Topic: Cell Specialization: Unicellular vs. Multicellular

Part One: Teacher Notes

Sate and National Standards:

Strand 3: Characteristic and Interactions of Living Organisms

1. There is a fundamental unity underlying the diversity of all living organisms

Cells are the fundamental units of structure and function of all living things

a. Recognize all organisms are composed of cells, the fundamental units of structure and function

2. Living organisms carry out life processes in order to survive

A. The cell contains a set of structures called organelles that interact to carry out life processes through physical and chemical means.

Concept:

The concept being addressed in this lesson is cell specialization. As cells grow, their shape and contents change so that they can be most competent at the work that they must do. There are two different types of cells; unicellular and multicellular. A unicellular organism is an animal or plant consisting of a single cell. The single-celled prokaryotic and eukaryotic cells lack the specialization we see in many plants and animals. A multicellular organism is an organism composed of many cells. Multicellular organisms depend on cell specialization, cell communication and cell cooperation.

Exploration:

The activity I have picked for this part of the lesson is a very simple. Students will be put in groups of four and will be presented with a picture that will force them to search for their prior knowledge and answer the questions asked. The questions will help introduce the topic and will involve the students in a discussion that will talk about unicellular and multicellular organisms.After all the groups have had time to answer the questions, we as a class will discuss the answers.

Term Introduction:

The exploration activity will introduce the topic and some terms that we will be discussing in this lesson. The exploration activity will let me know how much the students know about cell specialization, unicellular and multicellular organisms. This would be a great tool for me to figure out what I should include in my lecture. The following notes I have provided is a list terms and concepts the students should be familiarize with by the end of the lesson. Depending on how much the students already know, I might cover all the notes I have provided in the lecture or maybe just parts of it.

Term Introduction Notes:

As we all know by now and have discussed in previous lessons, cells are the basic units of all organisms, but sometimes a single cell is a little more than that. Sometimes, a cell is the organism. A single-celled organism is also called a unicellular organism. Unicellular organisms do everything that you would expect a living thing to do. They grow, respond to the environment, and reproduce.
Can anyone tell me if unicellular organisms include eukaryotes?
Can anyone tell me if unicellular organisms include prokaryotes? (Give the students about five seconds to answer). Unicellular organisms include both prokaryotes and eukaryotes. Prokaryotes, especially bacteria, are remarkably adaptable. Can anyone tell me where one could find bacteria? (Give the students about five seconds to answer). Bacteria lives almost everywhere-in the soil, on leaves, in the ocean, in the air, and even within the human body.

Many eukaryotes also spend their lives as single cells. Since we know what unicellular organisms are, can anyone tell me if we, humans would be considered as unicellular organism? (Give the students about five seconds to answer) Exactly, the answer is no. We, humans are multicellular organisms. The cells of multicellular organisms are interdependent, like the members of a baseball team. Each player has a function that contributes to the success of the team. Organisms that are made up of many cells that work together are called multicellular organisms. Multicellular organisms have cell specialization, which means that each type of cell has a separate role. Cells in multicellular organisms are specialized to perform particular functions within the organisms. Multicellular organisms depend on cell specialization, cell communication and cell cooperation.

Concept Application:

Students will be put in groups of four assigned by me and will be given directions for their application experiment. There will be eight different stations around the classroom; each station will have a microscope that is focused on a slide. The student’s tasks are to stop at each station and observe the slides at each station and fill out the work sheet (Application experiment table) provided as a group.

During their small group work, I will go around and check the students work to make sure they are doing their work right and I will answer any questions the students might have and will resolve any confusion the students might face.

After the students are done with the experiment, each group will give the class a summery of their results. At the end of the class, to clarify the concept, the will ask the students a question and we all as a class will discuss the answer. “Why is it an advantage to have different cells specialized to carry out particular functions?”

My answer to this question would be: One way to understand the advantage of cell specialization is to think of people in society. Think about all the professions essential to keep everything running in a society: farmers to provide food, doctors to preserve health, engineers to maintain road and rail network, teachers to prepare our next generation citizens, architectures to build our homes, and etc ... Each job requires unique, sophisticated skills that are acquired over several years and are kept up by persistent effort. It would be impossible to train each person for every profession. To provide those things that we depend on each day, people have shaped themselves to play roles in the larger social context. Organisms are just as complex as societies. Thus, cells must be shaped to perform specific functions in the context of the organism. If there was no cellular specialization, every cell in your body would be the same.

Material List:

For the application part, I will need eight different microscopes set up at different stations and I will also need eight slides for the students to look at.

History of Concepts:

•  At 1665, Robert Hooke who was an English scientist looked at a thin slice of cork (oak cork) through a compound microscope and observed tiny, hollow, room like structures, which he called “cells”. Robert Hooke only saw the outer walls (cell walls) because cork cells are not alive.

•  Around 1680’s, Anton van Leeuwenhoek, a Dutch fabric merchant and amateur scientist looked at blood, rainwater, scrapings from teeth through a simple microscope and observed living cells, which he called 'animalcules'. Some of these small 'animalcules' are now called bacteria.

•  At 1838, Matthias Schleiden, a German botanist viewed plant parts under a microscope and discovered that plant parts are made of cells

•  At 1839, Theodor Schwann, a German zoologist viewed animal parts under a microscope and discovered that animal parts are made of cells.

•  At 1855, Rudolph Virchow, a German physician stated that all living cells come only from other living cells.

Related Websites:

http://www.hhmi.org/cgi-bin/askascientist/highlight.pl?kw=&file=answers%2Fdevelopmental%2Fans_003.html

References:

Miller, levine. Biology. Pearson Education, Inc., New Jersey:2002.

http://www.hhmi.org/cgi-bin/askascientist/highlight.pl?kw=&file=answers%2Fdevelopmental%2Fans_003.html

http://www.usoe.k12.ut.us/curr/science/sciber00/7th/cells/sciber/cellhist.htm

Part Two: Students Pages

Exploration:

Take a close look at this picture below and answer the following questions related to the picture:

1.  What is shown in this picture? Explain your response?

2.  Is that how humans are made?

3.  Does that mean that we were made from a single cell?

4.  Does that mean we are single-celled organisms?

5.  How many cells do we humans have in our bodies? Is it just one?

6.  So, how did we become an organism with many many cells from a single cell egg?

Concept Application:

As you can see if you look around the room, there are eight stations provided with a microscope and a slide. Your group has to go through these stations. By stopping at each station, your group has to fill out the worksheet provided. One worksheet per group is fine; make sure everyone’s name is on that paper. Make sure your group answers the questions thoroughly. If the slide is out of focus or if you are not sure what you are supposed to be observing, raise your hand and I will help you.

Slides Provided:

Application experiment table:

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