Biology Archives

151. Which one of the following organisms does not possess notochord at any

Which one of the following organisms does not possess notochord at any stage of its life cycle?

[amp_mcq option1=”Holothuria” option2=”Herdmania” option3=”Exocoetus” option4=”Salamander” correct=”option1″]

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UPSC CAPF – 2021

The notochord is a flexible, rod-like structure found in chordates. It provides skeletal support and is usually present during embryonic development, being replaced by the vertebral column in most adult vertebrates.

Holothuria (sea cucumber) belongs to the phylum Echinodermata, which are non-chordates. Therefore, they do not possess a notochord at any stage of their life cycle. Herdmania (sea squirt) is a Urochordate (Tunicate), which is a subphylum of Chordata; it possesses a notochord in its larval stage. Exocoetus (flying fish) is a bony fish (Vertebrata, Chordata); it possesses a notochord during embryonic development, which develops into the vertebral column in the adult. Salamander (Amphibia, Vertebrata, Chordata) also possesses a notochord during embryonic development that is replaced by the vertebral column.

The four key characteristics of chordates are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail, present at some stage in their life cycle. Echinoderms, such as starfish, sea urchins, and sea cucumbers, are invertebrates and lack these chordate features.

152. Which one of the following statements about life processes in single-c

Which one of the following statements about life processes in single-celled organisms is not correct?

[amp_mcq option1=”They require separate organ for food uptake.” option2=”Separate organ is not needed for respiration.” option3=”Waste of excretory material is produced by these organisms.” option4=”They remain in contact with external environment.” correct=”option1″]

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UPSC CAPF – 2021

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Single-celled organisms are prokaryotic or eukaryotic organisms consisting of a single cell. All necessary life processes, such as nutrition, respiration, excretion, and reproduction, occur within this single cell.

Unlike multicellular organisms which have specialized organs for specific functions, single-celled organisms perform all functions through the mechanisms available within that single cell. Food uptake in organisms like Amoeba occurs through processes like phagocytosis or pinocytosis across the cell membrane, not through a separate organ. Gaseous exchange for respiration and elimination of waste materials occur directly through diffusion across the cell surface, which is in direct contact with the external environment.

The large surface area to volume ratio in single-celled organisms facilitates efficient exchange of materials, nutrients, gases, and waste products directly with their surroundings, making specialized organs unnecessary.

153. Which one of the following is not a function of chlorophyll?

Which one of the following is not a function of chlorophyll?

[amp_mcq option1=”Splitting of water” option2=”Absorption of photon” option3=”Oxidation of carbohydrate” option4=”Conversion of light energy into chemical energy” correct=”option3″]

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UPSC CAPF – 2021

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Chlorophyll is the primary pigment involved in photosynthesis in plants, algae, and cyanobacteria. It is located in chloroplasts and absorbs light energy necessary for the process.

Chlorophyll’s main functions in photosynthesis include the absorption of light energy (photons), initiation of the light-dependent reactions which include the splitting of water molecules (photolysis) to produce oxygen, protons, and electrons, and facilitating the conversion of light energy into chemical energy in the form of ATP and NADPH. The oxidation (breakdown) of carbohydrates, such as glucose, to release energy (ATP) is the process of cellular respiration, which occurs in mitochondria (or cytoplasm/cell membrane in some organisms) and is distinct from the function of chlorophyll and photosynthesis.

Photosynthesis involves two main stages: the light-dependent reactions, where light energy is captured and converted into chemical energy (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 carbohydrates. Chlorophyll is directly involved in the light-dependent reactions.

154. Which one of the following is not a breakdown product of glucose dur

Which one of the following is not a breakdown product of glucose during respiration?

[amp_mcq option1=”Ethanol” option2=”Lactic acid” option3=”Water” option4=”Methanol” correct=”option4″]

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UPSC CAPF – 2021

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The correct answer is D) Methanol.

Cellular respiration is the process by which glucose is broken down to release energy. This process begins with glycolysis, which converts glucose into pyruvate. Depending on the presence of oxygen, pyruvate can be further metabolized:
1. Aerobic respiration (in the presence of oxygen): Pyruvate is completely oxidized to carbon dioxide (CO₂) and water (H₂O).
2. Anaerobic respiration (fermentation, in the absence of oxygen): Pyruvate is converted into products like ethanol and carbon dioxide (in yeast and plants) or lactic acid (in muscle cells and some bacteria).
Ethanol, lactic acid, and water are all potential breakdown products of glucose during respiration. Methanol is not produced during the standard biological breakdown of glucose.

