In the embryonic period of human development, there are signs characteristic of all representatives of the chordate type: chord, neural tube on the dorsal side of the body, gill slits in the throat. The development of the vertebral column, two pairs of limbs, the location of the heart on the abdominal side of the body determines the person’s affiliation to the subtype of vertebrates.
In the early stages of development in humans, an axial skeleton is formed – a chord, a neural tube develops above it, and below it the primary intestine. In the adult state, the skeleton serves as a support for the human body. The central nervous system has a tubular structure, is represented by the spinal cord and brain, located in the spinal region of the body. The circulatory system is closed, consists of the heart and blood vessels. The breathing apparatus is light. All these signs refer a person to a subtype of vertebrate animals.
The signs that make it possible to classify humans as mammals are live births; feeding the young with milk .; constant high body temperature; the presence of a diaphragm; seven cervical vertebrae; two generations of differentiated teeth; framed lips and muscular cheeks; four-chamber heart; outer, middle and inner ear; the skin is covered with hair; the mammary glands have nipples.
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.