Test: Animal Kingdom - 3 - NEET MCQ

Sponges belong to the phylum Porifera. This phylum is characterized by animals that have a porous body and a simple level of organization. Sponges are primarily marine animals and are known for their unique water canal system that helps in their feeding, respiration, and excretion. Unlike the other options, where the animals are not correctly matched with their phyla (Earthworm belongs to Annelida, Jellyfish to Cnidaria, and Tapeworm to Platyhelminthes), the sponge is correctly placed in Porifera. An interesting fact about sponges is that they can regenerate from fragments, a process known as fragmentation.

Cnidarians, such as jellyfish, corals, and sea anemones, are known for having cnidoblasts (or cnidocytes), which are specialized cells that contain a stinging structure called a nematocyst. This feature is used for defense and capturing prey. Bilateral symmetry is characteristic of more advanced phyla like Chordata, the presence of a notochord defines Chordata, and a segmented body is a feature of Annelida and Arthropoda. An interesting fact about cnidarians is that they exhibit two basic body forms: the sessile polyp and the free-swimming medusa.

Platyhelminthes, or flatworms, are characterized by their bilateral symmetry, organ-level organization, and acoelomate body plan, meaning they do not have a coelom (body cavity). The presence of a coelom is not a feature of Platyhelminthes but rather of more advanced phyla like Annelida and Arthropoda. An interesting fact about Platyhelminthes is that despite their simple structure, some species have complex life cycles involving multiple hosts.

Annelids, such as earthworms, leeches, and polychaetes, are characterized by their segmented body and the presence of a coelom, which is a fluid-filled body cavity completely lined by tissue derived from mesoderm. Mollusca, Porifera, and Cnidaria do not exhibit segmented bodies; Molluscs have a non-segmented body, Porifera have a cellular level of organization without true tissues, and Cnidaria have a tissue level of organization without segmentation. An interesting fact about annelids is that their segmented body plan allows for greater flexibility and mobility.

Correct option is A.  Notochord is a characteristic feature of animals belonging to the phylum Chordata

Starfish, or sea stars, belong to the phylum Echinodermata, which is known for its members having radial symmetry (typically as adults), a water vascular system, and an endoskeleton of calcareous ossicles. Octopuses belong to Mollusca, earthworms to Annelida, and jellyfish to Cnidaria. An interesting fact about echinoderms is that they have the ability to regenerate lost limbs, and some can even regenerate an entire new organism from a single limb.

Arthropods, which include insects, arachnids, crustaceans, and myriapods, are characterized by their chitinous exoskeleton, jointed limbs, and segmented bodies. The presence of a notochord is unique to Chordata, radial symmetry is a feature of Cnidaria and Echinodermata (in their larval stage), and the water vascular system is specific to Echinodermata. An interesting fact about arthropods is that they undergo molting, shedding their exoskeleton to grow.

Nematodes, or roundworms, are characterized by their pseudocoelom, which is a fluid-filled body cavity that is not completely lined by mesoderm. This feature distinguishes them from the true coelomates and acoelomates. Radial symmetry is seen in Cnidaria and Echinodermata, the water vascular system is a feature of Echinodermata, and a chitinous exoskeleton is characteristic of Arthropoda. An interesting fact about nematodes is that they can be found in almost every habitat, from marine and freshwater environments to the soil and even in the bodies of plants and animals as parasites.

Mammals (Class Mammalia) are characterized by having a four-chambered heart, which allows for efficient separation of oxygenated and deoxygenated blood, facilitating a high metabolic rate. While birds (Aves) also have a four-chambered heart, reptiles generally have a three-chambered heart (except for crocodiles, which have a four-chambered heart), and amphibians have a three-chambered heart. An interesting fact about mammals is that they are the only vertebrates with hair on their bodies and the ability to produce milk through mammary glands to feed their young.

The phylum Echinodermata, which includes starfish, sea urchins, and sea cucumbers, is characterized by a unique water vascular system. This system is a network of hydraulic canals branching into tube feet that allow for locomotion, feeding, and gas exchange. Arthropoda, Mollusca, and Annelida do not have a water vascular system. An interesting fact about the water vascular system is that it operates based on hydraulic pressure, allowing echinoderms to move and manipulate objects in a coordinated manner despite lacking a brain.

The assertion is correct as the presence of a notochord at some stage in life is a defining characteristic of all chordates. The reason correctly explains the function of the notochord, which is to provide a scaffold for the developing nervous system and to act as a primary axial support structure in the embryonic stages of all chordates. This support is crucial for the body structure before the development of the vertebral column in vertebrates.

Arthropods, indeed, have an open circulatory system where the blood (or hemolymph) is not confined exclusively to blood vessels but flows freely through cavities in the body, bathing organs directly. This system allows for the distribution of nutrients and removal of waste products, albeit less efficiently than the closed circulatory systems found in higher organisms.

Echinoderms, such as starfish and sea urchins, indeed exhibit bilateral symmetry during their larval stages but transition to radial symmetry as adults. The reason provided, however, is not correct in this context. Bilateral symmetry is typically associated with mobility and a directed movement, which is beneficial for the larval stages that need to disperse. Sessile organisms, which do not move, often exhibit forms of symmetry that are not necessarily bilateral, as seen in adult echinoderms.

Nematodes, or roundworms, are indeed classified as pseudocoelomates because they possess a body cavity, known as a pseudocoel, which is not completely lined by tissue derived from mesoderm. The reason accurately explains what distinguishes pseudocoelomates from true coelomates, where the latter have a body cavity fully lined with mesoderm. This distinction is important for understanding the evolutionary relationships and functional anatomy of different animal groups.

Amphibians indeed have the ability to breathe through their skin, a process known as cutaneous respiration, which supplements lung breathing. This is possible due to their moist skin which allows gas exchange. However, the reason provided is not a direct explanation for this feature. While it's true that amphibians lack ribs and a diaphragm, which are important for lung ventilation in other animals, cutaneous respiration is more directly related to their life in both aquatic and terrestrial environments, allowing for gas exchange when submerged in water.