Size and Complexity of an Animal Essay Example | Topics and Well Written Essays - 750 words

Size and Complexity of an Animal - Essay Example The essay "Size and Complexity of an Animal" talks about the fundamental aspect of animal growth and the relationship between the growth in size and the surface area relative to its volume. The relationship between surface areas to volume ratio is best exemplified by reflection on phylum Porifera. The organism has a smaller surface area in relation to its volume. As a result, it depicts a simple form of exchange with the external environment. For example, nutrients are taken directly from water then enters through pores by cells lining the organism. On the other hand, complex organisms have a larger surface area to volume. As a result, these animals have trouble in acquiring nutrients. Therefore, they have developed a complex mechanism of feeding such as mesoderm in platyhelminths. The development of larger and complex bodies posed a challenge in respiration. The reason is that smaller animals such as sponges could take gasses directly from the surrounding water. As a result, there was no need for a development of the specialized organ. The challenge arises, as organism could not exchange oxygen and carbon dioxide directly with their cells. Moreover, in platyhelminths, the development of flat body enhanced efficient exchange of gasses through diffusion. The flat body help in providing a high surface area to volume ratio and hence easy supply and exchange of gasses. On the other hand, higher animals could not maintain gas exchange through their body surface. As a result, diffusion was not possible on their body surfaces.