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Thursday, October 1, 2020

Class Reptilia- NEET-Biology

 Class Reptilia

Fig: Sphenodon (Tuatara)

  • Reptilia= Creeping or crawling mode of locomotion.
  • It is considered the first animal on the land with the ability to live & multiply on land, with the help of their amniotic eggs.
  • Most of them are tetrapods, with four-legs or like-like appendages.

Important characteristics:

  • The skin is covered with scutes or scales & it has a high level of keratin, which prevents water loss through the skin.
  • Glands are usually absent.
  • Snakes & lizards shed their scales as skin cast (sloughing) routinely.
  • They are considered tetrapods with sets of paired limbs. In some reptiles, like snakes, worm lizards, the legs are absent, but it is believed that these animals evolve from some tetrapod ancestor.
  • Unlike amphibians, reptiles do not pass through an embryonic stage with gills. These animals breathe with well-developed lungs, right from birth. Most of them have two lungs, except for some snakes, which posses only a single lung.
  • All reptiles have three-chambered hearts, except crocodiles, which have four-chambered (2 atria, 2 ventricles), like mammals & birds. The three chambers in reptiles consist of two atria to receive blood & one partially divided ventricle for pumping blood.
  • Reptiles do not have external ear openings. The tympanum represents the ear.
  • Most of the reptiles lay eggs, but some of them give birth to young ones, by hatching the eggs inside the body of the mother.
  • Their characteristics also include internal fertilization, in this process sperm gets deposited into the reproductive tract of the female directly.
  • Being cold-blooded, the body temperature of the reptiles vary with the surrounding atmosphere.
  • Sexes are separate. Fertilization is internal.
  • They are oviparous & development is direct.
  • Example: Sphenodon (Tuatara), Varanus (Komodo dragon), Draco (Flying lizard), Ophiophagus (King cobra), Hydrophis (Sea snake), Crocodylus (Indian freshwater crocodile).
Fig: Ophiophagus (King cobra)



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