Methanol (CH₃OH) is a simple alcohol. It is produced industrially or by anaerobic metabolism of certain bacteria, but not as a standard product of glucose respiration in humans or most common organisms.

155. Which one of the following diseases does not transmit through fine d

Which one of the following diseases does not transmit through fine droplets coming out from mouth or nose of an infected person?

[amp_mcq option1=”Pneumonia” option2=”COVID-19″ option3=”HIV-AIDS” option4=”Tuberculosis” correct=”option3″]

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UPSC CAPF – 2021

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The correct answer is C) HIV-AIDS.

HIV (Human Immunodeficiency Virus), which causes AIDS (Acquired Immunodeficiency Syndrome), is primarily transmitted through specific bodily fluids: blood, semen, vaginal secretions, rectal fluids, and breast milk. The most common modes of transmission are sexual contact, sharing contaminated needles, and mother-to-child transmission during pregnancy, childbirth, or breastfeeding. It is NOT transmitted through casual contact or respiratory droplets like coughing or sneezing. Pneumonia and Tuberculosis are bacterial or viral infections often spread through airborne droplets expelled when an infected person coughs, sneezes, or talks. COVID-19 is a viral disease (caused by SARS-CoV-2) primarily spread through respiratory droplets.

Understanding the modes of transmission is crucial for implementing effective prevention strategies for infectious diseases. Respiratory illnesses are often transmitted via droplets or aerosols, while diseases like HIV are transmitted via specific fluid exchange.

156. Which one of the following organisms belongs to the kingdom Monera?

Which one of the following organisms belongs to the kingdom Monera?

[amp_mcq option1=”Diatom” option2=”Euglena” option3=”Anabaena” option4=”Ulothrix” correct=”option3″]

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UPSC CAPF – 2021

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The correct answer is C) Anabaena.

In the five-kingdom classification system (proposed by R.H. Whittaker), the kingdom Monera includes all prokaryotic organisms. This primarily consists of bacteria and cyanobacteria (formerly known as blue-green algae). Anabaena is a genus of filamentous cyanobacteria, and therefore belongs to the kingdom Monera. Diatoms and Euglena are eukaryotic single-celled organisms belonging to the kingdom Protista. Ulothrix is a filamentous green alga, which is eukaryotic and typically classified under the kingdom Plantae or Protista, but not Monera.

The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia. Monerans lack a true nucleus and membrane-bound organelles. Protists are eukaryotic unicellular organisms. Fungi are eukaryotic heterotrophic organisms. Plants are eukaryotic autotrophic organisms. Animals are eukaryotic heterotrophic, multicellular organisms.

157. Which one of the following is not a connective tissue?

Which one of the following is not a connective tissue?

[amp_mcq option1=”Ligament” option2=”Tendon” option3=”Smooth muscle” option4=”Cartilage” correct=”option3″]

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UPSC CAPF – 2021

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The correct answer is C) Smooth muscle.

Connective tissues are tissues that support, connect, or separate different types of tissues and organs in the body. Ligaments connect bone to bone, tendons connect muscle to bone, and cartilage is a flexible connective tissue found in joints, ear, nose, etc. All three (Ligament, Tendon, Cartilage) are types of connective tissue. Smooth muscle, however, is a type of muscle tissue, specialized for contraction, and is distinct from connective tissue.

There are four main types of tissues in animals: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Connective tissue includes bone, blood, adipose tissue, and fibrous connective tissue (like ligaments and tendons) in addition to cartilage. Muscle tissue is classified into skeletal muscle, smooth muscle, and cardiac muscle.

158. Which one of the following plant tissues has large air spaces?

Which one of the following plant tissues has large air spaces?

[amp_mcq option1=”Sclerenchyma” option2=”Meristem” option3=”Collenchyma” option4=”Aerenchyma” correct=”option4″]

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UPSC CAPF – 2021

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The question asks for a plant tissue characterized by large air spaces.
Let’s consider the options:
A) Sclerenchyma: This tissue provides mechanical support. It consists of cells with heavily thickened, often lignified walls, and the cells are usually dead at maturity. It does not contain large air spaces.
B) Meristem: Meristematic tissues consist of actively dividing cells involved in plant growth. The cells are small, thin-walled, and densely packed without significant intercellular spaces.
C) Collenchyma: This tissue provides mechanical support to growing parts of the plant. It consists of living cells with unevenly thickened primary cell walls. While there might be small intercellular spaces, they are not characterized by *large* air spaces.
D) Aerenchyma: This is a specialized type of parenchyma tissue that contains extensive intercellular air spaces. The word “aerenchyma” literally means “air tissue”. These air spaces facilitate gas exchange in plants growing in low-oxygen environments (like wetlands) and provide buoyancy to aquatic plants.
Therefore, Aerenchyma is the plant tissue with large air spaces.

