Question

Assertion: Earthworm possess moist body surface Reason: Earthworm respire through body surface

Short answer

The assertion and reason are both correct, and the reason accurately explains the assertion. Earthworms have a moist body surface because they respire through it.

Step-by-step solution

Understanding the Assertion

The assertion states that earthworms have a moist body surface. This is a factual piece of information, and it's right. Earthworms, like many other invertebrates, have a moist and slimy body surface.

Understanding the Reason

The reason in question suggests that earthworms respire through their body surface, which is also correct. Earthworms are skin breathers, which means they respire directly through their skin.

Establish whether the Reason accurately explains the Assertion

The explanation that earthworms have a moist skin because they respire through it is true. For oxygen and carbon dioxide to be exchanged, the respiratory surface must be moist. Since earthworms respire through their skin, it makes sense for their skin to be moist, facilitating this gas exchange.

Key concepts

Gas Exchange in Earthworms

Earthworms are fascinating creatures that exhibit a highly efficient respiratory mechanism. Unlike humans who rely on lungs for respiration, earthworms use their moist skin to facilitate this vital process. The moisture on their skin is crucial because it allows dissolved oxygen from the environment to diffuse directly into their bloodstream. Similarly, carbon dioxide, which is a waste product of metabolism, can diffuse out into the environment.

The process of gas exchange in earthworms is a wonderful illustration of the principle that in order for diffusion to occur, there must be a concentration gradient. In the case of earthworms, a higher concentration of oxygen in the environment compared to that in their body fluids drives oxygen into their circulatory system. Conversely, carbon dioxide follows its concentration gradient from the higher levels inside the earthworm's body to the lower levels outside, allowing it to be expelled.

Invertebrate Biology

Invertebrate biology encompasses the study of animals without a vertebral column, which constitutes a significant majority of animal species on Earth. Earthworms are a key subject of study within invertebrate biology due to their role in soil aeration and nutrient recycling. Understanding how earthworms and other invertebrates breathe without lungs can be essential to grasp the diversity of respiratory strategies in the animal kingdom.

Invertebrates display a wide range of respiratory mechanisms tailored to their environments and body plans. For example, in addition to skin breathing employed by earthworms, insects have tracheal systems, aquatic crustaceans use gills, and some amphibious mollusks utilize a combination of gills and lung-like structures. The study of these various breathing methods not only reveals the adaptability of invertebrates but also provides insight into evolutionary biology.

Skin Breathing Mechanisms

Skin breathing, also known as cutaneous respiration, is a form of gas exchange where the skin serves as a respiratory organ. This mechanism is employed by various animals, including amphibians and some small mammals, but is particularly well studied in earthworms. Their entire body surface acts as a respiratory membrane where gas exchange occurs.

To maintain effective respiration, earthworms require a moist environment. The mucus secreted by their skin keeps it wet, enhancing the exchange of gases through simple diffusion. It's important to note that while this method is efficient for small organisms, it wouldn't suffice for larger animals due to the relatively slow rate of diffusion through the skin. Moreover, skin breathing necessitates a thin enough skin to allow gases to pass, but also sturdy enough to protect the organism, balancing permeability with protection.