Category: Class 12 Biology Objective Questions

250+ TOP MCQs on Parasitic and Protozoan Diseases in Animals and Answers

Biology Multiple Choice Questions on “Parasitic and Protozoan Diseases in Animals”.

1. Which of the following is not an endoparasite?
a) Ticks
b) Tapeworm
c) Liver fluke
d) Roundworm
Answer: a
Clarification: Endoparasites live inside the body of animals. They also generally feed over animal fluids and semi-digested food in the alimentary canal. For example, Tapeworm, Liver fluke and Roundworm.

2. Where does liver fluke lives in sheep?
a) Brain
b) Kidney
c) Bile ducts
d) Pancreas
Answer: c
Clarification: Liver fluke causes liver rot or fascioliasis in sheep. The parasite lives in bile ducts. Liver fluke also passes a part of its life cycle in snails. Eradication of snails can help in the control of the disease.

3. Which of the following is not caused by liver fluke in animals?
a) Anaemia
b) Diarrhoea
c) Eosinophilia
d) AIDS
Answer: d
Clarification: Liver fluke causes inflammation of bile ducts, anaemia, diarrhoea, eosinophilia and liver rot which may lead to the death of the animal. Anthelminthic drugs like emetine hydrochloride and hexachloroethane are useful in treatment of the disease.

4. Ectoparasites live inside the body of the animal.
a) True
b) False
Answer: b
Clarification: Parasitic animals can live inside as well as outside of the body of the host. Ectoparasites live on the skin feeding over dead skin and animal fluids. For example, ticks.

5. Which of the following is a common roundworm which infects domestic animals?
a) Rhabditis
b) Ascaris
c) Enterobius
d) Ancylostoma
Answer: b
Clarification: Ascaris is a common roundworm which infects both domestic animals as well as human beings. The disease caused by it is ascariasis. The source of infection is contaminated food.

6. Where do the embryonated eggs of Ascaris hatch out in the animal?
a) Heart
b) Brain
c) Kidney
d) Intestine
Answer: d
Clarification: The embryonated eggs of Ascaris hatch out in the intestine. The larvae pass into hepatic portal vein, spleen, liver, heart, pulmonary arteries, lungs, trachea, larynx, pharynx, oesophagus and intestine again where they develop into adult male and female worms.

7. Which of the following is not caused by the movement of larvae through the body of animal?
a) Diarrhoea
b) Anaemia
c) Typhoid
d) Constipation
Answer: c
Clarification: During the movement of the larvae through the body of the animal, Ascaris damages various body parts and causes permanent injury. In the intestine, adults rob the animal of nutrition causing constipation, diarrhoea, weakness and anaemia. They may at times block the intestine which causes the death of the animal.

8. How does the fresh infection of Ascaris occur in various animals?
a) Contaminated feed
b) Contaminated clothes
c) Contact with infected animals
d) Eating healthy food
Answer: a
Clarification: Fresh infection of Ascaris occurs due to feed or grass or water contaminated with the faecal matter of infected animals. The infected animal can be treated by giving drugs like piperax, piperazine adipate, wormex, alcopar, chenopodium oil, etc.

9. Coccidiosis is an infection of _______
a) Brain
b) Intestine
c) Eyes
d) Tongue
Answer: b
Clarification: Coccidiosis is an intestinal infection of animals caused by a group of protozoa called coccidia. The disease occasionally occurs in human beings where it is due to protozoan Isospora hominis or Isospora belli. The infection is asymptomatic, but may sometimes cause watery mucus containing diarrhoea.

10. Which of the following is not a physiological change that occurs in the body of animals suffering from Coccidiosis?
a) Erosion of intestinal mucosa
b) Intestinal haemorrhage
c) Dysentery
d) Brain stroke
Answer: d
Clarification: In domesticated animals, coccidiosis is associated with protozoans Eimeria, Isospora and a few others. It causes erosions of the intestinal mucosa, intestinal haemorrhage, diarrhoea and sometimes fatal dysentery. Coccidiosis is highly infective in young poultry birds.

