Test: Hemichordata & Chordata - JAMB MCQ

Phylum Hemichordata does not possess a dorsal nerve cord, which is a characteristic of Chordates. Hemichordates, such as acorn worms, exhibit other features like the presence of pharyngeal slits, an atriopore for excretion, and a proboscis, which is a tubular structure used for feeding.

The subphylum Vertebrata includes the largest number of species among the Chordates. It comprises all the vertebrate animals, including fish, amphibians, reptiles, birds, and mammals.

The notochord is a flexible rod-like structure found in Chordates. Its primary function is to provide support to the body. In vertebrates, the notochord is usually replaced by the vertebral column during development.

A post-anal tail is a characteristic of all chordates at some stage of their life cycle. It is an extension of the body that extends beyond the anus and serves functions such as propulsion and balance.

The subphylum Urochordata, also known as tunicates or sea squirts, does not possess a notochord in the adult stage, although it is present in the larval stage. Other features of Urochordates include a tunicate covering, a filter-feeding apparatus, and a marine habitat.

The pharyngeal slits in chordates primarily function as a filter-feeding apparatus. They allow water to enter the pharynx and exit through the slits, while retaining food particles for consumption.

All vertebrates possess an endoskeleton made of either cartilage or bone, which provides structural support and protection. While some vertebrates have a notochord during their development, it is typically replaced by the vertebral column in adulthood.

The class Aves includes birds, which are the only vertebrates capable of true flight. Birds have adaptations such as wings, feathers, and lightweight skeletons that enable them to fly.

Class Mammalia is characterized by the presence of mammary glands, which produce milk for nourishing the young, and most mammals give birth to live young. Mammals have a warm-blooded metabolism and typically have fur or hair, not feathers. They also exhibit internal fertilization.

All chordates share the characteristic of having a notochord at some stage of their life cycle, although it may be present only in the embryonic or larval stage in some species. Jointed appendages, segmented body, and bilateral symmetry are characteristic of some chordates, but not all.