Chapter 4 – (a) Evolution : How Do Life Form Change Over Time ? | Life Science Solution Class 10

1. Mendel
2. Darwin
3. Lamarck
4. Spencer.

1. On land
2. In air
3. On mountain
4. In water.

1. Calyx
2. Ovary
3. Corolla
4. Stamens

1. Acquired characters
2. Struggle for existence
3. Mutation
4. Germplasm.

1. Species
2. Population
3. Family
4. Individual.

1. Laboratory preserved animal
2. Organic relic of the past
3. Dead animal of the past
4. Stuffed animal.

1. The age of the earth is about ____ million years.
2. Coal is the ____ of plants.
3. ____ is the modern horse.
4. Rhynia and Psilophyton are the Devonian ____ is the fossil plants.
5. ____ was born at Bajastin in France in 1744.
6. The theory of Lamarck is known as ____.
7. Origin same but functions differently and is known as ____ organ.
8. Function same but origin different is known as ____ organ.
9. Those things which live beyond their normal period preserving all primitive characteristics are called ____.
10. Once it was functional but gradually became functionless due to evolution is called ____.
11. Those animals possessing characters of two different classes are known as ____.
12. ____ acts as connecting link between reptiles and mammals.
13. ____ was the ancestor of modern horses. 
14. Natural Selection theory was proposed by ____.
15. The impression of organisms over a stone is called ____.
16. Equisetum plant is an example of ____.
17. The nictitating membrane is a ____.
18. H.M.S. Beagle left on 27th December ____. 
19. Darwin took extensive notes and collected a lot of specimens on the ____.
20. ____ is the connecting link between Pteridophyta and gymnosperm.
21. The living fossil is ____.
22. The name of a missing link is ____.
23. ____ is the name of a fossil plant.
24. _____ is a chemical compound treated as the precursor of life.
25. Philosopher ____ is the father of biology.
26. The struggle for food and shelter between two different species is called ____ ____.
27. _____ Islands are located nearest the West Coast of South America.
28. The organism that exists both as a fossil and living are termed ____ ____.
29. The Germplasm concept is proposed by _____.
30. New species are evolved by ____.
31. The developmental history of an organism is ____.
32. The name of the modern horse is ____.
33. Archaeopteryx is a fossil animal bearing characters of both ____ and birds.
34. Sphenodon is an example of ____.  
35. The animal fossil was first discovered by ____.
36. Darwin published Origin of Species by Means of Natural Selection in ____.
37. The struggle for food, shelter and reproduction between individuals of the same species is known as ____.
38. The term evolution was proposed by ____.
39. ‘Philosophic Zoologique’ was written by ____. 
40. Organic evolution proves that ____ appears in living beings due to external and internal influences. 

Answer

Very Short Answer (VSA) type questions

Question 1

Where was life first created?

Answer

Mineral-laden water emerging from a hydrothermal vent on the Niua underwater volcano in the Lau Basin, southwest Pacific Ocean.

Question 2

Answer

Organs that have a similar origin but different shapes, sizes, and functions are called homologous organs.

Question 3

What are organs of the living body which has a similarity in function but differences in structure and origin called?

Answer

Organs that have a similar function but different structures and origins are called analogous organs.

Question 4

Give an example of a homologous organ.

Answer

An example of a homologous organ is the forelimb of vertebrates, such as humans, dogs, whales, and bats.

Question 5

Give examples of an analogous organ.

Answer

Question 6

Give an example of two vestigial organs in man.

Answer

Two examples of vestigial organs in humans are:

1. Appendix
2. Wisdom teeth

Question 7

In which group of animals the heart is two chambered ?

Answer

The group of animals that have a two-chambered heart are the fish.

Question 8

In which group of animals the heart is three chambered?

Answer

The group of animals that have a three-chambered heart are amphibians and reptiles.

Question 9

Give an example of an animal fossil. 

Answer

One example of an animal fossil is the Tyrannosaurus rex, a large carnivorous dinosaur that lived during the Late Cretaceous period, approximately 68 to 66 million years ago.

Question 10

In which animal do you get combined reptilian and mammalian characters?

Answer

The platypus is an animal that exhibits combined reptilian and mammalian characteristics such as laying eggs like a reptile but also having mammary glands that produce milk to feed its young.

Question 11

Name one vestigial organ of plant.

