Ap Biology 1996 Essay

Topics: Reproduction, Oxygen, Male Pages: 1 (346 words) Published: April 24, 2011
With the evolution of animals living on land from animals living in the water, many changes needed to be made in order for survival. Each problem that these organisms may have experienced in the past has been dealt with a solution of some manner. One of the main problems was water storage. Because organisms in an aquatic environment are surrounded by water, they do no experience problems with water storage, but without an aquatic environment there are bound to be problems. The land organisms need to have water within their body that is able to be accessed when needed. A solution terrestrial organisms have developed is the loop of Henle in the kidneys. This is part of the nephron which makes a U-shape and is used to conserve and reabsorb water. Another solution to the problem of water loss is being nocturnal, which gives less water loss because of less heat. A second problem is gas exchange. Because oxygen is required, organisms needed to adapt to find a way to receive oxygen into their blood stream. Mammals do this through the alveoli’s moist membrane. This membrane allows for diffusion, and gas exchange is conducted across. The oxygen diffuses into the bloodstream while carbon dioxide diffuses out, and continues to exit the body. A third problem is reproduction. In an aquatic environment, male organisms released their sperm into the water which eventually ended up fertilizing a female organism. This is not possible on land because there is no way to travel easily through the environment. The solution to this was internal fertilization, where the male organism releases the sperm inside the female organism. The sperm would travel through the female (as the moist ideal environment) and eventually fertilize the egg. A last problem is temperature, where the heat is different from an aquatic environment. The heat in a terrestrial environment oscillates and drops unexpectedly. An adaptation made for this was the creation of endothermic organisms. Endotherms maintain a...
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