Biology MCQ Quiz - Objective Question with Answer for Biology - Download Free PDF

The correct answer is C nerve fibre

Concept:

• Nerve fibres are classified based on their diameter, conduction velocity, and function. The classification includes A, B, and C fibres, with A fibres further subdivided into A_α,A_β, A_γ, and A_δ
• Impulse conduction velocity depends on factors such as fibre diameter, myelination, and the type of nerve fibre.
• Myelination significantly increases conduction velocity, as the impulse "jumps" between the nodes of Ranvier in myelinated fibres (saltatory conduction).
• Unmyelinated fibres, such as C fibres, conduct impulses more slowly compared to myelinated fibres.

Explanation:

• C nerve fibres: These are unmyelinated fibres with the smallest diameter (0.4–1.2 µm) and the slowest conduction velocity (0.4–2 m/s). They are primarily involved in transmitting pain and temperature signals. The absence of myelination and small diameter contributes to their slow impulse conduction.
• Other options:
  • A_α $A\alpha$nerve fibres: These are heavily myelinated fibres with the largest diameter (13–20 µm) and the fastest conduction velocity (80–120 m/s). They are involved in motor functions and proprioception, making them unsuitable as the answer.
  • A_β nerve fibres: These fibres are myelinated with a slightly smaller diameter (6–12 µm) and conduction velocity (35–75 m/s) compared to AαAαAα $A\alpha$ . They are involved in touch and pressure sensation, so they are faster than C fibres.
  • B nerve fibres: These fibres are lightly myelinated, with a diameter of 1–3 µm and conduction velocity of 3–15 m/s. They are involved in autonomic nervous system functions and are slower than A fibres but faster than C fibres.

The correct answer is a poikilotherm

Explanation:

• Animals are often classified based on their ability to regulate body temperature. This classification determines whether their body temperature remains constant or fluctuates with environmental conditions.
• Poikilotherms are animals whose body temperature varies with the temperature of their surroundings. Unlike homeotherms, they do not maintain a constant internal body temperature. Organisms like amphibians, reptiles, and fish are common examples of poikilotherms as they rely on external heat sources to regulate their body temperature.
• Homoeotherm: These are animals that maintain a constant internal body temperature, regardless of environmental conditions. Examples include mammals and birds. 
• Ectotherm: While ectotherms also rely on external sources of heat for body temperature regulation, this term primarily refers to the source of heat rather than the fluctuation in body temperature.
• Endotherm: These are animals that generate internal heat through metabolic processes to maintain a stable body temperature. Examples include humans, cats, and dogs.

The correct answer is Blood

Explanation:

• Insulin and glucagon are hormones produced by the islets of Langerhans in the pancreas, which play crucial roles in maintaining blood glucose levels.
• The endocrine function of the pancreas involves the secretion of these hormones directly into the bloodstream, allowing them to reach their target cells in various parts of the body.
• Insulin and glucagon are secreted by the endocrine cells of the pancreas (beta cells for insulin and alpha cells for glucagon) into the blood.
• The blood serves as the transport medium for these hormones, carrying them to target tissues such as the liver, muscles, and fat cells.
• The bloodstream ensures rapid and efficient delivery, enabling the hormones to regulate blood sugar levels effectively.

The correct answer is Phytohemagglutinin

Explanation:

• Phytohemagglutinin (PHA) is a plant-derived lectin primarily extracted from beans, especially red kidney beans (Phaseolus vulgaris). It is known to stimulate lymphocytes, particularly T-lymphocytes, in laboratory settings, making it a potent mitogen for studying immune responses.
• PHA binds to carbohydrates on the surface of lymphocytes, triggering cell division (mitosis) and immune activation. This property is used extensively in immunological research and diagnostic applications.

