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 : Digestion is chiefly extracellular in ctenophores.
Reason : Ctenophores are diploblastic organisms.
(d) The digestion in ctenophores is both extracellular and intracellular. Ctenophores are diploblastic organisms with tissue level of organisation.
Assertion: Cnidoblasts are present on the tentacles and the body in cnidarians.
Reason: Cnidoblasts are used for anchorage, defence and capture of the prey.
b
Assertion: Sponges exhibit cellular level of organisation.
Reason: In sponges, cells are arranged as loose cell aggregates.
b
Assertion: Platyhelminthes are generally hermaphrodites.
Reason: In platyhelminthes, fertilisation is internal.
(b) Platyhelminthes are generally hermaphrodites, i.e., both the sexes are present in one organism. They show internal and cross fertilisation where male gametes of one organism fertilise female gametes of another organism.
Assertion: Digested and semi-digested food is absorbed by body surface in tapeworms.
Reason: Digestive organs are absent in tapeworms.
(a) The tapeworm does not have alimentary canal because it is an endoparasite. The digested food of the host is diffused directly through the general body surface.
Assertion: Aschelminthes are called as pseudocoelomates.
Reason: In aschelminthes, mesoderm is present as scattered pouches in between ectoderm and endoderm.
(a) In aschelminthes, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Hence, they are called pseudocoelomates.
Assertion: In molluscs, feather-like gills are present in mantle cavity.
Reason: These gills have respiratory and excretory functions.
(b) In molluscs, the space between the mantle and the hump is called mantle cavity in which feather-like gills are present. They have both respiratory and excretory functions.
Assertion: The body of hemichordates is divisible into proboscis, collar and trunk.
Reason: Proboscis gland helps in digestion.
(c) Hemichordates are worm-like marine animals. Their body is composed of an anterior proboscis, a collar and a long trunk. Proboscis gland is excretory in function.
Assertion: Claspers are a distinguishing feature of males in Class Chondricthyes.
Reason: Claspers help in copulation.
(b) In Chondricthyes, male can be distinguished from the female, as the former has a pair of hard elongated claspers attached to the pelvic fins. The claspers help in the copulation.
Assertion: Osteichthyes fishes swim constantly to avoid sinking.
Reason: Air bladder is present in fishes of Class Osteichthyes.
(d) Members of Class Chondrichthyes are marine with streamlined body having cartilaginous endoskeleton. Due to the absence of air bladder, they have to swim constantly to avoid sinking. Air bladder is present in osteichthyes which regulates buoyancy.
Assertion: Amphibian males and females produce lot of gametes.
Reason: Males lack copulatory organ in amphibians.
(b) In amphibians, fertilisation is external, hence males and females produce a lot gametes and release in water to maximise the chances of fertilisation. Males of Class Amphibia generally lack copulatory organs. The reproductive tracts open outside through the cloacal aperture.
Assertion: Calotes, Crocodilus and Chelone are members of Class Reptilia.
Reason: Heart is three chambered in Calotes, Crocodilus and Chelone.
(c) Calotes, Crocodilus and Chelone are members of Class Reptilia. Heart is four chambered in Crocodilus and three chambered in Calotes and Chelone.
Assertion: In birds, the skin is moist.
Reason: Birds possesses oil glands.
(d) The characteristic features of Aves (birds) are the presence of feathers and most of them can fly except flightless birds (e.g., ostrich). Skin is dry without glands except the oil gland at the base of the tail.
Assertion: Air sacs are connected to lungs in Class Aves.
Reason: Air sacs supplement respiration in birds.
(a) Respiration is by lungs in Class Aves (birds). The lungs are spongy and inelastic. Air sacs are connected to lungs to supplement respiration.
Assertion: Mammalian teeth are heterodont.
Reason: Mammalian teeth are embedded in a socket of the jaw.
(b) In Class Mammalia, teeth are of different types (heterodont) and are embedded in the socket of the jaw (thecodont). These are developed twice during the lifetime of the animal (diphyodont), i.e., milk and permanent teeth.
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