Biology For Class X - Chapter No. 7 - Man And His Environment - Review Exercise From Text Book

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CHAPTER 7: MAN AND HIS ENVIRONMENT
Review Exercise From Text Book

By Mrs. Ayesha Arif
Vice Principal
(Jauhar Progressive School)

A. MULTIPLE CHOICE QUESTIONS

Choose the correct answer:
1. The life sustaining envelop of earth is:
(a) Biomass
(b) Biomes
(c) Biosphere ✓
(d) Atmosphere

2. The group of organisms belong to the same species live in a particular area called:
(a) Community
(b) Species
(c) Genes
(d) Population ✓

3. An area where community interacts with non-living environment is called:
(a) Community
(b) Ecology
(c) Ecosystem ✓
(d) Biome

4. Any biological region recognized by its climate or vegetation is called:
(a) Ecosystem
(b) Biomes ✓
(c) Biosphere
(d) Biomass

5. The transfer of food material from producers through some organisms with repeated eating and being eaten is called:
(a) Food pyramid
(b) Food chain ✓
(c) Food web
(d) Ecological pyramid

6. The elements in ecosystem recycle through organisms with environment is called:
(a) Food chain
(b) Food web
(c) Chemical cycle
(d) Biogeochemical ✓

7. Process where nitrogenous compound of living organism convert into nitrates is called:
(a) Ammonification
(b) Nitrification ✓
(c) Denitrification
(d) Deamination

8. The cold war between the organisms of a community occupying the same habitat is called:
(a) Predation
(b) Competition ✓
(c) Mutualism
(d) Commensalism

9. The association between two different types of organism which get benefit to each other, cannot live without each other is called:
(a) Parasitism
(b) Commensalism
(c) Mutualism ✓
(d) Predation

10. The amount of solid waste or concentration of gases other than oxygen increase in atmosphere is called:
(a) Air pollution ✓
(b) Ozone depletion
(c) Acid rain
(d) Greenhouse effect

B. SHORT QUESTIONS

i) What is the effect of light on ecosystem?
Ans: LIGHT:
Light is the most vital factor, without it life can not exist. It is a source of energy for every ecosystem.
Plants convert light energy into chemical energy by the process of photosynthesis. This chemical energy is stored in the form of food which is needed by every living things.

Effect Of Light On Organism:
Light influence the ecosystem in many ways, directly or indirectly. Distribution of plants and animals is affected by:

1. The type Or the quality (wavelength)
2. Intensity of light,
3. Exposure time or duration of light (photoperiod)

1. Quality Or Type of Light:

• A small amount of light is utilized for photosynthesis i.e. out of seven colours of visible light, chlorophyll absorbs only red and blue light.
• Ultraviolet rays of light is harmful for life.
• Most of the light reaching the earth is converted to heat and thus it maintains the temperature of the earth and atmosphere in the ecosystem.

2. Intensity of Light:

• Intensity of light controls plants growth. 
• It may destroy the chlorophyll.
• It also affects opening and closing of the stomata, permeability of the cell membrane, height and surface area of plant etc.
• In animals light affects development of pigments.

2. Exposure time of light (Photoperiod):

• Light is also necessary for vision.
• Duration of light (photoperiod) affects starts of certain biological processes e.g. flowering of certain plants, leaf fall and other aspects of plant growth.
• In animals biological rhythms such as reproductive cycles, sleep cycles, hibernation, migration, are affected by light duration.
• Making Vitamin D in human being.

ii) Which one is the first trophic level of ecosystem and how?
Ans: FIRST TROPHIC LEVEL OF ECOSYSTEM OR PRODUCER:
Producers always occupy the first trophic level in any food chain because only producers have the ability to trap and convert solar energy (sunlight) with the help of chlorophyll into food molecules by the process of photosynthesis.

• The producers produce food for themselves and other organisms of ecosystem.
• They are primary source of energy for other organisms.
• All members of community depend, directly or indirectly on the producers for their food and energy.
• Producers utilize a part of their food while consumers and decomposers utilize the remaining food.
• Example:
  Green plants and algae are the major producers. Some types of photosynthetic bacteria are also producers.

iii) Define nitrogen cycle? What do we mean by nitrogen fixation and how it occurs in an ecosystem?
Ans: NITROGEN CYCLE:
Definition:
"The exchange of nitrogen between soil and atmosphere and its circulation through bodies of living organisms takes place through interrelated processes known as nitrogen cycle."
This cycle consist of three steps:

1. Nitrogen fixation
2. Nitrification
3. Denitrification

NITROGEN FIXATION:

"Conversion of atmospheric free nitrogen gas into soluble nitrogen compounds (nitrates) is called nitrogen fixation."

Nitrogen Fixation Occurs In Ecosystem:
Following are the sources of nitrogen fixation:

1. Nitrogen Fixation by Thunderstorm:
   The atmospheric Nitrogen combines with oxygen during lightning to make certain compound which ultimately form nitrates and reach to soil by rain water.
   
   
2. Nitrogen Fixation by Living Organism (Nitrogen Fixing Bacteria):
   The second source to fix atmospheric Nitrogen are three types of bacteria.
   * The first group lives in water are called cyanobacteria. They are photosynthetic.
   * Second group lives in soil.
   * Third group of bacteria lives in the roots of certain leguminous plants.
   These bacteria which help in nitrogen fixation are called nitrogen fixing bacteria.

iv) What is interaction?
Ans: INTERACTION OR RELATIONSHIP IN THE ECOSYSTEM:
In an ecosystem the living organisms develop number of relationship according to their needs. They not only interact with their physical environment but also with each other i.e. the herbivores develop their relation with producers, in the same manner carnivores depend on herbivores for their food. These association maintain balance in growth and population. Such interactions take place between the two organisms by permanent or temporary association. It may be beneficial or harmful.
Positive Interactions:
Such interaction may be beneficial for only one without harming the other or for both the associates.
Negative Interactions:
Such interaction may be beneficial to one and harmful to the other.

TYPES OR RELATIONSHIP:
Some types of relationships are:

• Competition
• Predation
• Symbiosis

v) What is pyramid of number?
Ans: PYRAMID OF NUMBERS:
The pyramid of numbers was advanced by Charles Elton in 1927. It is define as:

"Graphical representation of members of population in an area at different in trophic level is called pyramid of number."

It is an upright pyramid in an ecosystem. When number of organisms is counted at each level, it is observed that the producers are always more in number than other trophic levels and vice versa.

For example:

• The grasses sit at the lowest trophic level or the base of the number pyramid because of their abundance.
• The primary consumer, such as a grasshopper, occupies the next higher trophic level. Grasshoppers are fewer in number than grass.
• The next trophic level is a primary carnivore, such as mice. There are fewer mice than grasshoppers because they consume grasshoppers.
• Secondary carnivores, such as snakes, occupy the next higher trophic level and feed on mice.
• Subsequently snakes are eaten by hawks, which occupy the highest trophic level and are least in number.
• This relationship is also expressed in the form of pyramid known as pyramid of number.

OR

vi) What is greenhouse effect?
Ans: GREEN HOUSE EFFECT OR GLOBAL WARMING:
Due to excessive burning of fossil fuels, CO₂ and methane are produced which are generally called greenhouse gases.
These gases, if produced in high quantity in atmosphere, they will accumulate below the ozone layer, which do not allow heat energy of sun to reflect back in space. As a result, heat remains with in the earth’s atmosphere and increases the temperature. This phenomenon is called global warming or greenhouse effect.
Effects: The possible effects of global warming are:

• Due to global warming more evaporation of H₂O which ultimately reach to high rainfall.
• Melting of the polar ice and glaciers at high rate, rises the sea level and ultimately reach to flood.
• Warming of atmosphere can cause heavy rains and strong hurricanes and storms.

vii) What is algal bloom and how it destroy the life of an aquatic ecosystem?
Ans: EUTROPHICATION OR ALGAL BLOOM:

"Growth of algae with very high rate due to increase in phosphorous and nitrogen compounds is called algal bloom or eutrophication."