11. Tick fever is also known as _________
a) Fascioliasis
b) Ascariasis
c) Babesiosis
d) Coccidiosis
Answer: c
Clarification: Tick fever is also known as Babesiosis. Ticks are blood-sucking ectoparasites of cattle and other domesticated animals. The infectious agent or pathogen is protozoan Babesia, several species of which cause the disease but most common in Babesia bigemina.

12. Which of the following is not a symptom of Babesiosis?
a) Anaemia
b) Paralysis
c) Jaundice
d) Constipation
Answer: b
Clarification: Symptoms of Babesiosis include high but irregular fever, enlargement of lymph nodes, haemolytic anaemia, jaundice, constipation followed by diarrhoea. Infected animals are treated with an injection of trypan blue, acaprin or berenil.

13. Presence of heart-shaped parasites inside erythrocytes is the diagnostic feature of babesiosis.
a) True
b) False
Answer: b
Clarification: Presence of pear-shaped parasites inside erythrocytes is the diagnostic feature of this disease. Eradication of ticks through external insecticide treatment and sanitation are useful in preventing the disease. Fresh tick attack is further prevented by treating grazing ground with the insecticide.

250+ TOP MCQs on Microbes in Industrial Products-3 and Answers

Biology Online Quiz for BDS-Dental Entrance Exams on “Microbes in Industrial Products-3”.

1. What are the bioactive chemicals?
a) Chemicals which influence the functioning of the living system
b) Chemicals which actively participate
c) Chemicals which slough off other cells
d) Chemicals which help in the feedback mechanism
Answer: a
Clarification: Bioactive substances are those chemicals which influence the functioning of a living system and elicit a response for the same. E.g., statins, cyclosporine, streptokinase, lectins, etc.

2. Which of the following is the first organic acid produced through fermentation?
a) Acetic Acid
b) Lactic Acid
c) Citric Acid
d) Gallic Acid
Answer: b
Clarification: Lactic acid was the first organic acid produced through fermentation. It is obtained by the activity of several bacteria like Streptococcus lactis, Lactobacillus bulgaris, etc.

3. Which of the following organisms is responsible for the production of Citric Acid?
a) Bacteria
b) Archaebacteria
c) Protozoa
d) Yeast
Answer: d
Clarification: Species of Yeast like Mucor species, Aspergillus niger can ferment sugar to produce citric acid. Citric acid is a preservative and flavouring agent.

4. Which of the following organic acid is used for providing calcium to the infants?
a) Gallic acid
b) Gluconic acid
c) Butyric acid
d) Lactic acid
Answer: b
Clarification: Gluconic acid is manufactured by the agency of Penicillium purpurogenum, for use as calcium gluconate for providing calcium to infants, lactating mothers and treating milk fever in high milk yielding cows.

5. Butyric acid is formed by the activity of Aspergillus niger.
a) True
b) False
Answer: b
Clarification: Butyric acid or butanoic acid is formed by the activity of a bacterium, Clostridium butylicum. It is the acid that occurs in rancid butter.

6. Which of the following is a function of pectinases?
a) Clearing of fruit juices
b) Degumming of silk
c) Cleaning of hides
d) Manufacturing of soap
Answer: a
Clarification: Pectinases are obtained from fungi grown on pectin containing media. Pectinases are used in enhancing juice extraction from fruits, clearing of fruit juices, removing bitterness, retting of fibres and fermentation of green coffee.

7. Which of the following is not a function of Proteases?
a) Cleaning of hides
b) Synthesis of glue
c) Manufacturing of soap
d) Tenderness of meat
Answer: c
Clarification: Proteases are used for enhancing tenderness of the meat, extraction of fish liver oil, clarification and chill proofing of alcoholic drinks, softening of cheese and bread, cleaning of hides, degumming of silk, synthesis of glue, etc.

