"Biology and Human Welfare" for Class 12 CHSE Biology students.
Chapter: Biology and Human Welfare
Multiple Choice Questions (MCQ)
1. Which of the following diseases is caused by a protozoan?
a) Typhoid
b) Pneumonia
c) Malaria
d) Common cold
Answer: c) Malaria
2. The causative agent of elephantiasis (filariasis) is:
a) Salmonella typhi
b) Wuchereria bancrofti
c) Entamoeba histolytica
d) Ascaris lumbricoides
Answer: b) Wuchereria bancrofti
3. Which type of immunity is obtained by injecting pre-formed antibodies into a person?
a) Active immunity
b) Passive immunity
c) Innate immunity
d) Cell-mediated immunity
Answer: b) Passive immunity
4. The property of cancerous cells that distinguishes them from normal cells is:
a) Contact inhibition
b) Controlled cell division
c) Metastasis
d) Apoptosis
Answer: c) Metastasis
5. Which of the following tests is used for the diagnosis of AIDS?
a) Widal test
b) ELISA
c) MRI
d) ECG
Answer: b) ELISA
6. A commonly abused drug obtained from the poppy plant (Papaver somniferum) is:
a) Cocaine
b) Marijuana
c) Morphine
d) LSD
Answer: c) Morphine
7. Somaclonal variation is observed in plants produced by:
a) Traditional breeding
b) Tissue culture
c) Hybridization
d) Mutation breeding
Answer: b) Tissue culture
8. Which of the following is a biofortified crop?
a) Golden Rice (Vitamin A enriched)
b) BT Cotton
c) Flavr Savr Tomato
d) RoundUp Ready Soybean
Answer: a) Golden Rice (Vitamin A enriched)
9. Apiculture is the rearing of:
a) Fish
b) Silkworms
c) Honey bees
d) Poultry
Answer: c) Honey bees
10. "Pusa Swarnim" is a variety of which crop, resistant to white rust?
a) Wheat
b) Mustard
c) Rice
d) Maize
Answer: b) Mustard
11. Which bacterium is primarily responsible for converting milk into curd?
a) Acetobacter aceti
b) Saccharomyces cerevisiae
c) Lactic Acid Bacteria (LAB)
d) Propionibacterium shermanii
Answer: c) Lactic Acid Bacteria (LAB)
12. The gas produced during the primary treatment of sewage in an anaerobic sludge digester is mainly:
a) Oxygen
b) Carbon dioxide
c) Methane
d) Nitrogen
Answer: c) Methane
13. The fungus Trichoderma polysporum produces an immunosuppressive agent called:
a) Statins
b) Cyclosporin A
c) Penicillin
d) Streptokinase
Answer: b) Cyclosporin A
14. Bacillus thuringiensis (Bt) is used as a:
a) Biofertilizer
b) Biocontrol agent
c) Source of antibiotic
d) Industrial enzyme producer
Answer: b) Biocontrol agent
15. Which of the following is an example of a symbiotic biofertilizer?
a) Azotobacter
b) Anabaena
c) Rhizobium
d) Azospirillum
Answer: c) Rhizobium
Short Answer Questions (2-3 marks)
1. What are pathogens? Give two examples of human diseases caused by bacteria.
Answer: Pathogens are disease-causing microorganisms or agents. Examples of human diseases caused by bacteria include Typhoid (caused by Salmonella typhi) and Pneumonia (caused by Streptococcus pneumoniae or Haemophilus influenzae).
2. Name the causative agent of malaria and its vector.
Answer: The causative agent of malaria is a protozoan, Plasmodium (e.g., P. vivax, P. falciparum). Its vector is the female Anopheles mosquito.
3. Differentiate between innate and acquired immunity.
Answer:
* Innate Immunity: Non-specific, present from birth, and provides a general defense against various pathogens (e.g., skin, mucous membranes, fever, phagocytes).
* Acquired Immunity: Specific, developed during an individual's lifetime after exposure to a pathogen or antigen. It involves memory and can be active or passive (e.g., antibody production, T-cell responses).
4. What are vaccines? How do they provide immunity?
Answer: Vaccines are biological preparations (e.g., weakened/inactivated pathogens, their toxins, or parts of them) that provide active acquired immunity to a particular infectious disease. They work by stimulating the body's immune system to produce antibodies and memory cells without causing the disease itself, thereby providing protection against future infections.
5. What is contact inhibition? How is it related to cancer?
Answer: Contact inhibition is a property of normal cells where their growth and division are inhibited when they come into contact with other cells. Cancer cells, however, lose this property, leading to uncontrolled proliferation and the formation of tumors.
6. List two modes of transmission of HIV.
Answer: Two common modes of HIV transmission are:
* Sexual contact with an infected person.
