Given below are two statements: [2023]
One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): In gymnosperms, the pollen grains are released from the microsporangium and carried by air currents.
Reason (R): Air currents carry the pollen grains to the mouth of the archegonia where the male gametes are discharged and pollen tube is not formed.
In the light of the above statements, choose the correct answer from the options given below:
(A) is true but (R) is false.
(A) is false but (R) is true.
Both (A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true but (R) is not the correct explanation of A.
(1)
In gymnosperms, the male and the female gametophytes do not have an independent free-living existence. They remain within the sporangia retained on the sporophytes. The pollen grain is released from the microsporangium. They are carried in air currents and come in contact with the opening of the ovules borne on megasporophylls. The pollen tube carrying the male gametes grows towards archegonia in the ovules and discharges their contents near the mouth of the archegonia. Following fertilisation, the zygote develops into an embryo and the ovules into seeds.
Which of the following plants is monoecious? [2021]
Cycas circinalis
Carica papaya
Chara
Marchantia polymorpha
(3)
Chara is an example of a monoecious plant as both male sex organ (antheridium) and female sex organ (archegonium) are present on the same plant.
Which of the following statements is correct? [2018]
Ovules are not enclosed by ovary wall in gymnosperms.
Selaginella is heterosporous, while Salvinia is homosporous.
Horsetails are gymnosperms.
Stems are usually unbranched in both Cycas and Cedrus.
(1)
Gymnosperms have naked ovules. Selaginella and Salvinia both produce two kinds of spores, macro (large) and micro (small), hence called heterosporous. Equisetum (horsetail, scouring rush) is a pteridophyte. Stems are branched in Cedrus but unbranched in Cycas.
Select the mismatch. [2017]
Cycas – Dioecious
Salvinia – Heterosporous
Equisetum – Homosporous
Pinus – Dioecious
(4)
Pinus is a monoecious plant, i.e., in Pinus the male and female cones or strobili are borne on the same plant.
Conifers are adapted to tolerate extreme environmental conditions because of [2016]
broad hardy leaves
superficial stomata
thick cuticle
presence of vessels
(3)
Needle-like leaves with thick cuticle and sunken stomata are xerophytic adaptations of conifers for tolerating extreme environmental conditions.
Select the correct statement. [2016]
Sequoia is one of the tallest trees.
The leaves of gymnosperms are not well adapted to extremes of climate.
Gymnosperms are both homosporous and heterosporous.
Salvinia, Ginkgo, and Pinus all are gymnosperms.
(1)
Sequoia sempervirens is the tallest gymnosperm. The leaves of gymnosperms are well adapted to extremes of climate. This is the reason for gymnosperms to flourish in cold areas where instead of rain, snow is the source of water. Gymnosperms are heterosporous, i.e., produce two different kinds of spores—microspores and megaspores. Salvinia is an aquatic pteridophyte.
In which of the following, gametophyte is not independent free living? [2015]
Pteris
Pinus
Funaria
Marchantia
(2)
In gymnosperms (like Pinus), the male and female gametophytes do not have an independent free-living existence. They remain within the sporangia retained on the sporophytes, i.e., female gametophyte (within megasporangium) and male gametophyte (within microsporangium).
Read the following five statements (A to E) and select the option with all correct statements. [2015]
A. Mosses and lichens are the first organisms to colonise a bare rock.
B. Selaginella is a homosporous pteridophyte.
C. Coralloid roots in Cycas have VAM.
D. Main plant body in bryophytes is gametophytic, whereas in pteridophytes it is sporophytic.
E. In gymnosperms, male and female gametophytes are present within sporangia located on sporophyte.
A, D and E
B, C and E
A, C and D
B, C and D
(1)
Selaginella is a heterosporous pteridophyte. Coralloid roots of Cycas harbour blue-green algae like Nostoc, Anabaena and are not a type of VAM (vesicular arbuscular mycorrhiza) which is a symbiotic association with fungus.
Which one is a wrong statement? [2015]
Haploid endosperm is a typical feature of Gymnosperms.
Brown algae have chlorophyll a and c and fucoxanthin.
Archegonia are found in Bryophyta, Pteridophyta, and Gymnosperms.
Mucor has biflagellate zoospores.
(4)
Mucor is a member of Zygomycetes (the conjugation fungi) in which motile cells, e.g., zoospores, planogametes, etc., are absent. Asexual reproduction takes place by the formation of non-motile mitospores called sporangiospores. Sexual reproduction takes place by the formation of non-motile zygospores.
