Hydra and Obelia are representatives of class Hydrozoa. Hydrozoans often include polyp-dominant forms and colonial species with varied life cycles. This MCQ belongs to the Cnidaria topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Flatworms show bilateral symmetry and cephalization. This organization is linked with directional movement and concentration of sensory structures at the anterior end. This MCQ belongs to the Platyhelminthes topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Correct Answer: C. pseudocoelomates with complete gut
Explanation:
Aschelminthes is an older grouping often used for pseudocoelomate animals with a complete digestive tract. Modern classifications may separate these phyla based on phylogeny. This MCQ belongs to the Aschelminthes topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Traditional protozoan classification often used locomotory structures such as pseudopodia, flagella, and cilia. Although modern classification relies more on phylogeny, these features remain useful in practical identification. This MCQ belongs to the Protozoan taxonomy topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Pinacocytes are flattened cells forming the outer surface, or pinacoderm, of sponges. They help protect and maintain the body shape but do not form a true tissue in the strict sense. This MCQ belongs to the Porifera topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Sea anemones and corals belong to Anthozoa. Members of this class are polyp-only cnidarians and include many reef-building species. This MCQ belongs to the Cnidaria topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Correct Answer: C. parenchyma fills the body space
Explanation:
Acoelomate flatworms have parenchyma or mesenchymal tissue filling the space between the digestive tract and body wall. This confirms absence of a true body cavity. This MCQ belongs to the Platyhelminthes topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
The mantle is a key molluscan feature. It covers the visceral mass and often secretes the shell; the space between mantle and body forms the mantle cavity. This MCQ belongs to the Mollusca topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Correct Answer: A. absence of typical locomotory organelles in adult stage
Explanation:
Many sporozoans, including Plasmodium, lack obvious locomotory organelles in mature stages. They are parasitic protozoans with complex life cycles and specialized stages for invasion and transmission. This MCQ belongs to the Sporozoans topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Mesohyl is the gelatinous matrix inside sponge bodies. It contains archaeocytes, spicules, spongin fibers, and other cells, supporting the sponge body without forming true tissues. This MCQ belongs to the Porifera topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Ctenophores are commonly described as biradial because their body plan combines radial organization with paired structures. This distinguishes them from typical radial cnidarians. This MCQ belongs to the Ctenophora topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Nematodes are pseudocoelomate roundworms. Their body cavity acts as a hydrostatic skeleton and their cylindrical unsegmented form distinguishes them from flatworms and annelids. This MCQ belongs to the Nematoda topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.