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
151
Which category of vegetative trichomes is characterized by being multicellular and uniseriate, originating from an initial cell that undergoes a periclinal division?
Answer:
Uniseriate filiform trichomes
Trichomes are epidermal outgrowths. Filiform trichomes are thread-like structures. When they are uniseriate (a single row of cells) and arise from an initial cell that divides periclinally (parallel to the surface), they are classified as uniseriate filiform trichomes. This developmental pathway is distinct from other hair types found on plant surfaces.
152
What term defines tissues composed of only one type of cell, forming a homogeneous structural system?
Answer:
Simple primary permanent tissues
Simple permanent tissues are defined as tissues consisting of cells that are structurally and functionally similar, originating from the same meristematic source. Examples include parenchyma, collenchyma, and sclerenchyma, which form homogeneous systems within the plant body.
153
Match the type of vegetative propagation in List-I with the correct example in List-II.
Answer:
a-3, b-1, c-2, d-4
Vegetative propagation involves asexual reproduction using plant parts. Tubers (eyes) are found in potatoes (a-3). Bulbs are characteristic of garlic (b-1). Rose is commonly propagated via stem cuttings (c-2). Bryophyllum is well-known for producing plantlets at the margins of its leaves (d-4). Thus, the correct matching is a-3, b-1, c-2, d-4.
154
Which of the following is considered the hardest type of connective tissue in the human body?
Answer:
Bone
Bone is a specialized form of dense connective tissue characterized by a mineralized extracellular matrix containing calcium phosphate (hydroxyapatite). This mineralization provides the structural rigidity and hardness necessary to support the body and protect internal organs, distinguishing it from soft tissues like blood or adipose.
155
In the context of the Histogen theory, which meristematic layer is responsible for developing the tissues located between the epidermis and the central vascular cylinder?
Answer:
Periblem
According to Hanstein's Histogen theory, the apical meristem is divided into three distinct zones: the dermatogen, which forms the epidermis; the periblem, which gives rise to the cortex (the tissue between the epidermis and the vascular cylinder); and the plerome, which develops into the central vascular cylinder.
156
What is the specific anatomical term for the region on a plant stem where a leaf originates?
Answer:
node
In plant anatomy, the node is the critical junction point on a stem where leaves, branches, or aerial roots emerge. The space between two successive nodes is referred to as an internode. This structural arrangement is fundamental to plant morphology and growth patterns.
157
What is the term for the thick-walled endodermis found in certain monocotyledons?
Answer:
Phloeotrema
In some monocotyledonous roots, the endodermal cells undergo significant secondary wall thickening. This specialized structure is often referred to as 'phloeotrema' or 'passage cells' depending on the specific context of the anatomical study. These structures are essential for regulating the movement of water and solutes into the vascular cylinder.
158
What is the specialized multi-layered epidermis found in the aerial roots of certain orchids called?
Answer:
Velamen
Velamen is a spongy, multi-layered epidermis found in the aerial roots of epiphytic orchids. It functions to absorb moisture from the atmosphere and protects the root cortex from desiccation. This specialized tissue is an adaptation to the epiphytic lifestyle where water availability is intermittent.
159
During the process of abscission, where does the dissolution of the middle lamellae or the accumulation of liquid in the intercellular spaces typically occur?
Answer:
Vascular region
Abscission is the shedding of plant parts like leaves or fruits. The abscission zone forms at the base of the organ. The enzymatic breakdown of the middle lamella, which leads to cell separation, is most critical and pronounced in the vascular region to ensure the organ detaches cleanly from the main plant body.
160
Which pigment is primarily responsible for the yellow coloration observed in papaya fruit?
Answer:
Caricaxznthin
The yellow color of ripe papaya is attributed to the presence of carotenoid pigments, specifically violaxanthin and its derivatives, often referred to in literature as caricaxanthin. While other pigments like lycopene may be present in certain varieties, caricaxanthin is the specific compound associated with the characteristic yellow-orange hue of the fruit flesh.