WBBSE 10th Class Science Solutions Science & Environment Chapter 4 Evolution and Adaptation

Long Answer Type Questions

1. Phase 1-Origin of simple organic compounds: In the primitive ocean, several inorganic substances reacted with each other to synthesize simple organic compounds, like acetylene, methane, ethylene, etc. In these reactions ultraviolet ray, lightning, extreme heat, etc. supplied the requisite energy. Later, these organic substances reacted with water vapour to synthesize some hydrocarbon compounds, such as acetyldehyde.
2. Phase 2-Synthesis of complex organic compounds: The interaction of these simple organic compounds later gave rise to complex organic matters, like carbohydrates (glucose, fructose, etc.), fatty acids and glycerol, amino acids (alanine glycine, etc) etc. These complex compounds then reacted with each other to synthesize more complex and larger organic molecules, like simple proteins, nucleotides and lipids. Finally, nucleic acids and complex proteins were produced in the hot water of the primitive ocean.
3. Phase 3-Formation of coacervates: In course of time, the organic macromolecules interacted to produce numerous spherical, double membrane-bound, divisible, colloidal microparticles, which were denoted as coacervates by Oparin. According to Oparin and Haldane, these microparticles were composed of several components like proteins, nucleic acids, carbohydrates, etc. which were important for origin of life on earth. Sidney Fox opined that several protein molecules united in the primitive ocean to produce tiny proteinaceous particles called microspheres. According to him, life originated on earth from microspheres.
4. Phase 4-Origin of protocells: Scientists assumed that the tiny coacervates engulfed nucleic acids and proteins from environment, enlarged in size and finally took the shape of protocells. These protocells are thought to be the earliest forms of life on earth. RNA was the genetic material of these protocells. These were heterotrophic in nature. In course of organic evolution, chemosynthetic and photosynthetic forms of life emerged on earth. With the emergence of photosynthetic organisms, free oxygen was liberated into the primitive atmosphere.

3. What is hot dilute soup? Give a brief description of ‘biogeny’ of the ‘evolution of life’ on earth.

Ans. Hot dilute soup

Before the origin of life on earth, several simple organic compounds reacted with each other to synthesize complex organic matters, like amino acids, nucleotides, lipids, carbohydrates, etc. All these compounds remained suspended in hot water of the primitive ocean. Scientist Haldane described this mixture as ‘hot dilute soup! Sometimes it is also called ‘prebiotic soup! Scientists assumed that, life on earth originated in this ‘hot dilute soup!

Biogeny or evolution of life on earth

About 3.7 billion years back, life originated on earth in the form of protocell. The successive events during the origin of life on earth are mentioned below.

1. Origin of protocell: By the process of chemosynthesis, coacervates were formed in the primitive ocean. Later, nucleic acids and protein molecules fused with coacervates to form protocells.
2. Origin of autotrophs: The primitive organisms, evolved from the protocells were chemoheterotrophs. Later came the chemoautotrophs and then emerged the photosynthetic prokaryotic life forms. With the emergence of photosynthetic organisms, free oxygen was released into the primitive atmosphere. Thus, the character of the atmosphere changed from reducing to an oxidising one.
3. Origin of eukaryotes: About 1.5 billion years ago, unicellular, aerobic eukaryotes evolved on earth. In course of evolution, multicellular complex organisms came into being from those unicellular forms.

4. Explain the important events of organic evolution.

Ans. Important events of organic evolution

The whole event, starting from the origin of life on earth to the ongoing organic evolution, it has always been a very complex process. By assembling the concepts and theories of different scientists, we have developed some ideas on the origin of life on earth and the trend of organic evolution, which are mentioned below.

1. Origin of earth: Earth is the third planet in the solar system. It has originated from the solar nebula about 4.5 to 5.0 billion years back.
2. Origin of Life: About 3.5 to 3.7 billion years ago, life originated on earth. Two scientists, Haldane and Oparin, have put forward a clear idea on the origin of life in the water of primitive ocean by successive reactions among several inorganic and organic chemicals.
3. Origin of unicellular organisms: The first living forms on earth were the primitive unicellular forms, which were the primitive heterotrophic prokaryotes. From the prokaryotes, emerged the unicellular eukaryotes.
4. Origin of photosynthetic prokaryotes: From the primitive heterotrophic prokaryotes, there evolved some photosynthetic prokaryotes. With the emergence of photosynthetic forms, production of free oxygen started and the primitive reducing atmosphere transformed into an oxidising one.
5. Emergence of multicellular organisms: In course of evolution, multicellular organisms emerged on earth. These were more complex and advanced than their ancestors.
6. Emergence of different invertebrates and fish-like vertebrates: With gradual advancement, different invertebrates came into being. After the emergence of higher invertebrates, there came some fish-like vertebrates.
7. Emergence of terrestrial plants: The primitive plants originated in water. In course of evolution, the terrestrial plants emerged. These newly arrived terrestrial plants got themselves adapted to this new environment slowly and thereafter several advanced terrestrial plants emerged on earth.
8. Emergence of terrestrial animals: While living in aquatic environment, some fish-like forms have developed some organs suitable for terrestrial living. Gradually some of these forms, for instance; amphibians, rejected the aquatic life and started dwelling on land. Later, different advanced terrestrial forms, like mammals and birds,. emerged on earth.

5. Describe the brief outline of the chemical origin of life mentioning Miller and Urey’s experiment. 

Similar question, Briefly describe the experiment conducted by Miller and Urey on the origin of life.

Ans. Experiment of Miller and Urey

Based on the concept of chemosynthesis of life, proposed by Oparin and Haldane, Stanley Miller and Harold Urey performed an experiment in 1953 in the laboratory of Chicago University.

1. Procedure: They prepared a highly heat-resistant instrument with two inter-connected chambers of unequal diameters. The larger chamber was fitted with two electrodes and was filled with a mixture of hydrogen, methane and ammonia gases. The outlet pipe of the larger chamber was fitted with a cooling device and a tap which was used to tap down the contents from it. The smaller chamber was used as a boiler and a connecting pipe was fitted with it to supply vapour to the larger chamber.
   Powerful electric sparks were generated in the larger chamber to mimic the lightning-like situation (that prevailed in the primitive atmosphere). The water of the smaller chamber was boiled by heating it externally, thus the newly formed water vapour is pushed into the larger chamber. The machine was run continuously for one week and the product from the larger chamber was tapped down after condensation.
   
2. Observation: After analysing the product, scientists found a number of amino acids, viz. glycine, alanine, glutamic acid, aspartic acid, etc. in it.
3. Conclusion: From the result, Miller and Urey concluded that in the primitive, free oxygen lacking, reducing atmosphere, different inorganic matters reacted with each other to synthesize organic substances. In this reaction, heat, lightning, ultraviolet ray and other cosmic rays provided the of cells energy that needed. The organic matters, thus synthesized, acted as the building blocks and finally helped in the origin of life. Tap Experimental set up of Miller and Urey

Significance of Miller and Urey’s experiment

Miller and Urey’s experiment supports the abiogenetic theory of origin of life. According to this theory, life was originated from abiotic or inorganic substances around 3.7 billion years ago.

