Investigation 3 Microscopic Life Introduction to Elodea Observation

Investigation 3 Microscopic Life

Introduction to Elodea Observation The Microscope allows us to observe things that are too small to see with our naked eyes. Today we will use the microscopes to look at living material to see what we can learn. We will start by looking at the leaves of an aquatic plant called Elodea.

Wet Mount of an Elodea Leaf • Make sure your mount is with the top of the leaf facing up. • Use the water from the Elodea container to make the wet mount. Use a dropper to flow one drop of water under the coverslip. • Do not use too much water, we need conserve it. • Make sure to focus up and down through the leaf.

Questions-ONLY DO THE FIRST PART AT 100 X • 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?

Elodea Cells The boxes or bricks that you see in the Elodea are cells. Cells are units From which the Elodea leaf are made. They are too small to see with the naked eye.

Estimate the Size of Cells and Draw Them. • Conduct Part 2 at 400 X. • It is ok to draw a representative sample of the cells as long as the size is proportionate to the field of view.

Questions after Part 2 • Are all of the cells in an Elodea leaf the same size? • How many layers of the cells are there in an Elodea leaf? • Are the large cells on the top of the leaf or on the bottom? • How big are the Elodea cells?

In the middle of the 17 th Century Robert Hooke was the first to describe the tiny units in the plants as cells.

Cytoplasmic Streaming • Did you notice anything else moving inside the cells? What did it look like? • Cytoplasmic Streaming Video Cells are filled with a fluid called cytoplasm. Cytoplasm can sometimes Be seen moving inside the cells of living things.

Cell Wall: Protects the cell

Cytoplasm: Fluid inside a cell

Chloroplast: Structure that gives plants their green color

Did anyone see anything else? • Did you see anything else interesting in you slide? • Describe what you saw. • What do you think it is?

Did you know? ? • The cell is the basic unit of life. • Life happens in cells.

Stop Here!

Paramecia • The little “bug” you saw dashing around in the slide with the Elodea is a paramecium (plural, paramecia). Today we will have an opportunity to look at them more closely.

Preparing a Paramecium Wet Mount Video Paramecium Video Conduct the Paramecia Lab

Observations • What movements did you observe? • What did you see on the outside of the paramecium? • How big was it at 100 X? At 400 X? • Are they living or nonliving? What is your evidence? • Could you see if it was doing all of the things you have listed in your definition of a living organism? • What might we do to see some of these acivities?

Stop!

Similarities and Differences • Take a few minutes to construct a Double Bubble Map and fill in what you know. Elodea Leaf Paramecium

Paramecia are single-celled organisms- Add info to D. B. Map 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 paramecia is an individual cell. The Elodea plant is an organism. Elodea is a multicellular organism Because it is made up of many cells. The Paramecium is an organism. Paramecia are single-celled organisms because they are one cell.

Share Ideas • Remember, our definition of an organism is any living thing- a plant, an animal, or any other lifeform that is free-living. An organism is always free-living, that is it is not a part of a larger living organism. • • Can a single living cell be a living organism? Can a single living cell not be a living organism? Is an Elodea leaf cell a living organism? Is a paramecium cell a living organism?

Important Point in Our Investigation of Life We have been developing our definition of “living” by describing the characteristics of life-the functions (what they do) and requirements (what they need) that are common to all things we consider living. These things are also characteristics of cells. Cells are alive! Life happens in cells and only in cells. Some cells live alone and some live with millions of others. Both are alive, and both do all of the things that we recognize as living.

However… Not all cells are organisms, because not all cells are able to live independently (on their own).

Protist Paramecia are single-celled organisms in the kingdom of life called Protista (pro-TEES-ta). In Greek, proto means early, and protist means the very first. So single-celled organisms like paramecia are members of a kingdom of life that includes organisms that are similar to some of the very first life-forms on Earth. Protists are not animals! Animals are always multicellular. Protista is a separate kingdom whose members are mostly single-celled.

Characteristics of Life • So, should we add anything to our Characteristics of Life?

Feeding Time! • You will be adding one drop of Congo-reddyed yeast to a new paramecia wet mount slide. • Before we observe however…why the dye? – Congo red does two things. It makes it easier to see the yeast, and it is an acid indicator. Watch what happens when acid interacts with Congo red yeast. DEMONSTRATION.

Cilia: Used for movement The bubbles were water-expelling vesicles. Organelle: Paramecia’s guts

What can a Single- cell Organisms do? What can a Multi-cell organisms do? • ___Need Water • __Exchange Gases • ___Use Energy from Food • _____Grow • __Eliminate Waste • ____Reproduce

Mini pond Hunt

Volvox

Flagellates

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