– Understand the structure and function of different types of plant tissues.
– Recognize that aerenchyma is a specialized tissue adapted for gas exchange and buoyancy due to its large air spaces.
– Distinguish aerenchyma from other support tissues like sclerenchyma and collenchyma, and growth tissue like meristem.

Aerenchyma is often found in the stems and roots of aquatic plants (hydrophytes) and plants in marshy or waterlogged soils. It is a modification of parenchyma tissue, which is the most common type of ground tissue in plants.

159. Which one of the following organelles is not found in animal cells?

Which one of the following organelles is not found in animal cells?

[amp_mcq option1=”Cell membrane” option2=”Endoplasmic reticulum” option3=”Cell wall” option4=”Lysosome” correct=”option3″]

This question was previously asked in

UPSC CAPF – 2021

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The question asks which of the listed organelles is *not* found in animal cells. Let’s review each option:
A) Cell membrane: The cell membrane is the outer boundary of animal cells and is present in all eukaryotic cells, including plant cells (where it is inside the cell wall).
B) Endoplasmic reticulum: The endoplasmic reticulum (ER) is a network of membranes involved in protein synthesis (rough ER) and lipid synthesis (smooth ER). It is found in both animal and plant cells.
C) Cell wall: The cell wall is a rigid outer layer that provides structural support, protection, and shape to the cell. Cell walls are present in plant cells (made primarily of cellulose), fungi, bacteria, and some protists, but they are *absent* in animal cells.
D) Lysosome: Lysosomes are membrane-bound organelles containing digestive enzymes. They are primarily found in animal cells, where they are involved in breaking down waste materials and cellular debris. While some plant cells may have vacuoles with lytic activity similar to lysosomes, dedicated lysosomes as found in animal cells are generally considered absent in plant cells. However, the cell wall is definitively absent in animal cells, making it the correct answer.

– Recall the key organelles found in typical animal and plant cells.
– Note the distinguishing features between plant and animal cells, such as the presence of a cell wall, chloroplasts, and large central vacuoles in plants, and lysosomes and centrioles typically in animals.
– The cell wall is a defining feature of plant cells that is absent in animal cells.

Other organelles typically found in animal cells but not in plant cells include centrioles. Organelles typically found in plant cells but not in animal cells include cell walls (as mentioned), chloroplasts, and often a large central vacuole. Both cell types have cell membranes, nuclei, mitochondria, endoplasmic reticulum, Golgi apparatus, and ribosomes.

160. Which one of the following statements about the Acacia tree is/are cor

Which one of the following statements about the Acacia tree is/are correct ?

1. It has a long shallow root system which enables it to find moisture
2. It has thorny leaves to prevent water loss
3. It has wide crown so the foliage can absorb the maximum Sunlight

Select the correct answer using the code given below :

[amp_mcq option1=”1 only” option2=”2 and 3 only” option3=”1 and 2 only” option4=”1, 2 and 3″ correct=”option4″]

This question was previously asked in

UPSC CAPF – 2020

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All three statements about the Acacia tree are correct as adaptations for survival in arid/semi-arid and open environments.

1. A long shallow root system allows rapid absorption of infrequent surface rainfall common in dry areas.
2. Thorny stems/branches (often associated with leaves) deter herbivores, which is crucial for survival in environments where plant resources are scarce. While the phrasing “thorny leaves to prevent water loss” is botanically imprecise, thorns protect the plant, including its water-containing parts (leaves), indirectly contributing to survival in a water-limited environment. Also, reduced leaf size is a key adaptation for water loss prevention, often found in arid Acacias.
3. A wide crown maximizes light capture in open habitats like savannas, allowing for efficient photosynthesis when water is available.

Acacia species exhibit a range of adaptations depending on their specific environment, but the characteristics listed are common in many Acacias found in arid and semi-arid regions and savannas globally, helping them survive dry spells, intense sunlight, and herbivory.