Short Answer Type Questions

1. Define life.

Ans. Life is the condition that differentiates a living organism from a non-living object. Life shows the signs of growth, reproduction, metabolic activities, excitability, adaptability, ageing and senescence.

2. What do you mean by organic evolution? Or, What is meant by evolution? olution?

Ans. Organic evolution is the process of slow and steady changes in the characteristics of organisms. These changes result into origin of complex and higher descendent varieties or species from simpler and primitive ancestral the types. Organic evolution is cause of biodiversity on the earth.

3. What do you mean by cosmogenic origin of life?

Ans. Swiss author, Erik Von Daniken, in his number of books, claimed that life was introduced to earth from other planet of other galaxy. This pseudoscientific concept is known as the theory of cosmogenic origin of life.

4. What is meant by cyanogen theory of the origin of life on earth?

Ans. According to German scientist Pflüger, when the earth was cooling down, carbon and nitrogen combined to form a complex compound, named cyanogen. It is a protein-like compound, which in course of time produced protoplasm. This concept is known as cyanogen theory of origin of life.

5. What at is meant by spontaneous creation of life or abiogenesis?

Ans. Greek philosopher Aristotle and famous Belgian chemist, Van Helmont believed that life has originated on earth spontaneously from nonliving matters. This concept on the origin of life is known as spontaneous creation of life or abiogenesis or biopoiesis.

6. What is chemogeny?

Ans. Chemogeny is the origin of life on earth through ongoing synthesis of complex compounds by successive chemical reaction of different elements and simpler compounds.

7. How did free oxygen evolve in earth’s atmosphere?

Ans. In the primitive earth, the pioneer life forms were chemoheterotrophs. In course of evolution, these organisms were gradually transformed into photoautotrophs. These aerobic photosynthetic organisms released free oxygen in the primitive atmosphere by performing photosynthesis.

8. What are coacervates?

Ans. According to Alexander Oparin, in the organic compound-rich hot water of the primitive ocean, many spherical colloidal droplets were formed. These tiny droplets were composed of several amino acids, simple carbohydrates and lipid molecules. He denoted these colloidal droplets as coacervates.

9. Write down the characteristics of coacervate.

Ans. The characteristics of coacervate are-[1] It is large organic compound, composed of carbohydrates, amino acids, proteins, [2] Coacervate was covered by a lipid membrane. [3] Coacervate was able to absorb nutrients from the surroundings.

10. What are microspheres?

Ans. According to Sidney Fox, in the primitive ocean, many amino acid molecules united to form a double layered lipid membrane-bound, tiny, divisible, spherical droplets. These are called microspheres, which are assumed to be the precursor of primitive cells. Sidney Fox opined that life has originated from microspheres, not from coacervates.

11. Write down the characteristics of microsphere.

Ans. The charecteristics of microsphere are[1] Microsphere originates from polypeptide. [2] Microsphere is more durable than coacervate. [3] Microsphere is covered by double membrane. [4] It is capable of bud formátion and can use ATP as the source of energy. [5] It has self propagative property.

Very Short Answer Type Questions

Multiple Choice Questions & Answers [MCQ]

1. The theory of the origin of life was first proposed by-

A. Pasteur

B. Oparin

C. Darwin

D. Mendel

Ans. B

2. Scientist Stanley Miller was able to synthesize simple amino acids from a mixture of-

A. H₂, O₂, N₂ and H₂O

B. H₂, NH₃, CH₄ and water vapour (H₂O)

C. NH₃, CH₄, HCN

D. N₂, NH₃, HCN and O₂

Ans. B

3. Miller and Urey, in their experiment, were able to synthesize some preliminary constituents necessary for the creation of life. Identify the ones which were amino acids among them-

A. Lactic acid, Acetic acid

B. Urea, Adenine

C. Glycine, Alanine

D. Formic acid, Acetic acid

Ans. C

4. The most important organic matter for the origin of life is-

A. Nucleic acid

B. Nucleoside

C. Amino acid

D. Protein

Ans. A

5. The gas which was absent in the environment during the origin of life is-

A. Hydrogen

B. Oxygen

C. Methane

D. Ammonia

Ans. B

6. Who was the first to disapprove the doctrine of spontaneous generation of life?

A. Louis Pasteur

B. Alexander Oparin

C. Aristotle

D. Miller

Ans. A

7. The cause of biodiversity on earth is-

A. Metabolism

B. Locomotion

C. Evolution

D. Adaptation

Ans. C

8. Where did life originate on earth?

A. In ocean

B. On land

C. In space

D. Under soil

Ans. A

9. Cellular organisation appeared first in-

A. Nucleoproteins

B. Coacervates

C. Bionts

D. Protobionts

Ans. B

10. The chemosynthesis of life was clearly demonstrated by-

A. Lamarck and Darwin

B. Miller and Urey

C. Plato and Dante

D. Starling and Bayliss

Ans. B

11. Gradual development of modern organism from primitive one is called-

A. Variation

B. Evolution

C. Adaptation

D. Behaviour

Ans. B

12. The study of devlopment of an organism in its life-span is called

A. Organic evolution

B. Ontogeny

C. Mutation

D. Special creation

Ans. B

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SUB-TOPIC – 1.2

THEORIES OF ORGANIC EVOLUTION

SUMMARY

• There are various theories regarding the evolution, of which Lamarckism and Darwinism are most significant.
• In the year 1809, Lamarck publised his book ‘Philosophie Zoologique’ where he proposed and explain his theories regarding the evolution of new species.
• The main features of the theory of Lamarck are-
  [1] Internal vital force
  [2] New needs culminate in the formation of new organ
  [3] Law of use and disuse of organ
  [4] Inheritance of acquired characters
  [5] Formation of new species
• German biologist August Weismann conducted an experiment where he removed the tails of mice repeatedly over 22 generations and reported that no mice were born in consequence without a tail or even with a shorter tail. This experiment opposed the theory of inheritance of acquired characters of Lamarck.
• Charles Robert Darwin sailed around the world, as a naturalist, aboard the HMS Beagle and this experience and studies that he made, helped him to propose the theory of evolution which was publised. in his book, ‘Origin of Species by Means of Natural Selection.
• The salient features of the theory of Darwin are-
  [1] Prodigality of production
  [2] Limited food and shelter on earth
  [3] Struggle for existence
  [4] Variations
  [5] Survival of the fittest
  [6] Natural selection
  [7] Origin of new species
• Few limitations of Darwin’s theory concerns the origin of variation, origin of new characters, arrival of the fittest, etc.

Long Answer Type Questions

1. Briefly describe Lamarckian concept of evolution.

Part question, Describe two major tenets of Lamarck’s evolutionary theory.