* Transfusion of contaminated blood or blood products.
* Sharing infected needles (e.g., among intravenous drug users).
* From infected mother to child during pregnancy, childbirth, or breastfeeding.
7. What is biofortification? Give an example.
Answer: Biofortification is the process of breeding crops to increase their nutritional value (e.g., higher vitamins, minerals, or protein content). Example: Maize hybrids with twice the amount of amino acids lysine and tryptophan, or Vitamin-A enriched carrots and spinach.
8. Name two common Indian breeds of cattle used for dairy farming.
Answer: Sahiwal, Red Sindhi, Gir, Deoni. (Any two)
9. What is Single Cell Protein (SCP)? Mention one advantage of using SCP.
Answer: Single Cell Protein (SCP) refers to the biomass or protein extracted from cultivated microbial cells (like algae, fungi, bacteria, or yeast) used as a food or feed supplement. Advantage: High protein content, rapid growth rate, can be produced from various inexpensive substrates, reduces environmental pollution.
10. How are microbes used in household food processing (give two examples)?
Answer:
* Curd production: Lactic Acid Bacteria (LAB) convert milk into curd.
* Dough fermentation: Yeast (Saccharomyces cerevisiae) is used for fermenting dough in bread making and idli/dosa batter, producing CO2 that causes rising.
* Cheese production: Specific microbes (e.g., Propionibacterium shermanii for Swiss cheese, Penicillium roqueforti for Roquefort cheese) are used for fermentation and ripening.
11. Name two microbes used in the industrial production of antibiotics.
Answer:
* Penicillium notatum (for Penicillin)
* Streptomyces griseus (for Streptomycin)
12. Briefly explain the role of activated sludge in sewage treatment.
Answer: Activated sludge is the sediment formed during the secondary (biological) treatment of sewage. It is rich in aerobic microbes (bacteria and fungi) that rapidly consume the organic matter in the wastewater. A small part of this activated sludge is then pumped back into the aeration tank as an inoculum, while the rest is transferred to an anaerobic sludge digester for further treatment.
13. How are microbes used for energy generation? Give an example.
Answer: Microbes are used in anaerobic digestion to produce biogas, a mixture of gases (mainly methane) that can be used as fuel. This process involves methanogenic bacteria (e.g., Methanobacterium) acting on organic waste. Example: Biogas plants that convert agricultural waste, animal dung into biogas.
14. What are biocontrol agents? Give an example of a fungal biocontrol agent.
Answer: Biocontrol agents are living organisms (microbes, insects, etc.) used to control pests and diseases of plants without relying on chemical pesticides. Example of a fungal biocontrol agent: Trichoderma (used to control plant pathogens in the root ecosystem).
15. What are biofertilizers? Name a cyanobacterium that acts as a biofertilizer.
Answer: Biofertilizers are organisms that enrich the nutrient quality of the soil, mainly by fixing atmospheric nitrogen or solubilizing phosphates, making them available to plants. Cyanobacterium example: Anabaena, Nostoc (used as biofertilizers in paddy fields).
Long Answer Questions (5-6 marks)
1. Describe the various stages of the life cycle of Plasmodium in humans and mosquitoes. Explain the symptoms and prevention of malaria.
Answer:
The life cycle of Plasmodium (the malarial parasite) is complex, involving two hosts: humans (asexual reproduction) and Anopheles mosquitoes (sexual reproduction).
Life Cycle of Plasmodium:
A. In Human Host (Asexual Cycle):
Infection: When an infected female Anopheles mosquito bites a healthy human, it injects sporozoites (infectious form of Plasmodium) into the bloodstream.
Liver Stage (Exo-erythrocytic cycle): Sporozoites travel via the blood to the liver cells. Inside liver cells, they multiply asexually (schizogony) and develop into merozoites. The liver cells burst, releasing merozoites into the blood.
Red Blood Cell (RBC) Stage (Erythrocytic cycle): Merozoites invade fresh red blood cells. Inside RBCs, they multiply asexually, forming trophozoites which then develop into schizonts. The schizonts mature and burst the RBCs, releasing more merozoites, which infect new RBCs. This cyclical bursting of RBCs releases a toxic substance called haemozoin, which is responsible for the fever and chills characteristic of malaria.
Gametocyte Formation: Some merozoites, instead of forming schizonts, differentiate within RBCs into sexual stages called gametocytes (male and female). These gametocytes remain in the human blood, but cannot develop further in humans.
B. In Mosquito Host (Sexual Cycle):
Infection of Mosquito: When a female Anopheles mosquito bites an infected human, it ingests the blood meal containing gametocytes.
