1. Word of the Day Aberration (n)
A departure from what is normal, desirable, or typical. “The presence of cancer cells under a microscope is an aberration that no doctor wants to see.”

2. Biology: The Study Of Life

3. The Characteristics of Life
Biologists have devised a list of 8 characteristics that define life.
Something can be considered alive ONLY if it displays ALL 8 of the characteristics.
Anything that possesses all 8 of the characteristics of life is called an organism.

4. The Characteristics of Life
1. Display cellular organization:
Cell = the basic unit of structure and function in all living things.
Smallest unit that can perform all life’s
processes.
Living things are made of one cell (unicellular) or many cells (multicellular).

5. The Characteristics of Life
For complex multicellular organisms, cells specialize.
Levels of Organization:
-Cells form tissues
-Tissues form organs
-Organs form organ systems

6. The Characteristics of Life
2. Respond to Stimuli
They are able to react, or respond, to an environmental condition, or stimulus.
Discuss an example with a partner…get ready to share your ideas!
Venus flytrap

7. The Characteristics of Life
3. Maintains Homeostasis:
All organisms are able to maintain a relatively constant internal environment.
Homeostasis: The regulation of an organism’s internal environment to maintain conditions suitable for life.
Example – maintaining a constant body temperature – sweating

8. The Characteristics of Life
4. Metabolism
Organisms require energy to perform life processes such as repair, movement, and growth.
Metabolism = the sum of all the chemical reactions that take in and transform energy and materials from the environment.
Discuss (with a different partner) how different types of organisms might obtain their energy

9. The Characteristics of Life
5. Grow and Develop:
All living organisms grow and develop during their life spans.
Growth: an increase in the size of an organism due to an increase in the size and number of cells
Development: all of the changes that take place throughout the life span of an organism

10. The Characteristics of Life
6. Reproduction:
All organisms produce offspring
Although reproduction is not essential to the survival of an individual organism, it is essential for the continuation of a species.

11. The Characteristics of Life
7. Contain genetic information that can be passed on through generations:
Hereditary information is transmitted through a molecule called DNA.
Gene = segment of DNA that contains instructions for a specific trait.

12. The Characteristics of Life
8. Evolve Over Time
Individual organisms do not evolve.
However, populations of living things do change over time (evolve).
Ability to evolve is essential for survival in a changing world.

13. Viruses: Alive? Yes or No?
Discuss! Which of the 8 characteristics do they have?

14. Answer: It’s still up for debate.
Reasons people say “no”: Not made of cells, cannot reproduce on their own, don’t develop
Reasons people say “yes”: Have genetic material and evolve
Give me evidence for your decision
New research every day…that’s what makes biology exciting!