Ans. Lamarckian concept of evolution

In 1809, Lamarck proposed the concept of organic evolution in his famous book, titled ‘Philosophie Zoologique! This concept is popularly known as Lamarckism.

1. Internal vital force: An internal vital force or energy in all life forms, helps in the development of body and organs.
2. Development of new organs according to need: With the change in environment, a need develops among the organisms for morphological and behavioural change. Newly developed organs help the organisms to adapt in the changing environment.
3. Law of use and disuse: Any organ, which is used more, grows in size and strength, whereas, that which is used less, reduces in size, becomes weak and finally becomes extinct.
   Example of use of organ: Ancestors of giraffe had short necks. To collect the leaves of taller plants, they stretched their necks continuously. This conscious effort made their necks long and eventually, giraffes with longer necks evolved.
   Example of disuse of organ: The ancestors of snakes had limbs. While adapting to fossorial habitat, their limbs were left unused. Finally, limbs of snakes were lost during the course of evolution.
4. Inheritance of acquired characters: Any change in the characteristics of an organism, which an organism achieves by conscious effort, is inherited by its offspring.
5. Formation of new species: The characters acquired during the lifetime are passed onto the progeny and after a number of generations, new species is produced.
   To get leaves from tall trees, ancestors of giraffe stretched their necks. By this process one might have lengthened it a little, which was inherited directly by its offspring. This process continued for several thousand generations and finally completely different looking long-necked giraffe emerged as a new species from their ancestors.

1. Prodigality of production: Darwin opined that all organisms increase their population in geometric rate. For example, a pond snail lays 6 million eggs in a year. A female salmon fish releases 30 million eggs in a reproductive season.
2. Limited food and shelter on earth: The space on the earth and supply of food do not increase in proportion to the rate of increase in population. Therefore, a scarcity of food and shelter occurs in the living world.
3. Struggle for existence: Continuous increase in population size and scarcity of food and shelter results into conflicts among the organisms for survival. Darwin referred to it as the struggle for existence. This struggle of three types-[1] Intraspecific struggle-The conflict among the members of a same species population for food, shelter and mating partners. [2] Inter-specific struggle-The conflict among the members of different species for resources and shelter. [3] Environmental struggleThis struggle is for surviving against different natural calamities, like drought, flood, earthquake, etc.
   
4. Variation: Darwin indicated that, no two individuals of same species are identical. There must be some differences between them, which he stated as variations.
5. Survival of the fittest: Darwin mentioned two different types of variations-favourable and unfavourable. Favourable variations help an organism to adapt to changing environment but unfavourable variations cannot help in their adaptation. The individuals with unfavourable variations face a defeat in the struggle for existence and become extinct in course of time. Whereas, the organisms with favourable variations win that struggle and survive on earth. Scientist Herbert Spencer denoted this event as the ‘survival of the fittest’.
6. Natural Selection: According to Darwin, the organisms with favourable variations are selected by nature for survival because they are fittest to face their surroundings. Darwin explained this event as ‘natural selection. The naturally selected forms thrive successfully and propagate very fast to increase their population.
7. Origin of new species: Accumulation of many favourable variations in any group of organisms for generations makes their descendents widely different from their ancestors. Finally, these completely changed descendents emerge as new species.

1. Example of vestigial organs in animals: Muscles of pinna, nictitating membrane of eye, vermiform appendix are few examples of vestigial organs in man. Pelvic girdle bones of whale, wings of ostrich are some vestigial organs of other animals.
2. Example of vestigial organs in plants: Scale leaves of undergroundmodified stems, sterile gynoecia of coconut, staminodes of Cassia, scale-like leaves of Cuscuta are some vestigial organs in plants.

1. Lamarckian explanation: Lamarck believed that the necks of the ancestors of giraffe were almost similar to that of recent horses. To reach the leaves of taller trees they used to stretch their necks continuously. In this process, members of every generation lengthened their necks to a little extent. This changed feature was inherited by the next generation and this process continued for several successive generations. Finally, after thousands of generations, the longnecked giraffes have emerged as a new species.
2. Darwinian explanation: According to Darwin, in ancient days members of giraffe population had various lengths of necks. Those with longer necks could reach the leaves of taller trees and hence got more food than the ones with shorter necks. The long-necked giraffes became healthier and thrived successfully. On the other hand, the short-necked giraffes became weaker and reproductively incapable due to shortage of adequate food. Gradually, the number of these giraffes went down and at the end they became extinct. However, the long necked giraffes came out victorious in the struggle for existence and survived on earth as a new species.

Short Answer Type Questions

4. What is meant by germplasm theory?

Ans. According to Weismann, the inheritable features are never carried by the somatic cells from parents to offspring. Only the germ cells carry these characters from one generation to the next. This concept is known as the germplasm theory.

5. What is Neo-Lamarckism?

Ans. A number of modern scientists, viz., Waddington, Packard, Spencer and others modified the original theory of Lamarck under the light of interaction between life and environment. This modified form is known as Neo-Lamarckism.

6. Why was Charles Darwin famous?

Ans. In 1859, Charles Darwin published his concept on organic evolution in his book, titled ‘On the Origin of Species by Means of Natural Selection. In his book, he explained the role of natural selection on the origin of new species from an older one. This theory of natural selection made Darwin famous in the field of biology.

7. What is meant by struggle for existence?

Ans. To survive on earth, every individual organism has to face competition for food, shelter and mating partners. In this context, it comes across either with the members of same species or that of different species. Apart from this, it has to fight against different natural adversities, like flood, drought, volcanic eruptions, forest fire, etc. Charles Darwin described all these conflicts as the struggle for existence.

8. How many types of struggle for existence did save for det Darwin suggest?

Ans. Darwin suggested three different types of struggle for existence among the organisms on earth. These are-[1] Intra-specific struggle (competition among the members of the same species), [2] Inter-specific struggle (competition among the members of different species) and [3] Environmental struggle or the struggle against natural nature (struggle against different calamities).

9. ME What is intra-specific struggle?

Ans. Members of the same species often get involved in conflict among each other for food, shelter and mating partners. Darwin explained this type of conflict as intra-specific struggle. Example-Dogs often fight among themselves for food and mating partners.

10. What is inter-specific struggle?

Ans. Members of different species often fight with each other for food and shelter. Darwin explained this type of conflict as inter-specific struggle. Example-Dogs fighting with cat for same food, sparrow fighting with common myna for food and shelter.

11. Tigers are extinct but there are many deer in the jungle. A few tigers are brought from another sanctuary and released in such a jungle. Imagine and write the names of different kind of struggle for existence those tigers have to be involved in. 

Ans. The tigers, brought from another sanctuary, have to face mainly two types of struggle for existence. These are-[1] Inter-specific struggle: They have to get involved in inter-specific struggle with deer for food. [2] Struggle against nature: Firstly, the tigers will face difficulty in adjusting with the new environment and secondly, as the number of deer is high in that jungle, the jungle will be devoid of bushes which generally provide hiding space to tiger during hunting session.