Sewage water and agricultural field run off poses rich quantity of phosphorus and nitrogen containing compounds such as detergents. They accumulate in water reservoirs and promote algal growth upto dangerous level i.e. algal bloom.
Effects Of Algal Bloom On Aquatic life:
Algal bloom when floats on water surface:

• They spoil fishing, swimming and recreational qualities of water.
• These algal species when die not only add more organic matter to water but sometimes release toxins which have lethal effect to various organisms.
• The excessive growth of other decomposers also use the excessive oxygen present in water which leads to the death of fishes and other organisms due to deficiency of oxygen.
• It also reduces the light reaching to lower layer of water.

viii) What measure can be taken to control water pollution?
Ans: CONTROL OF WATER POLLUTION:

• Public awareness at all levels is important. It should be through social media, political leaders, institution from pre-primary level.
• Strict legislation and implementation is required on sewage treatment and industrial recycling processes.
• No industrial and agricultural waste should be added to water bodies before complete treatment.

ix) Write down the name of some endangered mammals of Pakistan.
Ans: ENDANGERED MAMMALS OF PAKISTAN:

• Punjab Urial
• Markhor
• Snow Leopard
• Asia snadspit green turtle
• Indus river dolphin
• Bear of Deosai

x) Draw the diagram of nitrogen cycle.

xi) Write down the name of some endangered birds of Pakistan.
Ans: ENDANGERED BIRDS OF PAKISTAN:

• Siberian Crane
• Falcon
• Cheer Pheasant
• Chacor
• Long Billed Vulture
• Red Avadavar

xii) Illustrate acid rain and its effect?
Ans: ACID RAIN:
Due to urbanization and industrialization more fuel burn, more acids are used in industries, as a result of these consumptions more CO₂, SO₂, NO₂ are liberated in air from their chimneys. When rain falls through these polluted air H₂O react with these gases in air and produce carbonic acid, sulphuric acid and nitric acid respectively. These acids remain as vapours and condense into liquid when temperature falls. Such rain is called acid rain.
Effect:
The acid destroy soil, microorganisms of soil, skin of animals, building material.

xiv) What is meant by ozone layer and depletion of ozone layer?
Ans: OZONE LAYER:
In upper atmosphere a protective layer of ozone (O₃) gas is present which is very important for us because it checks the ultraviolet radiations from sun which are lethal for living organisms. This layer is called ozone layer.

DEPLETION OF OZONE LAYER:
Scientist have found ozone layer is gradually depleting (getting thin) due to chlorofluorocarbon (CFC), as they react with ozone and convert it into O₂. This process is called depletion of ozone layer.
Cause: The CFC used as propellant in pressurized aerosol, foaming agent, refrigerators etc. Each one atom of chlorine converts more than 100000 molecules of ozone O₃ to Oxygen O₂.

xv) Draw diagram for sewage treatment?
Ans: SEWAGE TREATMENT:

C. EXTENSIVE RESPONSE QUESTIONS:

i. Describe biotic factors of an ecosystem.
Ans: BIOTIC COMPONENTS OF AN ECOSYSTEM:
The living organisms which interact in an ecosystem are called biotic component.
These living components include:

• Producers
• Consumers of all types and
• Decomposers.

1. Producers:
Producers always occupy the first trophic level in any food chain because only producers have the ability to trap and convert solar energy (sunlight) with the help of chlorophyll into food molecules by the process of photosynthesis.

• The producers produce food for themselves and other organisms of ecosystem.
• They are primary source of energy for other organisms.
• All members of community depend, directly or indirectly on the producers for their food and energy.
• Producers utilize a part of their food while consumers and decomposers utilize the remaining food.
• Example:
  Green plants and algae are the major producers. Some types of photosynthetic bacteria are also producers.

2. Consumers:
Animals and all other organisms which cannot make their own food are called consumers. They get energy and food from producers directly or indirectly.
Types Of Consumers:
On the basis of feeding level (trophic) mainly consumers are of three types:

1. Primary consumers:
   The consumers which directly feed on producers i.e. get energy and food directly from producers are called Primary consumers. They are basically herbivores.
   Example: A grasshopper or caterpillar feeding on leaves of plants are primary consumers.
   
   
2. Secondary consumers:
   The type of consumers which feed on primary consumers i.e. get energy and food from primary consumers are called secondary consumers. They are basically carnivores.
   Example: A bird is a secondary consumer gets its energy and food when it eats grasshopper or caterpillar.
   
   
3. Tertiary consumers:
   The organisms which eats the secondary consumers to get energy and food are called tertiary consumers and they are carnivores.
   Example: An eagle which eat the small bird, which has already eaten grasshopper.

3. Decomposers:
Microorganisms which break down complex food molecules of dead organisms are called decomposers.

• They recycle the nutrients because they return it by decomposing and converting the complex organic molecules into simple inorganic molecules.
• Example: They are generally bacteria and fungi.

ii. Describe nitrogen cycle as biochemical cycle in detail?
Ans: NITROGEN CYCLE:
Nitrogen is one of the important constituent of protein and DNA. It is therefore, an essential element in the structure of all living things. Plant use atmospheric nitrogen in the form of nitrates. Thus,
"The exchange of nitrogen between soil and atmosphere and its circulation through bodies of living organisms takes place through interrelated processes known as nitrogen cycle."
This cycle consist of three steps:

1. Nitrogen fixation
2. Nitrification
3. Denitrification

NITROGEN FIXATION:

"Conversion of atmospheric free nitrogen gas into soluble nitrogen compounds (nitrates) is called nitrogen fixation."

Nitrogen Fixation Occurs In Ecosystem:
The atmosphere contains about 78 percent nitrogen gas. It is an inert gas and the organisms cannot use it directly. Therefore, nitrogen is first changed to soluble nitrogen compounds such as nitrates (NO₃) which the plants can absorb from the soil.
Source of Nitrates: The following are the sources of nitrates for living organisms:

1. Nitrogen Fixation by Thunderstorm:
   The atmospheric Nitrogen combines with oxygen during lightning to make certain compound which ultimately form nitrates and reach to soil by rain water.
   
   
2. Nitrogen Fixation by Living Organism (Nitrogen Fixing Bacteria):
   The second source to fix atmospheric Nitrogen are three types of bacteria.
   * The first group lives in water are called cyanobacteria. They are photosynthetic.
   * Second group lives in soil.
   * Third group of bacteria lives in the roots of certain leguminous plants.
   These bacteria which help in nitrogen fixation are called nitrogen fixing bacteria.

NITRIFICATION:
Process where nitrogenous compounds of living organisms converts into nitrates is called Nitrification.
It is also performed by microorganisms who live in soil. These nitrates are reabsorbed by plants and the nitrogen cycle starts again. Protein of dead animals and plants, the excretory waste like ammonia, urea, uric acid are all nitrogenous wastes which are decomposed and the nitrates are recycled.

DENITRIFICATION:
The process of converting nitrogenous compounds into free nitrogen is called denitrification.

