1. Characteristics of Life

2. What Makes Something “Alive”?
Read and discuss “Is Sammy Alive?”
How do you define living?
Movement?
Making noise?
What else?
7 characteristics!!

3. 1. All living things are made of cells.
Cells are the smallest living unit that can carry out life processes.
Organisms are either:
Unicellular (made of one cell)
Or multicellular (made of two or more cells)

4. 2. All living things use energy.
The SUN is the ultimate source of energy… directly or indirectly.
Organisms can be classified based on how they obtain their energy.

5. 2. All living things use energy.
Autotroph- produce their own energy from sunlight or chemicals
Plants, algae, bacteria
Heterotroph- must obtain energy from another source
Fungi, animals
Metabolism- sum of all chemical processes that take in and use energy in an organism

6. 3. All living things respond to stimuli.
Respond to immediate and long-term changes in their environment
Shiver when cold, plants grow toward light
Homeostasis: tendency of an organism to maintain a constant (or balanced) internal condition

7. 4. All living things reproduce.
Reproduction must occur for a species to survive.
Can be either sexual or asexual.

8. Reproduction Asexual Sexual Requires 1 parent
Offspring are genetically identical
Sexual
Requires 2 parents
Offspring are formed from the joining of egg and sperm cells
Fertilization can be external! (ex: frogs)

9. 5. All living things grow and develop.
Growth means adding more cells.
Development means to change into an adult form (mature).

10. 6. All living things adapt to their environment.
This occurs on a species, rather than an individual, level.
Adaptations occur over a long period of time (100+ years).

11. 7. All living things have DNA.
DNA is the genetic material passed down through generations.
It is like a blueprint for the organism.

12. Are Viruses Alive?
Explain in your own words how a virus infects a host cell.
List three pieces of evidence from the article that suggest viruses are living.
List three pieces of evidence that suggest viruses are not alive.
What conclusion does the author come to concerning whether viruses are alive or not? Do you agree with the author? Give evidence from the article to support your opinion.