Category: Class 12 Biology Objective Questions

Biology Written Test Questions and Answers for Class 12 on “Population Attributes – 2”.

1. Which organisms are considered a population for the purpose of ecological studies?
a) Sexually reproducing organisms
b) Sexually as well as asexually reproducing organisms
c) Asexually reproducing organisms
d) Species
Answer: b
Clarification: For ecological studies of population, both sexually as well as asexually reproducing organisms are considered. The organisms formed from sexual reproduction are genetically different (except homozygotic twins). The organisms produced by asexual reproduction are genetically as well as morphologically similar.

2. Which of the following areas do population ecology links?
a) Ecology, population genetics, and evolution
b) Ecology, population genetics, and mathematics
c) Biology, physics and, history
d) Ecology, physics and, history
Answer: a
Clarification: Population ecology is a subject that studies the reasons, factors affecting population and how population change over time. It is important for biology conservation and it links ecology with population genetics and evolution.

3. Which of the following attribute does a population have?
a) Births
b) Birth rate
c) Deaths
d) Pyramid
Answer: b
Clarification: Among the given above birth rate is a population attribute. It is the number of individuals born in a population at a specific time. For humans, it is described as a number of individuals born per 1000 of the population per year.

4. Which of the following attribute does a population have?
a) Pyramid
b) Births
c) Deaths
d) Death rate
Answer: d
Clarification: Among the given above death rate is a population attribute. It is the number of individuals died in a population at a specific time. For humans, it is described as a number of deaths per 1000 of the population per year.

5. Which of the following attribute does a population have?
a) Deaths
b) Births
c) Sex ratio
d) Pyramid
Answer: c
Clarification: Among the given above sex ratio is a population attribute. It is the ratio of the number of males versus the number of females. Usually, the tendency of sexually reproducing organisms is to maintain a ratio of 1:1.

6. What does the plot of the age distribution of population results in?
a) Sex ratio
b) Age pyramid
c) Tree
d) Mountain
Answer: b
Clarification: When a plot of the age distribution of a population is made it results in a structure called age pyramid. It indicates the growth status of a population and tells whether a population is growing, stable or declining.

7. By which letter is the population density designated?
a) A
b) G
c) F
d) N
Answer: d
Clarification: The population density also known as population size is designated by the letter ‘N’. The population density tells about the number of individuals in a unit area (per square meter, per square kilometer or per hectare) at a specific time.

8. At which level does natural selection act?
a) Cellular level
b) Species level
c) Population level
d) Organism level
Answer: c
Clarification: Natural selection is a phenomenon that acts at a population level. Natural selection does not create mutations or variations rather it leads to the extinction of individuals who could not adapt to the changing environmental conditions.

9. On what basis is the tiger census in our national parks calculated?
a) Number of stripes
b) Number of legs
c) Number of limbs
d) Number of pug marks
Answer: d
Clarification: The tiger census in our national parks calculated on the basis of the number of pug marks. It is one of the most popular techniques to calculate the number of tigers. According to 2018 reports, the tiger population has increased up to 3000.

10. On what basis is the tiger census in our national parks calculated?
a) Number of stripes
b) Fecal pellets only
c) Number of pug marks and fecal pellets
d) Number of limbs
Answer: c
Clarification: The tiger census in our national parks calculated on the basis of the number of pug marks and fecal pellets which helps in determining the number of tigers along with their species. According to 2018 reports, the tiger population has increased up to 3000.

11. In which of the following case is the number of old people more?
a) Growing population
b) Declining population
c) Steady population
d) Reproductive population
Answer: b
Clarification: The population has a large number of individuals in a post-reproductive age is called a declining population. It is so-called because it has more number of old individuals, there will be fewer births and more deaths thus indicating negative population growth.

12. In which of the following case is the number of children (0-14years) more?
a) Steady population
b) Declining population
c) Expanding population
d) Reproductive population
Answer: c
Clarification: The expanding population has more number of children between 0-14years. It is the pre-reproductive age. It is so-called because fertile females can give rise to more children thus increasing the population.

13. Which of the following age pyramid indicates an expanding population?
a)

b)

c)

d)

Answer: a
Clarification: An expanding population has a triangular-shaped pyramid. In this, the individuals in pre-reproductive age are more, moderate in reproductive age while fewer individuals are present in post-reproductive age.

14. Which of the following age pyramid indicates a declining population?
a)

b)

c)

d)

Answer: d
Clarification: The declining population has an urn-shaped pyramid. In this, more individuals are present in reproductive age as compared to pre-reproductive age. It indicates the negative growth of the population.