• It takes place by special bacteria which lives in anaerobic condition of soil. These bacteria called denitrifying bacteria.
• These bacteria breaks ammonia and nitrates back into free nitrogen, which is released in air so as to complete the cycle and to keep the nitrogen balance in nature.

iii What is pollution? Describe different types of hazardous effects caused by air pollution.
Ans: POLLUTION:
Literally pollution means "destruction of purity."
Scientifically pollution may be define as:

"Any undesirable change in the physical, chemical or biological characteristics of environment (air, land, water and soil), which may or will harmfully affect human life, plants, animals or industrial processes, living conditions and cultural assets."

CLASSIFICATION OF POLLUTION:
Pollution is classified into two categories:
i) Material Pollution:
where some material or substance become excessive in environment; like air, water or soil pollution.

ii) Non-Material Pollution:
where material does not increase but environment disturb or become unbearable to live, i.e. noise, heat or radiation pollution.

AIR POLLUTION:
When amount of solid waste or concentration of gases other than oxygen increases in atmosphere it is called air or atmospheric pollution.

Hazardous Effects Caused By Air Pollution:
Industrial machines produce smoke, carbon monoxide (CO), carbon dioxide (CO₂), sulphur oxide (SO₂), nitrogen oxide (NO₂), chlorofluorocarbon (CFC) etc. Due to industrial toxic waste photochemical haze produces, as a result:

• Acid rain occur.
• Greenhouse effects or global warming take place.
• Ozone depletion occurs.

1. Acid Rain:
Due to urbanization and industrialization more fuel burn, more acids are used in industries, as a result of these consumptions more CO₂, SO₂, NO₂ are liberated in air from their chimneys. When rain falls through these polluted air H₂O react with these gases in air and produce carbonic acid, sulphuric acid and nitric acid respectively. These acids remain as vapours and condense into liquid when temperature falls. Such rain is called acid rain.
Effect:
The acid destroy soil, microorganisms of soil, skin of animals, building material.

2. Global Warming Or Greenhouse Effect:
Due to excessive burning of fossil fuels, CO₂ and methane are produced which are generally called greenhouse gases.
These gases, if produced in high quantity in atmosphere, they will accumulate below the ozone layer, which do not allow heat energy of sun to reflect back in space. As a result, heat remains with in the earth’s atmosphere and increases the temperature. This phenomenon is called global warming or greenhouse effect.
Effects: The possible effects of global warming are:

• Due to global warming more evaporation of H₂O which ultimately reach to high rainfall.
• Melting of the polar ice and glaciers at high rate, rises the sea level and ultimately reach to flood.
• Warming of atmosphere can cause heavy rains and strong hurricanes and storms.

DEPLETION OF OZONE LAYER:
Scientist have found ozone layer is gradually depleting (getting thin) due to chlorofluorocarbon (CFC), as they react with ozone and convert it into O₂. This process is called depletion of ozone layer.
Cause: The CFC used as propellant in pressurized aerosol, foaming agent, refrigerators etc. Each one atom of chlorine converts more than 100000 molecules of ozone O₃ to Oxygen O₂.

Source: Special Thanks To Sir Syed Arif Ali

Biology For Class X - Chapter No. 7 - Man And His Environment - Multiple Choice Questions And Fill In The Blanks By Sir Saeed Sarang

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CHAPTER 7: MAN AND HIS ENVIRONMENT

Multiple Choice Questions And Fill In The Blanks

Special Thanks To Sir Saeed Sarang (Sindh Text Book Board)
Contact # 03023006727
Youtube Channel # Shafquat Ali YouTube

A. MULTIPLE CHOICE QUESTIONS
Choose the correct answer:
1. The life sustaining envelop of earth is:
(a) Biomass
(b) Biomes
(c) Biosphere ✓
(d) Atmosphere

2. The group of organisms belong to the same species live in a particular area called:
(a) Community
(b) Species
(c) Genes
(d) Population ✓

3. An area where community interacts with non-living environment is called:
(a) Community
(b) Ecology
(c) Ecosystem ✓
(d) Biome

4. Any biological region recognized by its climate or vegetation is called:
(a) Ecosystem
(b) Biomes ✓
(c) Biosphere
(d) Biomass

5. The transfer of food material from producers through some organisms with repeated eating and being eaten is called:
(a) Food pyramid
(b) Food chain ✓
(c) Food web
(d) Ecological pyramid

6. The elements in ecosystem recycle through organisms with environment is called:
(a) Food chain
(b) Food web
(c) Chemical cycle
(d) Biogeochemical ✓

7. Process where nitrogenous compound of living organism convert into nitrates is called:
(a) Ammonification
(b) Nitrification ✓
(c) Denitrification
(d) Deamination

8. The cold war between the organisms of a community occupying the same habitat is called:
(a) Predation
(b) Competition ✓
(c) Mutualism
(d) Commensalism

9. The association between two different types of organism which get benefit to each other, cannot live without each other is called:
(a) Parasitism
(b) Commensalism
(c) Mutualism ✓
(d) Predation

10. The amount of solid waste or concentration of gases other than oxygen increase in atmosphere is called:
(a) Air pollution ✓
(b) Ozone depletion
(c) Acid rain
(d) Greenhouse effect

11. The area where an organism lives is called its:
(a) population
(b) habitat ✓
(c) community
(d) biome

12. The group of populations that lives in a particular area of habitat and interacts with each other is:
called:
(a) population
(b) community ✓
(c) biosphere
(d) biome

13. Enzyme activities of metabolic reactions are also altered with the changes in:
(a) light
(b) air
(c) water
(d) temperature ✓

14. The decomposed dead animals and plants are called:
(a) biomass
(b) biome
(c) humus ✓
(d) decomposer

15. It is an essential constituent of protein.
(a) Nitrogen ✓
(b) Oxygen
(c) Carbon
(d) Sodium

16. They are the primary source of energy for other organisms.
(a) Producers ✓
(b) Primary consumers
(c) Secondary consumers
(d) Decomposers

17. A bird that gets its energy and food when it eats grasshopper or caterpillar is:
(a) producers
(b) primary consumers
(c) secondary consumers ✓
(d) decomposers

18. Bacteria and fungi are:
(a) primary consumers
(b) secondary consumers
(c) tertiary consumers
(d) decomposers ✓

19. In a given ecosystem various food chains are linked together and interact with each other to form a complete network called:
(a) Food pyramid
(b) Food chain
(c) Food web ✓
(d) Ecological pyramid

20. Presentation of a number of individuals of amount of biomass or energy in various trophic levels from lower to a higher level is:
(a) Food pyramid
(b) food chain
(c) Food web
(d) Ecological pyramid ✓

21. Graphic presentation of members of the population in an area at different trophic levels is called:
(a) pyramid of number ✓
(b) pyramid of biomass
(c) food web
(d) food chain

22. The growth and life processes of living organisms require about:
(a) 47 elements
(b) 40 elements ✓
(c) 35 elements
(d) 24 elements

23. All biogeochemical cycles are closely interlinked with:
(a) water cycle
(b) energy flow in the ecosystem
(c) Both 'a' & 'b' ✓
(d) None of these

24. All the life on the earth is based on:
(a) carbon ✓
(b) oxygen
(c) hydrogen
(d) nitrogen

25. Respiration consumes it for the combustion of food for release of energy.
(a) hydrogen
(b) carbon dioxide
(c) nitrogen
(d) oxygen ✓

26. One of the Important constituent of protein and DNA.
(a) Carbon
(b) Nitrogen ✓
(c) Oxygen
(d) Sodium

27. Conversion of atmospheric free nitrogen gas into nitrates called:
(a) Nitrification
(b) Denitrification
(c) Nitrogen fixation ✓
(d) Deamination

