All living organisms that inhabit the Earth are open biological systems. To maintain their life, an influx of food, oxygen and water from the environment and the removal of metabolic products are necessary. It is clear that such a selection of toxins is necessary to maintain the homeostasis of a living organism. What does the absence of this principle lead to? Death occurs due to poisoning of the cells with their own metabolites.
Evolution has contributed to the appearance of organs that perform the function of removing toxins. Today, they have all the representatives of wildlife, ranging from simple and ending with man. In this article, we will find out what this selection is, and also study its features characteristic of the main groups of organisms.
general information
Organisms consisting of only one cell have a perfect system of self-regulation and elimination of toxins formed as a result of dissimilation. For example, common amoeba and euglena green remove toxins and excess water through the cell membrane and contractile vacuole. Let us clarify that such isolation of protozoa metabolites is an adaptation to the structure of the body and the aquatic environment. Multicellular organisms complicate the process of slag removal. In flat, round, annular worms and mollusks, tubules appear - proto- or methanephridia.
Crayfish are characterized by green glands, while insects develop malpighian vessels and a fatty body. The appearance of a chord and an internal skeleton dramatically changes the process of isolation. Biology of vertebrates reveals the formation of complex organs - paired kidneys. Consider their structure and functions below.
Excretory system evolution
Fish have ribbon-shaped trunk kidneys lying on both sides of the spine and filtering blood. In amphibians, compact excretory organs are located in the sacral vertebra. Of these, urine passes through the ureters to the cloaca. The appearance of pelvic kidneys in reptiles, birds, mammals and humans is an important aromorphosis.
Renal nephrons carry out two complex physicochemical processes: blood filtration and primary urine reabsorption. As a result, the blood is completely cleaned of toxins, which ensures a physiologically normal level of homeostasis.
Finally
In this article, we examined what selection is. Now you know the features of this process in various groups of living organisms.