Chordate Classes Practice Questions

Correct answer: Ventral solid nerve cord

Chordates are characterized by a dorsal hollow nerve cord. A ventral solid nerve cord is a feature typically found in non-chordates like annelids and arthropods.

Correct answer: Urochordata (Tunicata)

In Urochordata, the notochord is a temporary structure restricted to the tail of the larva and is lost during metamorphosis into an adult. Examples include Ascidia and Salpa.

Correct answer: Cyclostomata

Members of Class Cyclostomata, such as lampreys and hagfish, are jawless vertebrates. They possess an elongated body with 6-15 pairs of gill slits for respiration.

Correct answer: Chondrichthyes

Class Chondrichthyes includes marine animals like sharks and rays which have a cartilaginous endoskeleton. Their skin is tough, containing minute placoid scales.

Correct answer: Exocoetus (Flying fish)

Exocoetus belongs to Class Osteichthyes (bony fishes), which possess an air bladder to maintain buoyancy. Cartilaginous fishes (Chondrichthyes) lack this organ and must swim constantly to avoid sinking.

Correct answer: Live in both water and on land

The name Amphibia (Greek, Amphi: dual, bios: life) refers to their ability to live in both water and on land. Their skin is moist and generally lacks scales.

Correct answer: Crocodilus (Crocodile)

Most reptiles have a three-chambered heart, but crocodiles are an evolutionary exception. They possess a fully four-chambered heart, similar to birds and mammals.

Correct answer: Body covered with feathers

Feathers occur in no other living class of animals, so a feather covering is the defining character of Aves. Beaks are not unique to birds - turtles and the platypus have them too. Birds are also warm-blooded, carry hollow pneumatic bones rather than solid ones, and fertilization is internal.

Correct answer: Milk-producing mammary glands

The most unique mammalian characteristic is the presence of mammary glands, which are used to nourish the young with milk. They also uniquely possess hair on their skin.

Correct answer: Ornithorhynchus (Platypus)

While most mammals are viviparous (give birth to live young), the Platypus is an exception that lays eggs. It belongs to the order Monotremata.

Correct answer: Reptilia

Reptiles have dry and non-glandular skin covered by scales or scutes. This adaptation helps them conserve water in terrestrial environments.

Correct answer: Covering and protecting the gills

In Osteichthyes, there are four pairs of gills covered by an operculum on each side. Chondrichthyes lack an operculum, leaving their gill slits exposed.

Correct answer: Aves and Mammalia

Birds (Aves) and Mammals are homeothermic, meaning they can maintain a constant body temperature regardless of environmental changes. Fishes, amphibians, and reptiles are poikilothermic (cold-blooded).

Correct answer: Amphibia

Amphibians have a common chamber called the cloaca where the alimentary canal, urinary tract, and reproductive tracts terminate. It opens to the exterior.

Correct answer: Reduce body weight for flight

The endoskeleton of birds is fully ossified (bony), and the long bones are hollow with air cavities. This pneumatic structure provides strength while minimizing weight for efficient flight.

Correct answer: Head to tail and persists throughout life

In Cephalochordata, such as Branchiostoma (Amphioxus), the notochord extends the entire length of the body from head to tail. It is a permanent structure that remains throughout the animal's life.

Correct answer: Torpedo and Trygon

Some cartilaginous fishes have specialized organs for defense or predation: Torpedo possesses electric organs, while Trygon has a poisonous sting on its tail.

Correct answer: The mouth is usually terminal

Bony fishes (Osteichthyes) typically have a terminal mouth and cycloid/ctenoid scales. They are mostly oviparous with external fertilization, whereas cartilaginous fishes often have internal fertilization.

Correct answer: To supplement respiration

In Aves, respiration is pulmonary (via lungs), and air sacs connected to the lungs supplement the breathing process. This ensures a high and continuous supply of oxygen required for the high metabolic demands of flight.

Correct answer: Mammalia

Mammals are the only class of vertebrates that typically possess external ears or pinnae. In other classes like amphibians and reptiles, the ear is represented only by a tympanum.