General Q&A for Class 12 · Page 76
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What is the difference between osmoconformers and osmoregulators, and how are they represented graphically?
Osmoconformers are organisms whose internal osmotic concentration matches that of their external environment. These organisms, primarily marine invertebrates like jellyfish, sea stars, and mussels, do not actively regulate their internal osmotic pressure. Instead, their body fluids change in concentration as the external environment changes. This strategy requires minimal energy but limits these organisms to stable salinity environments. Osmoregulators</strong
- GeneralClass 12All
How do you determine phenotypic distribution using a Punnett Square for a cross between a homozygous female and heterozygous male?
When crossing a homozygous female with a heterozygous male for a single locus, the phenotypic distribution depends on which parent carries which genotype. Let's assume we're examining a trait where the dominant allele is represented by "A" and the recessive by "a." Example: Homozygous dominant female (AA) × Heterozygous male (Aa) The Punnett Square would show: Female gametes: A, A Male gametes: A, a Offspring genotypes:
- GeneralClass 12All
How many codons and nucleotides are required to form a protein chain with 50 amino acids?
To form a protein chain containing 50 amino acids, you need 50 codons since each codon codes for one amino acid. However, the actual number of codons required in the mRNA sequence is 51 because you need one additional codon (stop codon) to signal the termination of translation. Since each codon consists of three nucleotides, the calculation for nucleotides is: For 50 amino acids: 50 codons × 3 nucleotides = 150 nucleotides
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What phenotypic proportions result from crossing TtYy (tall with yellow seeds) with Ttyy (tall with green seeds)?
When crossing a tall plant with yellow seeds (TtYy) with a tall plant with green seeds (Ttyy), we're examining a dihybrid cross where one parent is heterozygous for both traits and the other is heterozygous for height but homozygous recessive for seed color. Gametes produced: TtYy produces: TY, Ty, tY, ty Ttyy produces: Ty, ty Phenotypic proportions in offspring: (a) Tall and green: The
- GeneralClass 12All
What is oogenesis and what are its various stages?
Oogenesis is the process of female gamete (ovum) formation in the ovaries. This complex developmental process begins before birth and continues through reproductive years, involving several distinct stages: Multiplication Phase: Primordial germ cells in the developing fetus undergo repeated mitotic divisions to produce diploid oogonia. This occurs during fetal development, creating millions of potential egg cells. Growth Pha
- GeneralClass 12All
What is the difference between osmoconformers and osmoregulators?
Osmoconformers and osmoregulators represent two fundamentally different strategies for managing internal salt and water balance in relation to the external environment. Osmoconformers are organisms that allow their internal osmotic concentration to match their surrounding environment. Rather than fighting against environmental changes, their body fluids naturally adjust to match external salinity levels. Marine invertebrates such as jellyfish, sea stars, and mussels a
- GeneralClass 12All
How are osmoconformers and osmoregulators represented graphically?
Graphical representation provides a clear visual distinction between these two osmoregulatory strategies, making it easier to understand their fundamental differences. In a standard graph, external osmotic concentration (or environmental salinity) is plotted on the x-axis, while internal osmotic concentration (body fluid concentration) is plotted on the y-axis. Osmoconformers are represented by a diagonal line with a slope of 1, running at a 45-degree angle from the origin. Th
- GeneralClass 12All
What is oogenesis
Oogenesis is the biological process through which female reproductive cells, or ova (eggs), are formed in the ovaries. This highly regulated developmental process is essential for sexual reproduction and represents one of the most remarkable examples of cellular differentiation in the human body. Unlike sperm production, which begins at puberty and continues throughout adult life, oogenesis actually begins during fetal development and spans decades. The process starts when a female is
- GeneralClass 12All
What are the various stages of oogenesis?
Oogenesis unfolds through several distinct phases, each critical to producing a mature, fertilization-competent egg: Multiplication Phase (Fetal Development) This earliest stage occurs before birth, during fetal development. Primordial germ cells migrate to the developing ovaries and undergo numerous mitotic divisions, producing millions of diploid cells called oogonia. By the fifth month of fetal development, a female fetus may have as many as
- GeneralClass 12All
How does oogenesis differ from spermatogenesis?