15. Which of the following age pyramid indicates a steady population?
a)

b)

c)

d)

Answer: b
Clarification: A steady population has a bell-shaped pyramid. In this, the individuals in pre-reproductive and reproductive age are almost equal while fewer individuals are present in post-reproductive age.

To practice Biology Written Test Questions and Answers for Class 12,

Biology Multiple Choice Questions on “Ecosystem – Energy Flow – 1”.

1. What the only source of energy for all ecosystems on Earth?
a) Water
b) Sun
c) Plants
d) Animals
Answer: b
Clarification: The only source of energy for all ecosystems on Earth is the sun. The radiant light and heat from the sun is the primary, original source for most of the organisms and is used for the production of electricity, fuel, thermal energy, agriculture, etc.

2. Which is an exception in an ecosystem where the sun is not the source of energy?
a) Deep-sea hydro-thermal ecosystem
b) Terrestrial ecosystem
c) Lake ecosystem
d) Desert ecosystem
Answer: a
Clarification: The deep-sea hydro-thermal ecosystem is an exception in the ecosystem where the sun is not the source of energy. The chemosynthesis, marine snow, and whale falls are the three main sources of energy and nutrients for deep-sea communities.

3. What is the spectral range of solar radiation in that photosynthetic organisms are able to use in the process of photosynthesis called?
a) Photosynthetically Reactive Radiation
b) Photosynthetically Active Radiation
c) Photosynthetically Deactive Radiation
d) Photosynthetically Trapped Radiation
Answer: b
Clarification: The spectral range of solar radiation in that photosynthetic organisms are able to use in the process of photosynthesis is called as Photosynthetically Active Radiation. It is designated as PAR and ranges from 400nm to 700nm.

4. What percent of the incident solar radiation is photosynthetically active radiation (PAR)?
a) 100%
b) 85%
c) 20%
d) 50%
Answer: d
Clarification: Almost less than equal to the 50% of the incident solar radiation is photosynthetically active radiation (PAR). It ranges from 400nm to 700nm.

5. What percent of PAR is captured by plants?
a) 1%
b) 20-30%
c) 2-10%
d) 50%
Answer: c
Clarification: The spectral range of solar radiation that photosynthetic organisms are able to use in the process of photosynthesis is called PAR (400 to 700nm). Almost 2-10% of PAR is captured by plants.

6. On what are the organisms are dependent on their food?
a) Consumers
b) Producers
c) Decomposers
d) Scavengers
Answer: b
Clarification: All organisms directly or indirectly are dependent on producers for their food production. Producers are organisms that make their own food with the help of energy obtained from chemicals or the sun, water, and air. They are also known as autotrophs.

7. How is the flow of energy from the sun to producers and then to consumers?
a) Multidirectional
b) Bidirectional
c) No direction
d) Unidirectional
Answer: d
Clarification: The movement of energy from the higher trophic levels and its distribution and loss as heat to the lower trophic levels in the environment is unidirectional. It means the energy moves in one direction only that is from higher to the lower-most level.

8. From which law of energy the ecosystem are not exempted?
a) Zeroth law
b) First law of thermodynamics
c) Second law of thermodynamics
d) Fifth law of thermodynamics
Answer: c
Clarification: The ecosystems are not exempted from the Second Law of thermodynamics since they require a constant energy supply for synthesis of food. This increases the tendency toward disorderliness.

9. What are the green plants in the ecosystem termed as?
a) Scavengers
b) Consumers
c) Decomposers
d) Producers
Answer: d
Clarification: Usually the green plants present in the ecosystem are termed as the producers. Producers (autotrophs) are organisms that make their own food with the help of energy obtained from chemicals or the sun, water, and air.

10. Who are the major producers in a terrestrial ecosystem?
a) Phytoplankton
b) Zooplankton
c) Green plants
d) Birds
Answer: c
Clarification: The green plants (herbaceous and woody plants) are the major producers in a terrestrial ecosystem. Producers (autotrophs) are organisms that are capable of producing their own food (organic molecules) with the help of energy obtained from chemicals or the sun, water, and air (inorganic sources).

11. Who are the major producers in an aquatic ecosystem?
a) Zooplankton
b) Phytoplankton
c) Fungi
d) Bacteria
Answer: b
Clarification: Phytoplankton is the major producers in an aquatic ecosystem. Producers (autotrophs) are organisms that make their own food with the help of energy obtained from chemicals or the sun, water, and air.

