Question

 Match the List-I with List-II. [NEET 2021]

Choose the correct answer from
the options given below.
      A B C D
(a) 4 3 1 2
(b) 3 4 1 2
(c) 3 4 2 1
(d) 4 1 2 3

Answer/Explanation

Ans. (c)
(c) $(\mathrm{A})-(3),(\mathrm{B} H(4),(\mathrm{CH}),(\mathrm{DH})(1)$
The annelid worms were thought to have evolved from a coelomate worm-like ancestor which developed metameric segmentation or metamerism and the segments were termed as somites or metameres.
Sponges or porifera have a water transport or canal system. Water enters via minute pore (ostia) in the body wall into the central cavity spongocoel from where it goes out via osculum.
The body of ctenophores bear eight external rows of ciliated comb plates which helps in locomotion.
The name Cnidaria is derived from cnidocytes or cnidoblast that are found on the tentacles and body of the organism.

Question

 Which of the following options does correctly represent the characteristic features of phylum-Annelida? [NEET (Oct.) 2020]

(a) Triploblastic, unsegmented body and bilaterally symmetrical

(b) Triploblastic, segmented body and bilaterally symmetrical

(c) Triploblastic, flattened body and acoelomate condition

(d) Diploblastic, mostly marine and radially symmetrical

Answer/Explanation

Ans. (b)

Animals belonging to phylum-Annelida are triploblastic, bilaterally symmetrical and metamerically segmented.
They exhibit organ system level of body organisation with presence of coelom. They may be aquatic (marine and freshwater) or terrestrial, free-living and sometimes parasitic.

Question

 Which of the following animals are true coelomates with bilateral symmetry? [NEET (Odisha) 2019]

(a) Adult echinoderms

(b) Aschelminthes

(c) Platyhelminthes

(d) Annelids

Answer/Explanation

Ans. (d)
Annelids are true coelomates with bilateral symmetry. These exhibit organ-system level of body organisation with true coelom. They are triploblastic, metamerically segmented and coelomate animals, e.g. earthworm.

Question

 Pheretima and its close relatives derive nourishment from [CBSE AIPMT 2012]

(a) sugarcane roots

(b) decaying fallen leaves and soil organic matter

(c) soil insects

(d) small pieces of fresh fallen leaves of maize

Answer/Explanation

Ans. (b)
Food of earthworm (Pheretima sp.) consists of organic matter, fallen decaying leaves, algae, etc. present in the soil. Food is swallowed along with soil by sucking action.

Question

One very special feature in the earthworm Pheretima is that [CBSE AIPMT 2011]

(a) the typhlosole greatly increases the effective absorption area of the digested food in the intestine

(b) the S-shaped setae embedded in the integument are the defensive weapons used against the enemies

(c) it has a long dorsal tubular heart

(d) fertilisation of eggs occurs inside the bodyp

Answer/Explanation

Ans. (a)
A pair of short and conical intestinal caecae project from the intestine on the 26th segment. The characteristic feature of the intestine between 26-35 segments is the presence of internal median fold of dorsal wall called typhlosole.
This increases the effective area of absorption in the intestine.

Question

 If a live earthworm is pricked with a needle on its outer surface without damaging its gut, the fluid that comes out is [CBSE AIPMT 2009]

(a) excretory fluid

(b) coelomic fluid

(c) haemolymph

(d) slimy mucus

Answer/Explanation

Ans. (b)

The body cavity of earthworm is true coelom (schizocoel) as it is formed by the division of mesoderm. The coelom is filled with milky, alkaline coelomic fluid, which contains different types of corpuscles. Thus, if alive earthworm is prickled with a needle on its outer surface, the coelomic fluid will come out.

Excretory fluids Excretory system regulate the chemical composition of body fluids by removing metabolic waste substances.
Haemolymph it is a fluid in the open circulatory system of arthropods, e.g. spiders, crustaceans etc.
It is analogous to the fluids and cells making both blood and interstitial fluid. Slimy mucus Mucus trap bacteria cell debris and prevents it from entering into lungs and in their body parts.

Question

Which one of the following is not a characteristic of phylum-Annelida? [CBSE AIPMT 2008]

(a) Closed circulatory system

(b) Segmentation

(c) Pseudocoelom

(d) Ventral nerve cord

Answer/Explanation

Ans. (c)
Name of the phylum-Annelida was first coined by Lamarck. The body of annelids is elongated, bilaterally symmetrical, triploblastic, truely coelomate and metamerically segmented into similar metameres. The coelom is true, schizocoelous. Blood vascular system is closed. The nervous system is with a pair of cerebral ganglia and a double ventral nerve cord bearing ganglia and lateral nerves in each segment.
The blood vascular system consists of blood vessels and capillaries. Blood is composed of fluid plasma and colourless corpuscles, physiologically comparable to the leucocytes of vertebrates.

Pseudocoelom is the body cavity of Aschelminthes(roundworm).

