In protostomes, the blastopore generally gives rise to the mouth. Many major invertebrate phyla such as molluscs, annelids, arthropods, and nematodes are protostomes. This MCQ belongs to the Animal evolution topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Triploblastic animals have three primary germ layers: ectoderm, mesoderm, and endoderm. The mesoderm supports more complex tissues, muscles, and organ systems than are possible in diploblastic animals. This MCQ belongs to the Germ layers topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
A true coelom is completely lined by mesoderm. This body cavity provides space for organs, allows more complex organ systems, and can function as a hydrostatic skeleton in many invertebrates. This MCQ belongs to the Body cavities topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
A pseudocoelom is a body cavity derived from the blastocoel and is only partly lined by mesoderm. Nematodes and rotifers are common examples of pseudocoelomate animals. This MCQ belongs to the Body cavities topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Acoelomates are triploblastic animals without a true body cavity. Their space between digestive tract and body wall is filled with mesenchyme or parenchyma rather than a coelom. This MCQ belongs to the Body cavities topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Bilateral symmetry is associated with active directional movement and cephalization. It produces right and left halves and often allows development of a head region containing sensory structures. This MCQ belongs to the Animal architecture topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Radial symmetry allows the body to be divided into similar halves along more than one plane through the central axis. It is common in many sessile or slow-moving aquatic animals such as cnidarians. This MCQ belongs to the Animal architecture topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Species is the basic and most specific unit used in biological classification. Higher ranks such as genus, family, order, class, and phylum group organisms more broadly and contain multiple species. This MCQ belongs to the Taxonomy topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
Phylogenetic relationships are best inferred from shared derived characters, also called synapomorphies. These traits appear in a common ancestor and are inherited by its descendants, so they are more useful than superficial similarities such as size, colour, or habitat. This MCQ belongs to the Taxonomy topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.
