Two of the most iconic animals of Australia are, Crocodiles and Kangaroos. Their are two species of crocodiles in Australia, including the salt water and fresh water crocodile. As for the kangaroo, there are over 60 different species including their close relatives. The purpose of this paper is to convey the knowledge that I have acquired from comparing the anatomy and physiology of the Salt Water Crocodile with the Red Kangaroo. I have a greater understanding of how this reptile and infraclass mammal adapt and live in their environments. With this knowledge I will be able to give an accurate analysis of these two lifeforms found here in Australia. Red kangaroos are one of the largest species of marsupial. Marsupials are the group of mammals commonly thought of as pouched mammals. They give live birth, but unlike placental mammals they don't have long gestation periods. Whereas, they give birth very early to a young helpless embryo that uses its senses to get from mother's birth canal to her nipples. Compared to other mammals kangaroos are born at a very early stage of nervous system development. Kangaroos have nervous systems similar to all other mammals, with an exception of a few particular characteristics. Kangaroos and other marsupials have a very distinct brain microcirculation, which refers to the small vessels that irrigate the organ. While in most mammals numerous capillary vessels connect in the brains forming a mesh-work, in kangaroos this connections occur in pairs, forming loops. This evolutionary feature has been related to the kangaroo's ability to survive in Australia's hot and arid zones. On average a fully grown Red Kangaroo is approximately 5 feet long and has a tail that is about 42 inches in length. This tail is used as a mechanism for balance. Red Kangaroos can not walk and are limited to hopping as means of transportation. However, this adaptation is extremely energy efficient and allows them to cover vast barren landscapes rather quickly. In fact it takes less energy to breath while a kangaroo is hopping versus standing still. According to Giuliodori MJ, who has a Major in Advanced Physiology Education, "Specifically, as the kangaroo hops upward, the abdominal organs lag behind, and the insertion of the diaphragm is pulled toward its origin, flattening the dome and increasing the vertical dimension of the thoracic cavity (the thoracic cavity and lungs enlarge). Increasing the volume of the thoracic cavity reduces alveolar pressure below atmospheric pressure (barometric pressure), and air moves into the alveoli by bulk flow. In contrast, the impact of the organs against the diaphragm at each landing causes expiration. Specifically, upon landing, the abdominal organs flop into the diaphragm, causing it to return to its dome shape and decreasing the vertical dimension of the thoracic cavity. This compresses the alveolar gas volume and elevates alveolar pressure above barometric pressure, so air is expelled". This massive jump of up to 29 feet in distance and approximately 6 feet in height, enables them to attain a speed of 35 mph for a short period of time. However they can maintain a speed of 12 mph for hours on end, conserving energy. The Red Kangaroos are well adapted to their barren environment including the inland woodlands and arid deserts. They shut down their reproductive system when conditions are too dry to breed successfully, and reboot it only when conditions improve. They are one of the most highly adapted animals to desert conditions, especially when it comes to breeding and nutritional needs. Red Kangaroos rely solely on plants for their nutritional needs, making them herbivores. When selecting plants to eat, they generally choose grasses, other plants, and shrubbery with a high water content. This species avoids the sweltering daylight sun by searching widely for food or provisions at night when temperatures are much cooler.