CUET UG Biology Booster Test 3 Male Gametophyte (Pollen) and Female Structures

According to NCERT, the outer layer of the pollen grain wall is called the exine and exhibits a Fascinating array of designs (II) and patterns. The exine is composed of sporopollenin, one of the most resilient organic materials known, which exhibits High resistance (B) specifically To strong acids and alkali (IV) as well as extreme temperatures. At certain points on the exine, there are distinct circular openings called the Germ pore (C), which are defined as an Area lacking sporopollenin (I) to allow for future pollen tube emergence. Because of this incredibly stable polymer wall, pollen grains are uniquely immune to microbial decay, meaning their long-term Fossilization (D) is directly Due to sporopollenin presence (III). Matching these pairs creates the sequence: (A)-(II), (B)-(IV), (C)-(I), (D)-(III), which corresponds to Option A.

The microspore wall is composed of specialized layers with distinct biochemical functions. Sporopollenin (A) is chemically classified as the Most resistant organic material (III) known in the plant kingdom. The high chemical Resistance (B) of this compound prevents biological breakdown, which directly leads to the excellent Preservation of pollen fossils (I) over millions of years. The exine features small, uncovered Apertures (C) called germ pores, which serve as specialized Sites for pollen tube growth (IV) during germination. The structural Hardness (D) of the outer exine layer provides vital mechanical defense, resulting in the physical Protection of male gametophyte (IV) cells from drying out or suffering damage. This yields the sequence: (A)-(III), (B)-(I), (C)-(IV), (D)-(II), matching Option A.

The Question requires arranging the structural layers of the pollen grain based on their developmental timeline and location, tracing from the innermost layer outward. In plant cell development, the primary boundary is the Plasma membrane boundary (III), which surrounds the cytoplasm. Next, the cell develops its inner wall layer through Pectin-cellulose layer formation (II), creating a thin, continuous inner wall (the intine). Finally, the outer layer is completed via Sporopollenin deposition (I), forming the tough, sculpted outer wall (the exine). Tracing this developmental sequence from the inside out follows the order: III - II - I, which matches Option A.

To arrange these structures by their permeability to moisture, we analyze their chemical physical properties from lowest to highest: 1. Sporopollenin exine (III): This layer has exceptionally Low permeability. It forms a tough, waterproof barrier that protects the pollen grain from drying out. 2. Intine (II): This pectin-cellulose layer has Moderate permeability. It acts like a standard, semi-permeable plant cell wall. 3. Germ pore (I): This open aperture has High permeability because it completely lacks sporopollenin, allowing water to enter quickly and the pollen tube to emerge. Arranging these components from lowest permeability to highest yields the sequence: III - II - I, matching Option A.

A mature pollen grain is a two-celled or three-celled structure containing a Large irregularly shaped nucleus of vegetative cell (A) and a small Spindle-shaped generative cell (B), with its internal cytoplasm enclosed by a cellular Plasma membrane surrounding cytoplasm (D). In contrast, the Triploid endosperm nucleus (C) is formed much later during double fertilization, when a male gamete fuses with the diploid secondary nucleus inside the distant embryo sac. Because this triploid structure is part of the developing seed rather than the pollen grain, it plays no role in the structural integrity of the pollen grain itself. This makes Option C the correct choice.

In plants that shed their pollen at the 2-celled stage, the generative cell travels down the growing pollen tube. While moving through the Vegetative cell cytoplasm (A), the generative cell uses its haploid Presence of a nucleus (D) to undergo a standard mitotic division. This mitotic division leads to the Formation of two male gametes (B). Because the generative cell is a product of previous microsporogenesis, it is already haploid ($n$) and cannot undergo a Meiotic reduction division (C), which would cut its chromosome number in half. Therefore, meiosis is not involved in this stage of development, making Option C the correct choice.

In approximately 40% of flowering plants, pollen grains undergo an extra step of development before shedding. This phase is reached via the Division of generative cell before shedding (C). This division creates Two male gametes (A), which exist alongside the large, nutrient-storing Vegetative cell (B) to form a 3-celled pollen grain. The Division of vegetative cell into gametes (D) does not occur; the vegetative cell functions only to build the pollen tube and nourish the gametes. This makes Option D the incorrect statement.

According to NCERT, pollen shedding occurs at two specific stages of development: the 2-celled stage (60%) (A), which contains a vegetative cell and a generative cell, and the 3-celled stage (gametes) (B), where the generative cell has already divided into two male gametes. Both stages require Vegetative cell presence (D) to support pollen tube growth. In contrast, the 7-celled stage (mature) (C) describes the female embryo sac (which contains 7 cells and 8 nuclei) located inside the ovule. This female structure has nothing to do with the developmental state of male pollen grains at shedding, making Option C the correct answer.

According to NCERT, Parthenium (carrot grass) is an invasive weed that became widespread in India after entering the country as a Contaminant in imported wheat (A). The weed exhibits complete Ubiquity in occurrence (B), spreading rapidly across both urban and rural environments. Its lightweight pollen grains act as a severe airborne allergen, serving as a well-known Cause of severe allergies (C) like asthma and contact dermatitis. Parthenium contains toxic chemicals like parthenin, meaning it has zero High nutritional value for humans (D) and is dangerous if consumed. This makes Option D the correct choice.

