Read the statements below about parthenogenesis and select the true set:
(I) The female gamete undergoes development to form new organisms without fertilization. (II) It occurs in rotifers, honeybees, and even some lizards and birds (such as turkey). (III) Parthenogenesis results in the formation of a diploid zygote that undergoes normal embryogenesis.
Which of the statements given above are correct?
Parthenogenesis is the development of an unfertilized female gamete into a new organism without fertilization. It occurs in rotifers, honeybees, some lizards and birds such as turkey. No zygote is formed during parthenogenesis; therefore statement (III) is incorrect.
Question 22 of 100
📘 CLASS XII
Examine the characteristics of external fertilization from the statements below:
(p) It is common in aquatic organisms such as a majority of algae, bony fishes, and amphibians. (q) Organisms showing external fertilization produce a very limited number of gametes to prevent overcrowding. (r) A major disadvantage is that offspring are highly vulnerable to predators, threatening their survival to adulthood.
Choose the correct option.
External fertilization is common in many aquatic organisms such as algae, bony fishes and amphibians. Such organisms release a very large number of gametes into water to increase the chances of fertilization. Their offspring remain highly vulnerable to predators. Hence statement (q) is incorrect.
Question 23 of 100
📘 CLASS XII
Select the correct combination of statements on zygote development:
(1) Zygote is a universal, diploid cell formed in all sexually reproducing organisms. (2) In fungi and algae, the zygote develops a thick wall resistant to desiccation and damage. (3) In organisms with haplontic life cycles, the zygote undergoes mitosis to form diploid vegetative cells.
Choose the correct option.
The zygote is the universal diploid stage of sexually reproducing organisms. In many algae and fungi, it develops a thick resistant wall. In haplontic life cycles, the zygote undergoes meiosis, not mitosis, to restore the haploid phase. Hence statement (3) is incorrect.
Question 24 of 100
📘 CLASS XII
Read these statements about cell division and differentiation during embryogenesis:
(i) Cell divisions (mitosis) increase the total number of cells in the developing embryo. (ii) Cell differentiation helps groups of cells undergo modifications to form specialized tissues and organs. (iii) Embryogenesis involves reduction division (meiosis) to establish diploid somatic chromosome numbers.
Choose the correct option.
Embryogenesis proceeds through repeated mitotic divisions followed by cell differentiation to produce specialized tissues and organs. Meiosis occurs during gamete formation, not embryogenesis. Therefore statement (iii) is incorrect.
Question 25 of 100
📘 CLASS XII
Evaluate the comparison between oviparous and viviparous animal groups:
(a) In oviparous animals, fertilized eggs covered by hard calcareous shells are laid in a safe environment. (b) Viviparous animals have proper embryonic care and protection inside the maternal body, leading to higher survival rates. (c) Reptiles and birds are viviparous organisms that hatch young ones directly from maternal tissues.
Choose the correct option.
Reptiles and birds are oviparous animals that lay hard-shelled eggs outside the body. Viviparous animals retain the embryo within the maternal body, providing nourishment and protection, resulting in a higher survival rate. Hence statement (c) is incorrect.
Question 26 of 100
📘 CLASS XII
Analyze the scientific contributions and milestones of Prof. Panchanan Maheshwari:
(I) He obtained his higher education D.Sc. from Allahabad and was inspired to specialize in Botany and morphology by Dr. W. Dudgeon. (II) He established the Department of Botany at the University of Delhi as an important research center in embryology and tissue culture. (III) He popularized the use of embryological characters in plant taxonomy. (IV) He led the NCERT initiative that published the very first Biology textbooks for Higher Secondary Schools in 1984.
Which of the statements given above are correct?
Prof. Panchanan Maheshwari obtained his D.Sc. from Allahabad, established the Botany Department at the University of Delhi as a centre for embryology and tissue culture, and popularized embryological characters in plant taxonomy. The first NCERT Biology textbooks were published in 1964, not 1984; therefore statement (IV) is incorrect.
Question 27 of 100
📘 CLASS XII
Read the statements below regarding lifespan and single-celled immortality:
(1) Lifespan represents the period from birth to the natural death of an organism. (2) Single-celled organisms are considered immortal because their parental cell body divides to form daughter cells, continuing its life. (3) Crows and parrots show highly similar lifespans since they possess roughly the same physical body size.
Which of the statements are correct?
Lifespan is the period from birth to natural death. Unicellular organisms are regarded as biologically immortal because the parent cell divides into daughter cells. Lifespan is not related to body size, so parrots and crows have very different lifespans despite similar sizes. Hence statement (3) is incorrect.
Question 28 of 100
📘 CLASS XII
Study these statements about asexual reproduction in Monera, Protista, and fungi:
(i) In Protists and Monerans, the cell division of the parent body is itself the mode of reproduction. (ii) Yeast reproduces through binary fission, where the cell splits equally into two halves. (iii) Unicellular algae like Chlamydomonas reproduce asexually primarily through non-motile conidia.
Choose the correct option.
In Monerans and Protists, cell division itself serves as reproduction. Yeast reproduces mainly by budding, not binary fission, and Chlamydomonas reproduces through motile zoospores rather than conidia. Therefore statements (ii) and (iii) are incorrect.
Question 29 of 100
📘 CLASS XII
Match the asexual reproductive structures with their structural features:
(a) Zoospores of Chlamydomonas are microscopic, flagellated, and motile structures. (b) Conidia of Penicillium are exogenous, non-motile asexual spores. (c) Gemmules represent the internal asexual buds of sponges. (d) Buds in Hydra are endogenous structures formed from the gastrovascular cavity lining.
Which of the statements given above are true?
Zoospores are motile, flagellated spores, conidia are non-motile exogenous spores, and gemmules are internal buds of sponges. Buds in Hydra are exogenous outgrowths formed on the outer body surface, making statement (d) incorrect.
Question 30 of 100
📘 CLASS XII
Read these statements on the classification and propagation of vegetative propagules:
(I) Units of vegetative propagation in plants such as runners, rhizomes, tubers, and offsets are collectively called vegetative propagules. (II) Formation of vegetative propagules involves two parent plants to ensure genetic diversity. (III) Offspring formed by vegetative propagation are genetically identical to the parent and are considered clones.
Choose the correct option.
Vegetative propagules are structures such as runners, rhizomes, tubers and offsets. Vegetative propagation is an asexual process involving only one parent and produces genetically identical offspring called clones. Hence statement (II) is incorrect.
