1. Level of Organization
Cells with a purpose!

3. Levels of Organization for cells:
The body is built upon levels. The levels of organization are: cells, tissues, organs, and organ systems.
The smallest unit is:
The largest unit is:

4. Cells
A cell is the basic unit of structure and function in a living thing.
The human body contains about 100 trillion cells.
Cells in the body are specialized, meaning they have a specific purpose.

5. Functions of Cells Carry on the process that keeps organisms alive.
Undergo chemical reactions.
Grow and reproduce
Get rid of waste products that result from these activities.

6. Tissues A group of similar cells that perform the same function.
Each tissue has its own unique shape.

7. Tissues
Muscle Tissue- can contract or shorten, making parts of the body move.
Nervous Tissue- directs and controls the process. It sends messages to the brain.
Connective Tissue- provides support for your body and connects all the parts. Ex. Bone tissue and fat.
Epithelial Tissue- coves your body inside and out. Ex. Skin, lining in the digestive system.

8. Organs
An organ is a structure that is composed of different kinds of tissue grouped together to form a bigger function.
Your stomach, heart, brain, and lungs are all examples of organs.
The job of an organ is more complex than that of a tissue.

10. Organ Systems
Organs group together to form a system. The systems together help make an organism.
The systems include: digestive, cardiovascular, nervous, excretory, circulatory, skeletal, immune, and reproductive.

13. Last 3 Systems Reproductive Integumentary(Skin)
Lymphatic System (Immune System)

14. Homeostasis
All the organ systems of the body work together and depend on one another.
Homeostasis is the process by which an organism’s internal environment is kept stable in spite of changes in the external environment.

15. Homeostasis
Your body’s ability to maintain a constant temperature is the body’s ability to maintain homeostasis.

17. Maintaining Homeostasis
If you are too warm, you will sweat, this helps to cool you down.
If you are too cold, you will shiver, this helps to promote heat.

18. Stress and Homeostasis
Stress is the reaction of your body to potentially threatening, challenging, or disturbing events.
Stress can be temporary and will allow your body to return to its normal state.

19. Organism
A group of organ systems working together to carry out the jobs needed for survival of the organism
In human body the organ systems are interconnected and depend upon each functioning properly
Ex. All other systems depend upon the circulatory system to transport the blood which supplies oxygen to all other cells in every system

20. Review Questions 1. What is the difference between tissues and organs?
2. What is homeostasis?
3. How does stress affect homeostasis?