Question

Earthworms have no skeleton but during burrowing, the anterior end becomes turgid and acts as a hydraulic skeleton. It is due to [CBSE AIPMT 2008]

(a) coelomic fluid

(b) blood

(c) gut peristalsis

(d) setae

Answer/Explanation

Ans. (a)

The body cavity (coelom) of earthworm is filled with an alkaline, colourless or milky coelomic fluid containing water, salts some proteins and four types of coelomic corpuscles i.e. phagocytes, mucocytes, circular nucleated cells and chloragogen cells. During burrowing the coelomic fluid becomes turgid and acts as hydraulic skeleton.

Earthworm (Pheretima posthuma) living in burrows made in moist earth. The body shows metameric segmentation. About the middle of each segment there is a ring of tiny curved bristles called setae or chaetae, formed of a horny nitrogenous organic substance known as chitin. The setae and musculature serve for locomotion as well as for anchoring body firmly in burrow.
The blood of earthworm is composed of a fluid plasma and colourless coruscles, physiologically comparable to the leucocytes of vertebrates.

Question

Which one of the following is correct matching pair of a body feature and the animal possessing it? [CBSE AIPMT 2007]

(a)Post-anal tail – Octopus

(b) Ventral central – Leech nervous system

(c) Pharyngeal gills slits – Chameleon absent in embryo

(d) Ventral heart – Scorpion

Answer/Explanation

Ans. (b)

The nervous system of leech consists of ventral central nervous system, peripheral nervous system and sympathetic nervous system.

Question

In which of the following chlorocruorin pigment is found? [CBSE AIPMT 2001]

(a) Annelida

(b) Echinodermata

(c) Insecta

(d) Lower Chordata

Answer/Explanation

Ans. (a)
Chlorocruorin is a respiratory pigment (green, fluorescing red) dissolved in the plasma of some polychaete worms (annelid).

Question

 Functionwise, just as there are nephridia in an earthworm, so are [CBSE AIPMT 1996]

(a) parotid glands in toad

(b) statocysts in prawn

(c) flame cells in liver fluke

(d) myotomes in fish

Answer/Explanation

Ans. (c)
Flame cells in liver fluke are excretory organs as nephridia in an earthworm.

Question

 True coelom is the space lying between the alimentary canal and body wall enclosed by the layers of [CBSE AIPMT 1996]

(a) ectoderm on both sides

(b) endoderm on one side and ectoderm on the other

(c) mesoderm on one side and ectoderm on the other

(d) mesoderm on both sides

Answer/Explanation

Ans. (d)

Coeloms are secondary body cavities bounded on all sides by mesodermal peritoneum. The true coelom arises within the mesoderm itself.

Question

 Coelom derived from blastocoel is known as [CBSE AIPMT 1994]

(a) enterocoelom

(b) schizocoelom

(c) pseudocoelom

(d) haemocoelom

Answer/Explanation

Ans. (c)
Coelom derived from blastocoel is pseudocoelom. These are cavities not entirely lined by peritoneum (thin cellular membrane derived from mesoderm).
Embryologically pseudocoel may be a persistent blastocoel. Such type of coelom is found in Nematohelminthes.

Question

 Which one assists in locomotion? [CBSE AIPMT 1993]

(a) Trichocysts in Paramecium

(b) Pedicellariae of starfish

(c) Clitellum in Pheretima

(d) Posterior sucker in Hirudinaria

Answer/Explanation

Ans. (d)
In Hirudinaria locomotion takes place by looping and swimming in which its posterior suckers provide help as setae are not present for locomotion.

Question

 Blood of Pheretima is [CBSE AIPMT 1990]

(a) blue with haemocyanin in corpuscles

(b) blue with haemocyanin in plasma

(c) red with haemoglobin in corpuscles

(d) red with haemoglobin in plasma

Answer/Explanation

Ans. (d)
Blood of Pheretima is red in colour and respiratory pigment haemoglobin is dissolved in blood plasma.

Question

 Pheretima posthuma is highly useful as [CBSE AIPMT 1990]

(a) their burrows make the soil loose

(b) they make the soil porous, leave their castings and take organic debris in the soil

(c) they are used as fish meal

(d) they kill the birds due to biomagnification of chlorinated hydrocarbons

Answer/Explanation

Ans. (b)
Pheretima posthuma is useful for farmers as they enrich the soil by their excretory wastes and make the soil porous.

Question

 Earthworms are [CBSE AIPMT 1989]

(a) useful

(b) harmful

(c) more useful than harmful

(d) more harmful

Answer/Explanation

Ans. (a)

Earthworms are friends of farmers because they enrich the soil by nephridial excretion, it increases the fertility of soil. They also help in ploughing of fields, make the soil porous. Earthworms are also used for dissection in laboratories.

Question

 Photoreceptors of earthworm occur on [CBSE AIPMT 1989]

(a) clitellum

(b) many eyes

(c) dorsal surface

(d)lateral sides

Answer/Explanation

Ans. (c)

Photoreceptors (with L-shaped lens or optic organelles)are present on the surface of skin on dorsal side.
Earthworm has no eyes,
photoreceptors are used to judge
intensity and duration of light, but do not have the capacity of vision.

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