Botany MCQs
Topic Notes: Botany
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
1
Which environmental factor is essential for the fertilization process in Riccia?
Answer:
Water
Like most bryophytes, Riccia requires the presence of external water for fertilization. The biflagellated antherozoids must swim through a film of water to reach the archegonium, where the egg is located, making water a critical limiting factor for their sexual reproduction.
2
In the structure of an archegonium, what is the designation of the lowermost cell?
Answer:
Basal cell
In the development of the archegonium in bryophytes, the initial cell divides to form an upper cover cell and a lower basal cell. The basal cell typically contributes to the stalk or the base of the archegonium, providing structural support for the developing gametangium.
3
What are the primary chemical components that constitute the endosporium of the spore wall?
Answer:
A and b both
The spore wall in bryophytes is typically composed of multiple layers. The endosporium, or inner layer, is primarily made up of cellulose and pectose. These polysaccharides provide structural integrity and protection to the developing spore, ensuring its viability during dispersal and germination in the environment.
4
What is the sexual reproductive condition of the species Riccia glauca?
Answer:
Monoecious
Riccia glauca is monoecious, meaning that both male (antheridia) and female (archegonia) reproductive organs are produced on the same thallus. This condition is common in many species of Riccia, facilitating self-fertilization, although cross-fertilization can also occur depending on environmental conditions and the proximity of other thalli.
5
Approximately how many species of the genus Riccia have been identified by botanists?
Answer:
200
The genus Riccia is a diverse group within the order Marchantiales. While estimates vary based on taxonomic classification and regional studies, many botanical sources cite approximately 200 recognized species distributed globally, particularly in temperate and tropical regions.
6
What is the name of the innermost layer of the spore wall in Riccia?
Answer:
Endosporium
The spore wall in Riccia, like many other bryophytes, is differentiated into distinct layers. The outermost layer is the exosporium (or exine), while the innermost layer is known as the endosporium (or intine). This layer is typically thin and delicate compared to the outer protective layers.
7
Which structure connects the capsule to the wall of the spore sac in mosses?
Answer:
Trabeculae
In the capsule of many mosses, such as Funaria, the spore sac is connected to the capsule wall by a network of filaments known as trabeculae. These structures provide structural support and facilitate the transport of nutrients to the developing spores within the spore sac.
8
Which structures are characteristically found on the ventral surface of the Riccia thallus?
Answer:
Rhizoids
The ventral surface of the Riccia thallus is characterized by the presence of rhizoids and scales. Rhizoids are unicellular, hair-like structures that serve the primary function of anchoring the plant to the substrate and absorbing water and minerals from the soil.
9
What is the typical sexual reproductive condition found in the majority of Riccia species?
Answer:
Monoecious
Most species of the genus Riccia are monoecious, meaning that both male (antheridia) and female (archegonia) reproductive organs are produced on the same thallus. This condition facilitates self-fertilization, which is a common reproductive strategy in many liverworts to ensure reproductive success in varying environmental conditions.
10
Which vegetative structure is developed by certain species of Riccia for perennation?
Answer:
Tubers
Under unfavorable environmental conditions, such as drought, some species of Riccia develop specialized vegetative structures known as tubers. These tubers are thickened, starch-storing portions of the thallus that remain dormant in the soil and regenerate into a new thallus when favorable conditions return.