Read the following statements on vegetative reproduction in plants:
(p) Vegetative propagation is a type of asexual reproduction that does not involve the fusion of male and female gametes. (q) Offspring produced by vegetative propagation are genetically identical and can be termed clones. (r) Vegetative propagation in plants can occur naturally using runners, suckers, tubers, and rhizomes.
Choose the correct option.
Vegetative propagation is an asexual mode of reproduction involving a single parent. The offspring are genetically and morphologically identical clones, and natural vegetative propagation occurs through structures such as runners, suckers, tubers and rhizomes.
Question 72 of 100
📘 CLASS XII
Determine the correctness of the following statements about cell division during gamete formation:
(a) Unicellular Protists and Monerans always have a diploid parent body and undergo meiosis to reproduce. (b) Several organisms belonging to fungi, algae, and bryophytes have haploid plant bodies. (c) In diploid organisms, specialized cells called meiocytes undergo meiosis to produce haploid gametes.
Choose the correct option.
Many Monerans and Protists possess haploid parent bodies and reproduce by mitotic cell division. Meiosis occurs only in diploid meiocytes to produce haploid gametes. Hence statement (a) is incorrect.
Question 73 of 100
📘 CLASS XII
Read these statements regarding the synchronization of sex cell release in external fertilizing organisms:
(i) Bony fishes and frogs release a large number of gametes into the surrounding water. (ii) This synchronous gamete release significantly increases the probability of successful syngamy. (iii) The surrounding aquatic medium protects the resulting embryos from predators up to adulthood.
Choose the correct option.
External fertilizers release numerous gametes synchronously to increase fertilization success. Their embryos and young ones remain highly vulnerable to predators, making statement (iii) incorrect.
Question 74 of 100
📘 CLASS XII
Evaluate these statements about the wall of the zygote in lower organisms:
(1) In fungi and algae, the zygote develops a thick wall resistant to desiccation and damage. (2) This thick-walled zygote undergoes an obligatory period of rest before germination. (3) The thick wall of the zygote is composed of calcareous shells similar to reptiles.
Choose the correct option.
The zygote of fungi and algae develops a thick resistant wall and undergoes a resting period. Calcareous shells are characteristic of the eggs of reptiles and birds, not fungal or algal zygotes. Hence statement (3) is incorrect.
Question 75 of 100
📘 CLASS XII
Read the statements below on the classification of mammals based on their cyclic changes:
(p) Non-primate mammals (like cows, sheep, dogs) show cyclic changes in ovaries called the oestrus cycle. (q) Primate mammals (monkeys, apes, humans) exhibit the menstrual cycle. (r) Seasonal breeders exhibit these reproductive cycles only during favorable seasons. (s) Continuous breeders remain reproductively active throughout their breeding phase.
Choose the correct option.
All four statements are correct. Non-primate mammals exhibit the oestrus cycle, primates exhibit the menstrual cycle, seasonal breeders reproduce only during favorable seasons, whereas continuous breeders remain reproductively active throughout their reproductive phase.
Question 76 of 100
📘 CLASS XII
Read the statements below concerning cell division and aging patterns in unicellular organisms:
(I) Unicellular organisms do not show natural death because they continue living as daughter cells. (II) In yeast, binary fission divides the parent cell into two equal halves. (III) Cell division is itself a mode of reproduction in Protists and Monerans.
Identify the correct combination.
In yeast, reproduction occurs by budding (unequal division), not binary fission. Binary fission is an equal division seen in organisms like Amoeba. Statements I and III are correct.
Question 77 of 100
📘 CLASS XII
Evaluate these biological traits of the invasive aquatic plant Water Hyacinth:
(p) Water hyacinth is an invasive aquatic weed that grows in standing water. (q) It removes dissolved oxygen from the water body, causing fish to suffocate and die. (r) It was introduced in India because of its nutritive edible roots. (s) It propagates vegetatively via runners at an alarming rate.
Which statements are correct?
Water hyacinth was introduced for its beautiful flowers and leaf shape, not edible roots. It propagates by offsets, not runners. Therefore, statements (r) and (s) are incorrect.
Question 78 of 100
📘 CLASS XII
Study these statements regarding the life cycle phases of different plant groups:
(i) Annual and biennial plants display clear-cut vegetative, reproductive, and senescent phases. (ii) Perennial plants display highly defined phases that can be easily demarcated. (iii) The inter-flowering phase in perennial plants is a mature phase, not a juvenile phase.
Which option correctly evaluates these statements?
Perennial plants do not show clearly demarcated vegetative, reproductive and senescent phases because of their long lifespan. Statement (ii) is incorrect.
Question 79 of 100
📘 CLASS XII
Read the statements below about the reproductive mechanism of parthenogenesis:
(a) Parthenogenesis involves development of a female gamete into a new organism without fertilization. (b) It is common in honeybees, rotifers, some lizards, and turkey. (c) The offspring of parthenogenesis are always triploid.
Which of the statements given above are correct?
Parthenogenetic offspring may be haploid or diploid depending on the organism and mechanism involved. They are not always triploid. Hence statement (c) is incorrect.
Question 80 of 100
📘 CLASS XII
Analyze the chromosome counts of various organisms listed in your syllabus:
(1) In a housefly, the meiocyte contains 12 chromosomes, while the gamete has 6. (2) In a fruit fly, the meiocyte has 8 chromosomes, while the gamete has 4. (3) In a butterfly, the meiocyte has 190 chromosomes, while the gamete has 380. (4) In an onion, the meiocyte has 16 chromosomes, while the gamete has 8.
Select the correct combination.
In butterflies, the meiocyte (2n) contains 380 chromosomes and the gamete (n) contains 190 chromosomes. Statement (3) reverses these values and is incorrect.
