Problem 272 - Objective Biology for NEET

Question

Assertion: In amphibian skin is generally moist. Reason: They shows cutaneous respiration.

Step-by-Step Solution

Answer

The assertion is correct and the reason is related to it. The moist skin of amphibians allows them to perform cutaneous respiration effectively.

Step 1: Understanding the Assertion

The assertion claims that the skin of amphibians is generally moist. It is well-known that many amphibians need to keep their skin moist for survival. Now it's important to understand why this might be the case.

Step 2: Understanding the Reason

The reason given is that they show cutaneous respiration. Cutaneous respiration refers to respiration through the skin. In other words, instead of relying solely on lungs or gills like many creatures, amphibians can absorb oxygen and release carbon dioxide directly through their skin.

Step 3: Connecting the Assertion and Reason

Combining the knowledge from the first two steps, it can be hypothesized that the moist environment of the amphibians' skin is necessary for cutaneous respiration to work properly. In non-aquatic conditions, amphibian skin would dry out, making it less permeable for gases, hindering respiration.

Key Concepts

Cutaneous Respiration

Amphibians have a unique way of breathing through their skin, a process known as cutaneous respiration. Unlike many animals that rely entirely on lungs or gills for gas exchange, amphibians can exchange gases directly through their skin. This means they can absorb oxygen and expel carbon dioxide through their epidermis.

Cutaneous respiration is a crucial adaptation for amphibians, as it allows them to thrive in a variety of environments, particularly those where other respiration methods might not be efficient. For example, in water, where dissolved oxygen levels might be low, this form of respiration can be a life-saving adaptation.

• Supplementing their lung-based respiration.
• Adjusting to aquatic and semi-aquatic habitats.
• Increasing survival in environments with varying oxygen availability.

However, for this method to be effective, certain conditions regarding their skin need to be met.

Amphibian Skin

The skin of amphibians is quite different compared to other vertebrates. It is thin and highly vascularized, allowing for efficient gas exchange to take place. This complex structure provides the necessary pathway for gases like oxygen and carbon dioxide to move across the skin barrier.

The permeability of amphibian skin cannot be overstated. This feature is crucial as it plays an integral role in cutaneous respiration. However, to remain permeable and effective for respiration, the skin must stay moist. This is because:

• Moist skin facilitates the diffusion of gases.
• Dried skin significantly lowers the rate of gas exchange.
• Natural protective secretions help maintain the skin's moisture.

Given the importance of skin in amphibian respiration, it's understandable why they have developed various strategies to keep their skin moist.

Moist Skin Importance

The importance of maintaining moist skin for amphibians cannot be emphasized enough. This moistness is essential for cutaneous respiration to function. Amphibians have evolved various methods to keep their skin moist and prevent it from drying out, even when they are not in water.

Here are some of the reasons why moist skin is vital for amphibians:

• Moisture is necessary for optimal gas exchange; dry skin hinders respiration.
• Providing a protective layer against environmental hazards.
• Maintains skin texture and integrity for survival.

Amphibians often inhabit humid environments and secrete mucous from their skin to retain needed moisture. In doing so, they ensure an adequate exchange of gases, which is essential for their survival in diverse habitats. Without this moisture, their ability to breathe through their skin would be severely compromised.