Answer

The vestigial organ of a plant is the phytolacca fruit, which is a non-functional, seedless structure that remains in some species of plants, such as the pokeweed.

Question 12

Which organ of a horse shows similarity with the wing of a bird according to their origin?

Answer

Horse forelimbs show similarity with bird wings according to their origin.

Question 13

“Birds are modifications of reptiles”- in which animal is it clearly seen?

Answer

The Archaeopteryx is the animal in which the statement “birds are modifications of reptiles” is clearly seen.

Question 14

Name a mammal which lays eggs.

Answer

The platypus (Ornithorhynchus anatinus) and the echidnas (Tachyglossidae) are the only mammals that lay eggs, a process known as oviparity.

Question 15

Name the fossil of the oldest forefather of the horse. 

Answer

The fossil of the oldest forefather of the horse is called Eohippus, also known as the “dawn horse,” which lived about 50 million years ago.

Question 16

Write the name of the modern horse.

Answer

The modern horse is called Equus ferus caballus.

Question 17

What is the name of the book of Lamarck?

Answer

The name of Lamarck’s book is “Philosophie Zoologique,” published in 1809.

Question 18

Are acquired characters inherited by the next generation?

Answer

No, acquired characteristics are not inherited by the next generation.

Question 19

Who proposed ‘the law of use & disuse’?

Answer

The law of use and disuse was proposed by Jean-Baptiste Lamarck.

Question 20

Who did propose the concept of the struggle for existence?

Answer

The concept of the struggle for existence was proposed by Charles Darwin.

Question 21

What is the full name of Lamarck ?

Answer

The full name of Lamarck is Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck.

Question 22

Name the famous book written by Charles Robert Darwin.

Answer

The famous book written by Charles Robert Darwin is called “On the Origin of Species.”

Question 23

Name the ship in which Darwin made his historical voyage for exploration ?

Answer

The ship in which Darwin made his historical voyage for exploration is called the HMS Beagle.

Question 24

‘Survival of the fittest-Who stated this? Or, Who proposed the theory of Survival of the fittest?

Answer

The theory of “survival of the fittest” was proposed by Charles Darwin and Alfred Russel Wallace as part of the theory of natural selection.

Question 25

Who proposed ‘Natural Selection’ theory?

Answer

The theory of natural selection was proposed by Charles Darwin and Alfred Russel Wallace.

Question 26

Who is the propounder of the idea-inheritance of acquired characters?

Answer

Jean-Baptiste Lamarck was the propounder of the idea of inheritance of acquired characters.

Question 27

Answer

The theory of natural selection by Darwin was published in 1859.

Question 28

Write the name of a book written by Charles Darwin. 

Answer

“On the Origin of Species” is a book written by Charles Darwin.

Question 29

Who proposed the Germplasm theory?

Answer

The Germplasm theory was proposed by August Weismann.

Question 30

Who did help Darwin to publish his theory on evolution?

Answer

Question 31

Why is Lamarck famous ?

Answer

Lamarck is famous for proposing the theory of inheritance of acquired characteristics and for being one of the early proponents of the idea of evolution.

Question 32

The origin of Species by means of natural selection suggested this concept ?

Answer

The concept of “Origin of Species by means of Natural Selection” was suggested by Charles Darwin.

Question 33

Why is the year 1859 famous in evolutionary history?

Answer

The year 1859 is famous in evolutionary history because it was the year in which Charles Darwin’s book “On the Origin of Species” was published, presenting his theory of evolution by natural selection.

Question 34

How many types of variations are there ? 

Answer

There are two types of variations: continuous variations, which are small, gradual differences that occur within a population, and discontinuous variations, which are large, distinct differences that can lead to the formation of new species over time.

Question 35

Write the name of an organism found both in fossilised and living condition?

Answer

The horseshoe crab is an organism found both in fossilized and living condition.

Question 36

Who is considered as the father of organic evolution?

Answer

Charles Darwin is considered as the father of organic evolution.

Question 37

What type of origin can be related to the wings of a bird?

Answer

The wings of a bird can be related to a modification of forelimbs, which have an evolutionary origin in a common ancestor shared with reptiles.

Question 38

Name one connecting link between pteridophyta and gymnosperm.

Answer

One connecting link between Pteridophyta (ferns) and Gymnosperms is the presence of vascular tissue that helps in the conduction of water and minerals from roots to the leaves.

Question 39

Name one connecting link between reptilia and aves (bird). 

