11. The messages received by and transmitted from the brain to the various parts of the body take the form of which of the following impulses? (UPSC Prelims 1983)
[A] Nervous impulses
[B] Chemical impulses
[C] Mechanical impulses
[D] Automatic impulses
Show Answer
Correct Answer: A [Nervous impulses]
Notes:
The nervous system communicates through electrochemical nerve impulses. Action potentials travel along nerve fibres, and chemical neurotransmitters carry signals across many synapses. Nervous impulses is the most complete description among these options.
12. Consider the following statements regarding bones in the human body:
- They consist of 80% solid matter and20% water.
- Solid matter in the bones is made mainly of cartilage.
- Impregnation of salts including carbonates and phosphates of lime imparts hardness to the bones.
- In old age, the proportion of lime decreases and bones become brittle and break easily.
Of these statements:
[A] 1,2 and 3 are correct
[B] 2 and 4 are correct
[C] 2 and 3 are correct
[D] 1, 2, 3 and 4 are correct
Show Answer
Correct Answer: D [1, 2, 3 and 4 are correct]
Notes:
All of them are correct.
Bones consist of living cells embedded in a mineralized organic matrix. This matrix consists of organic components, mainly type I collagen – “organic” referring to materials produced as a result of the human body – and inorganic components, primarily hydroxyapatite and other salts of calcium and phosphate.
13. In Mycorrhiza, symbiotic association occurs between which of the following organisms? (UPSC Prelims 1990)
[A] Bacteria and roots of higher plants
[B] Algae and roofs of orchids
[C] Fungi and roots of higher plants
[D] Protozoa and roots of higher plants
Show Answer
Correct Answer: C [Fungi and roots of higher plants]
Notes:
Mycorrhiza is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant’s rhizosphere, its root system.
14. Which of the following is the quality of the pitch of the voice of women? (UPSC Prelims 1994)
[A] marginally lower than that of men
[B] higher than that of men
[C] much lower than that of men
[D] the same as that of men
Show Answer
Correct Answer: B [higher than that of men]
Notes:
The larger the larynx, the longer and thicker the vocal folds and the lower the pitch of the voice. Typical male voices range in pitch from 85 hertz to 180 hertz. Typical female voices range from 165 hertz to 255 hertz.
15. Which one of the following is a membrane that protects the developing embryo from desiccation? (UPSC Prelims 1995)
[A] Amnion
[B] Allantois
[C] Chorion
[D] Yolk sac
Show Answer
Correct Answer: A [Amnion]
Notes:
The amnion or amniotic sac protects everyone embryo from desiccation, it contains amniotic fluid which cushions the embryo from shocks.
16. Which organelle in the cell, other than nucleus, contains DNA? (UPSC Prelims 2001)
[A] Centriole
[B] Golgi apparatus
[C] Lysosome
[D] Mitochondrion
Show Answer
Correct Answer: D [Mitochondrion]
Notes:
Mitochondrion is the organelle in the cell, other than nucleus that contains DNA. Mitochondria are the working organelles that keep the cell full of energy. Mitochondria are small organelles floating free throughout the cell. Some cells have several thousand mitochondria while others have none. Muscle cells need a lot of energy so they have loads of mitochondria.
17. Which among the following is not a part of Vitamin B complex?
[A] Vitamin B2
[B] Vitamin B4
[C] Vitamin B6
[D] Vitamin B12
Show Answer
Correct Answer: B [Vitamin B4]
Notes:
Vitamin B complex consists of 8 vitamins namely B1(Thiamine), B2(Riboflavin), B3(Niacin), B5(Pantothenic acid), B6(Pyridoxine), B7(Biotin), B9(Folate/Folic acid) and B12(Cobalamin).
18. Which among the following is an optimum temperature for wheat seed germination?
[A] 11-15 deg celsius
[B] 15-25 deg celsius
[C] 10-12 deg celsius
[D] 20-22 deg celsius
Show Answer
Correct Answer: C [10-12 deg celsius]
Notes:
10-12 deg celsius is the optimum temperature for wheat germination. 25-30 deg celsius is the optimum temperature for crop growth.
19. What are the major types of cytoskeleton filaments?
[A] Actin filaments
[B] microtubules
[C] Intermediate filaments
[D] All of them
Show Answer
Correct Answer: D [All of them]
Notes:
Three major types of filaments make up the cytoskeleton: actin filaments, microtubules, and intermediate filaments.
20. How many bacterial cells are there in the human body?
[A] around 28 trillion
[B] around 38 trillion
[C] around 48 trillion
[D] around 58 trillion
Show Answer
Correct Answer: B [around 38 trillion]
Notes:
The number of bacterial cells inside the human body is approximately 38 trillion. This is very close to the estimated 30 trillion human cells in the body.
