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MB 1.3

Last updated almost 3 years ago
13 questions
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MB 1.3 Observing Microorganisms

Objective: KWBAT compare the sizes of cells and molecules, then conduct a simulated investigation to gather evidence about microorganisms on the human body.
Part 1

Part 1: Do Now

0

You’ve been learning about tiny organisms that are made of a single cell! But are there objects even smaller than a cell?

Decide if the statements below are true or false.
It’s okay if you aren’t sure.

  • Cells are the smallest things that exist
  • Molecules are smaller than cells
  • Cells are smaller than molecules
  • Molecules are made of cells
  • Cells are made of molecules
  • TRUE
  • FALSE
0

What do you already know about molecules? It’s okay if it's not a lot!

1

What questions do you have about molecules or cells?

If you do not have any, please type in "I do not have any questions."

Part 2

Part 2: Comparing the Scale of Cells and Molecules

One of the things we’re trying to figure out is how big (or small) microorganisms really are. You’ve probably heard of molecules before; these are groups of two or more atoms stuck together. So, how do they compare?

Let’s look at two common examples: a DNA molecule and an E. coli bacteria (made up of one cell).

1

This means that an E. coli bacteria is about...

1

Your friend is looking at a model of an oxygen molecule and asks you how many cells it is made of. Your friend does not have any special tools.

Explain what is wrong with your friend’s question.

Part 3

Part 3: Investigating Microorganisms

Growing a Culture Excerpt

Microorganisms are microscopic—they are so small that we cannot see just one or two of them with the naked eye. But, when there are millions or trillions, we can actually see them without a microscope. One way that scientists can observe microorganisms is by letting them multiply (reproduce) until the populations are big enough to see with the naked eye. This is called growing a culture.

Example: you might not think that there are any microorganisms on this bread on Day 1. But 7 days later, the microorganisms have multiplied so many times that you can actually see them!

How to Grow a Culture

  • The diagram below shows how a scientist could grow a culture of the microorganisms on your hand.
  • They would rub your hand with a swab to pick up any microorganisms there.
  • Then, they would rub that swab onto a dish of agar (a gelatin-like substance that helps living things grow).
  • If there are any microorganisms on your hand, they would now be on the agar.
1

Summarize: what is the purpose of growing a culture of microorganisms?

Imagine you try to grow a culture from your own hand. Here is a picture of the petri dish with agar.
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Do you see any evidence of microorganisms in DAY 1? Explain.

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Do you see any evidence of microorganisms in DAY 5? Explain.

Part 4

Part 4: What are Bacteria?

1

Select the two misconceptions about bacteria discussed in the video

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True or False:

Bacteria are only found in specific places on our body.

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Describe one or two ways bacteria are GOOD for us.

1

True or false:

Bacteria come in all shapes and sizes.

Part 5

Part 5: Exit Ticket

2

How small are the microorganisms that live on and in the human body? Use at least 4 of the vocabulary words below in your response.
  • cell
  • micrometer
  • microscope
  • microscopic
  • molecule
  • culture
Sentence starter: The microorganisms that live on and in the human body….