This Question evaluates the direct health benefits and risks associated with pollen grains as outlined in NCERT. The benefits include their use as dietary supplements, which are processed into Nutrient-rich tablets (A) and liquid Syrups for athletes (B) to improve physical performance. The risks include environmental allergies, as inhaling airborne pollen can cause severe Bronchial afflictions (C) like asthma. In contrast, In-situ conservation of biodiversity (D) is a broad ecological 4. Strategy Used to protect wild species within their natural habitats (such as national parks). This conservation method is an environmental management practice that is completely unrelated to the direct health properties of pollen grains, making Option D the correct choice.

Pollen grains stored under normal ambient conditions quickly lose their viability due to cellular respiration and metabolic breakdown. According to the provided Passage:, pollen banks use liquid nitrogen (-196°C) to achieve cryopreservation. This extreme cold Arrests metabolic decline and maintains viability for years (B) by putting the cells into a state of suspended animation. This allows valuable genetic strains to be preserved indefinitely for plant breeding programs, making Option B the correct analytical explanation.

This Question evaluates how the differing lifespans of pollen grains affect plant breeding logistics. The provided Passage: notes: "Rice and wheat lose viability within 30 minutes, while members of Solanaceae maintain it for months." Because Solanaceae pollen remains viable for months, breeders have plenty of time to collect, transport, and use it. In contrast, Wheat pollen due to its 30-minute viability window (B) loses its ability to fertilize almost immediately after release. This short lifespan creates a major logistical challenge, as breeders must collect and use the wheat pollen immediately or freeze it in liquid nitrogen before the 30-minute window runs out.

NCERT uses specific plant examples to illustrate the terminology of the gynoecium. A flower that develops multiple individual carpels is classified as multicarpellary. When these individual carpels remain completely separate and Free from each other, the condition is defined as Apocarpous (B). The textbook explicitly highlights the genus Michelia to illustrate this multicarpellary, apocarpous arrangement, where many distinct carpels can be seen growing independently along a single central axis. This confirms Option B as the correct answer.

This Question evaluates the developmental connection between a flower's ovary and its mature fruit. Every seed found inside a fruit develops from an individual ovule that was successfully fertilized inside the ovary. Because fruits like papayas and watermelons contain hundreds of individual seeds, their flowers must develop an ovary that contains Many ovules. Additionally, handling this high reproductive load requires a large, complex ovary formed by the fusion of multiple carpels, which is classified as Multicarpellary. This confirms that these plants possess a Multicarpellary with many ovules (B) reproductive system, matching the explicit examples listed in NCERT.

This Question evaluates the structural differences between the two main types of multi-carpel ovaries described in the textbook. Both Papaver and Michelia are classified as multicarpellary because they develop multiple carpels. However, they differ in how those carpels are arranged. In Michelia, the carpels remain separate and free from one another. In contrast, the pistil of Papaver is classified as syncarpous because Its carpels are fused (B) together during development to form a single, unified ovary wall topped by a shared stigmatic disc. This makes Option B the correct distinguishing feature.

The terms apocarpous and syncarpous are used exclusively to describe the structural arrangement of the gynoecium (the female reproductive organ). In an apocarpous gynoecium, the flower develops multiple individual carpels or pistils. The word "free" indicates a complete lack of physical fusion between these Individual pistils (B), allowing them to grow independently along the central receptacle (as seen in Michelia). This independent arrangement means Option B is the correct definition.

According to NCERT, a standard individual pistil is divided into three distinct structural zones. At the very top sits the stigma, which functions as the landing platform for incoming pollen grains. At the very base sits the swollen ovary bulge, which houses the ovules. The physical transition zone connecting these two end pieces is the Style (B), which develops as an elongated, narrow tube. When a pollen grain germinates on the stigma, its pollen tube must grow down through the internal tissue of this style tube to reach the ovary cavity below. This makes Option B the correct anatomical path.

This Question evaluates how the physical structure of the pistil supports reproductive function. The style is the elongated tube that connects the top stigma platform down to the basal ovary cavity. After pollination occurs, the pollen grain germinates on the stigma and extends a long pollen tube. This tube must travel down through the internal tissue of the style to deliver the male gametes to the ovules below. If the style is surgically removed from the pistil, the physical pathway connecting the top and bottom is destroyed. This directly blocks the Growth of the pollen tube to the ovary (B), preventing fertilization even if pollen successfully lands on the remaining tissue.

According to NCERT, the basal section of the pistil is the ovary, and the internal space inside it is called the ovarian cavity or locule. This internal chamber provides the physical space needed to house the plant's female reproductive structures. The Placenta develops as a ridge of tissue along the inner walls of this locule cavity, serving as an anchor point from which the megasporangia (ovules) grow. Without this open internal chamber, there would be no space to house The placenta and ovules (B), making the locule a structural prerequisite for their placement.

While common cereal crops like wheat and paddy develop exactly one single ovule per ovary, other plant families follow a different reproductive Strategy. NCERT explicitly highlights specialized groups like Orchids and parasitic plants like Orobanche to illustrate the upper limits of ovule production. The ovaries of these plants develop a massive reproductive capacity, packing Thousands of tiny seeds/ovules (B) into a single flower. When fertilized, these ovaries mature into dry capsules that split open to release thousands of microscopic, dust-like seeds into the wind, confirming Option B as the correct description.