Problem 203 - Objective Biology for NEET

Question

Which of the following is incorrect about reptilia? (a) Body is covered by dry and cornified skin, epidermal scales or scutes. (b) Body is divisible into head, neck, trunk and tail. (c) Heart is usually three chambered. (d) Respiration occur through lungs and skin.

Step-by-Step Solution

Answer

Option (d) is incorrect. Reptiles only respire through lungs, not skin.

Step 1: Analyzing option (a)

Reptiles have dry, scaly skin. This feature helps in reducing water loss through evaporation, a characteristic feature for terrestrial life. Hence, statement (a) is correct.

Step 2: Analyzing option (b)

Reptiles' body structure would typically consist of a head, neck, trunk, and tail. Therefore, the statement (b) is correct.

Step 3: Analyzing option (c)

Reptiles usually have a three-chambered heart, with two atria and one ventricle. Hence, statement (c) is correct.

Step 4: Analyzing option (d)

Reptiles sure do respire, but only through their lungs and not the skin. Therefore, the statement (d) is incorrect, as reptiles do not respire through skin.

Key Concepts

Reptile Anatomy

Reptiles have a unique set of anatomical features that distinguish them from other vertebrate groups. One of the most noticeable characteristics is their skin. Unlike amphibians, whose skin is moist, reptilian skin is dry and cornified. This means the skin is coated with keratin-based scales or scutes, which help minimize moisture loss – an essential adaptation for life on land.
Reptilians exhibit a body plan that is typically divided into four main parts: head, neck, trunk, and tail. This structured arrangement not only aids in mobility but also supports the reptile's need to interact with its environment effectively.
Additionally, many reptiles have specialized body forms adapted to their ecological niches. For example, snakes have elongated bodies and no limbs, which is ideal for slithering through narrow spaces, while tortoises have sturdy, armored shells that provide protection and support.

Reptile Respiration

Reptilian respiration is primarily conducted through their lungs. Unlike amphibians that can breathe through their skin, reptiles have evolved to rely heavily on their lungs for the exchange of gases. This is due in part to their terrestrial lifestyle, where maintaining moisture isn't as crucial.
Reptile lungs are more developed than those of amphibians, with internal structures that increase surface area for gas exchange. Some reptiles also exhibit a unique feature called "tidal ventilation," where air is inhaled and exhaled in a more consistent flow, similar to human breathing.

• Lizards and snakes often employ a simple diaphragm-like muscle to help draw air into their lungs.
• Turtles and tortoises have a different mechanism due to their rigid shells, using muscles around their limb girdles to ventilate their lungs.

Reptile Heart Structure

The heart structure of reptiles is quite fascinating, as it exhibits a transition from the simpler two-chambered heart of fish to a more complex system found in birds and mammals. Typically, most reptiles possess a three-chambered heart.
This heart configuration includes two atria and one ventricle. The right atrium receives deoxygenated blood from the body, while the left atrium receives oxygenated blood from the lungs. These two blood streams are partially separated in the single ventricle, reducing the mixing of oxygenated and deoxygenated blood, though not as efficiently as the four-chambered hearts of birds and mammals.

• Crocodilians are a notable exception, as they have a uniquely adapted four-chambered heart, allowing them more efficient circulation needed for their active lifestyle.
• Reptiles regulate blood flow based on their activity levels and can reduce circulation to certain parts of the body depending on their oxygen needs.