Multiple Choice Questions & Answers [MCQ]

Answer in a single word or sentence

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SUB-TOPIC – 1.3

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.
   
   These evidences strongly indicate, that all vertebrates have evolved from same ancestor but separated from each other to adapt in separate environments.
2. Homologous organs in plants: The thorn of wood apple tree, stem tendril of passion flower plant, phylloclade of cactus, etc. are modifications of same organ but these perform different functions. The above mentioned examples prove that these organisms evolved from same ancestor but with time, their organs have changed their shapes and functions to adapt in separate environments.

4. How do analogous organs support organic evolution?

Ans. 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 modification of the forelimbs but the wings of insects are lateral folds of the cuticle of thorax. The sting of scorpion and sting of honeybee are functionally identical, however, the sting of scorpion is modification of telson and sting of honeybee is modified ovipositor.
   
2. Analogous organs in plants: Leaf tendril of pea plant and stem tendril of 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.
   Analogous organs indicate the adaptation of distantly related organisms in identical environment. Therefore, analogous organs provide strong support in favour of organic evolution.

1. Heart of vertebrates: The basic structure of heart of fishes, amphibians, reptiles, birds and mammals is similar. All of them have auricle as the blood receiving chamber and ventricle as the chamber that expels blood from heart. However, in 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, reptilian heart has a partially divided ventricle, in which partial mixing of oxygenated and deoxygenated blood occurs (exception-crocodile has 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
2. Forelimbs of different vertebrates: The basic skeletal structures of forelimbs of whale, bat, bird, horse and man 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. 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.

Answer in a single word or sentence

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TOPIC- 2

SURVIVAL STRATEGIES: ADAPTATION

SUMMARY

• The reaction of an organism in response to the environmental stimuli is called its behaviour. Behaviour helps in adaptation and evolution of an organism.
• Adaptation is the structural or functional changes of an organism which helps the organism to survive in new environment or their constantly changing current environment.
• Morphological adaptations can be observed in the followings-(i) The leaves of some desert plants turn into spines, even the number of leaves also decreases. These are to reduce the rate of transpiration in water deficit conditon. (ii) Air bladder is the buoyancy organ in fish which helps the fish to maintain its depth while swimming. (iii) Air sacs in birds helps them by increasing oxygen exchange capacity and lessen the specific gravity of birds thus enabling them fly higher.
• Physiological adaptation is observed in sundari plant, camel, etc. Removing excess salt by bark exfoliation and through salt gland present in leaves, conducting oxygen intake via pneumatophore, etc. are some physiological processes which enable sundari plant to survive in coastal saline soil. RBC of camel is small, oval and can expand upto 240% after water absorption. Besides, water production by oxidizing the fat stored in hump, releasing concentrated urine, etc. help camel to survive in extreme condition of desert region.
• Chimpanzee and honey bee show behavioural adaptation. Chimpanzees prepare sticks from twigs and use these as fishing tools to extract termites from their mound and eat them. They use rocks as hammer to break the shells of nuts. When they get infected by parasites they use herbs as medicines to treat themselves. Honey bees perform typical patterns of dance, like waggle dance, circular dance, to indicate the direction and distance of food source from the hive.

Long Answer Type Questions

1. What is the relation between adaptation and evolution? Mention the functions of spine in cactus to combat the arid environment. 

Ans. Relation between adaptation and evolution

Adaptation is the evolutionary process which enables an organism to survive in its habitat.

1. Adaptation-a step to evolution: To survive in a changing environment, organisms change their morphological, behavioural and physiological features accordingly. Those, which can adjust themselves successfully in a changing environment, get the favour of natural selection to survive and propagate. The favourable adaptive features are inherited by successive generations, which help in the origin of a new species or assist in evolution. Practically, adaptation is a step towards evolution.
2. Evolution a greater notion: Evolution is a very long and complex process. It is a continuous, ongoing process, since the origin of life on earth. On the other hand, adaptation occurs when any organism faces any problem related to its survival due to any change in environment. Therefore, evolution is a greater notion in comparison to adaptation.

Functions of the spine in cactus

The main functions of the spine in cactus are as follows-[1] The spines are modification of leaves which are transformed to prevent transpiration. [2] Spines also act defense organ against as herbivores.

2. What is the importance of air sacs in pigeons? Write down the role of air bladder in rohu fish maintaining body balance in water.

Part question, Prepare a list of roles air sacks of pigeon play to fly in the air.

Ans. Importance of air sacs in pigeon

Pigeon is a primary volant animal. It has nine nonvascular and non-muscular air sacs, emerging from the bronchioles, typically helping in flight. The importance air sacs in pigeon are-[1] During flight, pigeon needs extra energy, production of which requires additional oxygen. Oxygen concentration near the ground level is higher than that in high sky. Before flight, pigeons fill the air sacs with this oxygen-rich air. When in high sky, these air sacs supply oxygen-rich air to the lungs. [2] The air filled sacs decrease the specific gravity of the body of pegion, which is also beneficial for flight.

Importance of air bladder in rohu fish

[1] Air bladder in rohu fish helps it to move up and down in water. Air bladder changes the buoyancy of the body and thus, assists it to go at different depths of water. [2] The red gland in the anterior chamber of the air bladder fills gas in it to reduce specific gravity of the body and thus helps the fish to move upward in water. On the other hand, rete mirabile of the posterior chamber absorbs the gas to increase the specific gravity of the body of fish and helps the fish to go deeper in the water.

3. Briefly describe the adaptive features of sundari tree.

Ans. Adaptation of sundari tree

Sundari trees grow in saline muddy soil at coastal regions or river delta. This soil is rich in mineral salts. The oxygen content of this saline soil is also very low. Halophytes, like sundari trees, have following adaptations for surviving in this soil.

1. Adaptive changes in roots: [1] To get adequate oxygen from soil for the root system, several lateral branches of roots grow against gravity and emerge vertically above the soil. These aerial roots have numerous pores on the surface to absorb atmospheric oxygen. This type of root is called pneumatophore. [2] Sundari trees have plank-like lateral projections, called root buttresses, extending from the root base to support the tree from all sides to stand on soft soil. This type of roots in sundari trees help the plants to stand erect on muddy soil at the coastal region.
2. Adaptive changes in stem: [1] The surface of stem is coated with thick and waxy cuticle layer. This coating prevents transpiratory water loss through stem surface. [2] For better transportation of water and food, their vascular system is highly developed.
3. Adaptive changes in leaves: [1] Number of stomata is reduced and the existing stomata are sunken to reduce the rate of transpiration. [2] Leaf lamina is covered with waxy substance to prevent transpiration.

(Note: Absorption of water from saline soil is a serious problem for the halophytes. Therefore, these plants show some adaptations for conservation of water like xerophytes.)

4. Mention the physiological adaptations of camel.

Part question, How the special feature of RBC in camels is related to their ability to withstand extreme loss of water? 

