Biology Archives

311. A plant having yellow leaves with dead spots has the deficiency of

A plant having yellow leaves with dead spots has the deficiency of

[amp_mcq option1=”Potassium” option2=”Magnesium” option3=”Nitrate” option4=”Phosphate” correct=”option1″]

This question was previously asked in

UPSC NDA-2 – 2016

A plant having yellow leaves with dead spots likely has a deficiency of Potassium.

Potassium (K) is a mobile nutrient in plants. Deficiency symptoms typically appear first in older leaves because the plant translocates potassium to younger, growing tissues. Common symptoms of potassium deficiency include chlorosis (yellowing) along the margins and tips of older leaves, which progresses inwards. As the deficiency worsens, these yellow areas often develop into necrotic spots (dead tissue), giving the appearance of scorched or brown margins and tips.

Magnesium (Mg) deficiency also causes chlorosis but typically results in interveinal chlorosis (yellowing between the veins while the veins remain green). Nitrate (Nitrogen) deficiency causes general yellowing of the entire leaf, starting with older leaves. Phosphate (Phosphorus) deficiency can cause stunted growth and sometimes purplish discoloration, especially on stems and the undersides of leaves, but not typically yellowing with marginal necrosis.

312. A horse and a donkey can breed to produce mule which is an infertile a

A horse and a donkey can breed to produce mule which is an infertile animal. The infertility is because horse and donkey belong to different

[amp_mcq option1=”class” option2=”order” option3=”species” option4=”genus” correct=”option3″]

This question was previously asked in

UPSC NDA-2 – 2016

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Mules are infertile because horses and donkeys belong to different species.

A species is generally defined as a group of organisms that can interbreed and produce fertile offspring. While horses (Equus caballus) and donkeys (Equus asinus) can interbreed to produce a mule (or a hinny), their offspring are almost always sterile. This sterility arises because horses and donkeys have different numbers of chromosomes (horses have 64, donkeys have 62). The mule inherits 63 chromosomes, which cannot pair properly during meiosis, preventing the formation of viable gametes (sperm or eggs), thus leading to infertility.

Horses and donkeys belong to the same genus, Equus, which indicates a relatively recent common ancestor compared to differences at the order or class level. The ability to produce hybrid offspring, even if infertile, is common between closely related species within the same genus.

313. The genetic material of bacteria is found in

The genetic material of bacteria is found in

[amp_mcq option1=”nucleus” option2=”cytoplasm” option3=”cell membrane” option4=”ribosome” correct=”option2″]

This question was previously asked in

UPSC NDA-2 – 2016

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The genetic material of bacteria is found in the cytoplasm.

Bacteria are prokaryotic organisms, meaning their cells lack a membrane-bound nucleus. Their genetic material, which typically consists of a single circular chromosome, is located in a specific region within the cytoplasm called the nucleoid. Unlike eukaryotic cells, there is no nuclear envelope separating the genetic material from the rest of the cytoplasm.

In addition to the main chromosome in the nucleoid, bacteria may also contain smaller, circular DNA molecules called plasmids, which are also located in the cytoplasm. Ribosomes, also found in the cytoplasm, are the sites of protein synthesis, not the location of the primary genetic material. The cell membrane encloses the cytoplasm but does not contain the main genetic material.

314. A person is unable to read a newspaper without his glasses. He is most

A person is unable to read a newspaper without his glasses. He is most probably suffering from

[amp_mcq option1=”myopia” option2=”presbyopia” option3=”astigmatism” option4=”hypermetropia” correct=”option4″]

This question was previously asked in

UPSC NDA-2 – 2016

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Difficulty in reading a newspaper without glasses indicates a problem with focusing on near objects. This symptom is characteristic of hypermetropia (farsightedness) or presbyopia.

Hypermetropia is a refractive error where the eye focuses images behind the retina, making near objects appear blurry. Presbyopia is an age-related loss of the eye’s ability to focus on near objects. Both conditions require convex lenses (reading glasses) to correct near vision.

Myopia (A) causes difficulty seeing distant objects clearly. Astigmatism (C) causes blurred vision at various distances due to an irregularly shaped cornea or lens. While presbyopia (B) is a common cause of needing reading glasses, hypermetropia (D) is the underlying refractive error that also causes difficulty with near vision, often exacerbated by age into presbyopia. Given both are options and cause the same symptom, D (hypermetropia) is a fundamental refractive error leading to this symptom, while B (presbyopia) is the age-related form of this difficulty. However, hypermetropia alone in a young person can also cause the need for reading glasses if severe enough or if doing prolonged near work. Both are plausible, but D is listed as the answer. Let’s stick with D as it represents the refractive error causing the symptom, while presbyopia is a specific age-related manifestation. Upon review, some sources might prioritize presbyopia for this specific phrasing relating to “reading a newspaper” in typical MCQ context implying an older person. However, hypermetropia *is* difficulty seeing near objects. Without more context (age), both are possible. Let’s trust the provided answer key logic which points to D.

315. It is difficult to kill viruses because they

It is difficult to kill viruses because they

[amp_mcq option1=”consist of tough protein coat” option2=”are very small in size” option3=”lack cellular structure” option4=”spend a lot of time inside the host’s cells” correct=”option3″]

This question was previously asked in

UPSC NDA-2 – 2016

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Viruses lack cellular structure and metabolic machinery of their own. They are obligate intracellular parasites, relying entirely on the host cell’s machinery for replication.

The absence of their own metabolic processes means that many common antimicrobial treatments, such as antibiotics which target bacterial cellular functions, are ineffective against viruses. Developing antiviral drugs is challenging because they must target viral processes without harming the host cell’s similar processes.

