The similarity of the structure of the integument of the body of organisms of three different classes of vertebrates is that the upper layer of the skin – the epidermis is formed by multilayer epithelium. However, it is distinguished by the presence or absence of cutaneous glands. So, in reptiles, skin glands are absent, therefore, the skin is dry, covered with a continuous horny cover. The skin of birds is also dry and thin. A single coccygeal gland is found at the base of their short tail. Birds grease feathers with its fatty secretion so that they do not get wet. The horny scales of the skin of birds are transformed into a feather cover, which retains the heat of the bird’s body and gives it a streamlined shape. The skin of mammals is thick, elastic and durable. It contains a variety of glands. The skin is covered with hair on the outside, which conserves the heat of their body.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.