Ans. The physiological adaptations of camel

Camel is one of the best-adapted animals in desert environment. The adaptive features of camel with respect to conservation of water and modification of RBC are mentioned below.

1. Adaptive features helping in conservation of water: [1] The hump on the back of camel reserves fat, which is oxidised to produce water and energy during their long walk through desert. [2] Camels discharge highly concentrated urine to conserve water. [3] A camel can drink upto 36 litres of water at a time, which is stored in the water reservoir cells of its stomach. [4] The mucous membrane of the nasal passage absorbs moisture from the air that the camel exhales. [5] Body temperature of camel changes in accordance with the external temperature, which reduces perspiratory water loss, even at a high temperature of 49° celsius.
2. Adaptive modifications of RBC: [1] The RBCs of camel are very small and oval in shape. This modification facilitates the movement of these blood cells through finer blood capillaries even at very low water content in plasma. [2] When plasma contains adequate water, the RBCs of camels can expand up to about 240 times of its normal size, by absorbing water by endosmosis. These cells can withstand a high osmotic pressure and do not rupture even after the intake of huge quantity of water at a time.

5. Why is behaviour important for evolution? Mention three different behaviours of chimpanzees, which help in their adaptation. 

Part question, Give example of ways chimpanzees solve their problems intelligently for procuring food and preventing diseases.

Part question, Explain how do the chimpanzee hunt termites for food. 

Part question, How chimpanzee break open the hard shells for eating the nuts?

Ans. Importance of behaviour in evolution

Organisms show neurally controlled reactions in response to any visual, auditory or olfactory signals or any stimulus, like light, sound, smell or any action by other organisms. These responses are called behaviour. The favourable behaviours which help an organism to survive and propagate on earth, are selected by nature. The effect of these behaviours is so far-reaching that it may help in the course of evolution.

Adaptive behaviours of chimpanzees

Chimpanzees break branches of trees and then eat up the leaves to prepare a stick. With the stick, they make a hole in a termite mound. Then, they insert the thin stick into the mound to tease the termite colony inside it. As soon as the termites grab the probing stick, chimpanzees pull it out and lick them up. Few termites, which come out through the hole are eaten up by other chimpanzees. This particular behavioural adaptation of chimpanzee is known as termite fishing. [2] When a chimpanzee is attacked by parasites, it starts eating medicinal plants. Scientists revealed that chimpanzees can recognise and consume 19 different medicinal plants including Aspilia rudis, when attacked by parasites. [3] To crack hard nutshell, wild chimpanzees use a piece of rock as anvil and a strong branch of tree as hammer. They keep hard-shelled nuts on the rock and then hammer it with the woody branch to crack it. Finally, they remove the shell and eat the nut inside.

6. Describe with diagram how honeybees pass message to other members of the hive about the source of food.

Or, How a worker bee of beehive communicates with other worker bees, regarding source and location of food? 

Ans. Indication of honeybees about the source of food

In a honeycomb, there are two types of worker bees, of which, scouts go in the search of food and foragers fetch nectar. When any scout bee finds a source of food, it returns to its hive and performs a typical pattern of dance in front of the foragers to pass the message. There are two patterns of bee dances, waggle dance and circular dance, which are discussed below.

1. Waggle dance: If the source of food is at a distance of more than 75 metres, scout bees perform a typical dancing flight, known as waggle dance. In this dance, they fly in alternate left and right directions to create an ‘8’ shaped course and at the straight middle portion of the course, jerk the abdomen. An upward flight indicates that the source of food is along the direction of the sun. When the source of food is at opposite direction to the sun, they perform the dancing flight in downward direction. If they get the source at an angle of 30° from the hive, they perform the waggle dance at the same angle with the axis of the hive.
2. Circular dance: When they find the food at a distance within 50-75 metres, the scouts circular dance. As soon as the message is passed to the foragers, they leave the swarm and fly towards the source of food.

Short Answer Type Questions

1. What is adaptation?

Ans. Adaptation is morphological, physiological or behavioural adjustment of an organism to survive in a changing environment. Survival of any organism in a habitat depends upon its perfect adaptation to that environment.

2. What is the objective of adaptation? 1

Ans. The main objective of adaptation of an organism is to survive in a changing environment. The adaptation may be morphological, physiological or behavioural adjustment with its surrounding environment.

3. Adaptation is the change of shape, physiological functions and behaviour of organism’-Justify the statement with the help of any two examples. 

Ans. The canine teeth of carnivorous animals are large and sharp to tear flesh whereas the same are relatively small and blunt in herbivores. This change in shape of the teeth helps the organisms to consume particular types of food.

Kangaroo-rats survive without drinking water for a long time, camels possess some physiological adaptations that allow them to survive long time without drinking water. These are examples of physiological changes which help the animals to adapt in desert environment.

Camouflaging is a behavioural adaptation of certain organisms to hide in any particular environment. So it can be called that adaptation is the change in shape, physiological function and behaviour of organisms.

4. What is acclimatisation?

Ans. The physiological changes occurring in the organisms in accordance with the changes in its environment are collectively called acclimatisation. For example, people living at high altitude, have higher RBC count in blood and greater total lung capacity to acclimatise with low oxygen density in the atmosphere.

5. What is meant by behaviour?

Ans. Behaviour simply refers to the expression of any organism in an environment. It can be defined as the neurally controlled reaction, shown by an organism in response to any environmental signal or any specific stimulus or any action by other organisms.

6. How is behaviour related to the environment?

Ans. Behaviour is related to the environment in the following ways-[1] Every organism coordinates with the environment by its own behaviour. [2] The behaviour of an organism changes in accordance with the change in the environment.

7. What is ethology?

Ans. The branch of science that deals with study of behaviour of different animals, from small insects to large mammals, is called ethology. By studying ethology, one can have the idea on the nature of expression of an animal in response to any external or internal stimulus.

8. Distinguish between adaptation and evolution. 

Ans. The distinguishing features between adaptation and evolution are

Features	Adaptation	Evolution
1. Concept	It is the morphological, physiological and behavioural changes in an organism to adjust with the environment for survival	Evolution is the change in the heritable characteristics of biological population over successive generations
2. Change in time	It is a short-term change	It is a slow and prolonged process and cause long-term change
3. Interrelation	Adaptation is one of the main causes of evolution	Combination of several adaptations, when selected by nature, results into evolution of a new species

9. What is the relation between behaviour and evolution?

Ans. Behaviour of any organism helps it to survive and propagate in nature. As the environment changes, the organisms also change their behaviour to adapt in it. If these changes are selected by nature and propagate to the next progeny for several generations, new species evolves that possesses this changed behaviour.

10. Define morphological adaptation and give an example.

Ans. The permanent and beneficial physical changes, occurring either internally or externally in the body of an organism to help it survive in a changing environment, are called morphological adaptation. Example-Modification of leaves of cactus into spines is an example of morphological adaptation.

