Biology

171. Bending of shoot of a plant towards light can be referred to as

Bending of shoot of a plant towards light can be referred to as

[amp_mcq option1=”photonasty” option2=”positive phototropism” option3=”negative phototropism” option4=”photoperiodism” correct=”option2″]

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The correct answer is B, positive phototropism.
Phototropism is the growth of a plant in response to a light stimulus. When a plant shoot bends and grows towards the light source, it is exhibiting positive phototropism.
Photonasty is a non-directional plant movement in response to light intensity (e.g., opening and closing of flowers). Negative phototropism is growth away from a light source (e.g., roots). Photoperiodism is the physiological response of an organism to the length of day or night.

172. Which of the following organisms belongs to Coelenterata (Cnidaria) ?

Which of the following organisms belongs to Coelenterata (Cnidaria) ?

[amp_mcq option1=”Planaria and liverfluke” option2=”Sea urchin and sea cucumber” option3=”Hydra and sea anemone” option4=”Euplectella and sycon” correct=”option3″]

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The correct answer is C, Hydra and sea anemone.
Hydra and sea anemones are classic examples of organisms belonging to the phylum Coelenterata, also known as Cnidaria. This phylum includes organisms like jellyfish, corals, hydroids, and sea anemones, characterized by features like radial symmetry, a gastrovascular cavity, and specialized stinging cells called nematocysts.
Option A includes Planaria and liverfluke, which belong to the phylum Platyhelminthes (flatworms). Option B includes sea urchin and sea cucumber, which belong to the phylum Echinodermata. Option D includes Euplectella and sycon, which belong to the phylum Porifera (sponges).

173. Pollens are produced in

Pollens are produced in

[amp_mcq option1=”Corolla” option2=”Style” option3=”Stigma” option4=”Anther” correct=”option4″]

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Pollens, which contain the male gametes of flowering plants, are produced within the anthers. The anther is the part of the stamen, the male reproductive organ of a flower.
– The stamen consists of a filament and an anther.
– The anther contains pollen sacs where pollen grains develop.
– Pollen grains are released from the anther for pollination.
The corolla is made up of petals, which are often brightly colored to attract pollinators. The style and stigma are parts of the pistil (or carpel), the female reproductive organ. The stigma is the receptive tip where pollen lands during pollination, and the style is a stalk connecting the stigma to the ovary.

174. In plant cells, the turgidity and rigidity is provided by

In plant cells, the turgidity and rigidity is provided by

[amp_mcq option1=”ribosomes” option2=”mitochondria” option3=”golgi apparatus” option4=”vacuoles full of cell sap” correct=”option4″]

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Turgidity and rigidity in plant cells are primarily provided by the turgor pressure exerted by the vacuole against the cell wall. The large central vacuole in plant cells stores water and cell sap. When the cell absorbs water by osmosis, the vacuole swells, pushing the cytoplasm against the cell wall. The rigid cell wall prevents the cell from bursting, resulting in a firm, turgid state.
– Turgor pressure is the pressure exerted by the cell contents (driven by the vacuole) against the cell wall.
– The cell wall provides structural support and prevents bursting.
– Together, turgor pressure and the cell wall make the plant cell turgid and rigid.
Ribosomes are involved in protein synthesis. Mitochondria are the powerhouses of the cell, producing energy. The Golgi apparatus modifies, sorts, and packages proteins and lipids. None of these organelles directly provide turgidity or rigidity to the plant cell in the same way the vacuole and cell wall do.

