Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Chordates are characterized by the presence of a notochord, a dorsal hollow nerve cord, and paired pharyngeal gill slits. They exhibit bilateral symmetry, are triploblastic, and have a coelomate level of organization with an organ-system level of body plan.
Subphylum Urochordata (Tunicata): The notochord is present only in the larval tail, for example, and .
Subphylum Cephalochordata: The notochord extends from the head to the tail region and is persistent throughout their life, for example, (Amphioxus).
Subphylum Vertebrata: Members possess a notochord during the embryonic period, which is later replaced by a cartilaginous or bony vertebral column in the adult. Thus, 'all vertebrates are chordates, but all chordates are not vertebrates.'
Vertebrata is divided into Agnatha (lacks jaw, e.g., Class Cyclostomata) and Gnathostomata (bears jaw). Gnathostomata is further divided into Super-classes Pisces (fins) and Tetrapoda (limbs).
Class Chondrichthyes (Cartilaginous fishes) possess a ventral mouth, placoid scales, and lack an operculum (gill cover), whereas Class Osteichthyes (Bony fishes) have a terminal mouth, cycloid/ctenoid scales, and possess an operculum.
Tetrapods include Classes Amphibia, Reptilia, Aves, and Mammalia. Transition from -chambered hearts in Amphibians and most Reptiles to -chambered hearts in Crocodiles, Birds, and Mammals is a key evolutionary feature.
📐Formulae
💡Examples
Problem 1:
Distinguish between the circulatory systems of a (Reptile) and a (Pigeon/Aves).
Solution:
The typically possesses a -chambered heart (incomplete -chambered), whereas possesses a complete -chambered heart.
Explanation:
In Reptiles (except crocodiles), the ventricle is incompletely divided, leading to some mixing of oxygenated () and deoxygenated () blood. In Aves, the separation is complete, ensuring high efficiency for flight.
Problem 2:
Identify the unique feature of regarding their mouth and feeding habit.
Solution:
They have a sucking and circular mouth without jaws ().
Explanation:
Cyclostomes like (Lamprey) are ectoparasites on some fishes. Their jawless, circular mouth allows them to attach to the host's body.
Problem 3:
A fish is found with an air bladder that regulates buoyancy. To which class does it likely belong?
Solution:
Class Osteichthyes (Bony fishes).
Explanation:
The presence of an air bladder is a salient feature of bony fishes (), allowing them to maintain buoyancy without constant swimming, unlike (Cartilaginous fishes) which lack an air bladder and must swim constantly to avoid sinking.