Question

Explain how animals in Vertebrata are classified into further subgroups.

Answer 1

Hint: Vertebrata Is the subphylum of chordates consisting of animals with a segmented spinal column together with a few primitive forms in which the backbone is represented by a notochord.

Complete answer:
Vertebrates are classified according to several criteria like an exoskeleton, respiratory organs, method of giving birth, number of chambers in heart, mode of living, etc. Animals in Vertebrata are mainly classified into five classes:
- Pisces: This class consists of fishes that are aquatic, cold-blooded animals. Their body is covered by small rough structures known as scales or plates. It includes fish such as tuna, rohu, shark, etc. They possess special adaptive features such as a streamlined body, presence of a tail for movement, light-weighted body, gills, etc. which help them to survive in water.
- Amphibia: This class consists of cold-blooded animals that can live in both water and land. It includes frogs, toads, and salamanders. In the larval stage, the amphibians respire through gills, but in the adult stage, respiration occurs through the lungs or skin. They lay eggs in water.
- Reptilia: This class consists of cold-blooded animals that have a three-chambered heart. It includes reptiles such as lizards, snakes, turtles, etc. that move by creeping or crawling on land. They have, on their body, dry and cornified skin to prevent water loss. They lay eggs on land.
- Aves: This class consists of warm-blooded, oviparous vertebrates (egg-laying animals) covered with feathers. They possess a four-chambered heart. They include all birds such as sparrow, pigeon, crow, etc. They show some special modifications like their forelimbs are modified into wings for flight, while their hind limbs are modified for walking and catching prey.
- Mammalia: This class consists of warm-blooded animals. This class exclusively show the presence of milk-producing glands to nourish their young ones. The presence of mammary glands is an exclusive feature of the class Mammalia. Some are oviparous i.e.lay eggs (platypus) and some are viviparous i.e. they give birth to young ones (human beings). Their skin is characterized by the presence of hair and sweat glands so as to regulate their body temperature.

Note:
- The most defining characteristic of a vertebrate is the vertebral column, in which the notochord is found in all chordates.
- The notochord has been replaced by a segmented series of harder elements (vertebrae) separated by joints (intervertebral discs, derived embryonically, and evolutionarily from the notochord).
- However, a few vertebrates show exceptions retaining the notochord into adulthood. Example- sturgeon coelacanth, etc.
- All reptiles possess a three-chambered heart except crocodiles.