These are noted here to emphasize the importance of continuing to teach them. Reproduction is essential to the continuation of every species. The survival of a species depends on the ability of a living organism to have offspring. All living things go through a life cycle involving both reproduction and developmental stages.
Development follows an orderly sequence of events.
In humans, following formation of a small cluster of cells, tissues begin to form. During the first three months, organs begin to form. All organs and body features develop by the sixth month. During the last three months of pregnancy, organs and features develop well enough to function after birth. All organisms must be able to obtain and use resources, grow, reproduce, and maintain stable internal conditions while living in a constantly changing external environment.