Investigation 3:

Microscopic Life

At the end of Investigation 3 you will be able to:

• Examine and identify the structures of unicellular and multicellular organisms using a microscope.

• Compare and contrast Elodea cells and unicellular organisms.

• Describe the difference between living cells that are organisms and living cells that are not organisms.

Investigation 3 - Part 1Discovering Cells

The microscope allows us to observe things that are too small to be seen with our naked eyes. Today we will use microscopes to look at living materials to see what we can learn. We will start by looking at the leaves of an aquatic

plant called Elodea.

Lab Notebook Pg. 15

ELODEA- LAB NOTEBOOK PAGE 15

Today you will: prepare a wet mount of an Elodea leaf using the water from the container (not the dropper bottle) and complete page 15 .

• What do you see when you look at the Elodea?• When you focus up and down through the leaf

sample, what did you notice?

Are the rectangles flat, like designs drawn on the surface of the leaf, or are they three-dimensional?

Are the boxes empty?

How many layers of these bricks do you see?

Cells The boxes that you see in the Elodea

leaf are cells. Cells make up the leaf and they are too small to be seen with the naked eye, but they can be seen clearly with the microscope.

COMPLETE PART 2 ON PAGE 15• Look at page 11 in your lab notebook if you are

having trouble estimating the cell size.

• Draw only what you see in the field of view and use as much detail as possible.

• It is okay to draw a representative sample of the cells as long as the size is proportionate to the field of view.

Elodea Cells

• The cells in an Elodea leaf are NOT all the same size

• There are 2 layers in an Elodea leaf• Larger cells are on the top, smaller cells are on

the bottom -The larger ones are about 0.1mm. -The smaller ones are about 0.05mm

THE STORY OF ROBERT HOOKE

In the middle of the 17th century, more than 300

years ago, the microscope was a new invention. A

man named Robert Hooke was one of the first

people to use one to look at plants. He looked at a

thin slice of cork under the microscope and saw

that it was made of hundreds of subdivisions.

He thought they looked like little rooms.

In fact, they reminded him of tiny

rooms, called cells, that monks lived in

at the monastery. In a book that he

wrote in 1665, Robert Hooke was the

first to describe the tiny units in the

plants that he observed as cells. The

word caught on and is still used today.

Cytoplasmic Streaming Did you notice anything moving inside any of the cells?

What did it look like? -swirling or streaming of material inside the cells- tumbling or flowing of the green balls

Cells are filled with a fluid called cytoplasm.Cytoplasm can sometimes be seen moving inside of living plants.

Investigation 3

Part 2: Paramecia

WERE THE ELODEA LEAVES ALIVE?

Those little ‘bugs’ that you saw swimming around were actually paramecia. We will lookat them more closely today.

Did you see anything else in the Elodea slide that you think might be alive?

What made you think they were alive?

What do you think they are?

PARAMECIUM WET MOUNT*Paramecia tend to settle at the bottom of the container, so that is

where you should obtain your sample. 1. Use your eyedropper (in kit) to extract a sample and bring back

to your table to make a wet mount. 2. Before placing the cover slip on the sample, pull a FEW strands of

cotton from the cotton ball in your scope kit and place over the sample- then cover with the coverslip.

REMEMBER: Use only a few wisps of cotton.

DISCUSSION QUESTIONS• What movements did you observe?

• What did you see on the inside of the paramecium?

• What did you see on the outside of the paramecia?

• How big was it at 100X? At 400X?

• Are they living or non-living? What is your evidence?

• Could you see it eat? Eliminate waste? Reproduce?

Investigation 3 - Part 2Paramecia

BREAKPOINT

COMPARING PARAMECIA AND ELODEA

• What did the microscopic structure of the Elodea leaf look like?

• What did the microscopic structure of the paramecium look like? Did it look like it was made out of cells?

• Do the things inside of the paramecium look like the things inside of the Elodea cells?

Paramecia are not made of cells, because each paramecium itself is a single cell. Just like the individual green “bricks” in the elodea are individual cells, each paramecium is an individual cell.

