BIO 101 | Study Mode

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Question 161
A
isogamy 
B
anisogamy 
C
oogamy 
D
all of these. 
Explanation.
The class chlorophyceae is characterised by the members possessing grass-green chromatophores. The other distinguishing features of the class are the presence of starch-as reserve food material, pyrenoids commonly surrounded by starch sheaths, motile cells bearing anterior flagella of equal length, etc. <br /> In chlorophyceae, three types of sexual reproduction takes place namely isogamy, anisogamy and oogamy. Isogamous type : Here the fusing gametes are morphologically similar but physiologically distinct e.g., Chlamydomonas debaryanum and Ulothrix. Anisogamous type: Fusion takes place between morphologically and physiologically distinct gametes (anisogametes). Chlamydomonas braunii and Pandorina. Oogamous type: Most advanced type in which fusion of small biciliate or multiciliate, active male gamete with large, passive female gamete, Oedogonium, Chlamydomonas coccifera. <br /> nawed

Correct Option:
D
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Question 162
A
mitochondrial structure 
B
importance of homopolar bonds in their proteins 
C
cell wall structure 
D
modern cell organization. 
Explanation.
Some algae withstand or tolerate a very high temperature and these are often called thermal algae. Such forms are known to grow upto 85CC, nearly boiling water. Their cell wall is hard and protective. A typical cell wall of algae consists of two nonliving layers. <br /> The inner layer is firm consisting of microfibrils and outer layer is gelatinous and amorphous. Various polysaccharides such as cellulose, pectin, mucilage constitute the typical cell wall. The mucilage covering of the cell is thick and dense and is called the sheath. This sheath holds the cells in colonies together, is having water absorbing and water retaining capacity. It thus protects them under dessicating conditions. Thus they are able to survive under high temperature.

Correct Option:
C
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Question 163
A
gymnosperms and flowering plants 
B
pteridophytes and gymnosperms 
C
gymnosperms only 
D
bryophytes and pteridophytes. 
Explanation.
Bryophytes and pteridophytes both have alternation of generation. The gametophytic phase is dominant in bryophytes whereas in pteridophytes it is short lived. Sex organs are embedded is some members of bryophytes and pteridophytes. Sperms are flagellate and so water is required for fertilization. Sterile jacket is present around the sex organs for protection. Archegonium appeared for the first time in bryophytes in plant kingdom. <br /> It is a flask shaped structure. It has swollen basal portion called venter and upper elongated neck. The venter has egg cell and venter canal cell. There are 4-6 vertical rows of neck cells enclosing neck canal cells in bryophytes. The archegonia have short neck made of four rows of vertically elongated cells that encloses four neck canal cells in pteridophytes.

Correct Option:
D
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Question 164
A
completely sporophyte 
B
predominantly gametophyte with sporophyte 
C
completely gametophyte 
D
predominantly sporophyte with gametophyte. 
Explanation.
Funaria is known as common moss or green moss. The plant body is foliose that consists of stem axis which bears many leaves and instead of roots, rhizoids are present. It is gametophytic (n) and independent. <br /> It bears antheridia and archegonia on the same plant but on different branches. <br /> After fertilization the zygote (2n) divides to form the sporophyte which consists of foot, seta and capsule. The basal foot is embedded in the apex of female branch. It absorbs nutrients and provides support for the sporophyte. Inside the capsule haploid spores are produced as a result of meiosis. Thus again the gametophytic phase starts. So the gametophytic phase is the dominant phase of the life cycle of Funaria.

Correct Option:
B
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Question 165
A
12 
B
C
16 
D
24 
Explanation.
Gymnosperms show distinct alternation of generations. The sporophytic phase is dominant. The sporphyte is differentiated into root, stem and leaves. So the number of chromosomes in a leaf cell is diploid (2n), (2n = 16). Double fertilization is absent in gymnosperms. The endosperm develops before fertilization directly from the megaspore. So the number of chromosomes in endosperm will be 8(n = 8).

Correct Option:
B
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Question 166
A
Liverworts 
B
Marchantia 
C
Riccia 
D
Funaria. 
Explanation.
Marchanlia is a liverwort in which the sex organs are borne on disc shaped 8-Iobed receptacles borne at the tip of vertical gametophores. Sperms are attracted to opened archegonia by proteins and K+ salts. Fertilization produces a parasitic sporophyte made of foot, seta and capsule. The capsule encloses sporocytes and elaters. These elaters show twisting movements due to spiral bands of thickenings and this leads to liberation and dispersal of spores. In Riccia elaters are absent and in Funaria peristome teeth help in spore dispersal.

Correct Option:
B
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Question 167
A
640 
B
300 
C
1000 
D
900 
Explanation.
Gymnosperms originated about 200 million years ago and were dominant species at that time. However most of the members have become extinct now and only few living forms are known today. There are around 900 living species of this group.

Correct Option:
D
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Question 168
A
fucotfanthin 
B
haematochrome 
C
phycocyanin 
D
phycoerythrin. 
Explanation.
Brown algae are the members of the class phaeophyceae. Their chromatopores are ellipsoidal or discoid. They contain chlorophyll a, chl c, P- and c- carotenes and xanthophyll pigments (e.g., lutein, flavoxanthin, violaxanthin). They also contain large amount of a brown pigment fucoxanthin which masks the green colour of chlorophyll pigment. This gives characteristic brown colour to these plants, hence the name brown algae. <br /> The non-motile resting spores of Chlamydomonas contain a red pigment called hematochrome. phycocyanin and phycoerythrin are water soluble pigments found in red and blue-green algae.

Correct Option:
A
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Question 169
A
Chlorella 
B
Nostoc 
C
Spirogyra 
D
Ulothrix. 
Explanation.
Chlorella is a unicellular green alga that contains high percentage of proteins, lipids and most of the known vitamins (carotene, riboflavin, vitamin Bl2, choline etc) and grows more quickly than Porphyra, so scientists are doing research to obtain food from it. The nutritional value is comparable to the mixture of soybeans and spinach.

Correct Option:
A
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Question 170
A
Pinus 
B
Dryopteris 
C
Cycas 
D
Both (A) and (C). 
Explanation.
Transfusion tissue is a specialized tissue present on either side of midrib in between the palisade and spongy tissues of the leaf of Cycas and also in Pinus leaf at the sides of the sclerenchymtous region. It is made of horizontally arranged tracheids. These supply water and minerals to mesophyll tissue upto margins so that the mesophyll cells can carry out photosynthesis. It is of two types primary transfusion tissue present next to the midrib bundle and secondary transfusion tissue that runs upto margins of the leaf. In Pinus it consists of tracheids and albuminous cells.

Correct Option:
D

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