11. What is meant by xerophytic adaptation?

Ans. The morphological and physiological changes, which occur in plants to befit them in arid environment, are collectively known as xerophytic adaptation. This adaptation is seen in the desert plants, like cactus, babul, Aloe vera etc.

12. Which plants are called xerophytes?

Ans. The plants, which are adapted to survive in physically dry soil and in the atmosphere with very low moisture content, are known as xerophytes. Example-Cactus, Asparagus, babul, etc.

13. Which adaptive features are seen in cactus to reduce water loss due to transpiration? 

Ans. To reduce water loss by transpiration, following adaptations are seen in cactus-[1] Size and number of leaves reduce. Sunken stomata are present in leaves. [2] In some cacti, leaves are modified into spines to reduce the rate of transpiration. [3] The phylloclade is covered with cuticle to seal stomata thus preventing water loss.

14. Which morphological structures modify into spines of cactus and thorns of wood apple?

Ans. Spines of cactus are the modification of leaves. On the other hand, thorns of wood apple are modified form of axillary buds.

15. Who are the primary aquatic animals?

Ans. The aquatic animals, which have evolved from aquatic ancestors, are called primary aquatic animals. Example-Generally all fishes are primary aquatic animals.

16. Who are called secondary aquatic animals?

Ans. Certain animals which had terrestrial ancestors but have adapted themselves to aquatic life for certain reasons, are called secondary aquatic animals. Example-Whale, sea cow, etc.

17. Mention two aquatic adaptations of fishes.

Ans. Two aquatic adaptations of fishes are as follows-[1] Fishes have air bladder to move in different depths of water. [2] To swim in different directions and maintain balance in water, fishes have different types of fins.

18. What are the roles of swim bladder in the aquatic adaptation of rohu fish?

Ans. The swim bladder or air bladder in fish is a gas-filled internal organ and acts as a hydrostatic organ. It can increase or decrease the buoyancy of a fish by respectively increasing or decreasing the volume of gas within it. Thus, an air bladder helps a fish to go upto different depths of water without floating upward or sinking downwards.

19. What is rete mirabile?

Ans. Rete mirabile is a network of blood capillaries in the posterior chamber of the air bladder of fish. It absorbs gas from air bladder to increase specific gravity of the body of a fish and helps it to go deeper in water.

20. What problems a fish would have faced, if it lacked spindle-shaped body and lateral line lateral line sense organ? 

Ans. If a fish lacked a spindle-shaped body, it would have faced more physical resistance while swimming. If there had been no lateral line sense organ, a fish could not have felt pressure, temperature and depth of water.

21. Who are called primary volant animals?

Ans. The animals, adapted to aerial life, which have descended from flying ancestors, are called primary volant animals. Example-Pigeon, bat, etc.

22. Who are called secondary volant animals?

Ans. There are certain volant animals, which have evolved from non-flying ancestors. These animals are called secondary volant animals. ExampleFlying fish, flying squirrel, etc.

23. How is the body shape of a pigeon modified for flying?

Ans. For a flying bird like pigeon, an aerodynamic body shape is needed. This body shape helps to overcome air-resistance during fast flight. Hence to overcome the air-resistance, the body of a pigeon has become spindle-shaped.

24. Mention the roles of air sacs in volant adaptation of pigeon.

Or, What are the two adaptive significances of air sacks of pigeon? 

Ans. The roles of air sacs in volant adaptation of pigeon are-[1] Pigeon is a volant animal; hence it needs more supply of oxygen to generate extra energy during its flight. The air sacs, attached to its lungs, supply extra oxygen and therefore this process enhances the ability of the lungs. [2] These air sacs hold air to reduce the specific gravity of its body during flight.

25. What will happen to a pigeon if its air sacs become inactive?

Ans. If a pigeon has inactive air sacs, it will face the following problems-[1] Body weight will increase and double respiration will not occur. [2] Body balance and centre of gravity of body will get disrupted during flight. [3] It will not be able to collect highly oxygenated air from ground level to use it during high flight.

26. Which organs have disappeared from pigeon’s body to make it lighter?

Ans. For flying, an animal always requires a lighter body. So to make the body of pigeon lighter, certain organs have disappeared. These organs are teeth, gall bladder, rectum, right ovary and fallopian tube in female and penis in male.

27. Define physiological adaptation and give example.

Ans. The permanent and beneficial changes in various physiological activities of an organism to facilitate its survival in a changing environment, is called physiological adaptation.

Example-Development of pneumatophores in sundari tree is an example of physiological adaptation.

28. Which plants are called halophytes?

Ans. The plants, growing in the saline soil of the coastal areas or delta regions, are called halophytes. Example-Sundari, garan, hetal, etc.

29. Mention two adaptive features of sundari tree.

Ans. Two main adaptive features of sundari tree are-[1] Presence of specialised root structures known as pneumatophores. [2] Thick layer of cuticle on stem surface and leaves with fewer stomata to minimise water loss.

30. How sundari plant excretes the excess salt of its body?

Similar question, Mention one adaptation of sundari plant for salt tolerance.

Or, Describe any two adaptations in sundari plant for tolerance of salt. 

Ans. The mechanisms used by sundari plant to excrete the excess salt from its body are[1] presence of salt gland in leaf to excrete excess salt along with water, [2] deposition of excess salt in specialized cells of bark and root; later, by means of bark exfoliation and other specific mechamisms, the salt are eliminated from the plant body, [3] deposition of salt in mature leaves, in larger amount, so that it can be eliminated easily by leaf exfoliation, [4] deposition of excess salt in the cell sap of vacuoles and eliminate it when needed.

31. What are pneumatophores?

Ans. Halophytes, like sundari, garan, etc., grow in highly saline and muddy soil with low very oxygen content. To get adequate oxygen for the root system, some lateral branches of their roots grow against gravity and emerge vertically above the soil. These aerial roots have numerous pores on the surface to absorb atmospheric oxygen and such roots are known as pneumatophores or breathing roots.

32. How do pneumatophores help sundari trees to adapt in saline soil?

Ans. Sundari trees grow in highly saline muddy coastal soil. This type of soil has very low oxygen content and water logging during high tide is very common in this region. Therefore, the root system does not get enough oxygen. Pneumatophores are aerial roots which are negatively geotropic, thus help sundari trees to absorb aerial oxygen for the root system and help these plants to survive in the low oxygen-containing saline soil.

33. What is meant by viviparous germination?

Ans. The process of seed germination where the seed germinates within fruit while it is still attached with the plant is known as viviparous germination. Saline soil is not conducive for germination of seeds. To overcome this obstacle, viviparous germination occurs in some halophytes, like garan, Rhizophora, etc.

34. What is the advantage of viviparous germination?

Ans. In viviparous germination, seed germinates within the fruit and the radicle comes out of it as a pointed dagger-shaped structure even before its shedding from the tree. As it grows some inches long, the fruit drops from the branch and the pointed tip of the radicle penetrates the soft soil keeping the developing embryo above the saline soil. Thus, viviparous germination protects the developing embryo from hostile environment.

