7.2. Frogs

Frogs can live both on land and in freshwater and belong to class Amphibia of phylum Chordata. The most common species of frog found in India is Rana tigrina.

Frogs are versatile animals that can thrive in both terrestrial and aquatic environments. They belong to the Amphibia class, which means they have life stages in both water and land. The most common type of frog in India is Rana tigrina. This adaptability is crucial for their survival, allowing them to find food and shelter in various habitats.

Think of frogs like actors who can perform in different settings, whether on land or in water. Just like an actor might change their outfit and lines for a different stage, frogs change their behavior to thrive in different environments.

They do not have constant body temperature i.e., their body temperature varies with the temperature of the environment. Such animals are called cold blooded or poikilotherms.

Frogs are known as cold-blooded or poikilothermic animals because their body temperature is influenced by the surrounding environment. This means that when the temperature drops, so does their body temperature, and vice versa. This characteristic impacts their behavior, activity levels, and habitat choices.

Imagine how a cold-blooded animal is like a thermostat that adjusts based on the room temperature. If the room is hot, the thermostat's reading goes up; if it’s cold, it goes down. Frogs react similarly to their environment.

You might have also noticed changes in the colour of the frogs while they are in grasses and on dry land. They have the ability to change the colour to hide them from their enemies (camouflage). This protective coloration is called mimicry.

Frogs can change their skin color, which helps them blend into their surroundings. This ability to change color for hiding is known as camouflage. It makes it hard for predators to spot them. Mimicry, in this context, refers to their resemblance to their environment to avoid threats.

Think of frogs as living chameleons. Just like chameleons change their color to escape predators, frogs adapt their appearance to stay hidden in grass or leaves, effectively playing a game of hide and seek with potential threats.

You may also know that frogs are not seen during peak summer and winter. During this period they take shelter in deep burrows to protect them from extreme heat and cold. This is known as summer sleep (aestivation) and winter sleep (hibernation) respectively.

Frogs have developed survival strategies to cope with extreme temperatures. During very hot summers, they undergo aestivation, where they burrow into the ground to escape the heat. In contrast, during cold winters, they hibernate, entering a state of dormancy until warmer temperatures return.

Imagine a frog as a smart engineer, building a comfortable underground bunker to escape the summer sun or the winter chill. Just like we might retreat indoors during harsh weather, frogs find their own protective spaces to survive until conditions improve.

The skin is smooth and slippery due to the presence of mucus. The skin is always maintained in a moist condition. The colour of dorsal side of body is generally olive green with dark irregular spots. On the ventral side the skin is uniformly pale yellow.

Frog skin is unique; it is smooth and slippery because of mucus, which helps keep it moist. This moisture is essential for their respiration, especially since they can absorb water through their skin. The dorsal side has a camouflage coloration, while the ventral side is paler, which helps them blend into their environment from different angles.

Think of a frog like a well-equipped diver wearing a wetsuit and oxygen tank—its skin is the suit, helping it to stay hydrated and breathe, while its colors allow it to blend seamlessly into the underwater world.

The body cavity of frogs accommodates different organ systems such as digestive, circulatory, respiratory, nervous, excretory and reproductive systems with well-developed structures and functions.

Frogs have complex body systems that allow them to function effectively. These systems include the digestive system for processing food, the circulatory system for transporting nutrients and gases, and the respiratory system for breathing. They also possess a nervous system that coordinates their actions, an excretory system to remove waste, and reproductive organs for continuation of the species.

Consider a frog as a miniature city, where different sectors (organ systems) work together. The highways (circulatory system) ensure that resources (nutrients) flow to various parts of the city, while waste management (excretory system) keeps it clean and functional.

The digestive system consists of alimentary canal and digestive glands. The alimentary canal is short because frogs are carnivores and hence the length of intestine is reduced.

Frogs have a relatively short digestive system suited for their carnivorous diet. They consume meat (often insects), and the shorter alimentary canal helps them process food efficiently. The main components include the mouth, stomach, and intestines, along with the liver and pancreas as digestive glands.

Think of the frog's digestive system like a fast-food restaurant—designed for quick service (short alimentary canal) and efficiency to process specific meals (carnivorous diet).

Frogs respire on land and in the water by two different methods. In water, skin acts as aquatic respiratory organ (cutaneous respiration). Dissolved oxygen in the water is exchanged through the skin by diffusion.

Frogs can breathe in two ways: cutaneous respiration through their skin when underwater, and pulmonary respiration using lungs when on land. The skin is permeable and allows oxygen to diffuse in directly from the water. In contrast, when on land, they use their lungs to inhale air.

Imagine a frog as a dual-use tool. Just as a swiss army knife has different functions (screwdriver, cutter), a frog has specialized ways of breathing depending on whether it’s submerged in water or exposed to air.

The vascular system of frog is well-developed closed type. Frogs have a lymphatic system also. The blood vascular system involves heart, blood vessels and blood.

The frog's circulatory system is closed, meaning the blood travels within vessels. It consists of a muscular heart with three chambers, various blood vessels, and blood. The lymphatic system works alongside to manage excess fluids and immune responses.

Think of the frog's circular system as a well-planned public transportation system, where a central station (the heart) sends buses (blood) through routes (blood vessels) to different parts of the city (body), ensuring everyone gets where they need to go efficiently.

The elimination of nitrogenous wastes is carried out by a well-developed excretory system. The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder.

Frogs have evolved a complex excretory system that helps remove waste and regulate water. It consists of kidneys to filter blood, ureters to transport urine, and a cloaca that serves as a common outlet for urinary, fecal, and reproductive fluids.

Think of the excretory system like a city's waste management system. The kidneys are like waste processing plants that filter out unwanted materials, while the ureters are the trucks that carry the waste to be disposed of properly.

The system for control and coordination is highly evolved in the frog. It includes both neural system and endocrine glands. The nervous system is organised into a central nervous system (brain and spinal cord), a peripheral nervous system and an autonomic nervous system.

Frogs have a highly developed nervous and endocrine system for coordination and control. The nervous system comprises the central nervous system (brain and spinal cord), peripheral nerves, and autonomic systems that regulate involuntary functions. Endocrine glands release hormones for various bodily functions.

Imagine a well-run corporation where the brain acts as the CEO making decisions, the spinal cord is the communication network, and endocrine glands are the HR department ensuring employees (cells and organs) get the resources they need to function optimally.

Male reproductive organs consist of a pair of yellowish ovoid testes, which are found adhered to the upper part of kidneys. The female reproductive organs include a pair of ovaries. A mature female can lay 2500 to 3000 ova at a time.

Frogs have distinct male and female reproductive systems. Males have testes that produce sperm, while females have ovaries that produce eggs. Female frogs can lay thousands of eggs at once in water, leading to external fertilization, where eggs are fertilized outside the female’s body.

Think of the reproductive process in frogs like a farmer planting thousands of seeds (eggs) in a field (water) hoping they will grow into healthy plants (tadpoles). This strategy increases the chances of some surviving to adulthood.

Frogs are beneficial for mankind because they eat insects and protect the crop. Frogs maintain ecological balance because they serve as an important link of food chain and food web in the ecosystem.

Frogs play a crucial role in the ecosystem by controlling insect populations and serving as food for other animals. They are an integral part of the food chain, contributing to ecological balance and supporting biodiversity.

Consider frogs as the natural pest controllers in a garden. Just as we might hire gardeners to keep pests away, frogs eat harmful insects and help crops grow better, ensuring a healthy ecosystem.

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