Levels of Organization Chapter 2 Lesson 2

Single-Celled Organisms Prokaryotes: Single celled organisms that do not have membrane bound organelles. Example: Bacteria. Bacteria have structures with specific functions, but they do not have a nucleus or other organelles. Eukaryotes: More complex than bacteria. They have a nucleus and membrane bound organelles.

Multicellular Organisms Multicellular organisms have many cells and usually have more than one type of cell. They have more complex organization than single-celled organisms.

Humans are Multicellular organisms You started as a single cell. You grew by mitosis and cell division and now you are an organism with many types of cells. Make a list with you partner on pg # 68 in your notebook of all of the different types of cells that you can think of. Ex: Skin cells, brain cells, liver cells…etc… Remember, there are over 500 in humans alone! WHO CAN GET THE MOST?

How do we get so many different types of cells? All cells in your body start out as stem cells. Stem Cells are cells that can become different types of cells. Stem cells become different types of cells through a process called cell differentiation. Different cell types use different parts of the instructions on chromosomes (DNA). Think of this like an actor learning lines for a play. He only needs to memorize his lines, not the entire play!

Stem Cells We still have stem cells in our bodies, and they are in the middle of some of your bones. Stem Cells are undifferentiated cells, but under the right conditions, they can become many different types of cells! Brainstorm with your partner: How could stem cells be important for treating diseases?

Levels of Organization One of the characteristics of life is organization. Arrange the following from smallest to largest: Organ Organism Tissue Organ System

Levels of Organization Tissues are groups of cells that work together to perform a function. 4 types of tissue: Muscle tissue, Nervous tissue, Connective tissue, Epithelial tissue. An Organ is a group of similar tissues that work together to perform a function. An Organ System is one or more organs that work together and perform one or more functions. An Organism relies on organ systems.

Levels of Organization Without these levels of organization, your body would be a jumble!