frog

Frog

Frogs are members of the phylum Chordata's class Amphibia, which can live on land and in freshwater. Rana tigrina is the most common frog species in India. They do not have a steady body temperature; rather, their body temperature changes depending on the ambient temperature. Cold-blooded animals are known as poikilotherms. You may have also noticed that the frogs' color changes while they are in grasses or on dry soil. They can change their color to hide from their adversaries (camouflage). The term for this protective coloring is mimicry. During the summer and winter, the frogs are not visible. They take refuge in underground tunnels during this time to avoid the excessive heat and cold.Summer sleep (aestivation) and winter sleep (hibernation) are the two types of sleep.

(i) Morphology: Due to the presence of mucus, the skin is smooth and slippery. Moisture is always retained on the skin. The dorsal side of the body is olive green in color with dark irregular markings. The skin is uniformly pale yellow on the ventral side. The frog does not drink water; instead, it absorbs it through its skin. A frog's body is divided into two parts: head and trunk. There is no neck or tail. A pair of nostrils can be found above the mouth. The eyes protrude and are protected by a nictitating membrane while in the water. A membranous tympanum (ear) receives sound signals on either side of the eyes. Swimming, walking, leaping, and digging are all assisted by the forelimbs and hindlimbs.The hind limbs have five fingers and are larger and more muscular than the forelimbs, which have four. Webbed digits on the feet aid with swimming. Sexual dimorphism is seen in frogs. Male frogs can be recognized from female frogs by the presence of sound-producing vocal sacs and a copulatory pad on the first digit of the forelimbs.

(ii) Anatomy: Frogs' bodily cavities house many organ systems with well-developed structures and functions, including the digestive, circulatory, respiratory, nervous, excretory, and reproductive systems. The alimentary canal and digestive glands make up the digestive system. Because frogs are carnivores, the alimentary canal is short, resulting in a shorter gut. The pharynx connects the mouth to the buccal cavity, which leads to the esophagus. The esophagus is a short tube that connects the mouth to the stomach, then to the intestine, rectum, and finally to the cloaca. Bile is produced by the liver and stored in the gall bladder. Pancreatic juice, which contains digestive enzymes, is produced by the pancreas, a digestive gland. The bilobed tongue is responsible for capturing food.

Food is broken down by the action of Hydrochloric acid and gastric secretions released from the stomach's walls. Chyme, or partially digested food, is transferred from the stomach to the duodenum, the first segment of the small intestine. Through a shared bile duct, the duodenum receives bile from the gall bladder and pancreatic secretions from the pancreas. Pancreatic fluids digest carbs and proteins while bile emulsifies fat. The intestine is where the final digesting takes place. The many finger-like folds in the inner wall of the intestine called villi and microvilli absorb digested food. The undigested solid waste goes through the cloaca and into the rectum. Frogs have two different strategies to breathe on land and in water.

Skin serves as an aquatic respiratory organ in water (cutaneous respiration). Diffusion exchanges dissolved oxygen in the water through the skin. The buccal cavity, skin, and lungs serve as respiratory organs on land. Pulmonary respiration is the process of breathing through the lungs. The lungs are a pair of elongated, pink-colored sac-like structures located near the top of the trunk (thorax). Air enters the lungs via the nostrils, buccal cavity, and lungs. Gaseous exchange occurs through the skin during aestivation and hibernation. Frogs have a well-developed closed circulatory system. Frogs, like humans, have a lymphatic system. The heart, blood arteries, and blood make up the blood vascular system. Lymph, lymph channels, and lymph nodes make up the lymphatic system.

The heart is a muscle structure located in the upper body cavity. It has three chambers, two atria, and one ventricle, and is surrounded by a pericardium membrane. The right atrium is connected to the sinus venosus, a triangle structure. It receives blood through the vena cava, which are large veins. On the ventral side of the heart, the ventricle opens into a sac-like conus arteriosus. The arteries transport blood from the heart to all regions of the body (arterial system). The venous system collects blood from various regions of the body and transports it to the heart.