28. Process of converting nitrogenous compound Into free nitrogen called:
(a) Nitrification
(b) Denitrification ✓
(c) Nitrogen fixation
(d) Deamination

29. Competition between the members of different species is:
(a) specific
(b) intraspecific
(c) interspecific ✓
(d) ultraspecific

30. It is an association between the two organisms of different species which live together.
(a) Symbiosis ✓
(b) Competition
(c) Predation
(d) None of these

31. A kind of spiral-shaped bacteria, spirochaete, living between our teeth to obtain food is an example of:
(a) mutualism
(b) parasitism
(c) predation
(d) commensalism ✓

32. The term describes how the ecosystem is organized in a state of stability where species exist with other species and the environment.
(a) Pyramid of biomass
(b) Ecological balance ✓
(c) Ecological pyramid
(d) Food web

33. Burning of fossil fuels results in:
(a) increased oxygen level
(b) increases greenhouse gases ✓
(c) decreases greenhouse gases
(d) increased nitrogen level

34. Which of the following greenhouse gases is present in very high quantities?
(a) Carbon dioxide
(b) Methane
(c) Both 'a' & 'b' ✓
(d) None of these

35. The main contributors of acid rain are:
(a) CO₂ & SO₂
(b) CO₂ & NO₂
(c) SO₂ & NO₂
(d) CO₂, SO₂ & NO₂ ✓

36. The main cause of acid rain is:
(a) soil pollution
(b) water pollution
(c) air pollution ✓
(d) all of the above

37. Acid rain causes damage to:
(a) microorganisms of soil
(b) skin of animals
(c) building material
(d) all of the above ✓

38. Main cause of depletion of the ozone layer is the CFC used as the propellant in:
(a) pressurized aerosol
(b) foaming agent
(c) refrigerators
(d) all of these ✓

39. Growth of algae with very high rate due to increase in phosphorous and nitrogen-containing compounds called:
(a) algal bloom
(b) eutrophication
(c) Both 'a' & 'b' ✓
(d) None of these

40. The Scientific study of environment, ecology, evolution and global change with in a combined form is called:
(a) Community
(b) Ecology
(c) Ecosystem
(d) environmental biology ✓

41.The scientific study of the various relationships exists between organism and their environment is called:
(a) Community
(b) Ecology ✓
(c) Ecosystem
(d) environmental biology

42. The largest possible major community comprised of all living organisms on the earth is called:
(a) Ecosystem
(b) Biomes
(c) Biosphere ✓
(d) Biomass

43. Light, temperature, water, soil and air (non-living components) are _________ components of an ecosystem.
(a) Biotic
(b) Abiotic ✓
(c) genetic
(d) Biological

44. Producers, consumers of all types and decomposers (living components) are called _________ component.
(a) Biotic ✓
(b) Abiotic
(c) genetic
(d) Biological

45. Graphic presentation of members of population in an area at different trophic levels is called:
(a) Food pyramid
(b) Pyramid of numbers ✓
(c) pyramid of biomass
(d) food web

46. Habitat of frog is:
(a) Ocean
(b) Pond ✓
(c) Land
(d) Sea

47. ____ is a source of energy for every ecosystem.
(a) Light ✓
(b) Temperature
(c) Water
(d) Soil

48. _____ is necessary for vision, for the start of certain biological process, making vitamin D in human beings and migration of many animals.
(a) Air
(b) Temperature
(c) Light ✓
(d) Water

49. ____ is the major part of protoplasm.
(a) Air
(b) Sugar
(c) Water ✓
(d) Salt

50. ___ is the gaseous envelope which surrounds the earth.
(a) Light
(b) Temperature
(c) Water
(d) Air ✓

51. ___ is vital for respiration of all living organism.
(a) Oxygen ✓
(b) Nitrogen
(c) Water
(d) CO₂

52. ___ is the main requirement of photosynthesis to produce carbohydrates.
(a) Oxygen
(b) Nitrogen ✓
(c) Water
(d) CO₂

53. All living organism which can trap and convert energy into food molecules called:
(a) Producers ✓
(b) Consumers
(c) Decomposers
(d) None of these

54. ____ are photosynthetic bacteria, alga and plants.
(a) Producers ✓
(b) Consumers
(c) Decomposers
(d) None of these

55. Animals and all other organisms which can not make their own food are called:
(a) Producers
(b) Consumers ✓
(c) Decomposers
(d) None of them

56. _____ consumers are herbivores.
(a) Primary ✓
(b) Secondary
(c) Tertiary
(d) All the above

57. Grasshopper or caterpillar are examples of _____ consumers.
(a) Primary ✓
(b) Secondary
(c) Tertiary
(d) None of them

58. Secondary and tertiary consumers are:
(a) Herbivores
(b) Carnivores ✓
(c) Both (a) and (b)
(d) None of them

59. A bird is an examples of _____ consumers.
(a) Primary
(b) Secondary ✓
(c) Tertiary
(d) None of them

60. An eagle is an example of _____ consumers.
(a) Primary
(b) Secondary
(c) Tertiary ✓
(d) None of them

61. Microorganisms which break down complex food molecules of dead organisms called:
(a) Producers
(b) Consumers
(c) Decomposers ✓
(d) None of them

62. Nitrogen fixing bacteria, Rhizobium are good example of:
(a) Parasitism
(b) Symbiosis
(c) Mutualism ✓
(d) Commensalism


FILL IN THE BLANKS
1. An area where community interacts with non-living environment and flow of energy occur is called Ecosystem.
2. The area where an organism lives is called its habitat.
3. The group of population lives in a particular area of habitat and interact with each other is called community.
4. The term 'ecosystem' was first proposed by Tansley in 1935.
5. 'Eco' means the environment (house) and 'System' implies an interacting area.
6. The biosphere may be divided into sub-levels, biomes.
7. Plants convert light energy into chemical energy by the process of photosynthesis.
8. The upper layer of earth crust consists of particles of varying size and decomposed organic material by microorganism called soil.
9. The decompose dead animals and plants are called humus.
10. All the organisms in an ecosystem need energy to carry out their life activities.
11. Humidity is the quantity of H₂O vapours in the air.
12. Humidity controls the rate of evaporation of and transpiration in plants.
13. In an ecosystem, organic and inorganic material flow in two ways, as cyclic process.
14. In ecosystem, the flow of food material progresses through food chain.
15. The step wise transfer of energy food are called trophic levels.
16. The reduction in transfer of energy at various levels in an ecosystem is expressed in the form of a pyramids called pyramid of energy.
17. In a given ecosystem various food chains are linked together and interact with each other to form a complex network called food web.
18. An English ecologist Charles Elton develops the concept of ecological pyramids in 1927.
19. Presentation of number of individuals or amount of biomass or energy in various trophic levels from lower to higher level is called Ecological pyramids.
20. The pyramid of total biomass of organisms at each trophic level is total mass of dry organic matter per unit area.
21. The elements cycle continuous through organism and environment are called Biogeochemical Cycles.
22. In an ecosystem living organisms develop number of relationships according to their needs.
23. In the ecosystem, herbivores develop their relation with producers.
24. In the ecosystem, carnivores depends on herbivores for their food.
25. In an ecosystem, competition between the members of same species is called intraspecific.
26. In an ecosystem, competition between the members of different species s called interspecific.
27. Plants use atmospheric nitrogen in the from of nitrates.
28. One group of bacteria live in water which is photosymthetic called cyanobacteria.
29. A predator is an organism which captures and kill the live animals for its food.
30. The animal being killed is called prey.
31. Pitcher plant and venus fly trap are predators, these plants are called carnivore plants.
32. Symbiosis is an association between the two organism of different species which live together.
33. Parasites lives in or on the body of other organism to get their food. Such organisms are called host.
34. Parasitism associated between host and parasite.
35. Commensalism is a type of symbiotic relationship.
36. In commensalism one of the organism commensal, gets the benefit whereas the other is neither benefited nor harmed.
37. Spirochaetae is a kind of spiral bacteria, living between our teeth to obtain food but cause no harm to us.
38. In mutualism two different kinds of organisms get benefit from living together.
39. All the interactions of living organism are important and help to keep the ecosystem balanced. This is called Ecological balance.
40. All the miseries lie in three 'Ps' i.e. population, pollution and poverty.
41. Dr. Paul Ehlrich of Stanford University regards 'population explosion' as a 'population bomb'.
42. The birth rate at present is 55 Million per year about 1000 babies are born per minute.
43. During burning of fossils fuels, CO₂ and methane produce which are called greenhouse gases.
44. Heat remains with in the earth's atmosphere and increases the temperature is called global warming or greenhouse effect.
45. Forests are cutting or destroying, this process is called deforestation.
46. Pollution means destruction of purity.
47. All those substances that cause pollution called pollutants.
48. Development of new forest or plantation is called Afforestation.
49. Growth of algae with very high rate due to increase in phosphorous and nitrogen contain compounds called algal bloom or eutrophication.

