The species theory, polygenism, held that human races were of different lineages and suggested a hierarchy outlined in the Chain of Being that positioned Africans between man and lower primates.
No, they are involved in the Circulatory System which is responsible for pumping and channelling blood to and from the body and lungs with heart, blood and blood vessels. no veins are not considered an organ because they are a grouping of different tissues like a organ.
Liver vs Kidney. Liver and Kidneys are both organs in the organisms. Especially vertebrates have a well-developed organ system among other animal groups. A collection of different types of tissues organized to perform a particular function or functions is known as an âorganâ. Therefore, a tissue is the functional and structural unit of an organ. An organ system is composed of a group of organs that performs a particular function in the body. Basically, the vertebrates have 11 principal organ systems, which perform major activities in the body and keep the vertebrates alive.