175. The increase in length of stems and roots in plants is due to

The increase in length of stems and roots in plants is due to

[amp_mcq option1=”lateral meristem” option2=”intercalary meristem” option3=”apical meristem” option4=”secondary growth” correct=”option3″]

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The increase in length of stems and roots in plants is primarily due to the activity of apical meristems, located at the tips of shoots and roots. This growth is known as primary growth.
– Meristems are regions of actively dividing cells in plants responsible for growth.
– Apical meristems are located at the shoot apex and root apex and are responsible for primary growth (increase in length).
– Lateral meristems (vascular cambium and cork cambium) are responsible for secondary growth (increase in girth or diameter).
– Intercalary meristems are located between mature tissues (e.g., at nodes of grasses) and contribute to elongation in those specific regions.
Primary growth results in the formation of primary tissues (epidermis, ground tissues, primary xylem, and primary phloem). Secondary growth, mediated by lateral meristems, results in the formation of secondary tissues (e.g., wood and bark), leading to an increase in thickness, common in woody plants. While intercalary meristems cause elongation, the overall increase in length of the main axis of stems and roots is driven by apical meristems.

176. Rough endoplasmic reticulum (RER) looks rough under the microscope bec

Rough endoplasmic reticulum (RER) looks rough under the microscope because of the attachment of which one of following cell organelles to its surface ?

[amp_mcq option1=”Centrioles” option2=”Plastids” option3=”Lysosomes” option4=”Ribosomes” correct=”option4″]

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The rough appearance of the Rough Endoplasmic Reticulum (RER) under a microscope is due to the presence of ribosomes attached to its cytoplasmic surface.
– The Endoplasmic Reticulum (ER) is a network of membranes throughout the cytoplasm.
– There are two types: Rough ER (RER) and Smooth ER (SER).
– Ribosomes are responsible for protein synthesis.
– Ribosomes can be free in the cytoplasm or attached to the ER membrane.
– The attachment of ribosomes gives the RER its characteristic “rough” appearance.
Proteins synthesized on ribosomes attached to the RER are typically destined for secretion, insertion into cell membranes, or delivery to other organelles like lysosomes. The RER is involved in protein folding, modification, and transport. Centrioles are involved in cell division. Plastids (like chloroplasts) are involved in photosynthesis or storage. Lysosomes contain digestive enzymes. None of these attach to the ER to make it appear rough.

177. Which one of the following will happen if the medium surrounding the c

Which one of the following will happen if the medium surrounding the cell has a higher concentration than the cell ?

[amp_mcq option1=”The cell will gain water” option2=”The cell will die” option3=”There will be no change” option4=”The cell will lose water” correct=”option4″]

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If a cell is placed in a medium with a higher solute concentration than its cytoplasm (a hypertonic solution), water will move out of the cell into the surrounding medium by osmosis.
– Osmosis is the movement of water across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration (or from higher water potential to lower water potential).
– A hypertonic solution has a higher solute concentration and thus a lower water potential compared to the cell.
– Water moves from the cell (higher water potential) to the hypertonic medium (lower water potential).
If the surrounding medium had a lower concentration (hypotonic), the cell would gain water. If the concentration were equal (isotonic), there would be no net change in water movement. Losing water in a hypertonic solution can cause the cell to shrink (crenation in animal cells, plasmolysis in plant cells). Extreme water loss can lead to cell death, but the immediate effect described is water loss.

178. Which one of the following statements is correct ?

Which one of the following statements is correct ?

[amp_mcq option1=”Bacteria contain cytoplasm but viruses do not” option2=”Bacteria contain mitochondria but viruses do not” option3=”Viruses contain mitochondria but bacteria do not” option4=”Viruses have a cell membrane but bacteria do not” correct=”option1″]

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Bacteria are prokaryotic cells that contain cytoplasm enclosed within a cell membrane and usually a cell wall. Viruses are acellular entities; they consist of genetic material (DNA or RNA) enclosed in a protein coat (capsid) and sometimes an outer envelope, but they do not have cytoplasm or cellular organelles like mitochondria.
– Bacteria are living, single-celled organisms (prokaryotes).
– Viruses are non-living particles that require a host cell to reproduce.
– Prokaryotes (like bacteria) have cytoplasm but lack membrane-bound organelles like mitochondria.
– Viruses lack cellular structure, including cytoplasm, cell membrane, and organelles.
Option B is incorrect because bacteria do not have mitochondria (membrane-bound organelles). Option C is incorrect because neither viruses nor bacteria have mitochondria. Option D is incorrect because bacteria have a cell membrane, while viruses do not have a cell membrane in the cellular sense (though some have an envelope derived from host cell membrane).

