All living organisms, inhabitants of the Earth, are open biological systems. To maintain their life, an influx of food, oxygen and water from the external environment and the removal of metabolic products are necessary. It is clear that such excretion of toxins is essential for maintaining the homeostasis of a living organism. What does the absence of this principle lead to? Death occurs due to poisoning of cells by their own metabolites.
Evolution has contributed to the emergence of organs that perform the functions of removing toxins. Today, all representatives of wildlife have them, from protozoa to humans. In this article, we will find out what a selection is, as well as study its features that are characteristic of the main groups of organisms.
General information
Organisms, consisting of only one cell, have a perfect system of self-regulation and removal of toxins formed inthe result of dissimilation. For example, the common amoeba and green euglena remove toxins and excess water through the cell membrane and contractile vacuole. Let us clarify that such a release of protozoan metabolites is an adaptation to the structure of the body and the aquatic environment. Multicellular organisms complicate the process of removing toxins. In flat, round, annelids and molluscs, tubules appear - proto- or metanephridia.
Crayfish have green glands, while insects develop Malpighian vessels and a fat body. The appearance of the notochord and the internal skeleton radically changes the process of isolation. The biology of vertebrates reveals the formation of complex organs - paired kidneys. Let's consider their structure and functions further.
Evolution of the excretory system
Fish have ribbon-like trunk kidneys that lie on both sides of the spine and filter the blood. In amphibians, compact excretory organs are located in the region of the sacral vertebrae. Of these, urine passes through the ureters into the cloaca. The appearance of pelvic buds in reptiles, birds, mammals and humans is an important aromorphosis.
Renal nephrons carry out two complex physical and chemical processes: blood filtration and primary urine reabsorption. As a result, the blood is completely cleansed of toxins, which ensures a physiologically normal level of homeostasis.
In closing
In this article, we looked at what a selection is. Now you know the features of this process in various groups of livingorganisms.