35. Why sundari tree is called ‘looking glass tree’?

Ans. The leaves of sundari trees are covered with a thick cuticle layer and a thin and smooth layer of wax coating. Besides, the lower surface of the leaves have numerous glossy silvery hairs. When sunlight reflects from these leaf surfaces, it gives a beautiful glassy look, hence sundari tree is called ‘looking glass tree!

36. What are root buttresses? 

Ans. Root buttresses are the plank-like lateral projections extending from the root base to support a tree from all sides to stand on soft soil. This type of root in trees, like sundari, helps it to stand erect on muddy soil at the delta region.

37. Mention two adaptive features of camel.

Ans. Two adaptive features of camel are-[1] A hump, containing fat, is present on its back. [2] RBCs are nucleated, small in size and oval in shape.

38. Mention two adaptations of camels in conserving water.

Ans. To conserve water, camels have the following adaptive features-[1] Camels eliminate highly concentrated urine. [2] Mucous membrane of the inner lining of the nasal passage of camels effectively absorbs moisture from the air that the camels exhale.

39. Why erythrocytes of camels do not burst due to a huge intake of water after a prolonged thirst?

Ans. The erythrocytes of camels are oval in shape. Each of these red blood cells has a unique ability to expand about 240 times of its normal size. Therefore, these cells can withstand a very high osmotic pressure. Because of this, they do not burst even after a huge intake of water to quench a prolonged thirst. This is a physiological adaptation found in camels to survive in xeric habitat.

40. Define behavioural adaptation and give an example.

Ans. The behavioural changes of any organism, which help them to survive and better adapt to the environment, are collectively known as behavioural adaptation.

Example-Termite fishing, from termite mounds with thin sticks, made from twig, is an example of behavioural adaptation of chimpanzees.

41. What information on chimpanzees were obtained from the research of Jane Goodall?

Ans. The research on chimpanzees by Jane Goodall revealed that wild chimpanzees show several human-like behaviours. She found that chimpanzees collect termites from termite mounds using thin sticks. She also noticed that these wild animals consume medicinal plants, when they are infected by parasites.

42. How do wild chimpanzees break hard nutshells?

Ans. Wild chimpanzees use a piece of rock as anvil and a strong branch of tree as hammer. They keep hard-shelled nuts on the rock and hammer it with the woody tree branch to crack the hard nutshell.

43. What was Karl Von Frisch famous for? 

Ans. German scientist, Karl Von Frisch was famous for his studies of communication among honeybees. He was the first to interpret the signals given by scout honeybees to foragers of the hive by performing typical dancing flights to indicate the distance and the direction of the source of food.

44. What information do the scout honeybees pass to the forager bees of the hive by performing a typical bee dance?

Ans. By performing a typical bee dance, scout honeybees inform forager bees about the distance and direction of the source of food. The dancing pattern even indicates the angle of food source with the sun.

Very Short Answer Type Questions

Multiple Choice Questions & Answers [MCQ]

1. The survival strategy of living organisms is-

A. Adaptation

B. Reproduction

C. Heredity

D. Mutation

Ans. A

2. When attacked by parasites, which of the following animals eats medicinal plant Aspilia rudis to get rid of it?

A. Fish

B. Chimpanzee

C. Camel

D. Tiger

Ans. B

3. The neurally controlled reaction, shown by an organism in response to any environmental signal is-

A. Reproduction

B. Evolution

C. Migration

D. Behaviour

Ans. D

4. Which of the following helps an animal to survive and reproduce?

A. Migration

B. Evolution

C. Mutation

D. Adaptation

Ans. D

5. The structural, behavioural and physiological change of an organism in course of evolution is called –

A. Mutation

B. Adjustment

C. Adaptation

D. Accommodation

Ans. C

6. An example of morphological adaptation is-

A. Production of sweat to cool the body

B. Air sacks of pigeon

C. Hibernation in frog

D. Camel reserve fat in hump

Ans. B

7. A physiological adaptation is –

A. Air sacks of pigeon

B. Pneumatophore of sundari tree

C. Air bladder of rohu fish

D. Thorn of cactus

Ans. B

8. The process by which an organism can adjust with the changing environment, is known as-

A. Adaptation

B. Evolution

C. Mutation

D. Variation

Ans. A

9. The stem of cactus is called-

A. Rhizome

B. Phylloclade

C. Phyllode

D. Underground stem

Ans. B

10. The plants growing in desert are known as –

A. Xerophytes

B. Hydrophytes

C. Epiphytes

D. Mesophytes

Ans. A

11. Pneumatophores or breathing roots are seen in-

A. Sundari (Heritiera sp.) tree

B. Cactus

C. Pea plant

D. Date palm tree

Ans. A

12. In fish, the organ, that helps it to move in different depths of water is –

A. Air bladder

B. Fins

C. Scales

D. Tail

Ans. A

13. The lung-activity of pigeons is increased by –

A. Keel bone

B. Feather

C. Air sacs

D. Tail

Ans. C

14. Which is not a water conserving adaptation of camels?

A. Scanty sweating

B. Concentrated urination

C. Consumption of medicinal plants

D. Water storage cells in stomach

Ans. C

15. The animal having nucleus in RBC is-

A. Camel

B. Bird

C. Man

D. Mice

Ans. A

16. Myotome muscles are present in-

A. Human

B. Snake

C. Fish

D. Pigeon

Ans. C

17. Air sacks are present in –

A. Seals

B. Pigeons

C. Dolphins

D. Whales

Ans. B

18. ‘Waggle’ means-

A. Wobble/Shake

B. Circle

C. Angle

D. Swim

Ans. A

19. Which of the following is not a flight muscle of pigeon?

A. Pectoralis major

B. Pectoralis minor

C. Myotome

D. Coracobrachialis

Ans. C

20. Which of the following plants is not a halophyte?

A. Sundari (Heritiera sp.) tree

B. Cactus

C. Garan tree

D. Geona tree

Ans. B

21. The organs that help fishes in aquatic locomotion are-

A. Lateral line sense organ

B. Gills

C. Venous heart

D. Fins

Ans. D

22. The materials, which are difficult for the plants to collect from physiologically dry soil, are-

A. CO₂ and water

B. Minerals and water

C. Water and O₂

D. CO₂ and minerals

Ans. C

23. Identify the animal who communicates information with other members of its own group through specific dancing pattern regarding the sources of food. 