The Elodea plant is an organism. Elodea is made of many cells. Elodea is a multicellular organism.

The paramecium is an organism. The paramecium is, however, just one cell. Paramecium are single-celled organisms.

How are Elodea cells and paramecium cells different? Discuss this question for a few minutes.

ORGANISM

Remember, our definition of an organism is any living thing that is free-living, that is, it is not a part of another organism.

• Can a single living cell be an organism?

• Can a single living cell not be an organism?

• Is an Elodea leaf cell an organism?

• Is a Paramecium cell an organism?

YES

YES

NO

YES

Cells are alive. Life happens in cells and

only in cells. Cells are the fundamental

units of life. Some cells, like the

paramecium live alone. Some cells, like

the Elodea leaf cells, live with millions of

others. Both are alive, and both do all of

the things that we recognize as

characteristics of life.

Paramecia are single-celled organisms in a

kingdom of life called Protista. In Greek,

proto means early and protist means the

very first. So single-celled organisms like

paramecia are members of the kingdom of

life that includes organisms that are similar to

some of the very first life-forms on Earth.

KINGDOM PROTISTA

Bear in mind, protists are not

animals. Animals are always

multicellular. Protista is a separate

kingdom whose members are

mostly single-celled.

FEEDING THE PARAMECIALAB NOTEBOOK PAGE 17

We will feed them with Congo red-dyed yeast. The Congo red makes it easier to see the yeast and it is an acid indicator.

Watch what happens when acid interacts with Congo red-dyed yeast.

COMPLETE PAGE 17 IN YOUR LAB NOTEBOOK

• How do you think the paramecia move?• How do they get the yeast into their bodies?• Do the paramecia have mouths?• How do the paramecia get rid of waste

products?• What keeps their insides from spilling out?• What does the yeast inside a paramecium

look like?

HOMEWORK

Please complete the response sheet on page 19 of your lab notebook.

Please read The Lowly Paramecium on pages 24-26 of your resource book.

Investigation 3 - Part 3Microworlds

More Microorganisms

• Today we are going to look at a couple different types of microorganisms. Pay special attention to how they are similar to and different from the paramecia and each other.

The Amoeba and Euglena

Complete pages 20 and 21 in your lab notebook.

We have had time to look at a number of different organisms that live in water. They are similar in some ways and different in some ways.

In your journal, title a blank page “Microscopic Life”, and write your thoughts about life at the microscopic level. Try to include two observations about the similarities of the microorganisms and two observations about the differences.

Investigation 3 - Part 3Microworlds

Breakpoint

MINIPONDS

Just like any pond, your miniponds can be divided into different regions. Different regions of the pond might be used by different kinds of organisms. What regions might you sample?

Please avoid getting mud and dirt on the slide. It will prevent the cover slip from sitting flat on the sample.

MINIPOND SAFARI

What is a safari?

We will go trekking through the various regions of the pond, using the microscope as our means of transportation.

An organized trip into wild country to look for animals and other interesting things.

ORGANISMS YOU MAY SEE

Philodinia Stentor

Daphnia Tardigrade

ORGANISMS YOU MAY SEE

COMPLETE PAGE 25 IN YOUR LAB NOTEBOOK

PLEASE USE THE MICROORGANISM GUIDE ON PAGES 4-7 OF YOUR RESOURCE BOOK

TO TRY TO IDENTIFY SOME OF THE ORGANISMS THAT YOU ARE OBSERVING

Did you see anything alive in there when you put your pond together?

Where do you think all those organisms came from ? How did they get in your ponds?

Some microorganisms can lapse into a state of diapause, which is sort of like hibernation. During diapause the organism is sealed tightly against the outside environment. In this state it can blow around in the wind or lay on the dry ground, awaiting proper conditions to resume its aquatic existence.

Now where do you think the organisms in the pond came from?

What do you think might happen to these organisms if the water evaporates?

When we are through investigating our ponds, how should we dispose of them?