Directions: In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as:
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
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Assertion: Algae show only anisogamous type of reproduction.
Reason: In algae, gametes can be non-flagellated.
(d) Sexual reproduction in algae takes place through the fusion of two gametes by isogamy, anisogamy, and oogamy. These gametes can be flagellated and similar in size (as in Chlamydomonas) or non-flagellated (non-motile) but similar in size (as in Spirogyra).
Assertion: Chlorella and Spirulina are used as a food supplement by space travellers.
Reason: Chlorella and Spirulina are unicellular algae.
(b) Unicellular algae Chlorella and Spirulina are rich in proteins and hence used as a food supplement by space travellers.
So both the assertion and reason are correct, but the reason is not the correct explanation for the assertion.
Assertion: In Chlorophyceae, the plant body is usually grass green.
Reason: Members of Chlorophyceae possess chlorophyll a, c, carotenoids, and xanthophyll.
(c) Members of Chlorophyceae are commonly called green algae. The plant body is usually grass green due to the dominance of pigments, chlorophyll a and b.
Assertion: Brown algae vary from olive green to brown in colour.
Reason: Fucoxanthin is responsible for colour variation in brown algae.
(a) Brown algae vary in colour from olive green to various shades of brown depending upon the amount of the xanthophyll pigment, fucoxanthin present in them.
Assertion: Red colour of Rhodophyta is due to abundant formation of r-phycoerythrin.
Reason: r-Phycoerythrin is able to absorb blue-green wavelength of light and reflect red colour.
(a) The red colour of red algae (Rhodophyta) is due to the abundant formation of r-phycoerythrin which is a red colour pigment. Phycoerythrin absorbs bluegreen wavelengths of light and reflects red light and thus imparts a red colour to algae.
So the correct option is a.
Assertion: Bryophytes are called as terrestrial amphibians.
Reason: Bryophytes require an external layer of water on the soil surface for their existence.
(a) Correct answer is (a) If both assertion and reason are true and the reason is the correct explanation of assertion.
Assertion: Mosses are of great ecological importance.
Reason: Mosses prevent soil erosion by forming dense mat on the soil.
(a) Mosses along with lichens are the first organisms to colonise rocks and hence, are of great ecological importance. They decompose rocks making the substrate suitable for the growth of higher plants. Since mosses form dense mats on the soil, they reduce the impact of falling rain and prevent soil erosion.
Assertion: Spores in mosses are contained within the capsule.
Reason: Spores are formed by mitotic division in mosses.
(c) In mosses, after fertilisation, the zygote develops into a sporophyte, consisting of a foot, seta and capsule. The sporophyte in mosses is more elaborate than that in liverworts. The capsule contains spores. Spores are formed after meiosis and develop into new gametophyte.
Assertion: In pteridophytes, zygote produces a multicellular sporophyte.
Reason: Sporophyte is the dominant phase in life cycle of pteridophytes.
(b) In pteridophytes, gametophytes bear, male and female sex organs called antheridia and archegonia, respectively. Water is required for transfer of antherozoids -the male gametes are released from the antheridia to the mouth of the archegonium. Fusion of male gamete with the egg present in the archegonium results in the formation of zygote. Zygote thereafter produces a multicellular we 11-differentiated sporophyte which is the dominant phase of the pteridophytes.
So the correct answer is b.
Assertion: All pteridophytes are homosporus.
Reason: Different kinds of spores are produced in Selaginella and Salvinia.
(d) In majority of the pteridophytes, all the spores are of similar kinds; such plants are called homosporous. Genera like Selaginella and Salvinia which produce two kinds of spores i.e. macro (large) and micro (small) spores are known as heterosporous.
Assertion: Gymnosperms do not produce fruit.
Reason: Ovules of gymosperms are enclosed within the ovaries.
(c) The gymnosperms are plants in which the ovules are not enclosed by any ovary wall and remain exposed, both before and after fertilisation. The seeds that develop post-fertilisation, are not covered, i.e., are naked. After fertilisation, zygote develops into an embryo and ovules into naked seeds.
Assertion: Stomata are found on the surface of leaves in gymnosperms.
Reason: In gymnosperms, cuticle of leaves is thick.
(d) The leaves in gymnosperms are well-adapted to withstand extreme temperature, humidity, and wind. In conifers, the needle-like leaves reduce the surface area. Their thick cuticle and sunken stomata helps to reduce water loss.
Assertion: In gymnosperms, the male and female gametophytes do not have an independent existence.
Reason: They remain within the sporangia retained on the sporophyte.
(a) In gymnosperms, the male and female gametophytes do not have an independent existence because they remain within the sporangia retained on the sporophyte. So, the correct answer is (a).
Assertion: In angiosperms, each cell of the embryo sac is haploid.
Reason: In angiosperms, embryo sac formation is preceded by meiosis.
(a) In angiosperms, the pistil consists of an ovary enclosing one of many ovules. Within ovules, are present highly reduced female gametophytes termed embryo sacs. The embryo-sac formation starts after meiosis (preceded by meiosis). Hence, each of the cells of an embryo-sac is haploid. So the correct option is a.
Assertion: In diplontic life cycle, gametophyte is dominant.
Reason: In diplontic life cycle, there is a free-living sporophyte.
(d) In diplontic life cycle, the diploid sporophyte is the dominant, photosynthetic, and independent phase of the plant. Gametophyte is highly reduced and is retained within sporangia.
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