144. Which among bacteria, fungi, Paramecium and Chlamydomonas is generally NOT unicellular?
[RRB Technician Grade III, 30 Dec 2024 Shift 2]
(A) Bacteria
(B) Fungi
(C) Paramecium
(D) Chlamydomonas
Answer: (B) Fungi
Explanation: Fungi are generally multicellular and form hyphal networks, though yeast provides an important unicellular exception. Bacteria, Paramecium and Chlamydomonas are ordinarily single-celled organisms, making fungi the best general answer to the exam question.
143. Which description correctly identifies members of Platyhelminthes?
[SSC CGL Tier II, 02 March 2023]
(A) Triploblastic, bilaterally symmetrical and acoelomate
(B) Triploblastic, asymmetrical and acoelomate
(C) Diploblastic, bilateral and acoelomate
(D) Triploblastic, coelomate and asymmetrical
Answer: (A) Triploblastic, bilaterally symmetrical and acoelomate
Explanation: Flatworms possess three germ layers and bilateral symmetry, but they lack a true body cavity. This acoelomate organisation distinguishes them from pseudocoelomate nematodes and truly coelomate annelids, arthropods and chordates.
142. Identify the incorrect statement about Arthropoda.
[SSC CGL Tier I, 18 July 2023 Shift 4]
(A) Insecta is its largest class
(B) The exoskeleton is chiefly composed of lignin
(C) It includes an immense diversity of animal species
(D) Its members have jointed appendages
Answer: (B) The exoskeleton is chiefly composed of lignin
Explanation: Arthropods have a chitin-containing exoskeleton, not a lignin-based one. Lignin is a structural component of many plant cell walls. Jointed limbs and an extensive range of insect species are defining features of this animal phylum.
141. On which basis are Porifera commonly divided into classes?
[MP Police Constable, 24 August 2023]
(A) Nature of skeletal spicules
(B) Branching of appendages
(C) Mode of fertilisation alone
(D) Number of body segments
Answer: (A) Nature of skeletal spicules
Explanation: Sponges have internal supporting structures consisting of mineral spicules or spongin. Their composition and form provide key characters used to distinguish groups such as Calcarea, Hexactinellida and Demospongiae.
140. Which listed animal belongs to phylum Platyhelminthes?
[SSC CHSL, 20 March 2023]
(A) Sycon
(B) Leech
(C) Wuchereria
(D) Tapeworm
Answer: (D) Tapeworm
Explanation: Tapeworms are dorsoventrally flattened parasitic flatworms of phylum Platyhelminthes. Sycon is a sponge, leeches are segmented annelids, and Wuchereria is a filarial nematode. Their body plans reveal the underlying taxonomic distinctions.
139. In which animal phylum do ostia and osculum occur?
[CRPF Head Constable, 26 February 2023]
(A) Ctenophora
(B) Aschelminthes
(C) Porifera
(D) Annelida
Answer: (C) Porifera
Explanation: Sponges possess numerous tiny inlet pores called ostia and usually one or more larger outlet openings called oscula. Water enters through ostia, circulates through the canal system and exits through the osculum.
138. Which is not an arthropod?
[MP Police Constable, 29 August 2023]
(A) Octopus
(B) Scorpion
(C) Butterfly
(D) Locust
Answer: (A) Octopus
Explanation: Octopus is a cephalopod mollusc with a soft body and muscular arms. Scorpions, butterflies and locusts are arthropods, recognised by jointed appendages and an external cuticle containing chitin.
137. Which cells of sponges generally develop into gametes?
[MPSC Group B, 30 April 2023]
(A) Choanocytes
(B) Archaeocytes
(C) Myocytes
(D) Pinacocytes
Answer: (B) Archaeocytes
Explanation: Archaeocytes are mobile, undifferentiated sponge cells capable of differentiating into multiple cell types, including reproductive cells. Choanocytes primarily drive water currents and capture food, whereas pinacocytes cover external surfaces.
136. Which phylum ranks second after Arthropoda in number of described animal species?
[MP Police Constable, 31 August 2023]
(A) Locust
(B) Mollusca
(C) Prawn
(D) Annelida
Answer: (B) Mollusca
Explanation: Mollusca is widely described as the second-largest animal phylum after Arthropoda. It includes snails, clams, oysters, squids and octopuses, despite major differences in shell development and external appearance.
135. Which animal group commonly has an incomplete digestive tract?
[MP Patwari, 17 March 2023]
(A) Platyhelminthes
(B) Aschelminthes
(C) Porifera
(D) Echinodermata
Answer: (A) Platyhelminthes
Explanation: Many flatworms have a digestive cavity with one opening and therefore no separate anus. Tapeworms are an exception because they lack a digestive tract altogether. Nematodes have a complete alimentary canal.