12. How sunlight is much is reflected back out of the total sunlight reaching Earth?
a) 100%
b) 50%
c) 34%
d) 10%
Answer: c
Clarification: Almost 34 percent of light is reflected back out of the total sunlight reaching Earth. The heat and light from the sun is the original, primary source for most of the organisms and is used for the production of electricity, fuel, thermal energy, agriculture, etc.

13. How much percent of light reaches the Earth’s surface out of the total sunlight?
a) 20%
b) 56%
c) 0.1%
d) 30%
Answer: b
Clarification: Approximately 56-60 percent of light reaches the Earth’s surface out of the total sunlight. The heat and light from the sun is the original, primary source for most of the organisms and is used for the production of electricity, fuel, thermal energy, agriculture, etc.

14. What amount of sunlight is held the ozone layer, water vapor, and atmospheric gases out of total sunlight reaching Earth?
a) 50%
b) 8%
c) 20%
d) 10%
Answer: d
Clarification: 10% of sunlight is held the ozone layer, water vapor, and atmospheric gases out of total sunlight reaching Earth. The radiant light and heat from the sun is the primary, original source for most of the organisms.

15. What does this statement “The energy passed from producers to consumers (herbivores) does not go back to producers (autotrophs)” states about the flow of energy?
a) Flow is unidirectional
b) Flow has no specific direction
c) Flow is bidirectional
d) Flow is multidirectional
Answer: a
Clarification: The statement “The energy passed from producers to consumers (herbivores) does not go back to producers (autotrophs)” tells that the flow of energy is unidirectional. It means the energy moves in one direction only that is from higher to the lower-most level.

Biology Multiple Choice Questions on “Biodiversity Basics”.

1. The Earth consists of how many ant species?
a) 100,000
b) 20,000
c) 200,000
d) 2000
Answer: b
Clarification: Ants are eusocial (highly social) insects. They live together in organized colonies. There are approximately 20,000 species of ants on the Earth.

2. How many species of beetles are present on the Earth?
a) 3,00,000
b) 30,000
c) 3,000
d) 300
Answer: a
Clarification: Beetles are a group of winged insects and eat almost everything. They are prominent decomposers, and there are approximately 3,00,000 species of beetles on the Earth.

3. How many species of fishes are present on Earth?
a) 28,00,000
b) 28,000
c) 280
d) 28
Answer: b
Clarification: Fishes are limbless cold-blooded vertebrate gill-bearing aquatic craniate animals. They commonly have fins and are covered with scales. There are approximately 28,000 species of fishes on Earth.

4. How many species of orchids are present on Earth?
a) 200
b) 20
c) 2
d) 20,000
Answer: d
Clarification: An orchid growing on epiphyte is an example of commensalism. Epiphytes grow on trees for air and sunlight while the tree is not harmed due to its presence. Another epiphyte growing on trees is a fern. There are approximately 20,000 species of orchids on Earth.

5. Which of the following statements is true?
a) Diversity exists only at the species level
b) Diversity exists only at the macromolecular level
c) Diversity exists at all levels of biological organization
d) Diversity exists at the genetic level only
Answer: c
Clarification: Biodiversity is the variety and variability of all the levels of biological organization (plant and animal life) on Earth. The diversity exists not only at the genetic level but at all levels of biological organization.

6. Who popularized the term biodiversity?
a) Rudolf Virchow
b) Edward Wilson
c) Gregor Mendel
d) Robert Koch
Answer: b
Clarification: Edward Wilson popularized the term biodiversity. Biodiversity is the variety and variability of all the levels of biological organization (plant and animal life) on Earth.

7. What can a single species show?
a) No variation at the genetic level
b) No diversity at the genetic level
c) Low diversity at the genetic level
d) High diversity at the genetic level
Answer: d
Clarification: Genetic diversity is important among various levels of biodiversity. High genetic diversity can be seen only in a single species.

8. What is the feature of the biosphere?
a) No diversity
b) Homogeneity
c) Heterogeneity
d) Negligible diversity
Answer: c
Clarification: Biosphere is the total surface and atmosphere integrating all living beings and their relationships of the Earth. The biosphere is heterogeneous in nature and shows immense diversity. Thus heterogeneity is a feature of the biosphere.