Frogs have a unique venous connection between the liver and gut, as well as the kidney and lower body.The first is known as the hepatic portal system, whereas the second is known as the renal portal system. Plasma and cells are found in the blood. RBCs (red blood cells) or erythrocytes, WBCs (white blood cells) or leucocytes, and platelets are the blood cells. RBCs are nucleated and contain the pigment haemoglobin, which is red in color. Lymph is not the same as blood. It is deficient in proteins and RBCs. During circulation, the blood transports nutrients, gases, and water to their proper locations. The pumping activity of the muscular heart is responsible for blood circulation. A well-developed excretory system is responsible for the removal of nitrogenous wastes. A pair of kidneys, ureters, cloaca, and urine bladder make up the excretory system.

On both sides of the vertebral column, they are compact, dark red, bean-like structures located a bit posteriorly in the body cavity. Uriniferous tubules or nephrons are structural and functional units that make up each kidney. Male frogs have two ureters that arise from their kidneys. The ureters serve as a urinogenital channel, leading to the cloaca. The ureters and oviduct open separately in the cloaca in females. The rectum, which likewise opens in the cloaca, has a thin-walled urine bladder ventral to it. The frog is a ureotelic animal because it excretes urea. Blood transports excretory wastes to the kidney, where they are sorted and expelled. The frog's control and coordination system is highly developed.

It involves both the nervous and endocrine systems. Hormones released by the endocrine glands are responsible for the chemical coordination of the body's many organs. The pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals, and gonads are the most significant endocrine glands in frogs. The nervous system is arranged into a central nervous system (brain and spinal cord), a peripheral nervous system (cranial and spinal nerves), and an autonomic nervous system (sympathetic and parasympathetic) (sympathetic and parasympathetic). The brain gives rise to ten pairs of cranial nerves. The brain is protected by a bony structure known as the brain box (cranium). The forebrain, midbrain, and hindbrain are the three parts of the brain. The olfactory lobes, paired cerebral hemispheres, and unpaired diencephalon makes up the forebrain.

A pair of optic lobes distinguish the midbrain. The cerebellum and medulla oblongata make up the hindbrain. The medulla oblongata exits the foramen magnum and continues into the spinal cord, which is contained within the vertebral column. The sense organs of the frog are touch (sensory papillae), taste (taste buds), smell (nasal epithelium), vision (eyes), and hearing (ears) (tympanum with internal ears). Eyes and internal ears are well-organized structures, with the rest consisting of cellular aggregations around nerve endings. Frog eyes are a pair of spherical structures in the orbit of the skull. These are basic eyeballs (possessing only one unit). In frogs, the external ear is missing, leaving just the tympanum visible.

The ear is both a hearing and a balancing organ (equilibrium). Male and female reproductive systems in frogs are well-organized. A pair of yellowish ovoid testes are discovered adhering to the top section of the kidneys by a double fold of peritoneum called the mesorchium in male reproductive organs. The number of Vasa efferentia that emerge from the testes is 10-12. On their side, they enter the kidneys and open into Bidder's canal. Finally, it connects with the urinogenital duct, which runs from the kidneys to the cloaca. The cloaca is a small, midline chamber where faeces, urine, and sperms are passed to the outside.  A pair of ovaries are among the female reproductive organs.

The ovaries are close to the kidneys but have no functional relationship with them. Separate oviducts emerge from the ovaries and open into the cloaca. At any given time, a mature female can lay between 2500 and 3000 ova. External fertilization takes place in water. Tadpoles are in the larval stage of development. Tadpoles go through metamorphosis to become adults. Frogs are advantageous to humans because they consume insects and protect crops. Frogs keep the ecology in balance since they are a vital link in the food chain and food web. Humansconsume the muscular legs of frogs in several regions.