Human beings have made tools and machines to sense and do things that they could not otherwise sense or do at all, or as quickly, or as well. Artifacts and preserved remains provide some evidence of the physical characteristics and possible behavior of human beings who lived a very long time ago. Embryos are nourished by the mother, so substances she takes in will affect how well or poorly the baby develops.
Human beings live longer than most other animals, but all living things die.
There is a usual sequence of physical and mental development among human beings, although individuals differ in exactly when they learn things. People are usually able to have children before they are able to care for them properly. Following discussions of sounds and the effects on hearing, students research and report on hearing aids. Students focus on why people need them and how they work. The undigestible parts of food are eliminated.