21. What is the role of decomposers in the ecosystem?
a) Produce food for plants
b) Convert dead organic matter into nutrients
c) Fix nitrogen in the soil
d) Control population
Answer: b) Convert dead organic matter into nutrients
Explanation: Decomposers break down dead organisms and recycle nutrients into the soil.
6. Sustainable Management of Natural Resources
22. What is the primary aim of sustainable development?
a) Deplete resources
b) Overuse natural resources
c) Meet the needs of the present without compromising future generations
d) Promote industrialization
Answer: c) Meet the needs of the present without compromising future generations
Explanation: Sustainable development ensures responsible use of resources for long-term benefits.
23. Which method can be used to conserve water in agriculture?
a) Over-irrigation
b) Rainwater harvesting
c) Deforestation
d) Burning fossil fuels
Answer: b) Rainwater harvesting
Explanation: Rainwater harvesting collects and stores rainwater for irrigation and other uses.
24. Which of the following practices contributes to deforestation?
a) Planting trees
b) Urbanization
c) Agroforestry
d) Conservation projects
Answer: b) Urbanization
Explanation: Urbanization involves clearing forests for building infrastructure, leading to deforestation.
7. Evolution
25. Which evidence supports the theory of evolution?
a) Similar DNA sequences in different species
b) Unique characteristics in each species
c) All species have the same lifespan
d) Organisms are unchanging over time
Answer: a) Similar DNA sequences in different species
Explanation: Similar DNA sequences indicate common ancestry, supporting evolution.
26. What is a vestigial organ?
a) An organ with no known function
b) An organ that is fully functional
c) A newly evolved organ
d) An organ responsible for reproduction
Answer: a) An organ with no known function
Explanation: Vestigial organs are remnants of structures that were functional in ancestors but have lost their function.
Continuing with more MCQs from Class 8–10 Biology, maintaining a moderate to difficult level.
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8. Human Health and Diseases
27. Which pathogen causes malaria?
a) Bacteria
b) Protozoa
c) Virus
d) Fungus
Answer: b) Protozoa
Explanation: Malaria is caused by the protozoan parasite Plasmodium, transmitted through the female Anopheles mosquito.
28. Which disease is caused by the deficiency of vitamin C?
a) Rickets
b) Scurvy
c) Night blindness
d) Beriberi
Answer: b) Scurvy
Explanation: Scurvy results from vitamin C deficiency, leading to bleeding gums and weakened immunity.
29. What is the primary function of antibodies in the immune system?
a) Transport oxygen
b) Kill pathogens directly
c) Bind to antigens and neutralize pathogens
d) Destroy red blood cells
Answer: c) Bind to antigens and neutralize pathogens
Explanation: Antibodies are proteins produced by B cells that specifically target antigens.
30. What is the mode of transmission of dengue fever?
a) Contaminated water
b) Infected mosquito bite
c) Airborne droplets
d) Direct contact
Answer: b) Infected mosquito bite
Explanation: Dengue is transmitted by the Aedes mosquito.
9. Respiration in Organisms
31. What is the site of gaseous exchange in the human lungs?
a) Bronchi
b) Alveoli
c) Trachea
d) Diaphragm
Answer: b) Alveoli
Explanation: Alveoli are small air sacs in the lungs where oxygen is exchanged with carbon dioxide.
32. Which organisms perform anaerobic respiration?
a) Fish
b) Yeast
c) Humans
d) Birds
Answer: b) Yeast
Explanation: Yeast can respire anaerobically, producing ethanol and carbon dioxide in the absence of oxygen.
33. What happens to the diaphragm during inhalation?
a) It relaxes and moves upward
b) It contracts and moves downward
c) It becomes rigid
d) It splits into two parts
Answer: b) It contracts and moves downward
Explanation: During inhalation, the diaphragm contracts to increase lung volume and allow air to flow in.
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10. Transportation in Animals and Plants
34. Which blood vessels carry oxygen-rich blood?
a) Veins
b) Arteries
c) Capillaries
d) Lymph vessels
Answer: b) Arteries
Explanation: Arteries, except the pulmonary artery, carry oxygenated blood from the heart to the body.
35. What is the role of platelets in the blood?
a) Transport oxygen
b) Fight infections
c) Aid in blood clotting
d) Maintain blood pressure
Answer: c) Aid in blood clotting
Explanation: Platelets help form clots to prevent excessive bleeding when a blood vessel is injured.
36. What is the vascular tissue in plants that transports food?
a) Xylem
b) Phloem
c) Cambium
d) Epidermis
Answer: b) Phloem
Explanation: Phloem transports food made in the leaves to other parts of the plant.
11. Excretion in Animals
37. Which organ in the human body filters blood to form urine?
a) Liver
b) Kidneys
c) Lungs
d) Pancreas
Answer: b) Kidneys
Explanation: Kidneys filter waste products from the blood, which are excreted as urine.
38. Which nitrogenous waste product is excreted by humans?
a) Ammonia
b) Uric acid
c) Urea
d) Creatinine
Answer: c) Urea
Explanation: Urea is a major nitrogenous waste product in humans, excreted through urine.
39. Which structure in plants removes excess water?
a) Stomata
b) Root hair
c) Xylem
d) Phloem
Answer: a) Stomata
Explanation: Stomata release excess water through transpiration.
12. Reproduction in Plants
40. Which method of reproduction is seen in potato?
a) Sexual reproduction
b) Binary fission
c) Vegetative propagation
d) Pollination
Answer: c) Vegetative propagation
Explanation: Potatoes reproduce through vegetative propagation using their tubers.
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