Biology For Class X - Chapter No. 6 - Inheritance - Text Book Chapter

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CHAPTER 6: INHERITANCE

Text Book Chapter

Biology For Class X - Chapter No. 6 - Inheritance- Question Answers

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CHAPTER 6: INHERITANCE
Questions Answers

Q.1: Define the following terms: (i) Heredity (ii) Genetics (iii) Inheritance (iv) Variation
Ans: HEREDITY:
The characteristics of the offspring's to resemble their parents is called heredity.
In other words:
"Heredity is the way by which genes transmit characters from parents to offspring".

GENETICS:
The branch of biology which deals with the study of heredity and Variations is called genetics.

INHERITANCE:
The process by which characters are transmitted from parents to off springs is called inheritance.

VARIATION:
The difference in characters such as height, colour, etc. among individuals of same species are called variation.
Explanation:
Living things when reproduce sexually, their offspring differ somewhat from their parents. They show resemblance with one another as well as with their parents but they are not their exact copies, even than the brothers and sisters of one parent, neither resembles exactly with one another nor with their parents. Similarly puppies of the same female dog are not exactly alike. The same is true about plants, such differences are called variations.

Q.2: Genes control the inheritance of characters. Explain?
Ans: GENES CONTROL INHERITANCE OF CHARACTERS:
Life of every organism; every character of his structure; function and behaviour, at all levels of biological organization is programmed and controlled by a set of instructions. These instructions are in the form of coded biological information called genes. Gene is the smallest segment of DNA which is located at specific position on chromosome. It is the basic unit of biological information. It synthesize a protein which work as enzyme.
This biological information to offspring is passed through egg and sperm (gametes) which are the sex cells. We have also received our genes from our parents and they received their genes from their parents. Thus we and our brother and sisters share many genes of our parents and even of our grandparents. So the inherited characters are determined by genes which are transmitted from generation to generation. Therefore we can say that "Heredity is the way by which genes transmit characters from parents to offspring".

By Mrs. Ayesha Arif Vice Principal
(Jauhar Progressive School)

Q.3: Write a detailed note on Chromosomes.
Ans: CHROMOSOMES:

• The thread like structure present inside the nucleus and are bearer of hereditary character in the form of genes is called Chromosomes.
• Each kind of organism has specific number of chromosomes. These numbers and shapes remain constant in all individual of a species generation after generation.
• The genes are located at chromosomes and inherited through chromosomes during sexual reproduction.

EXAMPLE:
All human contains two sets of 23 chromosomes. One haploid set (n=23) is paternal in origin, which is contributed by sperm while the other haploid set (n=23) is maternal which comes from egg.

HOMOLOGOUS CHROMOSOMES:
The two chromosomes which are similar in their shape, size and position of centromeres present in a cell make one homologous pair of chromosome. These homologous sets of chromosomes provide the physical basis of heredity of an organism.

HETEROLOGOUS CHROMOSOMES:
A heterologous chromosome is a chromosome that contains different set of genes for a given trait.

COMPOSITION OF CHROMOSOMES:

• The chemical material that makes up chromosomes is called chromatin.
• Chromatin is basically a nucleo-protein (Deoxyribo Nucleoprotein) which is composed of 40% of DNA and 60% of Histone (special protein).
• DNA (Deoxyribo Nucleic Acid) is made up of billions of units called Deoxyribo Nucleotides.
• Each nucleotide is made up of deoxy ribose sugar (C₅H₁₀O₄), Phosphoric acid (H₃PO₄)and nitrogenous bases.
• The DNA of a chromosome exists as one very long double stranded, a duplex, which extends unbroken through the entire length of the chromosome. This long DNA (more than 7 feet or 2 meter) is coiled to fit into a much smaller spaces.
• The histone is positively charged while DNA is negatively charged. This beads of histone and DNA is called nucleosome.
• When the string of nucleosomes wraps up into high order coil called super coil. This super coiled chromomers form chromosome.

Diagram:

Q.4: What is DNA?
Ans: Deoxyribo Nucleic Acid (DNA):

• The DNA of a chromosome is one very long double stranded fiber, duplex which extend unbroken through the entire length of chromosome.
• A typical human chromosome contain about 140 million nucleotide in its DNA.

Size:

• If a strand of DNA from a single chromosome were laid out in a straight line, it would be more than 7 feet long (2 meter). This is too long to fit into a cell. Thus this long DNA is coiled to fit into a much smaller space.

Nucleosome:

• DNA resembles a string of beads. This bead is made up of histone and DNA and is called Nucleosome.

Q.5: Describe the Waston and Crick model of DNA?
Ans: Watson and Crick Model Of DNA:
The model of DNA was suggested by James Watson and Francis Crick, in 1953. This model is based on X-Rays, Photographs and chemical analysis of DNA. According to this model:

• Double Helix:
  (i) DNA is a double helical structure.
• Backbone of DNA:
  (ii) Each helix is a polynucleotide chain which are twisted around each other.
  (iii) The outer part is called Upright, which are made up of deoxyribose sugar and phosphate. The inner part called Rungs, made up of paired nitrogenous bases.
• Pairing of Bases:
  (iv) Both helix are complementary to each other which are held together by hydrogen bonds.
  (v) The complementary helix have complementary base pairs i.e Adenine pairs with Thymine and Cytosine always pairs with Guanine.

STRUCTURE OF DNA

Q.6: What is gene and how its work?
Ans: GENES:

Gene is the smallest segment of DNA which has genetic information in the form of code to synthesize a protein. Life of every organism, every character of his structure, function and behaviour, all the level of biological organization is programmed and controlled by a set of instructions. These instructions are in the form of coded biological information called 'Genes'. Thus:
Genes are the basic unit and structure of Biological information. They are unit of inheritance which is copied and inherited from generation to generation.

LOCATION:
Each gene is located at specific position on the chromosomes .This position of gene on chromosome is called Gene Locus (loci).