Fertilization: Inside the mosquito's gut (midgut), the gametocytes mature into male and female gametes, which then fuse (fertilization) to form a diploid zygote.
Ookinete and Oocyst: The zygote develops into an elongated, motile ookinete, which then penetrates the gut wall and forms a cyst-like structure called an oocyst on the outer surface of the midgut.
Sporozoite Formation: Inside the oocyst, multiple asexual divisions occur, producing thousands of infectious sporozoites.
Migration to Salivary Glands: The oocyst bursts, releasing sporozoites that migrate to the mosquito's salivary glands. From here, they can be injected into a new human host, completing the cycle.
Symptoms of Malaria:
Recurring cycles of high fever (up to 103-106°F) and chills, often appearing every 3-4 days (depending on Plasmodium species).
Headache, muscle pain, nausea, vomiting.
Fatigue, malaise.
In severe cases, anemia, enlarged spleen and liver, cerebral malaria (affecting brain), kidney failure, and death.
Prevention of Malaria:
Vector Control:
Controlling mosquito breeding by preventing water stagnation (e.g., draining puddles, covering water containers).
Spraying insecticides in stagnant water bodies and inside homes.
Introducing larvivorous fish (e.g., Gambusia) in ponds.
Personal Protection:
Using mosquito nets (especially insecticide-treated nets).
Wearing protective clothing.
Using mosquito repellents.
Chemoprophylaxis: Taking anti-malarial drugs before, during, and after travel to endemic areas to prevent infection.
Early Diagnosis and Treatment: Prompt treatment of infected individuals to prevent transmission to mosquitoes.
Vaccine Development: Research is ongoing for an effective malaria vaccine (e.g., RTS,S vaccine provides partial protection).
2. Describe the various methods employed in plant breeding to develop improved crop varieties. Explain the importance of single cell protein (SCP) and biofortification in enhancing food production.
Answer:
Methods Employed in Plant Breeding: Plant breeding is the purposeful manipulation of plant species to create desired plant types that are better suited for cultivation, yield more, and are disease resistant, etc. Key methods include:
Introduction and Acclimatization: Introducing new plant varieties from other places and allowing them to adapt to the new environment.
Selection: Identifying and propagating individual plants with desirable traits from a mixed population (mass selection, pure-line selection, clonal selection).
Hybridization: Crossing two genetically dissimilar parents to produce a hybrid with a combination of desirable traits from both parents. This is followed by selection and testing of superior recombinants.
Mutation Breeding: Inducing mutations in crops using mutagens (e.g., radiation, chemicals) to create new variations not naturally present, and then selecting for desirable mutants. (e.g., Mung bean resistant to yellow mosaic virus).
Polyploidy Breeding: Increasing the chromosome number in plants (polyploidy) to enhance vigor, fruit size, or create new species (e.g., triticale, a hybrid of wheat and rye).
Tissue Culture (Micropropagation): Growing plant cells, tissues, or organs in a sterile nutrient medium under controlled conditions to produce a large number of genetically identical plantlets (somaclones). This is useful for rapid multiplication, disease-free plant production, and germplasm conservation.
Genetic Engineering (Transgenic Plants): Introducing foreign genes (from other species, even unrelated ones) into plant genomes to achieve desired traits like pest resistance (e.g., Bt cotton), herbicide tolerance, or improved nutritional quality.
Importance of Single Cell Protein (SCP): Single Cell Protein (SCP) refers to the edible protein biomass obtained from microbial cells such as bacteria, yeast, algae, or fungi.
High Protein Content: Microbes are rich in protein, making SCP a valuable protein source, especially for animal feed and human dietary supplements.
Rapid Growth Rate: Microorganisms have a very high rate of biomass production compared to traditional agriculture (e.g., potato takes months, microbes hours/days).
Less Land and Water Requirement: SCP production requires significantly less land and water compared to conventional animal agriculture.
Utilization of Waste Products: Many microbes can grow on inexpensive and diverse substrates like agricultural waste, industrial effluents, and even sewage, thus helping in waste utilization and pollution reduction.
Addressing Protein Deficiency: SCP can contribute to alleviating the global problem of protein deficiency, especially in developing countries. Example: Spirulina (alga) can be grown easily and used as food rich in protein, minerals, fats, carbohydrates, and vitamins.
Importance of Biofortification: Biofortification is the process of breeding crops to increase their nutritional value.
Combating Malnutrition: It directly addresses hidden hunger and malnutrition caused by micronutrient deficiencies (e.g., Vitamin A deficiency, iron deficiency anemia) in populations that primarily rely on staple crops.
Cost-Effective: Once biofortified seeds are developed, they can be multiplied and distributed, making improved nutrition accessible to many farmers and consumers without ongoing costs like supplements.
