Major Functions of Humans
(things we need to do in order to live)
- Organization: The body must be organized… a fetus that starts to develop without good organization is not likely to live long.
- Metabolism: This refers to all of the chemical reactions that happen inside the body, especially those involving energy usage. If your body can’t do the chemistry you will not survive.
- Responsiveness: If your body can not react effectively to changes in the external or internal environment you will die.
- Movement: If you can’t move at all you can’t survive (your outside body needs to move so you can find food and not get hit by cars and things inside your body also need to move like your blood through vessels, urine out of body, food along the gut, etc.).
- Development: In order to survive humans need to be able to change from one life stage to the next (a fetus that does not develop a brain or heart will not survive).
Basic Requirements of Human Life
(environmental needs for human life)
- Pressure: The human body requires a certain range of atmospheric pressure in order to survive. In a zero pressure environment, such as outer space you would stay awake for only a few seconds and would die within minutes. You would not explode or quickly freeze however… those are myths.
- Levels of respiratory gasses: There must be adequate levels of oxygen in the air we breathe (normal air is around 21% oxygen… anything under 10% oxygen and you can easily get into trouble), and there can’t be too much carbon dioxide in the air we breathe (normal air CO2 is less than 1%… anything above 6% can be toxic).
- Temperature: Humans have adapted to a wide range of temperatures here on Earth, but we do have limits.
- Nutrients: Humans need available nutrients. We can live for a time without food, but only about month or a little more. We can only live a matter of days without water.