Answer

One connecting link between Reptilia and Aves (birds) is the presence of scales on their legs and feet, as well as their similar skeletal structure, such as the shape of their pelvic bones.

Question 40

Where did life originate ?

Answer

It is believed to have originated around 3.5 to 4 billion years ago in the oceans, possibly from chemical reactions between organic compounds and energy sources like lightning or volcanic heat.

Question 41

Which period is called the age of reptiles?

Answer

The period called the “Age of Reptiles” is the Mesozoic Era, which lasted from about 252 million years ago to 66 million years ago. It is also known as the “Age of Dinosaurs” because they were the dominant group of reptiles during this time.

Question 42

Which era is called the age of mammals?

Answer

The Cenozoic Era is called the “Age of Mammals” because it is the era in which mammals underwent a significant adaptive radiation and became the dominant terrestrial animals.

Short Answer (SA) type questions

Question 1

What is meant by organic evolution?

Answer

Organic evolution, also known as biological evolution, is the process by which species of organisms change over time through genetic, ecological, and environmental factors, resulting in the diversification and adaptation of life on Earth.

Question 2

Answer

The theory of abiogenesis is the idea that life can arise from non-living matter, while the theory of biogenesis is the idea that living organisms can only arise from other living organisms of the same kind.

Question 3

Indicate two important differences between homologous and analogous organs. 

Answer

Homologous organs have a similar structure but may have different functions, while analogous organs have a similar function but may have different structures.

Homologous organs indicate a common ancestry, while analogous organs are the result of convergent evolution.

Question 4

What are homologous organs? Give examples.

Answer

Homologous organs are organs in different organisms that have a similar structure but may have different functions, indicating a common ancestry. Examples of homologous organs include the forelimbs of mammals, the wings of birds, and the flippers of whales and dolphins, which have similar skeletal structures despite their different functions.

Question 5

What are analogous organs ?

Answer

Question 6

What is Vestigial organ? Give example of a vestigial organ in man.

Answer

A vestigial organ is an organ that has lost most or all of its original function in the course of evolution. An example of a vestigial organ in humans is the appendix, which is a small, finger-like organ attached to the large intestine.

Question 7

Write the name of three vestigial organs in plants.

Answer

Three vestigial organs in plants are:

1. Phytolacca fruit
2. Scale leaves
3. Non-functional flowers (e.g. in some orchids)

Question 8

Write the name of three vestigial organs of man.

Answer

Three vestigial organs in humans are:

1. Appendix
2. Wisdom teeth
3. Coccyx (tailbone)

Question 9

Name two vestigial organs in plants. 

Answer

Two vestigial organs in plants are:

1. Phytolacca fruit
2. Scale leaves

Question 10

Where is the vermiform appendix situated in human body?

Answer

The vermiform appendix is a small, finger-like projection attached to the large intestine and situated in the lower right quadrant of the human abdomen.

Question 11

What is petrification?

Answer

Petrification is the process by which organic material is converted into stone or a similar substance, often through a process of mineral replacement. This can result in the preservation of fossils or other organic remains in a solid form over long periods of time.

Question 12

What is fossil?

Answer

A fossil is the preserved remains or traces of an ancient organism, typically found in sedimentary rocks or other geologic deposits. Fossils can provide important information about the history of life on Earth, including the evolution and extinction of species, and the environmental conditions of the past.

Question 13

What is a living fossil ?

Answer

A living fossil is a species of plant or animal that has survived virtually unchanged in form and structure for millions of years and has no close living relatives. Examples of living fossils include the coelacanth, a type of fish, and the horseshoe crab, which have remained virtually unchanged for millions of years.

Question 14

What do you mean by missing link?

Answer

The term “missing link” refers to a hypothetical intermediate form or species that is believed to have existed between two different, but related, species in the course of evolution.

Question 15

Give an example of an animal as missing link.

Answer

One example of an animal that is often referred to as a “missing link” is the Archaeopteryx, which is considered to be a transitional form between dinosaurs and modern birds.

Question 16

Mention three reptilian features of Archaeopteryx. 

Answer

Three reptilian features of Archaeopteryx are:

1. Presence of teeth
2. Presence of a bony tail
3. Presence of claws on the wings

Question 17

Write three Avian features of Archaeopteryx.

