Question

Explain the general characters of reptilia with respect to respiration, excretion, and reproduction.

Answer 1

Hint: Reptiles are a group of air-breathing vertebrates that have internal fertilization, amniotic development, and epidermal scales all over their body.

Complete Answer:
Characters of reptilia with respect to respiration, excretion, and reproduction:
1. Respiration: All reptiles breathe using lungs.
- Lung ventilation is achieved differently in each main reptile group because even though there are many adaptations breathing is never fully gained without lungs.
For example, more permeable skin and modified cloaca in aquatic turtles to increase the area for gas exchange.
- The form of lungs also influences their activity by affecting the gas exchange efficiency. For example, Snakes have simple saclike structures having small pockets, or alveoli, in the walls.
- Crocodiles have a muscular diaphragm that is similar to the mammalian diaphragm.
- Most reptiles breathe by changing the volume of their body cavity. The volume of the body cavity is increased by contractions of the muscles moving the ribs, creating a negative pressure, which is restored to the atmospheric level by air entering into the lungs. By contraction of body muscles, the volume of the body cavity is reduced, forcing air out of the lungs.

2. Excretion: Excretion is done mainly by two small kidneys. In diapsids, uric acid is the main nitrogenous waste product. However, turtles excrete mainly urea.
- Reptile kidneys are unable to produce liquid urine more concentrated than their body fluid because they lack a loop of Henle, which is responsible for making the urine more concentrated by osmoregulation and reabsorption. Because of this, many reptiles use the colon for the reabsorption of water.
- Some are also able to take up water stored in the bladder. Excess salts are also excreted by nasal and lingual salt glands in some reptiles.
- In all reptiles, the urinogenital ducts and the anus both empty into an organ called a cloaca. Many turtles, tortoises, and lizards have proportionally very large bladders, an adaptation for living in remote islands and deserts where water is scarce. Large bladders can store a long-term reservoir of water for up to several months and aid in osmoregulation.

3. Reproduction: They are oviparous. Reptiles generally reproduce sexually, though some are capable of asexual reproduction.
- All reproductive activity occurs through the cloaca. Cloaca is the only exit/entrance at the base of the tail where waste is also eliminated. Most reptiles have copulatory organs, which are usually retracted or inverted and stored inside the body.
- Tuatara, however, lacks copulatory organs, and hence the male and female simply press their cloacas together as the male discharges sperm.
The structures differ from group to group, but all of them include erectile tissue as an important part of the mechanism, and all are protruded through the male’s cloaca into that of the female during copulation.

Note: Reptiles are ectothermic or cold-blooded animals. To control their body temperature, they have adopted certain features: Basking in the sum raises their temperature, and they move faster when warm. When hot, they remain in shady areas.