While both processes produce gametes for reproduction, oogenesis and spermatogenesis differ dramatically in several key aspects: Timing: Spermatogenesis begins at puberty and continues throughout adult life, producing sperm continuously. Oogenesis begins before birth, arrests multiple times, and doesn't complete until fertilization—potentially spanning 40+ years for a single cell. Cell Division: Spermatogenesis produces four equal, funct
- GeneralClass 12All
Who coined the term 'meristem' and what does it mean?
The term "meristem" was coined by Carl Wilhelm von Nägeli in 1858. Meristems are specialized plant tissues consisting of undifferentiated cells that have the remarkable ability to divide continuously throughout the plant's life. These growth regions are responsible for producing new cells that differentiate into various plant tissues and organs. Meristems are found in specific locations like root tips, shoot tips, and cambium layers, enabling plants to grow in length and
- GeneralClass 12All
What is promeristem and where is it located?
Promeristem refers to the earliest, most primitive form of meristematic tissue found at the extreme tips of roots and shoots. It represents the initial meristematic cells that give rise to all primary meristems in a plant. Promeristem cells are characterized by their small size, thin cell walls, dense cytoplasm, and large nuclei relative to cell size. These self-perpetuating cells continuously divide to produce new cells while maintaining their population. The promeristem is
- GeneralClass 12All
What are the conducting tissues of plants and what are their functions?
Plants have two primary conducting tissues: xylem and phloem. Xylem is responsible for transporting water and dissolved minerals from the roots upward to all parts of the plant. It consists of specialized cells including tracheids and vessel elements that form hollow tubes for efficient water conduction. Phloem, on the other hand, transports sugars and organic nutrients produced during photosynthesis from leaves to other plant parts. This bidirectional transp
- GeneralClass 12All
Who is known as the "father of plant anatomy"?
Nehemiah Grew (1641-1712) is widely recognized as the "father of plant anatomy." This English plant anatomist and physiologist made groundbreaking contributions to botanical science through his microscopic studies of plant structures. Grew's detailed observations and illustrations of plant tissues, published in works like "The Anatomy of Plants" (1682), laid the foundation for modern plant anatomy. He was among the first scientists to systematically study and document the int
- GeneralClass 12All
What is apospory in plants?
Apospory is a form of asexual reproduction in plants where the gametophyte develops directly from sporophytic tissue without undergoing meiosis. In this process, diploid cells from the sporophyte (typically from the nucellus or integument) develop into gametophytes without the reduction division that normally produces haploid spores. This results in diploid gametophytes rather than the typical haploid ones. Apospory is commonly observed in some ferns and seed plants, and it represents an alte
- GeneralClass 12All
Q. 7. What does the last sentence of the story suggest? What would the crocodile tell his wife?
Ans. The last sentence of the story suggests that the crocodile had learnt a lesson. He realised that he had lost a good friend because of his wife’s stupid desire. So it seems that the crocodile would rebuke his wife for her greed.
- GeneralClass 12All
Q. 6. How did the monkey save himself?
Ans. The monkey told a lie that he did not carry his heart. It was still there in the tree. He asked the crocodile to carry him back on his back. He would bring his heart then. The foolish crocodile carried him to the river bank. The monkey jumped on the tree and saved himself.
- GeneralClass 12All
Q. 5. What did the crocodile tell the monkey midstream?
Ans. The crocodile carried the monkey on his back and reached the midstream. There he said to the monkey, “I’ve brought you here to kill you. My wife cannot survive without eating our heart.”
- GeneralClass 12All
Q. 3. Why was the crocodile’s wife annoyed with her husband one day?
Ans. One day, the crocodile was held up longer than usual. The crocodile’s wife kept waiting for his return. The baby crocodiles troubled her. Therefore, she got annoyed with him.
- GeneralClass 12All
Q. 2. What did the two friends generally talk about?
Ans. The monkey and the crocodile were fast friends. They generally talked about birds and animals and villagers nearby. They also talked about their difficulties in raising crops when rain failed.