NEET Practice Questions (MCQs) with Answers & Solutions

The exoskeleton of arthropods is made of chitin, a long-chain polymer that provides both strength and flexibility. This chitinous exoskeleton serves as a protective barrier and provides structural support.

Echinodermata (e.g., starfish) exhibit a unique characteristic where adults show radial symmetry, while their larvae exhibit bilateral symmetry. This transition during development is a key feature of this phylum and helps in distinguishing it from others.

Starfish (Echinodermata) do not have a specialized excretory system. Instead, they excrete waste through diffusion across their body surfaces and through structures called tube feet. This is different from organisms like sepia (cuttlefish), crabs, and earthworms, which have more specialized excretory systems.

In Hemichordata, the circulatory system is open, respiration occurs through gills, and the excretory system includes a proboscis gland. This aligns with the option I = circulatory system - open, II = Respiration - gills, III = Excretory system - proboscis gland.

Vertebrates can have a variety of heart structures depending on the subgroup. Fishes typically have a 2-chambered heart, amphibians and reptiles (except crocodiles) have a 3-chambered heart, and birds and mammals have a 4-chambered heart. Therefore, the correct option is 'All above'.

Lampreys have a sucking and circular mouth without jaws. This is a distinctive feature of this jawless fish (agnathan) group.

In poriferans, the spongocoel is lined with flagellated cells called choanocytes. These cells are crucial for water circulation and nutrient capture within the sponge. The flagella of choanocytes create water currents that help in the movement of water through the sponge's body, allowing it to filter out food particles from the water.

Chondrichthyes, also known as cartilaginous fishes, are characterized by having a ventral mouth and placoid scales. Placoid scales are small, tooth-like structures that cover the skin, providing protection and reducing friction while swimming. The ventral mouth is located on the underside of the head.

Air bladder is absent in dogfish. Dogfish is a type of cartilaginous fish (Chondrichthyes), which lack air bladders. Instead, they rely on their liver, which is rich in oil, to maintain buoyancy. In contrast, bony fish (Osteichthyes) often have an air bladder that helps them regulate buoyancy.