Characteristics of Life Chapter 1.3 Studying Life

 What is Life? What distinguishes living things from non-living things? Why is a firefly alive, but fire is not? Both give off light and move in their own way….

Cars and clouds, which are not alive, move while mushrooms and trees, which ARE alive, do not. Even so, there are several characteristics which most organisms share...

1) Living things are based on a universal genetic code- DNA!! (deoxyribonucleic acid) DNA is passed from parents to offspring.

2) Living things grow and develop. Each organism follows its own pattern of growth and development. As cells divide, they differentiate.

3) Living things respond to their environment. Organisms respond to stimuli, or signals, around them.

4) Living things are made up of living cells. They are composed of one or more cells. Cells are the smallest unit considered to be alive.

5) Living things reproduce, meaning produce new, similar organisms. This is done through sexual reproduction and asexual reproduction.

6) Living things maintain a stable internal environment – homeostasis.  Describes the relatively constant internal physical and chemical conditions that organisms maintain despite changes internal and external environments.  pH, temperature, etc.

Feedback Inhibition (Negative Feedback)  The process in which a stimulus produces a response that opposes the original stimulus  Example: furnace in your house  Biological example: 1.Cold environment causes body temperature to decrease.  2. Hypothalamus senses temperature change and sends signals that start heat production.  3. Body temperature increases.  4. Body temperature restabilizes, so hypothalamus stops heat production.  SHIVERING!!!

Positive feedback  Just the opposite of negative feedback… enhances the original stimulus  Examples: childbirth, blood clotting

7) Living things obtain and use material and energy. All organisms must take in materials and energy to grow, develop, and reproduce. The combination of chemical reactions through which an organism builds up or breaks down materials is called metabolism.

8) TAKEN AS A GROUP, THINGS EVOLVE. OVER GENERATIONS, GROUPS OF ORGANISMS EVOLVE, OR CHANGE OVER TIME.