8. Which of the following is not a function of amylases?
a) Manufacturing of soap
b) Sweetening of bread
c) Separation and desizing of fibres
d) Clearing starch related turbidity in fruit juices
Answer: a
Clarification: Amylases are starch digesting enzymes that are used in softening and sweetening of bread, separation and desizing of fibres, clearing of starch related turbidity in juices and clearing starch related stains on utensils and clothes.

9. Depending on the type of raw material used for fermentation and the type of processing, different types of alcoholic drinks are obtained.
a) True
b) False
Answer: a
Clarification: We can obtain different types of alcoholic drinks by using different raw materials for fermentation and by using different techniques for processing like processing alcoholic drinks with distillation or without distillation. For example, wine and beer are produced without distillation whereas whisky, brandy and rum are produced by distillation.

10. Which of the following is the function of lipases?
a) Manufacturing of soaps
b) Clearing of hides
c) Sweetening of bread
d) Removing bitterness
Answer: a
Clarification: Lipases are lipid digesting enzymes used in flavouring cheese, hydrolysing oils for manufacture of soap and in detergent formulations for removing fat-based stains.

11. Colonies of which microbe can be seen in the diagram below?

a) Fungi
b) Bacteria
c) Virus
d) Protozoa
Answer: a
Clarification: The given diagram represents a fungal colony growing in a petri-dish. These colonies can be seen with naked eyes and such cultures are useful in the studies of micro-organisms.

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250+ TOP MCQs on Biotechnology Applications – Pest Resistant Plants and Answers

Biology Written Test Questions for Schools on “Biotechnology Applications – Pest Resistant Plants – 2”.

1. Which agriculturally important bacterial gene is isolated from Rhizobium?
a) Nif gene
b) E-gene
c) F-gene
d) T-DNA
Answer: a
Clarification: Nif genes are a set of genes that are involved in atmospheric nitrogen fixation. They are isolated from a bacterium Rhizobium. It is a Gram-negative bacterium which symbiotically assists the leguminous plants and fix nitrogen.

2. Delay in the ripening of tomato is due to_____
a) virulent gene
b) antisense PG
c) antibiotic resistance gene
d) mutation
Answer: b
Clarification: PG stands for an enzyme called polygalacturonase which is responsible for pectin degradation leading to early ripening. Antisense PG inhibits the formation of polygalacturonase thus delaying the process of ripening.

3. The transgenic tomato variety with an improved shelf life is ______
a) Lyco 100
b) PHB tomato
c) Bt tomato
d) Flavr savr
Answer: d
Clarification: Flavr savr is a genetically modified tomato. It was the first GM food crop to be used commercially. It has a longer shelf life due to the incorporation of the antisense genes within its genome.

4. The transgenic plant ‘Flavr savr’ tomato carries an artificial gene for ______
a) delaying ripening process
b) added flavours
c) both delaying ripening process and added flavours
d) insect resistance
Answer: c
Clarification: The Flavr savr tomato carries an antisense PG gene which inhibits the activity of pectin degrading enzyme called polygalacturonase. This artificial gene delays the ripening process and increasing shelf life. It also adds flavor to the tomato.

5. Two bacteria found to be very useful in genetic engineering experiments are _______
a) Nitrosomonas and Klebsiella
b) Nitrobacter and Azotobacter
c) Escherichia and Agrobacterium
d) Rhizobium and Diplococcus
Answer: c
Clarification: Escherichia and Agrobacterium are the two most widely used bacteria for genetic engineering. Escherichia is useful for obtaining many products such as insulin while Agrobacterium is used for producing Bt crops.

6. Transgenic plants carry desirable traits like _______
a) harmful genes
b) herbicide resistance
c) lactose intolerance
d) complementary genes
Answer: b
Clarification: Transgenic plants carry desirable traits like herbicide resistance. Few herbs are weeds that interfere with the growth of normal desirable plants. Transgenic plants also carry other characteristics like disease-resistance, insect-resistance, etc.