Answer

Three avian features of Archaeopteryx are:

1. Presence of feathers
2. Presence of wings with primary and secondary feathers
3. Presence of a wishbone or furcula, which is a characteristic feature of modern birds

Question 18

What is the relation between adaptation and evolution?

Answer

Adaptation is a process by which an organism becomes better suited to its environment through natural selection or other mechanisms. Evolution, on the other hand, is a broader process by which species of organisms change over time, including the development of new adaptations. Adaptation is one of the key mechanisms driving evolution, as those individuals with adaptations that are better suited to their environment are more likely to survive and reproduce, passing on their advantageous traits to their offspring.

Question 19

Why is Lamarck famous?

Answer

Lamarck is famous for his theory of inheritance of acquired characteristics, which proposed that organisms could pass on characteristics that they acquired during their lifetime to their offspring, leading to the evolution of species over time. Although his theory was later disproved, it was an important early contribution to the field of evolutionary biology.

Question 20

What is Neo-Darwinism?

Answer

Neo-Darwinism is a modern synthesis of Charles Darwin’s theory of evolution by natural selection and Gregor Mendel’s theory of genetics, which proposes that evolution occurs through changes in the frequency of alleles (variants of genes) in populations over time. This theory combines the principles of inheritance and variation with the concept of natural selection to explain the diversity of life on Earth.

Question 21

What is the modern idea of evolution?

Answer

The modern idea of evolution is based on the principles of genetic variation, inheritance, and natural selection, and explains the diversity of life on Earth through the gradual accumulation of small genetic changes over time.

Question 22

What are intermediate organisms?

Answer

Intermediate organisms, also known as transitional forms, are organisms that exhibit characteristics that are intermediate between two different, but related, species in the course of evolution. These organisms can provide important evidence for evolutionary relationships and can help to fill in gaps in the fossil record.

Question 23

Cite an example of vestigial organ in man and explain the significance of the presence of vestigial organs in animals.

Answer

One example of a vestigial organ in humans is the appendix, which is a small pouch attached to the large intestine that has lost its original function in digestion.

The significance of vestigial organs in animals is that they provide evidence for the process of evolution and the common ancestry of different groups of organisms.

Question 24

What is fossil ? Mention the importance of fossil with reference to organic evolution. 

Answer

Fossils are the preserved remains or traces of ancient organisms.

The importance of fossil with reference to organic evolution

• Fossils provide evidence of past life and the history of life on Earth.
• Fossils help scientists to infer the morphology, behavior, ecology, relationships, and evolution of ancient organisms, and provide insights into biogeography and environmental change.

Question 25

Indicate the important differences between homologous and analogous organs.

Answer

Homologous Organs	Analogous Organs
Have a similar structure due to a common ancestry	Have a similar function due to similar selection pressures
May have different functions in different species	Have a different structure and embryonic origin

Question 26

What are Annelid and Arthropod characters in Peripatus?

Answer

Peripatus, also known as velvet worms, exhibit both Annelid and Arthropod characters. Some of their Annelid characters include a segmented body, the presence of excretory organs called nephridia, and the absence of a hard exoskeleton. Some of their Arthropod characters include the presence of jointed legs, the presence of a tracheal respiratory system, and the possession of a pair of antennae.

Question 27

Answer

One of the most striking similarities found in the embryos of vertebrates is the presence of pharyngeal arches or gill arches, which give rise to structures such as the jaw, ear, and larynx in humans.

Question 28

What are the reptilian and mammalian characters in Duckbilled platypus (Monotremata) ?

Answer

Duckbilled platypus exhibits reptilian characters such as laying eggs and the presence of cloaca, as well as mammalian characters such as the production of milk for young and possession of fur. They also have a unique feature of electroreceptors in their bills, which is not found in other mammals.

Question 29

What are the reptilian and bird or avian characters of Archaeopteryx?

Answer

Archaeopteryx exhibits both reptilian and avian characters. Some of their reptilian characteristics include the presence of teeth, a long bony tail, and claws on their wings. Some of their avian characters include the presence of feathers, wings for flight, and a bird-like beak.

Question 30

How does the fossil of horse act as an evidence in support of organic evolution?

Answer

Question 31

Cite an example of vestigial organ in man and explain the significance of the presence of vestigial organs in animals.

Answer

One example of a vestigial organ in humans is the appendix, which no longer has a clear function in the digestive system.

The presence of vestigial organs provides evidence for the process of evolution and the common ancestry of different groups of organisms.

