Assess the following biological traits of the invasive weed Water Hyacinth:
(p) It is known as the "Terror of Bengal" because it is an invasive weed of standing water. (q) It was introduced in India because of its high protein content and edible tubers. (r) It deprives aquatic ecosystems of oxygen by draining dissolved oxygen, leading directly to the death of fish. (s) It spreads vegetatively at an extremely rapid rate via offsets.
Choose the correct option.
Water hyacinth is called the "Terror of Bengal" because of its rapid spread in freshwater bodies. It depletes dissolved oxygen, killing fishes, and spreads rapidly through offsets. It was introduced for its attractive flowers and leaves, not for edible tubers. Hence statement (q) is incorrect.
Question 32 of 100
📘 CLASS XII
Analyze the site of origin of new plantlets in modified plant organs:
(1) Plantlets in ginger and banana arise from adventitious buds located on their leaf surfaces. (2) New plants in potato arise from the eyes, which are nodes of the modified stem tuber. (3) Adventitious leaf buds arise from notches present at the margins of leaves in Bryophyllum.
Choose the correct option.
Potato produces new plants from the eyes present on the stem tuber, and Bryophyllum develops adventitious buds from leaf margins. Ginger and banana produce new plants from underground modified stems (rhizomes), not from leaves. Therefore statement (1) is incorrect.
Question 33 of 100
📘 CLASS XII
Evaluate the biological purpose of algae and fungi transitioning their modes of reproduction under adverse conditions:
(i) Fungi and algae rely purely on sexual reproduction under normal conditions but switch to asexual reproduction before winter. (ii) Asexual reproduction is favored during unfavorable conditions because it requires less energy. (iii) Simple organisms switch to sexual reproduction just before the onset of adverse conditions to survive harsh environments.
Choose the correct option.
Algae and fungi reproduce mainly by asexual methods during favourable conditions. Just before the onset of adverse conditions, they switch to sexual reproduction because the zygote develops a thick resistant wall that survives harsh environmental conditions. Hence statements (i) and (ii) are incorrect.
Question 34 of 100
📘 CLASS XII
Examine the general characteristics of sexual reproduction:
(a) It is an elaborate, complex, and slow process compared to asexual reproduction. (b) It involves the formation and subsequent fusion of haploid male and female gametes. (c) The offspring produced are morphological and genetic clones of their parents.
Which of the following statements are correct?
Sexual reproduction is a comparatively slow and elaborate process involving the formation and fusion of haploid gametes. The offspring produced show genetic variation and are not clones of their parents. Therefore statement (c) is incorrect.
Question 35 of 100
📘 CLASS XII
Read these statements concerning physiological growth phases in organisms:
(I) The juvenile phase represents a pre-reproductive phase of growth and physical maturity. (II) In plants, the juvenile phase is termed the vegetative phase and is of constant duration across all families. (III) In perennial species, it is highly challenging to clearly define the distinct vegetative, reproductive, and senescent phases.
Choose the correct option.
The juvenile phase is the pre-reproductive phase and is called the vegetative phase in plants. Its duration varies greatly among different organisms, especially perennial plants. Therefore statement (II) is incorrect.
Question 36 of 100
📘 CLASS XII
Focus on the unusual flowering behavior of Bamboo and Strobilanthus kunthiana:
(p) Bamboo species flower once every 12 years, produce vast numbers of fruits, and then die. (q) Strobilanthus kunthiana (Neelakuranji) flowers once in 12 years, with its mass flowering turning large hilly areas of Southern India into blue stretches. (r) Both bamboo and Strobilanthus kunthiana are annual plants that show clear-cut flowering every season.
Choose the correct option.
Neelakuranji flowers once every 12 years. Bamboo generally flowers only once in its lifetime after about 50 to 100 years and then dies. Both are perennial plants, not annuals. Hence statements (p) and (r) are incorrect.
Question 37 of 100
📘 CLASS XII
Read the statements below regarding reproductive cyclicity in placental mammals:
(1) Non-primate mammals (e.g., cows, sheep, dogs) show cyclic changes during the breeding phase called the oestrus cycle. (2) Primate mammals (e.g., monkeys, apes, humans) exhibit cyclic changes called the menstrual cycle. (3) Seasonal breeders are active and reproductively capable throughout the year, regardless of the season. (4) Continuous breeders remain reproductively active throughout their entire reproductive phase.
Choose the correct option.
Non-primate mammals exhibit the oestrus cycle, whereas primates exhibit the menstrual cycle. Seasonal breeders reproduce only during favourable seasons, while continuous breeders remain reproductively active throughout the reproductive phase. Hence statement (3) is incorrect.
Question 38 of 100
📘 CLASS XII
Study these statements regarding senescence and old age regulatory mechanisms:
(i) Old age is biochemically marked by the slowing of metabolism and other physiological processes. (ii) The transition between juvenile, reproductive, and senescent phases is regulated solely by external temperature. (iii) The end of the reproductive phase is considered one of the parameters of senescence.
Choose the correct option.
Senescence is characterized by slowing of metabolism and physiological processes, and the end of the reproductive phase marks one of its parameters. The transitions between life phases are regulated by both hormones and environmental factors, not temperature alone. Therefore statement (ii) is incorrect.
Question 39 of 100
📘 CLASS XII
Identify the correct sexuality terminology used in fungi and flowering plants:
(a) Bisexual conditions in plants are denoted by terms like homothallic and monoecious. (b) Unisexual conditions in plants are described using heterothallic and dioecious. (c) Papaya and date palm are excellent examples of monoecious plants. (d) Cucurbits and coconuts are typical examples of dioecious plants.
Choose the correct option.
Papaya and date palm are dioecious plants, whereas cucurbits and coconuts are monoecious. Therefore statements (c) and (d) are incorrect.
Question 40 of 100
📘 CLASS XII
Analyze the distribution of sexual organs in animal species:
(I) Animals like earthworms, sponges, tapeworms, and leeches are hermaphrodites because they possess both male and female sex organs. (II) Cockroach is an example of a unisexual species where male and female individuals are distinct. (III) All invertebrates are strictly bisexual, while all vertebrates are strictly unisexual.
Choose the correct option.
Earthworms, sponges, tapeworms and leeches are hermaphrodites, while cockroaches are unisexual. Many invertebrates are unisexual and several are hermaphrodites, making statement (III) incorrect.