7. Strains of Bacillus thuringiensis are being used for designing ______
a) biomineralization
b) biofertilizers
c) biometallurgical techniques
d) bioinsecticidal plants
Answer: d
Clarification: Bacillus thuringiensis is mainly used for the production of bioinsecticidal plants. Bacillus thuringiensis along has a cry gene that kills the organism. This gene is carried with a vector of Agrobacterium tumefaciens.

8. Natural genetic engineer is ________
a) Pseudomonas putida
b) Escherichia coli
c) Agrobacterium tumefaciens
d) Bacillus subtilis
Answer: c
Clarification: the natural genetic engineer is Agrobacterium tumefaciens. It is so-called because its plasmid (Ti plasmid) is used as a vector for the transfer of the insect-resistance gene called cry gene obtained from Bacillus thuringiensis.

9. Flavr savr variety of tomato is the improved variety developed through ________
a) hybridization between old varieties
b) mutation variety
c) incorporation of a transgene
d) hybridization between a modern variety and a wild variety
Answer: c
Clarification: Flavr savr is a genetically modified tomato developed through the incorporation of a transgene. The transgene introduced was the antisense PG gene which interferes with the enzyme called polygalacturonase thus increasing the shelf life of tomato.

10. Insect pest resistance Bt-cotton plant was developed using ________
a) transgenic technology
b) somaclonal variation
c) micropropagation
d) somatic hybridization
Answer: a
Clarification: Transgenic technology was used to develop Bt-cotton. It allows the introduction of the new and functional genes in the cell. This produces a new and better variety of crops. For example, Bt-cotton is a transgenic crop and is insect resistance.

11. A desirable change in the genotype of an organism is obtained by _______
a) m-RNA formation
b) DNA replication
c) protein synthesis
d) rDNA technology
Answer: d
Clarification: rDNA technology is a series of processes in which molecules of DNA from two different species of the organism are inserted within a host to introduce new characters within that host. This often lead to the formation of new and better host species.

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250+ TOP MCQs on Organisms and Populations – Adaptations and Answers

Biology Multiple Choice Questions on “Organisms and Populations – Adaptations – 1”.

1. What is an attribute of the organism that enables the organism to survive and reproduce in its habitat called?
a) Homeostasis
b) Adaptation
c) Migration
d) Hibernation
Answer: b
Clarification: Any attribute of the organism that enables the organism to survive and reproduce in its habitat called adaptation. It is an evolutionary process that takes place from generation to generation. It involves a character or feature or trait that helps an organism in a given habitat.

2. At what height does a person experience altitude sickness?
a) >3500 m
b) <3500 m
c) >500 feet
d) <500 feet
Answer: a
Clarification: A person experiences altitude sickness >3500 m or >8,000 feet. It is also known as mountain sickness. It occurs due to a decrease in pressure around a person due to which there is a decrease in oxygen level.

3. Which of the following is a symptom of altitude sickness?
a) Irritation
b) Heart palpitations
c) Bleeding
d) Hunger
Answer: b
Clarification: Among the above-given options heart palpitation is a symptom of altitude sickness. It occurs due to a decrease in pressure around a person due to which there is a decrease in oxygen level. Some other symptoms are nausea, fatigue, etc.

4. By what mechanism does the body compensate for low oxygen availability in altitude sickness?
a) Increasing the binding affinity of hemoglobin
b) Decreasing breathing rate
c) Decreasing the binding affinity of hemoglobin
d) Increasing red blood cell formation
Answer: d
Clarification: The body compensates for low oxygen availability in altitude sickness by increasing red blood cell formation that will increase the uptake of oxygen. A person experiences altitude sickness >3500 m or >8,000 feet.

5. Which one among the following statements is incorrect?
a) Siberian crane is a migratory bird
b) Archaebacteria flourishes in hot springs where the temperature exceeds >95°C
c) Desert lizard has the ability to keep the constant body temperature
d) Fishes can thrive in Antarctic water where the temperature is always below zero
Answer: c
Clarification: Among the above-given sentences, the desert lizard has the ability to keep a constant body temperature is an incorrect statement. This is so because lizards are ectotherms, cold-blooded whose temperature changes as per the temperature of surroundings.