Question 32

What are the principles of Lamarck’s theory on which the inheritance of acquired characters is based?

Answer

Lamarck’s theory on the inheritance of acquired characters is based on two main principles:

1. The principle of use and disuse, which states that organs or traits that are used more often will become more developed, while those that are not used will deteriorate over time.
2. The principle of inheritance of acquired characteristics, which suggests that these acquired traits can be passed on to offspring, leading to evolutionary change over time.

Question 33

What is the germplasm theory?

Answer

According to this theory, changes or modifications that occur in somatic cells during an organism’s lifetime cannot be passed on to its offspring, as the germ cells remain unchanged and carry only the genetic information that was present at the time of the organism’s conception.

Question 34

What do you mean by Interspecific and intraspecific struggles?

Answer

Interspecific struggle refers to competition between individuals or populations of different species for limited resources, such as food, water, or shelter. In contrast, intraspecific struggle refers to competition between individuals or populations of the same species for the same limited resources.

Question 35

What is Variation? 

Answer

Variation refers to the differences that exist between individuals or populations of the same species. These differences can be physical, behavioral, or genetic in nature, and may be caused by a variety of factors, such as mutations, genetic recombination, environmental influences, or random chance.

Question 36

What is continuous variation?

Answer

Continuous variation refers to the variation that exists within a population for a particular trait or characteristic that can take on a range of values along a continuum. For example, height is a trait that shows a continuous variation, as individuals can vary in height from very short to very tall, with many possible values in between.

Question 37

State different evidences to explain organic evolution.

Answer

There are several types of evidence that support the theory of organic evolution, including:

1. Fossil evidence – the presence of transitional fossils and the progressive changes in organisms over time provide evidence for the process of evolution.
2. Comparative anatomy – similarities and differences in the anatomy of different organisms can provide insights into their evolutionary relationships.

Question 38

What do you mean by connecting links and missing links ?

Answer

Connecting links and missing links are terms used in evolutionary biology to describe transitional species that help to connect different groups of organisms in the evolutionary tree of life.

Long Answer (LA) type questions

Question 1

What is evolution? Give an outline of the origin of life and its gradual complexities.

Answer

Evolution is the process by which different species of organisms develop and change over time, through a combination of genetic variation, natural selection, and other mechanisms.

The origin of life on Earth is thought to have occurred around 3.5 to 4 billion years ago, in the oceans or other bodies of water. It is thought to have involved a combination of organic molecules, such as amino acids, that eventually combined to form self-replicating structures or proto-cells.

Over time, these proto-cells became more complex and developed into the first true cells, which were able to carry out metabolic processes and exchange genetic information. Through a process of natural selection, cells with advantageous traits were able to survive and reproduce, leading to the diversification of life forms.

Question 2

Answer

Evolution in Plant Kingdom:

1. Origin of the first photosynthetic organisms around 3.5 billion years ago.
2. Development of multicellularity in algae and plants around 1.2 billion years ago.
3. Emergence of land plants around 500 million years ago.
4. Diversification of land plants into mosses, ferns, gymnosperms, and angiosperms.
5. Development of seeds, flowers, and fruits in flowering plants.
6. Adaptation to diverse environments, including deserts, forests, and aquatic habitats.
7. Evolution of symbiotic relationships with animals, such as pollination by insects and birds.
8. Continued diversification and speciation, leading to the vast array of plant species we see today.

Evolution in Animal Kingdom:

1. Emergence of the first multicellular animals around 600 million years ago.
2. Diversification of animal body plans, including radial symmetry, bilateral symmetry, and segmentation.
3. Development of complex nervous systems and sensory organs.
4. Emergence of the first vertebrates around 500 million years ago.
5. Diversification of vertebrates into fish, amphibians, reptiles, birds, and mammals.
6. Evolution of specialized adaptations, such as wings, fins, teeth, and claws.
7. Adaptation to diverse environments, including land, sea, and air.
8. Continued diversification and speciation, leading to the vast array of animal species we see today.

Question 3

Discuss the basic structures of heart in different groups of vertebrate animals as evidence of organic evolution. Or, Substantiate evolution with the help of morphological evidence.

