BIO 101 | Study Mode

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Question 201
A
some diatoms and several cyanobacteria
B
some cyanobacteria and many diatoms
C
several cyanobacteria and several diatoms
D
several diatoms and a few cyanobacteria.
Explanation
Until 1907, auxospore formation was regarded as asexual process but now it is considered as an act of sexual process. The auxospores may be autogamous, isogamous, anisogamous or oogamous. <br /> Their pattern of formation differs in pennate and centric diatoms. Formation of hormogonia is the common method of reproduction in Nostoc which is produced by accidental breaking of trichome into several pieces. It may also be formed by death and decay of ordinary intercalary cells. Soon, the hormogonium escapes from mucilage and grows into a new filament and then into a new colony.

Correct option: D
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Question 202
A
manufactures food for itself, as well as for the gametophyte
B
is partially parasitic on the gametophyte
C
produces gametes that give rise to the gametophyte
D
arises from a spore produced from the gametophyte
Explanation
Mosses like Funaria are bryophytes. They are non-vascular plants. The main plant body is gametophytic (n) which is independent and foliose. It forms major part of the life cycle. The sporophytic phase starts with zygote which divides to form sporogenous tissue that is differentiated into foot, seta and capsule. The sporophytic phase is short lived. The foot absorbs nutrients and provides support to the sporophyte.

Correct option: B
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Question 203
A
formation of endosperm before fertilization
B
production of seeds from ovules
C
lack of xylem tracheids
D
absence of pollen tubes
Explanation
Conifers belong to gymnosperms. They are seed bearing plants in which the sporophylls are aggregated to form cones and the seeds develop in exposed state over the surface of megasporophylls. Vascular strand consists of tracheids and sieve cells. Female gametophyte forms archegonia, provides nourishment to developing embryo and later gets transformed into food-laden tissue or endosperm inside the seed. <br /> This endosperm is formed before fertilization so it is haploid in nature. It provides nourishment for growth of seedlings at the time of seed germination. Grass is an anoiospermic plant and endosperm is produced after fertilization.

Correct option: A
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Question 204
A
it serves as a disinfectant
B
it is easily available
C
it is hygroscopic
D
it reduces transpiration
Explanation
The partially decomposed Sphagnum mass accumulates to form compressed mass called peat, which after drying is used as coal. So it is also called peat moss. Sphagnum has the capacity to retain water for long periods and thus it is used to cover plant roots during transportation.

Correct option: C
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Question 205
A
there is high degree of sterility
B
one can conclude that the plant is apomictic
C
self fertilization is prevented
D
there is no change in success rate of fertilization.
Explanation
In prothallus of vascular cryptogams the antherozoids and eggs mature at different times. The spore on germination gives rise to prothallus. The antherozoids are biflagellated or multiflagellated. The egg is produced inside the venter, water is essential for fertilization and it is always cross-fertilization. Self fertilization is prevented.

Correct option: C
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Question 206
A
nature of stored food materials in the cell
B
structural organization of thallus
C
chemical composition of the cell wall
D
types of pigments present in the cell.
Explanation
Algae are a group of chlorophyllous, nonvascular plants with thallose plant body. Different algae show different pigments present in the cell like chlorophyll a, b, xanthophylls, carotenes etc. These pigments provide the base for classification of various groups of algae into different classes. Chlorophyceae possess Chlorophyll a, b pigments, bacillariophyceae contains diatomin pigment, phaeophyceae has fucoxanthin, rhoaopl.yceae has r-phycocyanin and r- phycoerythrin, cyanophyceae has phycobilin pigment.

Correct option: D
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Question 207
A
Zygnema, Saprolegnia and Hydrilla
B
Fucus, Marsilea and Calotropis
C
Riccia, Dryopteris and Cycas
D
Anthoceros, Funaria and Spirogyra.
Explanation
Flagellated male gametes are mostly seen lower groups of plants like algae, bryophytes, pteridophytes. It is also seen in certain gymnosperms like Cycas. The bryophytes like Riccia have the male gametes which are biflagellate.

Correct option: C
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Question 208
A
indusium
B
calyptra
C
peristome teeth
D
elaters.
Explanation
An elater is a cell (or structure attached to a cell) that is hygroscopic, and therefore will change shape in response to changes in moisture in the environment. Elaters come in a variety of forms, but are always associated with plant spores. In plants that do not have seeds, they function in dispersing the spores to a new location. In the liverworts, elaters are cells that develop in the sporophyte alongside the spores. <br /> They are complete cells, usually with helcial thickenings at maturity that respond to moisture content. In most liverworts, the elaters are unattached, but in some leafy species (such as Frullania) a few elaters will remain attached to the inside of the sporangium (spore capsule). The elaters by hygroscopic movement help in spore dispersal.

Correct option: C
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Question 209
A
a cavity in the ovule in which pollen grains are stored after pollination
B
an opening in the megagametophyte through which the pollen tube approaches the egg
C
the microsporangium in which pollen grains develop
D
a cell in the pollen grain in which the sperms are formed.
Explanation
In gymnosperms, pollen chamber represents the microsporangium in which pollen grains develop. The microspore is generally a globular sac like structure having large number of microspores. The microspores are also termed as pollen grains.

Correct option: C
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Question 210
A
plankton
B
pelagic
C
benthos
D
neritic.
Explanation
Plankton are minute pelagic organisms that drift or float passively with the current in a sea or lake. Plankton includes many microscopic organisms, such as algae, protozoans, various animal larvae, and some worms. Pelagic are the organisms that swim or drift in a sea or a lake. Benthos consists of flora and fauna occurring on the bottom of a sea or lake. Neritic zone is the region of the sea over the continental shelf, which is less than 200 metres deep.

Correct option: A

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