6. What are the plants living in the desert called?
a) Hydrophytes
b) Mesophytes
c) Sciophytes
d) Hydrophytes
Answer: b
Clarification: Sciophytes are photophobous, shade-loving plants and are found in deserts. They have thinner leaves, large photosynthetic units, and lens-shaped epidermal cells. They also have high chlorophyll content per unit leaf volume.

7. In which plants do stomata open at night?
a) Hydrophytes
b) Neem
c) Mango
d) Succulents
Answer: d
Clarification: The stomata open during the night in succulents. These plants show an inverted stomatal rhythm as compared to normal plants. The succulents are usually seen in desert areas. To reduce transpiration these plants secrete waxes or resins.

8. Which is the adaptive radiation is used by poikilotherms to protect against extreme heat?
a) Migration
b) Cooling
c) Aestivation
d) Hibernation
Answer: c
Clarification: The poikilotherms use aestivation as a protective mechanism against extreme heat. The suspension of metabolic activities during summer is called aestivation. It helps in maintaining body temperature and avoids water loss in mostly cold-blooded animals such as snails, bees, tortoise, crocodile, etc.

9. In which region do succulents grow?
a) Tropical
b) Temperate
c) Antarctica
d) Desert
Answer: d
Clarification: The succulents are usually seen in desert areas. These are thick, fleshy and retain water in arid conditions. They are drought resistant, follow Crassulacean acid metabolism (CAM) pathway and store water in leaves and stems.

10. In which plants do sunken stomata is seen?
a) Temperate plants
b) Hydrophytes
c) Xerophytes
d) Tropical plants
Answer: c
Clarification: Sunken stomata are a feature of xerophytes. It is an adaptation made by desert or icy area plants to avoid water loss. Some examples of xerophytes are some Gymnosperm plants, cacti, pineapple, etc.

11. Through which part does photosynthesis occur in xerophytes?
a) Scaly leaves
b) Modified stems
c) Root
d) Chlorophyll
Answer: b
Clarification: In xerophytes, there is an adaption in which photosynthesis occurs with the help of modified stems to avoid water loss. Roots of xerophytes help in the storage of water. Scaly leaves do not help much in photosynthesis.

12. Which of the following animal excretes solid urine?
a) Crow
b) Fishes
c) Kangaroo rat
d) Camel
Answer: c
Clarification: Solid urine is excreted by kangaroo rat to avoid excess loss of water. They are rodents and their kidneys have developed mechanisms to highly concentrate their urine. They have longer papilla in their kidneys.

13. In which plants mechanical tissue is best developed?
a) Mesophytes
b) Xerophytes
c) Psammophytes
d) Hydrophytes
Answer: b
Clarification: The mechanical tissue that is collenchyma is best developed in xerophytes. These are enclosed within rigid channels to avoid water loss. Along with this bark of xerophytes is also well developed to retain water.

14. What are plants adapted to grow in the sand called?
a) Halophytes
b) Hydrophytes
c) Mesophytes
d) Psammophytes
Answer: d
Clarification: The plants adapted to live in the sand are called psammophytes. They have an adventitious root system. They are also found along seas, sands along rivers and large lakes where sand is available.

15. Where are stomata present in submerged hydrophytes?
a) Nowhere
b) On lower surface
c) In the corners
d) On the upper surface
Answer: a
Clarification: In submerged hydrophytes stomata are absent. These are true water plants in which plant cells are used to absorb nutrients, water, and dissolved gases in water. Some examples of submerged hydrophytes are Hydrilla, Potamogeton, Utricularia, etc.

250+ TOP MCQs on Ecosystem – Productivity and Answers

Biology Quiz for Pharmacy Entrance Exams on “Ecosystem – Productivity – 2”.