Answer

The basic structure of the heart varies among different groups of vertebrate animals, providing evidence of organic evolution:

1. Fish: The heart of fish is a simple, two-chambered structure consisting of an atrium and a ventricle. The atrium receives deoxygenated blood from the body, while the ventricle pumps it to the gills for oxygenation.
2. Amphibians: The heart of amphibians is a three-chambered structure consisting of two atria and a single ventricle. The right atrium receives deoxygenated blood from the body, while the left atrium receives oxygenated blood from the lungs. The ventricle pumps a mixture of oxygenated and deoxygenated blood to the body and lungs.
3. Reptiles: The heart of reptiles is also a three-chambered structure, but with a partially divided ventricle that separates oxygenated and deoxygenated blood to some extent. This improves oxygenation and allows reptiles to survive in diverse environments.
4. Birds and mammals: The heart of birds and mammals is a four-chambered structure consisting of two atria and two ventricles. The right atrium receives deoxygenated blood from the body, while the left atrium receives oxygenated blood from the lungs. The right ventricle pumps deoxygenated blood to the lungs, while the left ventricle pumps oxygenated blood to the body. This separation of oxygenated and deoxygenated blood allows for greater efficiency in oxygen delivery to tissues.

Question 4

(a) What do you mean by homologous organs? (b) Explain how the homology of forelimbs in vertebrates gives support in favour of evolution. 

Answer

(a) Homologous organs are organs that have similar structures but may have different functions and are thought to have evolved from a common ancestral structure.

(b) The homology of forelimbs in vertebrates provides evidence in favour of evolution by demonstrating that diverse species have similar bone structures despite differences in their habitats, lifestyles, and functions. For example, the forelimbs of humans, bats, whales, and birds have the same basic bone structure, including the humerus, radius, and ulna. However, the functions of these structures are different, with wings for birds, flippers for whales, and arms for humans. This suggests that these species share a common ancestor with similar forelimbs, which were then modified to suit different environments and purposes.

Question 5

How are homologous organs of plants helpful in explaining evolution?

Answer

Homologous organs of plants are helpful in explaining evolution because they provide evidence of common ancestry and evolutionary relationships between different plant groups. For example, the flowers of different plant species may have different structures, but they often have a similar basic structure and develop from the same floral parts, including the sepals, petals, stamens, and carpels. This suggests that these plant groups share a common ancestor with similar floral structures, which were then modified to suit different environments and purposes.

Question 6

What do you mean by analogous organs? Write in brief the analogous organs of animals and plants.

Answer

Analogous organs are organs that have a similar function and/or appearance in different species but have a different evolutionary origin. Here are some examples of analogous organs in animals and plants:

Analogous organs in animals:

1. Wings of birds and bats
2. Streamlined body shape and fins of sharks and dolphins
3. Eyes of vertebrates and cephalopods
4. Legs of insects and spiders

Analogous organs in plants:

1. Thorns and spines of cacti and roses
2. Convergent evolution of succulent tissues in cacti and other desert plants
3. Convergent evolution of water storage structures in bromeliads and cacti
4. Convergent evolution of carnivorous traps in different plant families

Question 7

How do the homologous and analogous organs give evidence in favour of evolution?

Answer

Homologous and analogous organs provide evidence in support of evolution in different ways:

Homologous organs:

1. They have the same basic structure but different functions.
2. They suggest a common ancestry and gradual divergence of organisms over time.
3. They provide evidence of divergent evolution.
4. They can be used to construct evolutionary trees and classify organisms.
5. Examples include the forelimbs of different vertebrates and the wings of bats and birds.

Analogous organs:

1. They have different structures but the same function.
2. They suggest convergent evolution and adaptation to similar environments.
3. They provide evidence of convergent evolution.
4. They can be used to infer the ecological relationships between different organisms.
5. Examples include the wings of birds and bats, the fins of fish and whales, and the eyes of insects and mammals.

Question 8

What is vestigial organ? Write in brief the vestigial organs of plants and animals

Answer

Vestigial organs are structures that have lost their original function over the course of evolution. Here are some examples of vestigial organs in plants and animals:

Vestigial organs in plants:

1. Stipules – small leaf-like structures that are found at the base of some plant leaves.
2. Floral nectaries – structures that produce nectar but are no longer necessary for pollination.
3. Seed coats – structures that protect the seed but are no longer necessary in some plants that have evolved other means of protection.