179. Which one of the following statements regarding insulin hormone is

Which one of the following statements regarding insulin hormone is correct?

[amp_mcq option1=”Insulin is a protein hormone which is not produced in human body.” option2=”Insulin is a steroid hormone which is produced in human body.” option3=”Insulin is a cholesterol-driven hormone given to human.” option4=”Insulin is a protein hormone which is produced in human body.” correct=”option4″]

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Insulin is a hormone produced by the beta cells of the islets of Langerhans in the pancreas. It is crucial for regulating blood glucose levels by promoting glucose uptake and storage in various tissues. Chemically, insulin is classified as a peptide hormone (a type of protein hormone), composed of amino acids. It is not a steroid hormone, which are derived from cholesterol. Insulin is naturally produced in a healthy human body. People with type 1 diabetes, whose beta cells are destroyed, require exogenous insulin administration, but this does not mean it is not produced in the human body under normal circumstances.
Let’s evaluate the options:
A) Insulin is a protein hormone which is not produced in human body. Incorrect, it is produced in the human body.
B) Insulin is a steroid hormone which is produced in human body. Incorrect, it is produced but is a protein hormone.
C) Insulin is a cholesterol-driven hormone given to human. Incorrect, it is a protein hormone, not cholesterol-driven, though it is given to treat diabetes.
D) Insulin is a protein hormone which is produced in human body. Correct.
Insulin is a protein hormone produced by the pancreas in the human body, primarily involved in regulating blood glucose levels.
Other important hormones involved in glucose regulation include glucagon (also produced by the pancreas), which has opposite effects to insulin, raising blood glucose levels. Insulin and glucagon work together to maintain glucose homeostasis.

180. Which one of the following statements is correct?

Which one of the following statements is correct?

[amp_mcq option1=”In photosynthesis by green plants, carbon dioxide is used for making carbohydrate.” option2=”During photosynthesis, plants use oxygen for making carbohydrate.” option3=”The carbohydrate generated by plants comes from soil.” option4=”The carbohydrate generated by plants comes from urea.” correct=”option1″]

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UPSC CAPF – 2018
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Photosynthesis is the process by which green plants convert light energy into chemical energy in the form of organic compounds (carbohydrates). The inputs for photosynthesis are carbon dioxide (CO₂) and water (H₂O), and the outputs are glucose (a carbohydrate, C₆H₁₂O₆) and oxygen (O₂). The overall chemical equation is approximately 6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂. This equation shows that carbon dioxide is directly incorporated into the carbohydrate molecule. Plants absorb CO₂ from the atmosphere through their stomata.
Let’s evaluate the other options:
B) Oxygen is produced as a byproduct during photosynthesis, not used to make carbohydrate.
C) While water and minerals essential for plant growth come from the soil, the carbon atoms that form the backbone of the carbohydrate molecule come from atmospheric carbon dioxide.
D) Urea is a nitrogenous compound used as a fertilizer to provide nitrogen for plant growth. Nitrogen is essential for synthesizing proteins and nucleic acids, but the carbon backbone of carbohydrates comes from CO₂.
Therefore, the correct statement is that carbon dioxide is used for making carbohydrate in photosynthesis.
In photosynthesis, plants use carbon dioxide and water, with the help of light energy and chlorophyll, to synthesize carbohydrates and release oxygen. Carbon dioxide is the source of carbon atoms in the carbohydrate.
Photosynthesis occurs in two main stages: the light-dependent reactions (where light energy is converted into chemical energy in the form of ATP and NADPH, and water is split) and the light-independent reactions (Calvin cycle), where the chemical energy is used to fix carbon dioxide and synthesize glucose.
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