BIO 101 | Study Mode

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Question 221
A
acoelous
B
heterocoelous
C
amphicoelous
D
procoelous.
Explanation
Bird vertebrae are heterocoelous i.e., the centra of vertebrae have saddle shaped ends. Acoelous refers to vertebrae that are flat on both ends (mammals). Amphicoelous means both ends of the centrum are concave (fish). Procoelous means concave in front and convex in back (anurans and reptiles).

Correct option: B
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Question 222
A
rodentia
B
chiroptera
C
primata
D
cetacea.
Explanation
Order cetacea includes whales, dolphins and porpoises. These are the most highly modified mammals. They have a fish-like body with smooth, hairless skin devoid of sweat and oil glands, far posterior nares, small eyes, minute ear openings without pinnae, paddle-like forelimbs, no hindlimbs, abdominal testes and flattened tail ending in two horizontal flaps or flukes.

Correct option: D
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Question 223
A
adaptation
B
mimicry
C
homology
D
analogy.
Explanation
Mimicry is resemblance of one species with another in order to obtain advantage, especially, against predation. The species which is imitated is called model while the animal which imitates is known as mimic or mimictic. Model is either ferocious or distasteful to predator. Adaptation is any quality of the organism (morphological, physiological, and behavioral) that enables the organism to survive and reproduce in its habitat. Mimicry is an example of adaption. Homology is the phenomenon in which origin of organs is same but functions are different and analogy is the phenomenon in which origin of organs is different but functions are same.

Correct option: B
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Question 224
A
Eel
B
carp
C
cat fish
D
Gambusia.
Explanation
Gambusia is a species of freshwater fish. It is remarkably hardy, surviving in waters of very low oxygen saturations, high salinities and high temperatures. For these reasons, this species may now be the most widespread freshwater fish in the world, having being introduced as a biocontrol in certain countries to control mosquitoes. It feeds on larval and pupal stages of mosquitoes.

Correct option: D
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Question 225
A
hydrozoa
B
scyphozoa
C
anthozoa
D
none of these.
Explanation
Jelly fish belongs to the class scyphozoa of the phylum cnidaria. Its genus is Aurelia. Amelia is found in the coastal waters of the tropical and temperate seas. Aurelia may float passively or swim actively, singly or in shoals. It is carnivorous and unisexual. Aurelia has a soft, gelatinous, saucer-like body. Its margin bears numerous short tentacles and 8 sense organs, called rhopalia, in notches of the margin. Each sense organ is enclosed by a pair of leaf-like lappets. At the centre of the lower (subumbrellar) surface is the squarish mouth surrounded by 4 long oral arms.

Correct option: B
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Question 226
A
oncosphere
B
cysticercus
C
morula
D
egg.
Explanation
Eggs of Taenia undergo cleavage to form morula. Morula, at its morphologically posterior end, develops three pairs of chitinous hooks secreted by differentiated cells, called onchoblasts. This six-hooked embryo, called hexacanth, possesses a pair of large penetration glands; it is surrounded by two hexacanth membranes. The hexacanth, together with all the membranes surrounding it, is known as onchosphere. <br /> The secondary or intermediate host acquires infection by ingesting the onchospheres. Pig, which regularly feeds on human excreta is the usual secondary host, but dog, monkey and sheep are also known to get the infection. Man himself may serve as the secondary host by ingesting onchospheres with inadequately cooked or raw vegetables.

Correct option: A
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Question 227
A
clitellum
B
many eyes
C
dorsal surface
D
lateral sides.
Explanation
Poto-receptors restricted only to dorsal surface, are more numerous on prostomium and peristomium of earthworm and gradually reduce in number towards posterior end of body. They are totally absent in clitellum. <br /> Each photoreceptor consists of a single ovoid cell, with a nucleus and clear cytoplasm containing a network of neurofibrillae and a small transparent L-shaped lens or optic organelle or phaosome, made up of a hyaline substance. Photoreceptors enable worms to judge the intensity and duration of light.

Correct option: C
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Question 228
A
useful
B
harmful
C
more useful than harmful
D
more harmful.
Explanation
Earthworms are very useful. All over the world they are used as bait for fishing. Earthworms are in general beneficial to agriculture. Their habit of burrowing and swallowing earth increases fertility of soil in many ways. <br /> Their burrows permit penetration of air and moisture in porous soil, improve drainage, and make easier the downward growth of roots. Excretory wastes and other secretions of worms also enrich soil by adding nitrogenous matters that form important plant food. <br /> Earthworms were used variously as medicines in the past. Earthworms were used to cure stones in bladder, yellowness of jaundice, pyorrhoea, piles, rheumatism or gout, diarrhoea. Earthworms are easily obtained and are of convenient size for dissections. They are, therefore, universally employed for class studies and for investigations in general and comparative physiology.

Correct option: A
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Question 229
A
gills
B
spiracles
C
post-anal tail
D
chitinous exoskeleton.
Explanation
The diagnostic characters of chordates are notochord. dorsal hollow nerve cord, pharyngeal slits and post anal tail. Tail is the part of the body behind the cloacal or anal opening. It contains skeletal elements, muscles, blood vessels and nerves but no viscera. It provides much of propulsive force in aquatic species. The tail is reduced or absent in the adults of some chordates.

Correct option: C
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Question 230
A
clavicle
B
keel of sternum
C
scapula
D
coracoid.
Explanation
In birds, the pectoral and supracoracoideus muscles that power the wings are anchored to a large bony keel along the midline of the sternum.

Correct option: B

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