Vestigial organs in animals:

1. Human appendix – a small, finger-like structure at the end of the large intestine that has lost its original function in digestion.
2. Wings of flightless birds – such as ostriches and emus, which have wings that are too small to support flight.
3. Pelvic bones in whales – vestigial remnants of the ancestral hind limbs that have lost their function in swimming.

Question 9

What is missing link? Give examples of missing link from animals and plants.

Answer

The extinct organism bearing characters of two different groups are known as missing links.

Examples of missing links from animals:

• Archaeopteryx: a fossil bird that has features of both reptiles and birds, such as teeth, a long bony tail, and feathers.
• Tiktaalik: a fossil fish that has features of both fish and tetrapods, such as a flat head, lungs, and a shoulder girdle.

Examples of missing links from plants:

• Rhynia: a fossil plant that shows features of both bryophytes and vascular plants, such as simple conducting tissues and sporangia.
• Archaeosperma: a fossil plant that shows features of both seedless plants and gymnosperms, such as branched stems and ovules with exposed seeds.

Question 10

(a) What is fossil? (b) Explain with an example how do fossils act as evidences in favour of organic evolution.

Answer

(a) Fossil refers to the remains or traces of organisms that lived in the past, which have been preserved in the Earth’s crust through natural processes.

(b) Fossils serve as evidence in favour of organic evolution in several ways:

• Fossils provide a record of the past diversity of life on Earth, which shows how organisms have changed over time and gives insights into their relationships and adaptations.
• Fossils can reveal the age of rocks and the sequence of events that have shaped the Earth’s surface and its biota.
• Fossils can also show the geographic distribution of ancient organisms and the changes in climate and habitats that have affected them.

Question 11

Explain the main idea regarding the theories of Lamarck.

Answer

The main idea regarding the theories of Lamarck

• Lamarck proposed that organisms can change during their lifetimes through the use and disuse of body parts, and that these changes can be passed on to their offspring.
• He also suggested that organisms can acquire traits through their environment and behaviour, which can be inherited by their offspring.
• Lamarck believed that these acquired traits could accumulate over time, leading to the evolution of new species.
• However, Lamarck’s ideas about the inheritance of acquired traits have been largely discredited by modern genetics and evolutionary biology.

Question 12

What are the different weaknesses of Lamarckism?

Answer

There are several weaknesses of Lamarckism, including:

1. Lack of evidence: Lamarck’s theory was not supported by experimental evidence and relied on anecdotal observations.
2. Inheritance of acquired traits: Lamarckism proposes that acquired traits can be inherited, which has been shown to be untrue in most cases.
3. Lack of mechanism: Lamarck’s theory did not provide a clear mechanism for how acquired traits were passed on to offspring.
4. No account for natural selection: Lamarck’s theory did not account for the role of natural selection in shaping the course of evolution.
5. Contradictory evidence: Some examples of Lamarckian inheritance have been refuted by scientific studies, such as the case of the inheritance of acquired immunity.

Question 13

Write down the name of the book where Charles Darwin published his theory. What do you mean by over-prodigality of production?

Answer

The name of the book where Charles Darwin published his theory is “On the Origin of Species by Means of Natural Selection”.

Over prodigality of production refers to the excessive production of offspring by living organisms, often beyond what is necessary for the continuation of the species. This results in a struggle for survival, where only the fittest individuals are able to survive and reproduce.

Question 14

Explain the struggle for existence and variation in the light of Darwin’s theory

Answer

According to Darwin’s theory of evolution, all living organisms have variations, which are inherited traits that make them better adapted to their environment. The struggle for existence refers to the competition for resources such as food, water, and mates that occurs between individuals of the same species, as well as between different species that occupy the same ecological niche.

Darwin proposed that organisms with variations that provide them with a survival advantage are more likely to survive and reproduce, passing on their advantageous traits to their offspring. This process, known as natural selection, results in the evolution of new species over time.

Question 15

State in brief how the name H. M. S. Beagle is associated with Darwin’s theory. What do you mean by Heredity and Origin of Species ?

Answer

H.M.S. Beagle was the ship that Charles Darwin sailed on for a five-year voyage, during which he collected specimens and made observations that contributed to the development of his theory of evolution. The voyage took him to places like the Galapagos Islands, where he observed the diversity of species and developed his ideas on natural selection.

Heredity refers to the passing down of traits from parents to offspring, while the origin of species refers to the process of how new species arise through the process of evolution. Darwin’s theory of evolution by natural selection provides a mechanism for explaining how heredity and variation can lead to the origin of new species over time.