1. Which of the following is estimated in either the photosynthetic number or chlorophyll content?
a) Gross primary productivity
b) Net primary productivity
c) Primary productivity
d) Net productivity
Answer: b
Clarification: The rate of production of organic matter during photosynthesis is defined as the gross primary productivity (GPP). It is estimated in either the photosynthetic number or chlorophyll content.

2. On whom does the primary productivity depend on?
a) Plants
b) Animals
c) Sunlight
d) Wing
Answer: a
Clarification: The rate at which solar energy is converted and stored by the producers per unit area over a time period is called primary productivity. It mainly depends on the variety of plant species residing in a particular area.

3. What is the approximate amount of the annual net primary productivity of the whole biosphere?
a) 80 million tons of organic matter
b) 170 billion tons of organic matter
c) 10 billion tons of organic matter
d) 2 million tons of organic matter
Answer: b
Clarification: The net primary productivity is the energy left after the respiration i.e. the gross primary productivity subtracted by respiration losses. It is approximately 170 billion tons of organic matter of the whole biosphere.

4. How much of Earth’s surface is occupied by oceans?
a) 90%
b) 1%
c) 65%
d)70%
Answer: d
Clarification: Almost 70% of Earth’s surface is occupied by oceans. An ocean is the largest body of water comprising of much of the planet’s hydrosphere. In all, there are 5 oceans on Earth namely Pacific, Atlantic, Indian, Antarctic, and Arctic oceans.

5. How much is the productivity of oceans?
a) 10 billion tons
b) 170 billion tons
c) 55 billion tons
d) 2 million tons
Answer: c
Clarification: Productivity is the rate of new biomass production by an individual, population, community within an ecosystem. The productivity of oceans is approximately 55 billion tons.

6. How much is the productivity of landmass?
a) 115 billion tons
b) 170 billion tons
c) 55 million tons
d) 170 million tons
Answer: a
Clarification: Productivity is the rate of new biomass production by an individual, population, community within an ecosystem. The productivity of landmass is approximately 115 billion tons.

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250+ TOP MCQs on Ecosystem – Carbon Cycle and Answers

Biology Multiple Choice Questions on “Ecosystem – Carbon Cycle”.

1. What percent of dry weight does carbon constitute in the living organisms?
a) 55 percent
b) 49 percent
c) 20 percent
d) 90 percent
Answer: b
Clarification: The carbon constitutes approximately 49 percent of the total dry weight of living things. It is the second most abundant thing found in nature next to the water. It is the fourth most abundant element of the universe.

2. Which is the most abundant constituent found in living organisms?
a) Water
b) Oxygen
c) Ammonia
d) Hydrogen bicarbonate
Answer: a
Clarification: The most abundant compound found in living organisms is water. It is the most important compound for the survival of living organisms. A human body consists of 60% water.

3. Out of the total quantity of global carbon, what percent of carbon is found dissolved in oceans?
a) 50 %
b) 71 %
c) 90 %
d) 25 %
Answer: b
Clarification: Almost 71 percent of carbon is found dissolved in oceans out of the total quantity of global carbon. Out of this 71 percent, almost 90 percent is found in oceans. The oceans consist of 38,000- 40,000 gigatons (Gt) of carbon.

4. Which reservoir regulates the amount of carbon dioxide in the atmosphere?
a) Gaseous reservoir
b) Sedimentary reservoir
c) Atmospheric reservoir
d) Oceanic reservoir
Answer: d
Clarification: Almost 71 percent of carbon is found dissolved in oceans out of the total quantity of global carbon. Out of this 71 percent, almost 90 percent is found in oceans. The regulation of carbon dioxide in the atmosphere is done by this oceanic reservoir

5. What percent of total global carbon does the atmosphere contain?
a) 5 %
b) 50 %
c) 1%
d) 20 %
Answer: c
Clarification: Almost 49 percent of the total dry weight of living things is constituted by carbon. The atmosphere consists of only 1 % of the total global carbon. It is the fourth most abundant element of the universe.