A. Chimpanzee

B. Cockroach

C. Peacock

D. Honey bee

Ans. D

24. Which of the following takes part in waggle dance?

A. Queen bee

B. Worker bees

C. Drones

D. King bee

Ans. B

25. Decide for which of the following purpose bees demonstrate waggle dance-

A. Search for reproductive mates

B. Inform other worker bees about the direction and the distance of the source of food from the bee hive

C. Selecting place for the construction of the new bee hive

D. Avoid attack by probable enemy

Ans. B

26. To indicate a distant source of nectar, bees perform-

A. Angular dance

B. Square dance

C. Waggle dance

D. Rotation dance

Ans. C

27. The plant, which is adapted to physiologically dry soil, is-

A. Cactus

B. Lotus

C. Sundari

D. Pine

Ans. C

28. The skin of the animals living in desert area is-

A. Very thin

B. Thin

C. Moderately thick

D. Very thick

Ans. D

29. The sole of foot is padded with thick, soft muscle in-

A. Camel

B. Horse

C. Buffalo

D. Donkey

Ans. A

30. The animal, having eyelids lined by long eyelashes, is-

A. Dog

B. Cat

C. Camel

D. Fox

Ans. C

31. This animal which has water-conserving system in the body, is-

A. Cow

B. Horse

C. Camel

D. Chimpanzee

Ans. C

32. The main hydrostatic organ of fish is-

A. Fin

B. Lateral line sense organ

C. Operculum

D. Air bladder

Ans. D

33. Which of the following absorbes the gas of swim bladder of bony fishes?

A. Red gland

B. Anterior chamber

C. Gastric gland

D. Rete mirabile

Ans. D

Answer in a single word or sentence

1. To which group of plants does cactus belong?

Ans. Xerophytes

2. Why do the leaves of cactus modify into spines?

Ans. To prevent excess water loss by transpiration

3. Mention one morphological adaptation of cactus to prevent transpiration.

Ans. The modification of leaves of cactus into spine

4. In which plant do you find phylloclade?

Ans. In cactus, like Opuntia

5. The leaves of cactus modify into spines. In that case, which organ organ helps it in photosynthesis?

Ans. The green, thick and succulent stem of cactus helps in photosynthesis.

6. Which part of cactus grows elaborately to absorb water?

Ans. Root

7. What do you call the changes that occur in organisms to adjust themselves to the changing environment?

Ans. Adaptations

8. What do you call the adaptation that occurs in organisms to adapt themselves in the environment of their origin? 

Ans. Primary adaptation

9. What do you call the adaptation that occurs in organisms to adapt themselves in the environment other than their site of origin?

Ans. Secondary adaptation

10. What do you call the two separate types of adaptations that occur in organisms living in two different environments?

Ans. Dual adaptation

11. Who carried out extensive research on honeybees to find out their language?

Ans. Karl Von Frisch

12. Which behavioural scientist was the first to carry out long research on behaviour of wild chimpanzees?

Ans. Jane Goodall

13. How many air sacs are associated with the lungs of pigeon?

Ans. Nine

14. Mention one adaptive feature of sundari (Heritiera) tree or halophytic plants.

Ans. Presence of pneumatophores

15. Name two plants with pneumatophores.

Ans. Sundari and garan

16. Name an animal with primary aquatic adaptation.

Ans. Fish

17. Name an animal with secondary aquatic adaptation.

Ans. Whale

18. Which fin of a fish helps to change its direction?

Ans. Tail fin

19. Name an aquatic mammal.

Ans. Whale

20. Name an animal with primary volant adaptation.

Ans. Pigeon

21. Name an animal with secondary volant adaptation.

Ans. Flying squirrel

22. How many paired and unpaired air sacs are present in pigeon?

Ans. A pigeon has 4 paired and 1 unpaired air sacs.

23. Which animal can absorb water with its skin?

Ans. A desert lizard, named Moloch horridus

24. Name a desert mammal.

Ans. Camel

25. Which animals use thin sticks to collect termites from termite mounds?

Ans. Chimpanzees

26. Which chemical plays an important role in controlling the behaviour of honeybees?

Ans. Pheromones

26. Which type of dance do honeybees perform to indicate a source of food at a distance between 50-75 metres?

Ans. Circular dance

28. Which type of dance do honeybees perform to indicate a source of food at a distance of more than 75 metres?

Ans. Waggle dance

29. In which year did Karl Von Frisch receive the Nobel prize for discovering the language of bee dance?

Ans. 1973

30. How does the course of waggle dance of honeybees appear?

Ans. The course of waggle dance of honeybees appears like the English numerical ‘8’

31. Why do honeybees perform waggle dance?

Ans. Honeybees perform waggle dance to inform other members of the hive about the distance (more than 75 metres) and direction of the source of food, i.e., nectar.

32. Name a plant with root buttresses.

Ans. Sundari (Heritiera fomes)

33. Which portion of the body of a fish possesses the air bladder?

Ans. A fish possesses an air bladder at the upper portion of the abdominal cavity in between intestine and kidneys.

34. Which animal discharges concentrated urine to conserve body fluid?

Ans. Camel

35. What is the utility of the oval RBCs in camels?

Ans. Oval RBCs of camels can move through fine blood capillaries even with very low water content in plasma.

36. What is pneumathode?

Ans. The pore on the pneumatophores of halophytes, through which it absorbs oxygen, is called pneumathode.

37. To break the nutshells, chimpanzees use hammer and anvil. What do they use as anvil?

Ans. Rock platform

38. Name a plant with stilt roots.

Ans. Sundari

39. What is phylloclade?

Ans. Flattend, thick, green, fleshy, photosynthetic stem of cactus is called phylloclade.

40. Which portion of air bladder produce gas?

Ans. Red gland

Fill in the blanks

1. The leaves of cactus are modified into ………. 

Ans. Spines

2. In spite of being a halophyte, ……….. trees do not show viviparous germination.

Ans. Sundari

3. Presence of ……….. in the eyes of pigeon provides it a sharper vision.

Ans. Pectin

4. Sundari is a perennial ………..

Ans. Halophyte

5. Cacti grow in desert land, therefore, these are called ………. plants.

Ans. Xerophytic

6. The body cells of ……….. contain mucilage, hence these plants are capable of conserving excess water.

Ans. Cactus

7. The animals, which inhabit in aquatic environment since their origin are called ………. aquatic animals.

Ans. Primary

8. The animals which possess adaptive features to perform aerial movement are called ………… animals.

Ans. Volant

9. Certain animals can fly for a brief period. These animals are called ………. volant animals.

Ans. Secondary

10. While flying, the ………. -shaped body of pigeon facilitates it to overcome aerial resistance.

Ans. Spindle

11. The ‘V’ shaped muscles at two lateral sides of the body help fishes in swimming.

Ans. Myotome

12. The air bladder of rohu fish is an example of ……….. adaptation.

Ans. Morphological

13. While flying, the ……….. of pigeon help to supply extra energy. 

Ans. Air sacs

14. Excessive saline soil of coastal area is called ………. dry soil.

Ans. Physiologically

15. Bee dance is performed only by the ………. bees.

Ans. Worker

16. The ……….. of sundari trees help it in absorbing atmospheric oxygen for respiration.  

Ans. Pneumatophores

17. The red blood cells of camel can expand upto ………. times of their normal size.

Ans. 240