Question 16

(a) What do you mean by Natural Selection? (b) What are the demerits of Darwin’s theory?

Answer

(a) Natural selection is a process by which certain individuals within a species are better adapted to their environment and have a higher chance of survival and reproduction, leading to the gradual evolution of the species over time.

(b) Some of the demerits of Darwin’s theory include:

1. Lack of understanding of the mechanisms of inheritance – Darwin did not know about genetics and how traits are inherited, so he couldn’t explain how variation arises in the first place.
2. Incomplete fossil record – Darwin’s theory relied heavily on the fossil record to support the idea of evolution, but the fossil record was incomplete at the time and many important transitional forms were missing.
3. Limited knowledge of geology – Darwin did not have a full understanding of geological processes and the age of the Earth, which made it difficult to explain the slow, gradual changes required for evolution.
4. Lack of explanation for the origin of life – Darwin’s theory only explained how existing species evolve over time, but did not address the origin of life itself.

Question 17

What is the relation between evolution and adaptation?

Answer

The relation between evolution and adaptation

• Evolution and adaptation are closely related concepts in biology.
• Evolution is the process of change over time in the inherited traits of populations of organisms, resulting in the formation of new species and the diversity of life on Earth.
• Adaptation is the process by which organisms become better suited to their environment, through the development of traits that improve their chances of survival and reproduction.
• Adaptation is an important mechanism of evolution, as it allows organisms to survive and reproduce more successfully in their environment, leading to changes in the gene pool of populations over time.
• Adaptation can occur through natural selection, where advantageous traits are favoured and passed on to the next generation, or through other mechanisms such as genetic drift and gene flow.

Question 18

Briefly discuss the ideas of Lamarck and Darwin regarding the evolution of long necked giraffes.

Answer

Lamarck proposed that the long necks of giraffes were acquired by stretching their necks to reach leaves on high trees, and this acquired trait was passed down to their offspring. However, Darwin proposed that giraffes with longer necks had a survival advantage in their struggle for existence, allowing them to reach food sources that were higher up and out of reach of other herbivores. As a result, these individuals had a better chance of survival and reproducing, passing down their advantageous trait of long necks to their offspring. This idea is known as natural selection.

Question 19

(a) What is meant by ‘Inheritance of Acquired Character’? Who is the propounder of that idea? (b) What is meant by ‘Survival of the fittest? (c) What do you mean by “Natural Selection? Who proposed it?

Answer

(a) The idea of ‘Inheritance of Acquired Character’ suggests that an organism can pass on the traits it acquired during its lifetime to its offspring. Jean-Baptiste Lamarck was the propounder of this idea.

(b) ‘Survival of the fittest’ refers to the idea that organisms that are better adapted to their environment are more likely to survive and reproduce. This term was coined by Herbert Spencer, although it is often associated with Charles Darwin.

(c) ‘Natural Selection’ is a process by which certain traits become more or less common in a population over time, depending on whether they increase or decrease an organism’s chances of survival and reproduction. This concept was proposed by Charles Darwin.

Question 20

What are the differences between Lamarckism and Darwinism?

Answer

• Lamarckism:
  • Inherited acquired characteristics
  • No role for natural selection
  • Insufficient scientific evidence
  • Not widely accepted
• Darwinism:
  • No inherited acquired characteristics
  • The key role of natural selection
  • Strong scientific evidence
  • Widely accepted

Question 21

What do you understand by Neo-Darwinism? Explain.

Answer

Neo-Darwinism is a term used to describe the modern synthesis of Charles Darwin’s theory of evolution by natural selection and Gregor Mendel’s theory of genetics. It combines the principles of natural selection and genetic variation to explain how populations change over time and how new species can arise.

Some key features of Neo-Darwinism include:

1. Evolution occurs through the process of natural selection acting on genetic variation within a population.
2. Genetic mutations provide the raw material for evolutionary change, but natural selection determines which mutations become fixed or lost over time.
3. The mechanism of inheritance is governed by genes located on chromosomes, which undergo random assortment and recombination during sexual reproduction.
4. Evolution is a gradual process that occurs over long periods of time but can be influenced by sudden events such as genetic drift, migration, and natural catastrophes.

Drawing Based Questions

Question 1

Draw the different stages of evolution of horse.

Answer

Question 2

Draw the comparative study of the vertebrate heart.

Answer