6. Whose reservoir does fossil fuel represent?
a) Oxygen
b) Carbon
c) Helium
d) Argon
Answer: b
Clarification: The fossil fuel represents the reservoir of carbon. Almost 21.3 gigatons of carbon dioxide are released per year due to the burning of fossil fuels.

7. From which stages does the carbon cycling occur?
a) Dead organisms → Living organisms → Oceans
b) Atmosphere → Living organisms → Dead organisms
c) Oceans → Atmosphere → Dead organisms
d) Atmosphere → Oceans → Living organisms → Dead organisms
Answer: d
Clarification: The carbon from the atmosphere in the form of carbon dioxide gets into oceans. Through this, the carbon enters into living organisms and then to dead organisms. This carbon from dead organisms enters the Earth’s crust.

8. What amount of carbon is fixed in the biosphere through photosynthesis annually?
a) 1013 kg
b) 20 × 1020 kg
c) 4 × 1013 kg
d) 80 × 1035 kg
Answer: c
Clarification: Photosynthesis is a process in which producers (green plants) in the presence of CO2, water, sunlight, and chlorophyll yield energy and oxygen is released in the form of gas. The amount of carbon fixed in the biosphere through photosynthesis annually is approximately 4 × 1013 kg.

9. By which process does the carbon return to the atmosphere as CO2?
a) Decayed organisms
b) Calcareous sediments
c) Photosynthesis
d) Respiration
Answer: d
Clarification: The respiration is the process in which the organisms exchange gases with the environment. In this, the organisms take in the atmospheric oxygen for various cellular activities and release carbon dioxide. Thus the carbon returns to the atmosphere as CO2 with the help of respiration.

10. Which of the following organism contributes to the CO2 pool by the processing of waste materials and dead organic matter?
a) Carnivores
b) Herbivores
c) Decomposers
d) Producers
Answer: c
Clarification: The organisms that are responsible for the break down complex organic matter (dead or decaying organisms) into inorganic substances are called decomposers (detritivores). They process the dead matter present on land and oceans. The decomposers or detritivores may include invertebrates, fungus or bacteria.

11. Which human activities have significantly influenced the carbon cycle?
a) Afforestation
b) Deforestation only
c) Burning of fossil fuel only
d) Both deforestation and burning of fossil fuel
Answer: d
Clarification: The human activities like excessive deforestation and burning of fossil fuel has greatly influenced the carbon cycle. These activities have increased the rate of release of carbon dioxide into the atmosphere.

12. In which form does the carbon dioxide precipitate after dissolving in water?
a) Calcium oxide
b) Carbon mono-oxide
c) Calcium carbonate
d) Calcium phosphate
Answer: c
Clarification: The CO2 in gaseous form is quite soluble in water. When carbon dioxide dissolves in water, it precipitates and leads to the formation of calcium carbonate.

13. What product does the plants from by photosynthesis using carbon dioxide?
a) Lipids
b) Carbohydrates
c) Proteins
d) Salts
Answer: b
Clarification: The plants form carbohydrates using carbon dioxide through photosynthesis. Photosynthesis is a process in which producers (green plants) in the presence of CO2, water, sunlight, and chlorophyll yield energy and oxygen is released in the form of gas.

14. Which one of the following plants use as a source for carbon dioxide?
a) Carbonate rocks
b) Calcium rocks
c) Fossils
d) Atmospheric CO2
Answer: d
Clarification: The plants use atmospheric CO2 as a source of carbon dioxide for food production. They produce food using photosynthesis. Photosynthesis is a process in which producers (green plants) in the presence of CO2, water, sunlight, and chlorophyll yield energy and oxygen is released in the form of gas.

15. For releasing CO2 in the atmosphere, how are fossil fuels exploited?
a) Mined and burned
b) Fragmented and leached
c) Leached and burned
d) Mined and fragmented
Answer: a
Clarification: A fuel formed by anaerobic decomposition of buried dead organisms, containing energy is known as a fossil fuel. These are fossil fuels Mined and burned contributing to the atmospheric CO2.