Describe the characteristics necessary for life

1. Living things are composed of cells:

• Single-cell organisms have everything they need to be self-sufficient.
• In mutlicellular organisms, specialization increases until some cells do only certain things.

2. Living things have different levels of organization:

• Both molecules and cellular organization.
• Living things must be able to organize simple substances into complex ones.
• Living things organize cells at several levels:

1. Tissue- a group of cells that perform a common funtcion
2. Organ- a group of tissues that perform a common function
3. Organ system- a group of organs that perform a common function
4. Organism- any complete living thing

3. Living Things use Energy:

• Living things take in energy and use it for maintenance and growth

4. Living thins respond to their environment:

• Living things will make changes in response to a stimulus in their environment
• A behavior is a complex set of responses

5. Living things Grow:

• Cell division- the orderly formation of new cells
• Cell enlargement- the increase in sized of a cell. Cells grow to a certain size and then divide.
• An organism gets larger as the number of its cells increase.

6. Living things Reproduce: 

• Reproduction is not essential for the survival of individual organisms, but must occur for a species to survive.
• All living things reproduce in one of the following ways:

1. Asexual reproduction- Producing offspring without the use of gametes
2. Sexual reproduction- Producing offspring  by the joining of sex cells

7. Living Things Adapt To Their Environment: 

• Adaptations are traits giving an organism an advantage in a certain environment.
• Variation of individuals is important for a healthy species