Among the following animals, which one is able to breathe through its moist skin in addition to using lungs, especially when in water?

Introduction / Context:
Different groups of animals have evolved different respiratory systems to obtain oxygen from their environment. Fish use gills, insects use tracheal tubes, mammals use lungs, and some animals use more than one method. Amphibians such as frogs are especially interesting because they can exchange gases through their skin as well as through lungs at different stages of life or in different conditions. This question tests understanding of which animal from the list can breathe through its skin.

Given Data / Assumptions:
- Frog is an amphibian that lives both in water and on land during its life cycle.
- Shark is a fish that lives entirely in water and uses gills.
- Whale is a mammal that lives in water but breathes air using lungs.
- Cockroach is an insect that uses a system of tracheae and spiracles for respiration.
- We are looking for an animal that can breathe through its skin, especially when in water or at rest.

Concept / Approach:
Adult frogs have lungs, but they also possess thin, moist skin richly supplied with blood vessels. This allows them to carry out cutaneous respiration, meaning gas exchange across the skin. When underwater or during hibernation, frogs can rely heavily on this skin based respiration. Sharks breathe using gills, which extract dissolved oxygen from water; they do not use their skin as a primary gas exchange surface. Whales are mammals with lungs and must surface to breathe air through blowholes; their thick skin and blubber are not adapted for gas exchange. Cockroaches use a network of air filled tubes called tracheae that open to the outside through spiracles, rather than using skin or lungs. Therefore, the frog is the only animal in the list that breathes through its skin in addition to using lungs.

Step-by-Step Solution:
Step 1: Recall that amphibians, particularly frogs, are known for having moist, permeable skin used for respiration. Step 2: Recognise that sharks are fish with gills that filter oxygen from water, and their skin is not used for breathing. Step 3: Remember that whales are mammals with lungs and must come to the surface to breathe air; they do not exchange gases through the skin. Step 4: Note that cockroaches, like many insects, have a tracheal system for respiration, not skin based gas exchange. Step 5: Conclude that the frog is the correct answer as it can breathe through its skin.

Verification / Alternative check:
Biology textbooks on animal respiration explain that frogs and other amphibians have three modes of respiration: through gills (as tadpoles), through lungs (as adults on land), and through skin (cutaneous respiration) at all stages. They often highlight that the skin of amphibians must remain moist to allow oxygen and carbon dioxide to pass through. In contrast, fish, whales, and insects are discussed under separate headings with distinct respiratory structures. This confirms that among the animals listed, the frog is the one that can breathe through its skin.

Why Other Options Are Wrong:
- Shark, a fish that breathes only through gills, does not use its skin for gas exchange.
- Whale, a mammal that breathes only through lungs, relies on surfacing to inhale air and cannot rely on skin for respiration.
- Cockroach, an insect that breathes through a tracheal system, uses spiracles and tubes, not skin, for oxygen transport.

Common Pitfalls:
Some learners may mistakenly think that all aquatic animals breathe through their skin or that all animals in water use gills. It is important to distinguish amphibians from fish: amphibians can live both on land and in water and have unique adaptations like cutaneous respiration. Remembering that frogs have moist, permeable skin specifically adapted for gas exchange helps avoid confusion and leads to the correct answer.

Final Answer:
The animal that can breathe through its skin is the Frog, an amphibian that can exchange gases through its skin.