Biology Archives

281. Which one of the following diseases may be caused by the deficiency of

Which one of the following diseases may be caused by the deficiency of vitamin C ?

[amp_mcq option1=”Rickets” option2=”Rabies” option3=”Hepatitis” option4=”Scurvy” correct=”option4″]

This question was previously asked in

UPSC NDA-2 – 2019

The correct option is D) Scurvy.

Scurvy is a disease resulting from a deficiency of vitamin C (ascorbic acid).

Vitamin C is essential for the synthesis of collagen, a protein required for healthy skin, gums, blood vessels, bones, and connective tissue. Symptoms of scurvy include fatigue, gum disease, joint pain, poor wound healing, and bleeding. Rickets is caused by Vitamin D deficiency. Rabies is a viral infection. Hepatitis is typically a viral infection causing liver inflammation.

282. Which one of the following statements regarding viruses is not true

Which one of the following statements regarding viruses is not true ?

[amp_mcq option1=”Viruses need living cells to reproduce.” option2=”All viruses are parasites.” option3=”Viruses can synthesize their food through photosynthesis.” option4=”Viruses are similar to chemical substances outside the host.” correct=”option3″]

This question was previously asked in

UPSC NDA-2 – 2019

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The correct option is C) Viruses can synthesize their food through photosynthesis.

Viruses are acellular entities that lack the metabolic machinery necessary for processes like photosynthesis or self-synthesis of food. They are obligate intracellular parasites.

Viruses require a host cell to reproduce because they lack the necessary enzymes and ribosomes. They hijack the host cell’s machinery to replicate. Outside a host cell, a virus particle is essentially an inert complex of genetic material and protein, behaving like a chemical substance. They obtain energy and building blocks from the host cell, not through photosynthesis or any independent metabolic activity.

283. Which one of the following is a bacterium that causes disease in the h

Which one of the following is a bacterium that causes disease in the human body ?

[amp_mcq option1=”Varicella zoster” option2=”Trypanosoma gambiense” option3=”Salmonella typhi” option4=”Plasmodium falciparum” correct=”option3″]

This question was previously asked in

UPSC NDA-2 – 2019

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The correct option is C) Salmonella typhi.

The question asks to identify a bacterium from the given options that causes disease in humans.

Salmonella typhi is a rod-shaped, Gram-negative bacterium that causes typhoid fever in humans. Varicella zoster is a virus (causes chickenpox and shingles). Trypanosoma gambiense is a protozoan (causes African sleeping sickness). Plasmodium falciparum is a protozoan (causes malaria).

284. Thyroid gland produces a hormone called “Thyroxine” which

Thyroid gland produces a hormone called “Thyroxine” which

[amp_mcq option1=”controls blood glucose levels.” option2=”controls ovulation.” option3=”controls metabolic rate.” option4=”maintains pregnancy.” correct=”option3″]

This question was previously asked in

UPSC NDA-2 – 2019

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The correct option is C) controls metabolic rate.

Thyroxine, produced by the thyroid gland, is the main hormone responsible for regulating the body’s metabolism, including how fast the body uses energy and makes proteins.

Thyroxine (T4) and triiodothyronine (T3), the active form, affect almost every cell in the body. They increase the basal metabolic rate, influence protein synthesis, help regulate long bone growth, and play a role in neural maturation. Blood glucose levels are primarily controlled by insulin and glucagon, ovulation by FSH, LH, and estrogen, and maintenance of pregnancy mainly by progesterone.

285. Who among the following popularized the use of embryological character

Who among the following popularized the use of embryological characters in taxonomy ?

[amp_mcq option1=”Carl Linnaeus” option2=”Panchanan Maheshwari” option3=”Birbal Sahni” option4=”Bentham and Hooker” correct=”option2″]

This question was previously asked in

UPSC NDA-2 – 2019

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The correct answer is B) Panchanan Maheshwari.

Panchanan Maheshwari was a renowned Indian botanist who made significant contributions to the study of angiosperm embryology. He extensively studied the embryological features of plants and emphasized their importance in understanding plant relationships and classification (taxonomy).

Carl Linnaeus is known as the father of modern taxonomy and is famous for his binomial nomenclature system. Birbal Sahni was an Indian paleobotanist. Bentham and Hooker developed a widely used system of classification based primarily on morphological characters. Panchanan Maheshwari’s work helped integrate embryological data into taxonomic studies, particularly for flowering plants.

286. Mitochondria are able to produce their own

Mitochondria are able to produce their own

[amp_mcq option1=”Nucleus” option2=”Proteins” option3=”Chloroplasts” option4=”Digestive enzymes” correct=”option2″]

This question was previously asked in

UPSC NDA-2 – 2019

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The correct answer is B) Proteins.

Mitochondria contain their own DNA and ribosomes, enabling them to synthesize some of the proteins they need for their function. This makes them semi-autonomous organelles.

Mitochondria are often called the “powerhouses” of the cell because they generate most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy. They are believed to have originated from symbiotic bacteria, which is supported by the presence of their own DNA (circular, similar to bacterial DNA) and ribosomes (70S, similar to bacterial ribosomes).