FUNCTION:

• Gene is the localised part of DNA which has a coded information to synthesize a protein which works as enzyme.
• Each gene has specific function e.g. a gene determines the height of plant; another gene determines the colour of their petals etc.
• The coded information may change due to any reason which is called genetic variation caused by mutation. This genetic variation among off spring lead to tremendous variety in their traits.
• The variation in the genes of a trait give rise two or more than two alternative forms of a gene. These alternative form of gene are called alleles or allomorph.
• All the inherited characters are determined by genes which are transmitted from generation to generation.

Q.7 Explain how gene is the unit of hereditary information with reference to replication of DNA?
Ans: A UNIT OF INHERITANCE:
Gene is a Unit of inheritance which is copied and Inherited to the next Generation.

Importance Of  The Complementary arrangement Of Nucleotide:

• The complementary arrangement of nucleotide is of great importance in DNA molecule.
• If the sequence of bases in one strand is known, the sequence of bases in the other strand will be automatically known due to specific base-pairing.
• This property of the two strands of double helix makes DNA a unique molecule best suited to store, copy and transfer genetic information from generation to generation.

REPLICATION OF DNA:
"DNA is able to make its exact copy itself in nucleus of cell before cell division. This process of duplication of DNA is called DNA replication."
Gametes are haploid cell that carry one copy of replicated DNA. This copy carry genes from parents to offspring through these gametes.
The Watson and Crick Model of DNA ideally proposed the mechanism of self replication:
The hydrogen bond that hold together the double helix of DNA are broken up from one end to another end like a zip. The double helix gradually “unzip” along its length and each new nucleotide of the complementary nucleotide would be added to separate chains sequentially.

REPLICATION OF DNA

Q.8: What do you understand by Central dogma of Protein synthesis? How gene expresses describe in detail?
Ans: CENTRAL DOGMA:
"A set of beliefs where a gene expresses by synthesizing a protein is termed as central dogma."
This protein is work as enzyme, which carry down a chemical reaction to produce a metabolic product. This metabolic product either develops a character or lead to develop a character.

RNAs:
DNA is located in the nucleus of eukaryotic cell while the protein synthesis and metabolic reactions occur in cytoplasm under the instructions of DNA (genes). Therefore DNA requires some other molecules to carry its genetic information from nucleus to cytoplasm. These molecules are different types of RNAs (Ribo Nucleic Acid).

GENE EXPRESSION:
All functions in the body of an organism are controlled by genes. A function expressed or performed by a gene is called gene expression.

Process of Gene Expression:
Genetic information flows from DNA to mRNA and then to ribosomes in cytoplasm. This is a two step process of gene expression for protein (enzyme) synthesis.

1. Transcription
2. Translation

1. Transcription:
The step of protein synthesis where information which contained in a specific segment of DNA (gene) is copied in complimentary from (genetic codes) i.e. RNA. This RNA carries information of DNA sequences to ribosome from nucleus to cytoplasm are called messenger RNA or mRNA. The process of copying DNA information to mRNA is called Transcription.

2. Translation:
In the second step two other types of RNA called tRNA(transfer RNA) and ribosomal RNA(rRNA) translate the information of mRNA into the specific sequence of amino acids which help to synthesize the proteins. This process is called Translation.

Q.9: What lead Mendel to present laws of genetics?
Ans: MENDEL AND HIS LAWS OF INHERITANCE:
Gregor John Mendel was an Austrian Monk. He explained the mechanism of  hereditary. He is known as the Father of Genetics.

Mendel’s Experiment:

• Mendel carried out breeding experiments on garden pea plant (Pisum sativum). He studied seven traits in pea plant one by one. These traits were height, seed shape, pod shape, seed colour, flower colour, flower position and pod colour.
• He has chosen to study the contrasting pairs of these above traits because they were easily distinguishable like Tall and Dwarf.
• These varieties continued to produce offspring identical to their parents generation after generation, as long as they were self-pollinated. Such varieties are called true breeders and their offspring are pure- breeds.
• Pure-breed means that if an organism is self fertilized, the offspring always look exactly like parents e.g. if a parent pea is tall and have purple flowers perform self pollination to produce next generation, the offspring will always be tall and have purple flowers.
• Mendel study was based on these seven pairs of contrasting characters but considering the inheritance of single pair of contrasting characters at a time.
• He counted and recorded the parents and offspring of each of his cross.

Laws Of Inheritance:
Based on experiments and observations and keen interest in Mathematics, Mendel had formulated certain hypothesis which led him to presents Laws Of Genetics or Law Of Hereditary or Laws Of Inheritance. These laws are:

1. Law of complete Dominance
2. Law of Segregation
3. Law of independent assortment.

Q.10: State the Mendel's Law of complete Dominance and also explain the experiment and its conclusions.
Ans: LAW OF COMPLETE DOMINANCE:
Statement: According to this law:

"When a pair of contrasting characters (heterozygous) is brought together in cross , only one factor will express in the off spring while other will be masked."

It means that in heterozygous condition one factor is completely dominant over the other. Law of dominance is also known as the first law of inheritance.

EXPERIMENT:
Selection Of Parents On The Basis Of Gene:
Mendel took gene as factor, he told that both parents donate one factor as a trait.

• Homozygous:
  Mendel explained that if both parents donate same factor of the trait, the organism is pure or homozygous for this trait like Pure tall i.e. TT or the pure short (dwarf) i.e. tt.
  
  
• Heterozygous:
  Mendel explained that if both parents donate different factors (allele) of a trait, the organism is heterozygous or hybrid for the trait i.e. Tt for tall.

Crossing Over:

• Mendel took pure tall stem and short stem varieties and crossed them.
• All the seeds were collected and allowed to grow.
• He observed that all the plants were of tall stem, no plant with intermediate stem were found to grow in that generation.
• He repeated his experiment on pea plants with different traits having contrasting characters, found same result than he presented the law of complete dominance.

Conclusion:
In first filial generation (F1) all plants are tall (Phenotype) with (Tt) Genotype.

Q.11: Define following terms:
(i) Dominant (ii) Recessive (iii) Phenotype (iv) Genotype (v) Homozygous (vi) Heterozygous (vii) Parental generation (P1) (viii) Filial one Generation (ix) Second Filial Generation
Ans: (i) DOMINANT:
The factor (gene) which express and masks the expression of other factor in heterozygous condition is said to be Dominant factor (allele). Mendel represent it with capital letter like T for tall.

(ii) RECESSIVE:
The factor which is unable to express or masked in heterozygous condition is said to be recessive. It represents by small letter of same alphabet like t for small (dwarf).

(iii) PHENOTYPE:
It is the physical appearance of the trait on the basis of inherited genes like tall, dwarf, round seed, wrinkled seed etc.

(iv) GENOTYPE:
The genetic makeup or genetic constitution of a trait like TT, Tt, tt etc.

(v) HOMOZYGOUS:
An individual having same factors (allele) of a trait called homozygous. For example, TT (factor for tallness).

(vi) HETEROZYGOUS:
An individual having different factors of a trait called heterozygous. For example, Tt (factors of tallness and dwarfness both).

(vii) PARENTAL GENERATION (P1):
The original true breeding organisms were called parental generation or P1 by Mendel.

(viii) FIRST FILIAL OR FILIAL ONE GENERATION (F1):
The offspring of true breeding organism were called First Filial Generation or F1.

(ix) SECOND FILIAL GENERATION:
The offspring of filial one generation produced by crossing self-fertilization were called Second Filial generation or F2.