Other Options:

• Complement: Complement refers to a group of proteins in the immune system that enhances (or "complements") the ability of antibodies and phagocytic cells to clear pathogens from the body. While the complement system is crucial for immune defense, it does not act as a potent antigen or mitogen for lymphocytes.
• Interleukin-1: Interleukin-1 (IL-1) is a cytokine produced by activated macrophages and is involved in the regulation of immune and inflammatory responses. Although IL-1 plays an essential role in modulating immune reactions, it does not directly act as a mitogen for lymphocytes.
• Endotoxin: Endotoxins are lipopolysaccharides derived from the outer membrane of Gram-negative bacteria. They trigger an immune response and can lead to inflammation, but they are not specific stimulators of lymphocyte mitosis or activation. Endotoxins act more broadly and are associated with systemic effects like fever and septic shock rather than direct lymphocyte activation.

The correct answer is A strategy of parasites to evade a host's immune response for their survival probability

Explanation:

• Immunological evasion refers to the ability of pathogens (including parasites, bacteria, viruses, and fungi) to avoid or suppress the host's immune system to ensure their survival and replication.
• The immune system is the body's defense mechanism designed to identify and eliminate foreign invaders, but some pathogens have evolved strategies to "evade" this defense.
• Parasites and other pathogens employ complex mechanisms to evade immune responses, ensuring their survival in the host. This process often contributes to prolonged infections, chronic diseases, or host damage.

Pathogens use various strategies, including:

• Antigenic variation: Pathogens frequently change the proteins on their surface (antigens) to avoid being recognized by the host's immune system.
• Immune suppression: Some pathogens produce molecules that suppress the immune response, reducing the ability of the host to fight back effectively.
• Camouflage: Some pathogens mimic host molecules to escape detection by the immune system.
• Intracellular hiding: Certain pathogens hide inside host cells to avoid immune detection.
• Examples:
  • Plasmodium (causative agent of malaria) uses antigenic variation to evade the immune system.
  • HIV suppresses immune cells, including T-helper cells, to avoid detection and destruction.

The correct answer is Male gamete.

Key Points

• Sperm or spermatozoa is a gamete (sex cell) produced in the male reproductive system.
• It is a mobile cell with one goal - to fertilize a female egg.
• Each sperm contains the entire genome of the male that produced it.
• Combined with the female genome contained in the egg, a zygote is formed - a single pluripotent stem cell containing the fused male and female genomes.
• Sperm cells were first described in the late 17th century by Antonie van Leeuwenhoek.

Additional Information

• Isogamete:
  • Isogamete is a gamete that is similar in shape, size, and behavior to another gamete with which it can produce a zygote.
  • They are also known as homogametes.
• Female gamete:
  • Female gametes are produced in the ovary. It is called an egg or egg.
  • Each month, the female produces one egg during her menstrual cycle.
• Gamete:
  • A gamete is a haploid cell that fuses with another haploid cell during fertilization in sexually reproducing organisms.
  • Gametes are reproductive cells of an organism, also known as sex cells.

Concept:

• Thermoregulation is the mechanism by which some animals like mammals maintain their core body temperature irrespective of the changing environmental temperature.
• Based on whether an animal can maintain their body temperature or not they are divided into two: Homeotherm and Poikilotherms.

1. Homeotherm: An animal that can maintain constant internal body temperature. Birds and mammals are homeotherms.
2. Poikilotherm: An animal that cannot maintain a constant internal body temperature. The internal temperature in these animals varies generally with the varying environmental temperatures. Amphibians and reptiles are poikilotherms.

Explanation:

• Frogs are poikilotherms i.e. they cannot maintain a constant body temperature.
• Their body temperature fluctuates with that of the environment.
• During winters, the frog's body temperature becomes too low. As a result of which all the body activities of the frog get ceased and it becomes sluggish.
• Similarly during summers, due to high temperatures again the body's activities cease and the animal becomes sluggish.
• To avoid such harsh environmental conditions, frogs undergo special adaptations that enable them to survive in unfavorable conditions.
• Hibernation and Aestivation are the two adaptations taken up by the frog to avoid unfavorable conditions.

HIBERNATION:

• Hibernation is also known as winter sleep.
• During winters, frogs dig deep down into damp earth at the bottom of the ponds and rest there.
• During hibernation, lung breathing is stopped in the frog.
• The skin continues breathing which suffices the oxygen requirement of the frog during hibernation.