Sustainable: It is a sustainable and long-term solution for improving nutritional quality as the trait is genetically embedded in the crop itself.
Improved Health Outcomes: Consumption of biofortified crops can lead to better health outcomes, reduced disease burden, and improved cognitive development, especially in children and women.
Examples: Iron-fortified rice, Vitamin A-enriched maize/rice (Golden Rice), protein-enriched beans, and mineral-fortified sweet potato.
3. Elaborate on the diverse roles of microbes in human welfare, specifically focusing on their contributions in industrial production, sewage treatment, and as biofertilizers.
Answer:
Microbes (bacteria, fungi, yeasts, etc.) play indispensable and diverse roles in human welfare, impacting various aspects of our lives from food to environmental management.
A. Microbes in Industrial Production: Microbes are used in large-scale industrial processes for the production of a wide range of products:
Fermented Beverages: Yeast (Saccharomyces cerevisiae, brewer's yeast) is used for fermenting malted cereals and fruit juices to produce alcoholic beverages like beer, wine, whisky, brandy, and rum.
Antibiotics: Microbes are the primary source of antibiotics, which are chemical substances produced by some microbes that kill or retard the growth of other (disease-causing) microbes. Example: Penicillin, the first antibiotic, was discovered by Alexander Fleming from the fungus Penicillium notatum.
Organic Acids: Specific microbes produce various organic acids. Examples: Aspergillus niger (fungus) for citric acid, Acetobacter aceti (bacterium) for acetic acid, Clostridium butylicum (bacterium) for butyric acid, Lactobacillus for lactic acid.
Alcohols: Yeast is used for the commercial production of ethanol.
Enzymes: Many enzymes are produced industrially using microbes. Examples: Lipases (from Candida species) for detergent formulations, Pectinases and Proteases (from bacteria and fungi) for clarifying bottled juices, Streptokinase (from Streptococcus bacterium) as a 'clot buster' for removing clots from blood vessels of MI patients.
Bioactive Molecules:
Cyclosporin A: Produced by the fungus Trichoderma polysporum, used as an immunosuppressive agent in organ transplant patients.
Statins: Produced by the yeast Monascus purpureus, used as blood cholesterol-lowering agents.
B. Microbes in Sewage Treatment: Microbes are crucial for treating municipal wastewater (sewage) before its discharge into natural water bodies, significantly reducing pollution.
Primary Treatment (Physical): Involves physical removal of large and small particles through filtration and sedimentation. The settled solids form primary sludge, and the supernatant forms the effluent.
Secondary Treatment (Biological Treatment):
The primary effluent is passed into large aeration tanks, where it is continuously agitated and air is pumped into it. This allows vigorous growth of useful aerobic microbes (bacteria and fungi) into flocs (masses of bacteria associated with fungal filaments).
These microbes consume the major part of the organic matter present in the effluent, significantly reducing its Biochemical Oxygen Demand (BOD).
Once the BOD is reduced, the effluent is passed into a settling tank where the bacterial flocs settle down, forming activated sludge.
A small part of the activated sludge is pumped back into the aeration tank as an inoculum, while the remaining major part is transferred to large tanks called anaerobic sludge digesters.
In the digesters, other anaerobic bacteria digest the organic matter and the microbes in the sludge, producing a mixture of gases like methane, hydrogen sulphide, and CO2 (biogas), which can be used as energy.
The final effluent from the secondary treatment plant is then usually discharged into natural water bodies.
C. Microbes as Biofertilizers: Biofertilizers are organisms that enrich the nutrient quality of the soil, making essential nutrients available to plants. They reduce the reliance on chemical fertilizers.
Nitrogen-fixing Microbes:
Symbiotic: Rhizobium bacteria form symbiotic associations with the roots of leguminous plants, forming root nodules. They fix atmospheric nitrogen into organic forms that can be utilized by the plant.
Free-living: Azotobacter and Azospirillum (bacteria) and Anabaena, Nostoc (cyanobacteria/blue-green algae) are free-living nitrogen fixers in the soil, enriching its nitrogen content. Cyanobacteria are particularly important in paddy fields.
Phosphate Solubilizing Microbes: Some bacteria and fungi (e.g., species of Bacillus, Pseudomonas, Aspergillus) can solubilize insoluble phosphates in the soil, making them available to plants.
Mycorrhizae (Fungi): Fungi like Glomus form symbiotic associations with the roots of higher plants (mycorrhiza). They absorb phosphorus from the soil and transfer it to the plant, also providing resistance to root-borne pathogens and enhancing tolerance to salinity and drought.
In summary, microbes are vital for sustaining life on Earth and contributing immensely to human well-being through their roles in various industrial processes, environmental clean-up (sewage treatment), and promoting sustainable agriculture.