Q.12: State and explain the law of Segregation Or law of Purity of gametes of Mendel's.
Ans: LAW OF SEGREGATION (MENDEL’s FIRST LAW) OR LAW OF PURITY OF GAMETES:
Statement:

"In an organism, the factors (genes) exist in pairs but during gametes formation these factors segregate cleanly from each other, so each gamete has only one factor of a trait."

Experiment:

• Mendel when crossed pure tall and dwarf plants, he got all tall plants in F1 generation but unlike the P1 tall, these plants of F1 generation were heterozygous (Tt).
• Mendel did not stop his experiment here. He planted all the seeds of F1 generation and allowed them to self pollinate.
• He observed that in the generation (F2), both Parental type i.e. tall and dwarf stem varieties were produced. When he counted these, he found that in F2 generation, the two types of individuals were present in the ratio of 3:1, tall and dwarf respectively.

Results:
Mendel perceived from these results that

• When the plants of F1 generation form their gametes, the factors (allele) separate or segregate again in such a way that only one of the two alleles enters each gamete.
• On the basis of these observation, results and conclusions from experiment he presented the law called the "Law of segregation or law of purity of gametes".

Q.13: State and explain the law of Independent assortment OR Explain the crossing over of dihybrid by law.
Ans: LAW OF INDEPENDENT ASSORTMENT:
Statement:

"The genes of assorted traits are independent in their inheritance."
OR
"Members of one pair of genes separate from each other during gametes formation."

Dihybrid - Cross And Dihybrid Ratio:
Mendel crossed between two individuals (pea plant) differing in two traits. He called it Dihybrid - Cross and the ratio obtained in F2 generation is called Dihybrid-ratio.

Inheritance of two traits:
The results achieved as a consequence of dihybrid-cross is known as Inheritance of two traits.

Experiment:

• In his experiments Mendel crossed between two individual (pea plants) differing in two or more character traits as well.
• Mendel crossed yellow cotyledon and rounded seed containing plant with green cotyledon and wrinkled seed containing plant.
• The F1 generation had all plants with yellow cotyledon and round seeds.
• This proved Mendel previous finding that allele for round seed was dominant over wrinkled while yellow cotyledon over green.
• Mendel self fertilized the F1 generation and expecting any of the two following possibilities:
  i) If the genes for round seed and yellow colour are inseparable (dependent on each other), as well as those for wrinkled shape and green colour, then in F2 generation ³/₄ of the seeds will be round and yellow and ¹/₄ will be wrinkled seed and green.
  
  ii) If the genes for seed shape and cotyledon colour are separable (independent) and distributed to the gametes independent to each other, then in F2 generation some plants will produce round seeds with green cotyledon and some will have wrinkled seeds with yellow cotyledon along with parental combination.

Result:
Mendel actually obtained four different kind of phenotypes in F2 generation. Out of a total 556 seeds, he obtained four different phenotypes i.e.
Phenotype:

• Round and Yellow seeds = 315
• Wrinkled and Yellow seeds = 101
• Round and Green seeds = 108
• Wrinkled and Green seeds = 32

Genotype:

• Genotypes for round and yellow seeds RRYY, RRYy, RrYY, RrYy.
• Genotypes for round and green seeds RRyy, Rryy.
• Genotypes for wrinkled and yellow seeds rrYY, rrYy.
• Genotypes for wrinkled and green seeds rryy.

Dihybrid-cross ratio:
These numbers are in a ratio of about 9:3:3:1 for the four phenotype.

Conclusion:
It showed that the genes for seed colour and shape are independent in their inheritance. They do not necessarily stay together in the combination in which they occurred in parents.

Q.14: Explain the concept of multiple allele with reference to human blood groups.
Ans: ALLELE:
"The alternative form of gene developed as a result of variation is called allele or allomorph."
Some gene may have as many as 300 alleles. A diploid cell thus have any two of these multiple alleles while a haploid have one allele. Alleles are described as either dominant or recessive depending on their associated traits. 

MULTIPLE ALLELES:
A gene controlling a trait may two or more than alternative forms (alleles). These traits are called Multiple Allelic Trait or  Multiple Alleles. ABO blood group system in human population was the first discovered multiple allelic trait.

EXAMPLES OF MULTIPLE ALLELES:
Human Blood Group
A well-known example of multiple alleles in humans is the inheritance of ABO blood group system.
Karl Landsteiner in 1901 discovered ABO blood group system. There are four type of phenotype due  to the presence or absence of two specific antigen on the surface of the RBCs.
The genetic basis of ABO system was explained by Bernstein in 1925.
Antigens:
There are two types of these antigens:

• Antigen A and
• Antigen B

Blood Groups:

• "A": A person with antigen “A” has blood group "A".
• "B": A person with antigen “B” has blood group "B".
• "AB": With both antigens A and B, a person has blood group “AB”.
• "O": If there is none of the two antigens, the blood group of a person will be "O".

Gene "I":
The ABO blood group system is controlled by a polymeric gene "I" on chromosome 9. The Gene "I" contains three alleles represented by the symbols I^A, I^B and i.

• The allele I^A is responsible for production of antigen A.
• The allele I^B produces antigen B.
• While the third allele i does not produce any of the antigens.

OR

Blood Group	Genotype	Phenotype	Antigen
Group A	IA IA  IA i	A—Homozygous  A—Heterozygous	A
Group B	IB IB  IB i	B—Homozygous  B—Heterozygous	B
Group AB	IA IB	AB—Heterozygous	AB
Group O	i i	O—Homozygous	NO

R^h Blood Type ( R = Rhesus):

• The R^h blood group is one of the most complex blood groups known in humans.
• This protein was first time observed in rhesus monkey the another mendelian gene found in human.
• This gene produce a protein which is found on the surface of R.B.C as well.
• This trait has 2 allele a dominant R^h and r^h recessive.
• The R^h protein produce R^h protein therefore person is called R^h +ve whereas r^h gene is unable to produce R^h protein so the person is called R^h -ve, will be r^hr^h.

Q.15: Discuss the role of antibodies for AB and Rh in blood transfusion.
Ans: ANTIBODIES:
The chemical cells or organs of an organism work as antigen to other organism. When these antigens enter in the body of other organism, this organism produce defense protein against this antigen to protect itself. These proteins are called antibodies.

Role of antibodies for AB and R^h in blood transfusion:

• The blood group alleles (I^A, I^B, i) start their expression at embryonic stage and keep expressing till death.
• A person also produces anti-A, anti-B antibodies during first few months after birth.
• The person of A-blood group produces anti-B antibodies.
• Person of B-blood group produces both anti-A and anti-B antibody.
• Person with AB blood group does not produce any of these antibodies.
• Person with AB blood serum containing antibodies called antibody. The blood serum containing antibodies called antiserum.

Role in transfusion:

OR

Blood group	Blood group recipient	Reason
A B AB	A and AB B and AB AB only	Recipient donot have antibodies A.  Recipient donot have antibodies B.  Recipient neither have antibody A or antibody B.
O	O, A, B, AB	* Blood group have antibody A and antibody B so it can receive only O blood group.  * O blood can be donated to A, B and AB because donor’s antibodies are quickly absorbed by other. Tissue or diluted in recipient blood. Therefore O blood is called universal donor.

Preventive Measures For Transfusion Of Blood:
For ABO Blood Group system:

• The person of A blood group which contain anti-B antibodies if given blood of B-group.
• The R.B.C of this B-blood group will work as antigen in the person of A-blood group and its anti-B antibodies will work against the donor R.B.Cs of B-blood group and clumped cells called agglutination.
• It leads to a serious problem as these clumped cells can not pass through fine capillaries. Therefore during transfusion of blood the people must be careful about blood group.