AESTIVATION:

• Aestivation is also known as summer sleep.
• Just like in hibernation, during aestivation too frogs burrow themselves into the damp earth.
• On the arrival of the rainy season, the animal resumes its normal body activities.

So from the above-given information, the correct answer is option 4 (Skin only).

Additional Information

•  Ectotherm: Ectotherms rely on the external environment to regulate their body temperature. These are also called cold-blooded animals. Poikilotherms are regarded as ectotherms.
• Endotherm: Endotherms are animals that maintain their own body temperature through metabolic activities. These are also called warm-blooded animals. Homeotherms are regarded as endotherms.

The correct answer is autotrophic nutrition.Key Points

• Autotrophic nutrition is the mode of nutrition in which organisms make their food themselves from simple substances.
• The process of autotrophic nutrition involves the use of light energy (in photosynthesis) or chemical energy (in chemosynthesis) to produce organic compounds.
• Autotrophs are organisms that carry out autotrophic nutrition, such as plants, algae, and some bacteria.

Additional Information

• Heterotrophic nutrition is the mode of nutrition in which organisms obtain their food by consuming other organisms or organic matter.
• Saprotrophic nutrition is a type of heterotrophic nutrition in which organisms obtain their food by decomposing dead organic matter.
• Phototrophic nutrition is a subcategory of autotrophic nutrition, in which organisms use light energy to produce their own food.

The correct answer is i - b, ii - c, iii - d, iv - a.

Key Points

The trophic levels represent the hierarchical levels in an ecological food chain, indicating the position of organisms based on their feeding relationships. Here's the explanation for the correct match:

• First trophic level - phytoplankton:
  • The first trophic level typically consists of primary producers that convert sunlight into energy through photosynthesis.
  • Phytoplankton are microscopic plants that form the base of aquatic food chains.
• Second trophic level - zooplankton:
  • The second trophic level comprises primary consumers that feed on the primary producers.
  • Zooplankton, which includes tiny animals, consume phytoplankton, placing them at the second trophic level.
• Third trophic level - fishes:
  • The third trophic level involves secondary consumers that feed on primary consumers.
  • In aquatic ecosystems, fishes are often positioned at the third trophic level as they consume zooplankton or other smaller organisms.
• Fourth trophic level - human:
  • The fourth trophic level represents tertiary consumers, which are higher-order predators.
  • Humans, being omnivores or carnivores, are often placed at the fourth trophic level in food chains when they consume animals from lower trophic levels.​ 

The correct answer is a - iv, b - iii, c - ii, d - i.

Key Points

• Blue-green Algae (Cyanobacteria)
  • Blue-green algae are actually bacteria and are also known as Cyanobacteria.
  • They are photosynthetic organisms and can live in a wide variety of environments, including freshwater, seawater, damp soil, or rocks.
  • Cyanobacteria are known for their significant contribution to the Earth's oxygen atmosphere.
  • They can exist as single cells or can form colonies.
• Red Algae (Rhodophyta)
  • Red algae, often called Rhodophyta, have been identified as one of the oldest groups of eukaryotic algae.
  • They are mostly found in the warmer waters of the ocean.
  • Red algae are of great economic value because of their use in the production of agar and carrageenan, substances used as thickening agents in various food products.
  • Their red colour is due to the pigment, phycoerythrin.
• Green Algae (Chlamydomonas)
  • Green algae are a diverse group of algae from which plants evolved. Chlamydomonas is a genus of unicellular green algae.
  • Chlamydomonas species are widely distributed worldwide and are found in soil and freshwater.
  • They have two flagella that allow them to move.
  • They are known for their green colour due to the presence of chlorophyll.
• Brown Algae (Sargassum)
  • Brown algae are the most complex type of algae; many are seaweeds.
  • Sargassum is a brown algae, known for forming massive floating forests in the ocean.
  • It is primarily marine and is found in warm-temperate and tropical oceans.
  • They provide important ecological functions such as providing habitats for a wide variety of marine species.
  • The brown colour is due to the presence of a pigment called fucoxanthin, which masks the green colour of chlorophyll.