9. How many strains of rice does India have?
a) 50
b) 500
c) 5,000
d) 50,000
Answer: d
Clarification: India consists of approximately 50,000 strains of rice. Rice is an edible starchy cereal grain, seed of the grass species Oryza. Rice is said to be the most widely consumed staple food.

10. How many varieties of mango does India have?
a) 2
b) 10
c) 1,000
d) 20
Answer: c
Clarification: Mango is an edible stone fruit (drupe) belonging to the flowering plant genus Mangifera. They grow mostly in tropical areas. India consists of approximately more than 1,000 varieties of mango.

11. What is the feature of the biosphere?
a) No diversity
b) Species diversity
c) Low diversity
d) Negligible diversity
Answer: b
Clarification: The diversity observed at the species level is known as the species diversity. It is the number and abundance of each species in a particular area. Species diversity is one of the important features of the biosphere.

12. Which organism’s species have greater diversity in the Western Ghats than the Eastern Ghats?
a) Reptiles
b) Fishes
c) Amphibians
d) Mammals
Answer: c
Clarification: Amphibians have more species diversity in the Western Ghats than the Eastern Ghats. A chain of mountains running parallel to India’s western coast (Sahyadri) and the mountain ranges run parallel to the Bay of Bengal are the western and eastern ghats respectively.

13. What is the feature of the biosphere?
a) Low diversity
b) Ecological diversity
c) Negligible diversity
d) No diversity
Answer: b
Clarification: Ecological diversity is one of the important features of the biosphere. It deals with the variations in ecosystems and their overall impact on human existence and the environment within a geographical area.

14. How many years did evolution required?
a) Tens
b) Hundreds
c) Trillions
d) Millions
Answer: d
Clarification: Evolution is the result of the process of slow and gradual changes in millions of years. As evolution proceeds, organisms become more and more complex. The complexity of organisms can be given by studying various processes of biological organization.

Biology Multiple Choice Questions on “Environmental Issues – Ozone Depletion in the Stratosphere”.

1. In which part of the atmosphere is the good ozone found?
a) Ionosphere
b) Stratosphere
c) Lithosphere
d) Hydrosphere
Answer: b
Clarification: The stratosphere found in the upper layer of the atmosphere has good ozone. This layer acts as a shield and absorbs the harmful, injurious ultraviolet (UV) radiations from the sun.

2. How is the thickness of the ozone in a column of air from the ground to the top of the atmosphere measured?
a) Dobson units
b) Hertz
c) Centimeter
d) Ampere
Answer: a
Clarification: Dobson unit (DU) is used to measure the thickness of the ozone in a column of air from the ground to the top of the atmosphere. A layer of pure ozone that is 0.01 mm thick at standard temperature and pressure is equivalent to one Dobson unit.

3. Who enhances the degradation of ozone?
a) Hydrogen
b) Chlorofluorocarbons
c) Oxygen
d) Water vapors
Answer: b
Clarification: Chlorofluorocarbons (CFCs) enhances the degradation of ozone by disturbing the cycle of ozone formation. CFCs upon entering in stratosphere react with UV and release chlorine ions. These ions act as catalysts and degrade ozone releasing molecular oxygen.

4. In which region is the depletion of ozone particularly marked?
a) Equatorial region
b) Temperate region
c) Tropical region
d) Antarctic region
Answer: d
Clarification: The stratosphere found in the upper layer of the atmosphere has good ozone. This layer acts as a shield and absorbs the harmful, injurious ultraviolet (UV) radiations from the sun. In the Antarctic region, the depletion of ozone particularly marked.

5. What does the continuous depletion of ozone lead to?
a) Proper rains
b) Ozone formation
c) Ozone hole
d) Good yield
Answer: c
Clarification: Due to the continuous degradation of ozone, the depletion of ozone occurs. This thinning in the layer of ozone is known as the ozone hole.

6. Which of the following is an effect of the high dose of UV-B?
a) Night-blindness
b) Snow-blindness
c) Fatigue
d) Nausea
Answer: b
Clarification: UV-B is the shorter wavelength of UV. It penetrates deeper into the skin causing aging of skin and cancers. A high dose of UB-B leads to snow-blindness, also known as arc eye or photokeratitis.

7. Which protocol was signed to control the emission of ozone-depleting substances?
a) France Protocol
b) Germany Protocol
c) India Protocol
d) Montreal Protocol
Answer: d
Clarification: To control the emission of ozone-depleting substances an international treaty, known as the Montreal Protocol, was signed. It was signed in 1987 by more than 175 countries in Montreal (Canada).

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