For R^h Factor:

• Anti-R^h antibodies do not produce automatically. The production of anti-R^h antibodies require stimulus which is R^h human protein itself. It work as antigen.
• If an R^h -ve person receive R^h protein (antigen) through wrong R^h +ve blood transfusion, he will begin to produce anti-R^h antibodies against R^h antigens.
• R^h-ve blood does not contain any R^h protein (antigen) so it can be transferred to R^h +ve person (recipient).

Q.16: Explain the concept of co-dominance and incomplete dominance?
Ans: CO-DOMINANCE:
The phenomenon of inheritance where both alleles are dominant and expressed equally is called Co-Dominance.

Explanation:
According to Mendel’s law of dominance only one factor is expressed in heterozygous condition but it was also found that some traits has alleles that are equally dominant and are both expressed themselves in a heterozygous condition ( in phenotype) independently.
As a result the heterozygous offspring displays the phenotype of both the homozygous parents and none of the two alleles masks the appearance of the other.

Example:
AB blood group, where both alleles I^A and I^B express and produce antigen A and B both.

INCOMPLETE DOMINANCE:
The term ”incomplete dominance” was proposed by Carl Correns in 1899.
Definition:
"The phenomenon of inheritance where both alleles of a trait  is expressed in heterozygous conditions and their expression get blended to produce new phenotype called incomplete dominance or partial dominance."

Experiment:

• Carl Corren crossed a pure breed red flowered Japanese 4 O’clock plant (Mirabilis jalapa) with pure breed white flowers.
• He found pink flowered plants in F1 generation , these result were against the law of dominance. This new phenotype was intermediate between those parents.
• When Correns self-pollinated F1 pink flowered plant, the F2 generation showed all three phenotypes of flowers in the ratio 1 red, 2 pink and 1 white flowers, i.e. 1:2:1.
• Red and white are homozygous for their respective alleles.
• It was also found that when alleles for red and white were present together (heterozygous) in the same plant, neither of them masked the effect of other, therefore expression of both genes blended to produce new phenotype, i.e. pink.

Q.17: What do you mean by similarities? OR Define the species which have similarities in features?
Ans: SIMILARITIES:
Living things exists in great variety.  Species are interrelated in some ways. They have many features in common. For instance, there are fundamental similarities in their chemical structure. Not in in chemistry, but there exist similarities in morphology also. Thus:
"Similarities suggest that species are more closely interrelated in some ways, some species are more closely interrelated than the others."
Example: Such as rats with mice, turtle with tortoise, frog with toads etc.

Q.18: Explain the concept of variation with types and causes.
Ans: VARIATIONS:
"The differences in characters such as height, colour, etc. among individuals of same species are called variations." Variation may be caused either by the effect of environment or by the changes in the genetic material.

TYPES OF VARIATIONS:
On the basis of causes variation can be classified into the following types:
1. Environmental variation:
Variations caused by environmental factors among the members of same species, are called environmental variations . They are not inherited to the offspring.
e.g. Development of muscles in athletes, loss of some body parts due to accident or diseases etc.

2. Heritable Variations:
The variation caused due to changes in genetic material is called genetic or heritable variation. This type of variation is consider as raw material for evolution.

On the basis of effects there are other two types of variations.
1. Continuous Variation:
These variations refers to small differences in characters of the members of a species. Such variations are neither purely genetical nor purely environmental. They appear to be the combination of both factors.
e.g. Height, Skin colour, Intelligence, Eye colour etc.

2. Discontinuous variations:
These variations are sudden and sharp differences among the members of same species. They are heritable and purely caused by genetic material.
e.g. Blood group, Six fingers in hand or foot, tongue rolling etc are common examples in man.

CAUSES OF VARIATIONS:
Some important causes of variations are as follows:
1. Mutation:
The phenomenon of producing sudden changes is called mutation. It can be defined as the sudden changes in the genetic material {genome) of an organism. It is the major source of heritable variation among the organisms which is considered as the starting point of new species.
e.g. Some person has six fingers in hand or foot

2. Crossing over:
The process of mutual exchange of segments of chromatids between non-sister chromatids of homologous pair of chromosome which occurs during prophase of 1^st meiotic division is called crossing over. The maternal and paternal alleles are mixed and segregated in this process So the indefinite combinations of alleles are made.
e.g. Due to this crossing over and segregation, offspring of same parents become variable.

3. Environment:
Number of environmental factors affects the body cells to cause variations in body cells.
e.g. the changes in the pigmentation of skin due to extent of exposure to sunlight or development of muscles due to exercise etc.

4. Independent assortment of chromosomes:
During metaphase of first meiotic division homologous chromosomes come together in the form of pairs and subsequently segregate during anaphase I into the daughter cells independently. This produce a wide variety of different gametes.

5. Fertilization:
The set of alleles carried by chromosomes of each gametes is unique and always differ from each other. There are number of male gametes available to fertilize a single female gametes. Thus different combination of characters in an individual are possible as a result of fertilization.

Q.19: Define Evolution and organic evolution? Explain the Darwin theory of natural selection.
Ans: EVOLUTION:
Evolution is a process where descends become better than ancestors.

ORGANIC EVOLUTION:
The organic evolution explains that present day living things are modified from simple ancestral forms during the course of time through a gradual and continual process of modification.
Theories of organic evolution not explain that living things have become so varied, but it also explains 
their basic similarities as well.

THEORY OF NATURAL SELECTION:
Charles Darwin (1809 - 1882) was an Englishman. He studied different plants and animals, collected new specimens and categorized them. In the year, 1859, he published a book “Origin Of Species” where he proposed the "Theory of Natural Selection", in which he presented the mechanism of origin of species.

FACTORS INVOLVED IN NATURAL SELECTION OR MAIN POINTS OF DARWIN'S THEORY:
The main points of the Darwin's theory are as follows:
1. Over Production:
Living organisms reproduce rapidly so that the number of their offspring could increase rapidly.

2. Struggle for Existence:
Due to the limited available resources of food, shelter, etc. the offspring of species compete not only with each other but also with the members of different species to share these resources. In this struggle a large number of individuals of each species are eliminated. As a result the population remains stable.

3. Heritable Variation:
Individual of a species differ from each other in their ability to obtain resources, withstand environmental extremes etc. These differences in character are called minor variations.
Darwin concluded that survival in struggle for existence is not random but depends upon in part on the heredity constitution of the surviving individuals. Those individuals whose inherited characters fit them best to their environment would survive and produce more offspring than less fit individuals who will vanish.

4. Natural selection:
Nature selects the fittest individuals to survive and reproduce. Therefore only the favourable variations are preserved through their inheritance to new young ones.

Conclusion:
Over millions of year of variations, natural selection and inheritance might have led to the accumulation within the species a number of characters with survival values. As a result, a species may slowly change to a better new species. 
Number of evidence are reported in support of evolution from comparative anatomy, homologous organs, analogous organs, vestigial organs and fossils.

Q.20: Write a short note on artificial selection?
Ans: ARTIFICIAL SELECTION:

"Artificial selection is the cross breeding of domestic animals and plants to produce specific desirable features."

Example:
Various breeds of dogs, pigeons, sheep, horse, cattle, cow, buffalo, hen etc. among the animals have been developed through artificial selection.

Explanation:
Darwin was very much convinced by Artificial selection. He convinced biologists that the process of artificial selection could produce so many changes in a species in relatively short period of time, then natural selection should be capable of considerable modification of species over thousands of generations.

Source: Special Thanks To Sir Syed Arif Ali