeckel, ontogeny repeats ________.
Answer: Phylogeny

Question 16. The name of the modern horse is ________.
Answer: Equus

Question 17. The earliest ancestor in the evolution of the horse is ________.
Answer: Eohippus

 

Chapter 4 Evidence For The Theory Of Evolution State True Or False

Question 1. Although a crocodile is a reptile, it has a four-chambered heart.
Answer: True

Question 2. The reptilian heart has a partly segmented ventricle.
Answer: True

Question 3. The sequence of vertebrate evolution can be represented as, fishes → amphibians → reptiles → birds and mammals.
Answer: True

Question 4. The wings of birds and insects are examples of analogous organs.
Answer: True

Question 5. The organs of different organisms, having same origin and fundamental structures but performing different functions, are called analogous organs.
Answer: False

Question 6. The hands of humans and the wings of birds are analogous organs.
Answer: False

Question 7. The Stem tendril of the passion flower plant and the thorn of the wood apple tree are examples of homologous organs.
Answer: True

Question 8. The branch of science that deals with the study of fossils to find out the line of evolution of any organism, is known as palaeontology.
Answer: True

Question 9. Staminodes of Cassia are its vestigial organs.
Answer: True

Question 10. Mesohippus is the earliest ancestor of the modern horse.
Answer: False

Question 11. Among the ancestors of horses, hoofs developed first in Merychippus.
Answer: True

Question 12. Pliohippus is called a ruminating horse.
Answer: False

Question 13. The pinnae are vestigial organs of the human body.
Answer: True

 

Chapter 4 Evidence For The Theory Of Evolution Match The Columns

1.

Answer: 1. C, 2. E, 3. A, 4. D, 5. B, 6. F

2.

Answer: 1. C, 2. F, 3. A, 4. E, 5. B, 6. D

3.

Answer: 1. B, 2. A, 3. E, 4. C, 5. D, 6. G

 

Chapter 4 Evidence For The Theory Of Evolution Find The Odd One Out

Question 1. Forelegs of the horse, Wings of a pigeon, Wings of the bat, Wings of a butterfly
Answer: Wings of butterfly

Question 2. Eohippus, Merychippus, Mesohippus, Mammoth
Answer: Mammoth

Question 3. Eohippus, Dinosaur Archaeopteryx, Crocodile,
Answer: Crocodile

Question 4. Coccyx, Spleen, Appendix, Nictitating membrane
Answer: Spleen

Question 5. Wings of a bird, Forelegs of the horse, Hands of a human, Tail of a whale
Answer: Tail of a whale

Question 6. Adaptation in a particular environment, Analogous organ, Convergent evolution, Divergent evolution
Answer: Divergent evolution

 

Chapter 4 Evidence For The Theory Of Evolution Fill In The Blanks By Looking At The First Pair

Question 1. Amphibian heart: Mixed blood:: Reptilian heart: ___________
Answer: Partially mixed blood

Question 2. Vermiform appendix and nictitating membrane of man: Vestigial organ:: Wings of birds and insects: ___________
Answer: Analogous organs

Question 3. Biogenetic law: Ernst Haeckel:: Mutation theory: ___________
Answer: Hugo de Vries

Question 4. Eocene: Eohippus :: Oligocene: ___________
Answer: Mesohippus

Question 5. Homologous Organ: Divergent evolution Analogous organ: ___________
Answer: Convergent evolution

Question 6. Mammals Four chambered heart:: Amphibians: ___________
Answer: Three-chambered heart

Question 7. Functionally different: Homologous organ:: Difference in origin:___________
Answer: Analogous Organ

Question 8. Eohippus: Oldest ancestor of horse:: Equus: ___________
Answer: Modern horse

 

Chapter 4 Evidence For The Theory Of Evolution Among The Four Concepts Given Three Of Them Belong To One Find That

Question 1. Flippers of whales and hands of humans, Structurally similar but functionally different organs, Homologous organs, Wings of birds and bats
Answer: Homologous organs

Question 2. Reduction in the number of toes, Increasing running ability, Lengthening of legs, Development of single hard hoof all
Answer: Increasing running ability

Question 3. Pliohippus, Fossils of horse, Merychippus, Mesohippus
Answer: Fossils of horse

Question 4. Staminode, Wings of kiwi, Pistilode, Vestigial organs
Answer: Vestigial organ

Question 5. Human heart, Heart of a bird, Double circuit heart, Heart of a frog
Answer: Double-circuit heart

Question 6. Concept of evolution, the Concept of ancient environment, the Importance of fossils, Concept of the origin of an organism
Answer: The importance of fossil