Lesson 4.3 - Organization of Life

Welcome back!

Living things or “organisms” are like machines. Some machines have only one part. But most machines have many parts. Some organisms, like bacteria and yeast, exist as a single cell. Other organisms, like people and pea plants, have many cells. Your body organizes all of your cells into different groups based on their structure (shape) and function (job). For example, scientists estimate that people have around 50 billion specialized fat cells, and around 2 billion specialized heart muscle cells. If you added up all of the cells in your body you’d have approximately 37,200,000,000,000 (37.2 trillion) cells! By the way, that doesn’t even include any of the millions of microbes living on you…

By the end of this lesson, you should be able to recognize the characteristics and advantages of multicellular organisms, and explain why cells differentiate or specialize.

Consider the following questions while you are working through the lesson:

In what ways can you define an organism? Compare and contrast unicellular and multicellular organisms, and identify examples of each. Describe the benefits of being multicellular over unicellular. What is the relationship of stem cells to other types of cells? Compare and contrast cell differentiation between plant and animal cells. Describe the seven levels of organization in a multicellular organism.

Summary Instructions for Lesson 4.3

Now that you've completed your notes for this lesson, it's time to carefully review them. To receive credit, your summary must reach a minimum word count, and must include all of the required vocabulary terms listed below.

Use your notes and the Guiding Questions in the lesson Introduction to help you.

Required Vocabulary Terms:

organism, function, structure, tissue, organ, organ system, stem cell, cell differentiation

Minimum Length: 50