287. Blood is a type of

Blood is a type of

[amp_mcq option1=”Epithelial tissue” option2=”Muscular tissue” option3=”Nervous tissue” option4=”Connective tissue” correct=”option4″]

This question was previously asked in

UPSC NDA-2 – 2019

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Animal tissues are broadly classified into four primary types: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Each type has distinct structures and functions.
A) Epithelial tissue forms linings and coverings of surfaces and cavities, and constitutes glands.
B) Muscular tissue is responsible for movement through contraction.
C) Nervous tissue transmits electrical and chemical signals throughout the body.
D) Connective tissue supports, connects, or separates different types of tissues and organs. Connective tissues are characterized by having cells dispersed within an extracellular matrix. Blood consists of various cell types (red blood cells, white blood cells, platelets) suspended in a liquid extracellular matrix called plasma. Plasma accounts for a significant portion of blood volume and its components are produced by cells. Due to its structure (cells in an extracellular matrix) and function (connecting different parts of the body through transport), blood is classified as a specialized type of connective tissue.

– There are four main types of animal tissue: epithelial, connective, muscle, and nervous.
– Connective tissue supports and connects other tissues and organs.
– Blood consists of cells suspended in plasma, an extracellular matrix.
– Blood fits the definition and characteristics of connective tissue.

Other examples of connective tissue include bone, cartilage, adipose tissue (fat), and loose connective tissue found under the skin. Blood is sometimes considered a “fluid connective tissue” due to its liquid matrix (plasma).

288. Net movement of water from a dilute to a concentrated solution through

Net movement of water from a dilute to a concentrated solution through a selectively permeable membrane is called

[amp_mcq option1=”Diffusion” option2=”Dispersion” option3=”Osmosis” option4=”Absorption” correct=”option3″]

This question was previously asked in

UPSC NDA-2 – 2019

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The description “Net movement of water from a dilute to a concentrated solution through a selectively permeable membrane” is the definition of osmosis.
A) Diffusion is the net movement of particles (solute or solvent) from a region of higher concentration to lower concentration, which can occur with or without a membrane. It is driven by a concentration gradient.
B) Dispersion refers to the spreading out of particles or substances.
C) Osmosis is specifically the movement of solvent (usually water) across a selectively permeable membrane from an area of higher water potential (dilute solution, lower solute concentration) to an area of lower water potential (concentrated solution, higher solute concentration). This movement occurs down the water potential gradient and fits the description perfectly.
D) Absorption is the process by which one substance is taken into another, either physically or chemically. While osmosis results in the absorption of water by the concentrated solution, “osmosis” is the specific term for the described process of water movement across a membrane due to concentration differences.

– Osmosis is the movement of solvent (water) across a selectively permeable membrane.
– Water moves from a region of higher water concentration (dilute solution) to lower water concentration (concentrated solution).
– Diffusion is the general movement of particles from high to low concentration.

A selectively permeable (or semi-permeable) membrane allows certain molecules or ions to pass through by diffusion, and occasionally specialized facilitated diffusion. The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Osmosis is a specific type of diffusion involving the solvent.

289. If one set of chromosomes for a given plant is represented as N; in ca

If one set of chromosomes for a given plant is represented as N; in case of double fertilization, the zygote and the endosperm nucleus of a diploid plant would have how many sets of chromosomes respectively?

[amp_mcq option1=”N and 2N” option2=”2N and 2N” option3=”N and 3N” option4=”2N and 3N” correct=”option4″]

This question was previously asked in

UPSC NDA-2 – 2018

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In double fertilization in a diploid plant (where N represents the haploid set of chromosomes), the zygote is formed by the fusion of a haploid male gamete (N) and a haploid egg cell (N), resulting in a diploid zygote (2N). The endosperm nucleus is typically formed by the fusion of a haploid male gamete (N) with the diploid central cell (usually containing two haploid polar nuclei, N+N=2N), resulting in a triploid primary endosperm nucleus (N + 2N = 3N).

– Double fertilization is a unique process in flowering plants involving two sperm cells.
– One sperm cell fertilizes the egg to form the diploid zygote (embryo).
– The other sperm cell fertilizes the central cell of the embryo sac to form the primary endosperm nucleus.
– In most diploid angiosperms, the central cell contains two polar nuclei, both usually haploid (N). Their fusion with a haploid sperm (N) results in a triploid (3N) endosperm.

The zygote develops into the embryo. The primary endosperm nucleus develops into the endosperm, which serves as nutritive tissue for the developing embryo. The ploidy level of the central cell can vary in some species, potentially leading to different ploidy levels for the endosperm.

290. Which one of the following depicts the correct circuit of a reflex

Which one of the following depicts the correct circuit of a reflex arc?

[amp_mcq option1=”Effector—sensory neuron—spinal cord—motor neuron—receptor” option2=”Receptor—sensory neuron—spinal cord—motor neuron—effector” option3=”Receptor—sensory neuron—brain—motor neuron—effector” option4=”Sensory neuron—receptor—brain—effector—motor neuron” correct=”option2″]

This question was previously asked in

UPSC NDA-2 – 2018

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The correct sequence of components in a typical reflex arc is Receptor → Sensory neuron → Spinal cord (integration center) → Motor neuron → Effector.

– A reflex arc is the neural pathway that mediates a reflex action.
– The receptor detects the stimulus.
– The sensory (afferent) neuron transmits the impulse from the receptor towards the central nervous system (CNS).
– The integration center (in simple reflexes, often the spinal cord) processes the signal.
– The motor (efferent) neuron transmits the impulse from the CNS to the effector.
– The effector (muscle or gland) carries out the response.

In a simple monosynaptic reflex arc, the sensory neuron synapses directly with the motor neuron in the spinal cord. In polysynaptic reflexes, interneurons are involved between the sensory and motor neurons. While the brain can be involved in modulating reflexes or perceiving the stimulus, the basic reflex arc for many rapid reflexes is processed in the spinal cord.