While having a protein coat (A) and small size (B) are characteristics of viruses, they don’t inherently make them difficult to kill compared to other microbes. Spending time inside host cells (D) makes them inaccessible to some therapies and antibodies, contributing to the difficulty in *treating* viral infections, but the fundamental reason for the difficulty in *killing* them selectively lies in their non-cellular nature and dependence on host processes.

316. Malarial parasite is a

Malarial parasite is a

[amp_mcq option1=”bacteria” option2=”protozoa” option3=”virus” option4=”fungus” correct=”option2″]

This question was previously asked in

UPSC NDA-2 – 2016

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The malarial parasite, Plasmodium, is a single-celled eukaryotic organism belonging to the phylum Apicomplexa. Organisms in this group are commonly classified as protozoa.

Protozoa are diverse group of unicellular eukaryotic organisms, many of which are motile and include parasitic forms like Plasmodium.

Malaria is caused by the Plasmodium parasite, which is transmitted to humans through the bite of infected female Anopheles mosquitoes. Bacteria are prokaryotic; viruses and fungi are different classes of microorganisms.

317. In which one of the following, methano- gens, i.e., methane producing

In which one of the following, methano- gens, i.e., methane producing bacteria are not present ?

[amp_mcq option1=”Rumen of cattle” option2=”Aerobic environment” option3=”Anaerobic sludge” option4=”Excreta of cattle” correct=”option2″]

This question was previously asked in

UPSC NDA-2 – 2016

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Methanogens are a group of anaerobic archaea that produce methane as a metabolic byproduct in anoxic conditions. They are strictly anaerobic, meaning oxygen is toxic to them.

Methanogens thrive in environments where oxygen is absent and organic matter is undergoing decomposition. Examples include the digestive tracts of ruminants (like cattle rumen), anaerobic sludge digesters in wastewater treatment, and sediments in swamps and marshes.

The rumen of cattle is a highly anaerobic environment where methanogens play a crucial role in the digestion of cellulose. Anaerobic sludge in sewage treatment plants is another common habitat. Cattle excreta, being partially digested material from the rumen and exposed to anaerobic conditions during storage, also contains active methanogens. An aerobic environment, however, is unsuitable for methanogens due to the presence of oxygen.

318. Consider the following statements about cactus : 1. The leaves are r

Consider the following statements about cactus :

1. The leaves are reduced to spines.
2. The stem does the photosynthesis.

Which of the statements given above is/are correct ?

[amp_mcq option1=”1 only” option2=”2 only” option3=”Both 1 and 2″ option4=”Neither 1 nor 2″ correct=”option3″]

This question was previously asked in

UPSC NDA-2 – 2016

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Both statements about cactus adaptations are correct. Cacti are succulents adapted to arid environments. Their leaves are typically reduced to spines to minimize water loss through transpiration and provide defense. The fleshy green stems take over the function of photosynthesis, which is usually carried out by leaves in most plants.

– Statement 1 is correct: Reduction of leaves to spines is a key adaptation of cacti to reduce surface area and thus water loss through transpiration in hot, dry climates. Spines also deter herbivores.
– Statement 2 is correct: Cacti stems contain chlorophyll and are the primary sites of photosynthesis in the absence of significant leaf area. They are also succulent, storing water.

Cacti also have other adaptations for survival in arid environments, such as shallow but extensive root systems to absorb water quickly from rainfall, a waxy cuticle on the stem to reduce evaporation, and CAM photosynthesis, which allows them to keep their stomata closed during the day to conserve water.

319. Statement I : Too much salt content in diet could be one of the reason

Statement I : Too much salt content in diet could be one of the reasons for kidney failure.
Statement II : High salt may cause high blood pressure.

[amp_mcq option1=”Both the statements are individually true and Statement II is the correct explanation of Statement I” option2=”Both the statements are individually true but Statement II is not the correct explanation of Statement I” option3=”Statement I is true but Statement II is false” option4=”Statement I is false but Statement II is true” correct=”option1″]

This question was previously asked in

UPSC NDA-2 – 2016

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Statement I: Too much salt content in diet could be one of the reasons for kidney failure. (True)
Statement II: High salt may cause high blood pressure. (True)
Both the statements are individually true and Statement II is the correct explanation of Statement I.

– High dietary salt intake is a major risk factor for hypertension (high blood pressure).
– High blood pressure is a leading cause of chronic kidney disease and, eventually, kidney failure.

– Statement II describes the causal link between high salt intake and high blood pressure. Statement I indicates a possible consequence of high salt intake.
– Since high blood pressure caused by high salt is a significant contributor to kidney damage, Statement II provides the mechanism by which Statement I can be true. Therefore, Statement II correctly explains one way too much salt can lead to kidney failure.

320. Which one of the following is useful in the paper manufacturing

Which one of the following is useful in the paper manufacturing industry?

[amp_mcq option1=”Fibrous plants” option2=”Orchids” option3=”Non-flowering plants” option4=”Plants growing in high altitude” correct=”option1″]

This question was previously asked in

UPSC NDA-2 – 2015

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The correct answer is A) Fibrous plants. Paper is primarily made from cellulose fibers, which are obtained from plants. Fibrous plants, particularly trees (wood pulp) and other plants like bamboo, cotton, and hemp, are rich in these fibers and are the main raw materials for the paper manufacturing industry.

Paper production relies on extracting cellulose fibers from plant sources.

While other plants exist (like orchids, non-flowering plants, high-altitude plants), the key characteristic relevant to paper making is the presence of suitable fibers. Orchids are not used for paper. Non-flowering plants is too broad; while some non-flowering plants like conifers are used, the term “fibrous plants” is a more direct description of the useful property. Plants growing in high altitude is irrelevant to their suitability for paper making based on fiber content.