Concept: 

• Fruit refers to a mature or ripened ovary, developed after fertilization.
• The fruit consists of a wall or pericarp and seeds.
• When the pericarp is thick and fleshy, it is differentiated into the outer epicarp, the middle mesocarp, and the inner endocarp. 

Explanation:

• Fruit is said to be false fruit when the fruit is formed from the other parts of the flower as well as the ovary like the receptacle (base), the perianth, thalamus, inflorescence, or calyx.

• Examples of such fruits are strawberries, pineapple, mulberry, apples, pears, etc.

• The given figure is of a false fruit.

• False fruit develops from other floral parts and the thalamus along with the development of the ovary wall.

• Therefore, the correct answer is option 4.

Additional Information If the fruit is formed without fertilization of the ovary, it is called a parthenocarpic fruit.

The correct answer is Collar cells.

 Key Points

• The body of sponges (poriferans) has several minute pores called ostia through which the water enters into the central cavity, spongocoel.
• The flagellated cells called choanocytes (collar cells) line the spongocoel.
• These cells generate a flow of water and the water current helps in food gathering, respiratory exchange and removal of waste.
• The water finally goes out of the body through a large pore called osculum. (Plural: oscula).
• The body wall of the sponge is composed of two layers: outer pinacoderm and inner choanoderm. In between these two layers, mesenchyme is present with various mesenchymal cells.

Additional Information

• Somatic cells make up the connective tissue, skin, blood, bones and internal organs.
• White blood cells are made in the bone marrow. They are stored in your blood and lymph tissues.
• These sex cells are also called reproductive cells or gametes. Sperm cells are produced in men's testicles and egg cells are produced in women's ovaries

The correct answer is Rhodophyceae.Key Points

• Red algae:-
  • It is a type of marine algae that are predominantly red in color due to the presence of pigments such as phycoerythrins and phycocyanins.
  • They are found in both tropical and temperate waters and play an important role in marine ecosystems as primary producers and as a food source for herbivorous marine animals.
  • Some species of red algae are also used by humans for various purposes such as food, medicine, and cosmetics.
  • Red algae are known for their ability to survive in extreme environments such as deep-sea hydrothermal vents and polar regions.

Additional Information

• Chlorophyceae:
  • This is a class of green algae that are mostly freshwater species and are commonly found in ponds, lakes, and streams.
• Liverwort:
  • This is a type of non-vascular plant that grows in damp habitats such as forests, bogs, and riverbanks.
  • They are commonly found in temperate and tropical regions and play an important role in soil formation and nutrient cycling.
• Phaeophyceae:
  • This is a class of brown algae that are predominantly marine and are commonly found in temperate and cold waters.
  • They are important primary producers in coastal ecosystems and are also used by humans for food and other purposes.

The correct answer is i - b, ii - a, iii - c, iv - d

Key Points

• The cell physically expands, duplicates organelles, and creates the molecular building blocks it will require in subsequent stages during G1phase, also known as the first gap phase.
• The cell creates a full copy of the DNA in its nucleus during the S phase. Moreover, it makes duplicates of the centrosome, a structure that organises microtubules. During M phase, the centrosomes aid in the separation of DNA.
• The second gap phase, also known as the G2 phase, is a time of increased cell growth, protein and organelle production, and content reorganisation in preparation for mitosis.
• The cell's nuclear DNA condenses into its visible chromosomes during mitosis and is separated by the mitotic spindle, a specialised microtubule-based structure.

Additional Information

•  Stages of the cell cycle
  • ​A cell must grow, replicate its genetic material (DNA), and physically split into two daughter cells before it may divide.
  • The cell cycle is a structured, predictable series of actions that cells take to complete these goals.
  • Because the two daughter cells can restart the entire process from the beginning after each cycle, the cell cycle is a cycle rather than a linear pathway.

The correct answer is Ground tissue.

• The term cortex refers to the outermost layer of a structure.
• In the brain, the cortex most often refers to the cerebral cortex, although the cerebellum also has an outer layer called the cerebellar cortex.
• The three types of ground tissue: parenchyma, collenchyma, and sclerenchyma.
  • A function included photosynthesis, storage, regeneration, support, and protection.

Important Points

Additional Information