Biology MCQs
Topic Notes: Biology
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
271
Which complex organic polymer is responsible for providing structural rigidity and hardening the cell walls of sclerenchyma tissues?
Answer:
lignin
Lignin is a complex phenolic polymer deposited in the secondary cell walls of sclerenchyma cells. It provides significant mechanical strength and rigidity, allowing plants to remain upright and resist environmental stresses.
272
In rhizomes, what structure is produced from the lower surface?
Answer:
adventitious roots
A rhizome is a modified underground stem that grows horizontally. Adventitious roots typically emerge from the nodes on the lower surface of the rhizome to anchor the plant and absorb water and nutrients from the soil, while shoots grow upward from the upper nodes.
273
Which biological tissue provides the structural framework for the human nose and ears?
Answer:
Cartilage
Cartilage is a resilient and smooth elastic tissue that serves as a structural component in various parts of the body. Specifically, elastic cartilage provides the necessary flexibility and shape to the external ears (pinnae) and the tip of the nose. Unlike bone, it is flexible enough to withstand pressure and return to its original shape, making it ideal for these anatomical structures.
274
Which type of cartilage is characterized by high toughness and reduced flexibility due to a dense concentration of collagen fibers?
Answer:
fibrous cartilage
Fibrocartilage (fibrous cartilage) contains thick bundles of collagen fibers dispersed throughout its matrix. This structural composition provides high tensile strength and rigidity, making it ideal for areas subjected to heavy pressure, such as the intervertebral discs.
275
Which type of vegetative propagation involves fleshy leaves surrounding a short, underground stem?
Answer:
bulbs
Bulbs are specialized underground storage organs consisting of a short stem base surrounded by fleshy, scale-like leaves that store nutrients, allowing the plant to survive dormant periods and propagate vegetatively.
276
What is the characteristic shape of the guard cells surrounding a stoma?
Answer:
Kidney-shaped
Guard cells are specialized plant cells that surround stomata. In most dicotyledonous plants, these cells are characteristically kidney-shaped or bean-shaped. Their turgor pressure changes allow them to open or close the stomatal pore, thereby regulating gas exchange and transpiration rates in the leaf.
277
Which layer is the first to be deposited during the formation of the plant cell wall?
Answer:
Primary wall
During cytokinesis, the cell plate forms, which eventually matures into the middle lamella. The primary cell wall is then synthesized and deposited on either side of the middle lamella while the cell is still growing. It is characterized by its thin, flexible nature compared to the later-developed secondary wall.
278
What is the name of the single layer of cells that immediately surrounds the pericycle in plant roots?
Answer:
endodermis
The endodermis is the innermost layer of the root cortex, forming a boundary between the cortex and the vascular cylinder (stele). It surrounds the pericycle and contains the Casparian strip, which regulates the flow of water and solutes into the vascular tissue.
279
Which structural feature is characteristically absent in meristematic plant tissues?
Answer:
inter cellular tissues
Meristematic cells are characterized by their small size, dense cytoplasm, and thin cell walls. Because these cells are tightly packed to facilitate rapid division, they lack the intercellular spaces commonly found in mature, differentiated plant tissues.
280
In histological terms, where is the lacuna, a fluid-filled space, located within cartilage tissue?
Answer:
matrix of cartilage
In cartilage tissue, chondrocytes are specialized cells that reside within small cavities known as lacunae. These lacunae are embedded within the dense, extracellular matrix of the cartilage, providing a protected environment for the cells to maintain the surrounding tissue structure.