1. LIFE

2. SO….What does it mean to be living?
Biology…What is it?
Biology is the study of life.
SO….What does it mean to be living?

3. Characteristics of Life
To be considered living, an organism must…..
Be based on a universal genetic code.
DNA
2. Grow and develop

4. Characteristics of Life
3. Be able to Reproduce
-Asexually
-Sexually
4. Use materials and energy -Metabolism

5. Characteristics of Life
5. Be able to respond to their environment -stimulus response
Humans:
Plants:

6. Characteristics of Life
6. Maintain stable internal environment -Homeostasis

7. Characteristics of Life
7. Change over time, as a group. -Evolution
Made of units called Cells -Unicellular -Multicellular

8. Cell Theory Cell Theory all living things are made up of cells
Matthias Schleiden
concluded that all plants are made of cells (1838)
Theodore Schwann
concluded that all animals are made of cells (1839)
Rudolf Virchow
concluded that all cells came from pre-existing cells (1855)
Cell Theory
all living things are made up of cells
cells are the basic units of structure and function in an organism
new cells are produced from existing cells

9. Levels of Organization
Function
Example
Organism
Single living thing
Organ System
Different organs function together
Organ
Different tissues function together
Tissues
Similar cells function together
Cells
Smallest unit of life
Molecules
Smallest unit of a substance with the same properties
Atom
Smallest unit of matter
Human
Nervous
System
Brain
Nervous Tissue
Nerve
Cell
Protein
Carbon

10. Viruses…Living or not?
Viruses come in many different shapes and they cause many different diseases but, they all have something in common….
Now that we know what makes something living, let’s look at a virus.

11. Viruses and Living Cells
Characteristic
Virus
Cell
Structure
Genetic material surrounded by a protein capsid
Cell membrane, cytoplasm; genetic material, ribosomes
Reproduction
Only within a host cell
Yes, sexually and asexually
Genetic Code
DNA or RNA
DNA
Growth and Development No
Yes
Obtain and Use Energy
Response to Environment
Evolve
Homeostasis

12. Verdict?
No, Viruses are not considered a living thing because they do not meet all of the living characteristics.