Overview
In this activity, students explore the structure and function of the
cell. They begin by identifying the cell as the common unit of life in
all living organisms, large and small. Students learn about single-celled
organisms and how they carry out different life functions. Then they
use a Web activity to explore how cells divide during the process
of mitosis. Next, students learn how cell specialization takes place
in vertebrate embryos. They explore a gallery of different kinds of
specialized cells and compare each cell's structure and function. After
making drawings of these cells, they place their drawings in the
appropriate location on a human body outline. Finally, students complete
a Web activity that demonstrates how white blood cells are specialized
to fight viruses.
Objectives
- Identify the common unit of life in all organisms: the cell
- Learn how single-celled organisms carry out different
life functions
- Explore how cells divide during the process of mitosis
- Learn how cell specialization occurs in embryos
- Compare the structure and function of different
specialized cells and identify their location in the body
- Explain how white blood cells are specialized to fight
viruses
Suggested Time
- Two to three class periods
Multimedia Resources
Materials
- Unlined 3 in. x 5 in. index cards (3-4 per student)
for cell drawings
- Life-size outline drawing of human body on newsprint
or butcher paper
- Tape
Before the Lesson
- Have students research the largest and smallest
organisms that exist.
- Make a life-size outline of a human body on either
sheets of newsprint taped together or a large piece of butcher paper.
The Lesson
Part I
1.
Ask students to report their research on the largest and
smallest living organisms. Then ask:
- What do you think the largest and smallest living
organisms have in common?
- What is the smallest functioning structural
unit of life?
2.
Show the Single-Celled Organisms video
and discuss the following:
- What characteristics do unicellular (single-celled)
organisms have in common? How do they differ from one
another?
- What characteristics do unicellular organisms such as
the ones you have just seen share with multicellular
organisms such as insects, birds, dogs, or humans?
- How do these unicellular organisms get nourishment, water,
and oxygen and get rid of wastes?
- How do unicellular organisms move?
- How do unicellular organisms reproduce?
3.
Show the Mitosis video.
Explain that cells divide during a process called mitosis.
Single-celled organisms can reproduce by this method to produce
two identical cells. Multicellular organisms use mitosis to grow
and to replace worn-out cells.
4.
Have students complete the mitosis section of the
How Cells Divide: Mitosis vs. Meiosis Web activity
Part II
5.
Explain that multicellular organisms are more complex than
unicellular ones. They have tissues and organs made of
specialized cells that perform various functions such as
digesting and circulating nutrients and oxygen and getting
rid of wastes. Ask:
- How do multicellular organisms get nourishment, water,
and oxygen and get rid of wastes?
- If all multicellular organisms start from a single
cell -- the fertilized egg -- how do they develop specialized
tissues, organs, and systems like the heart and circulatory
system, the stomach and digestive system, and the kidneys
and excretory system?
6.
Show the Cell Differentiation video
followed by the
The Embryo Takes Shape video.
Discuss the following:
- Why do you think the heart forms early in the embryo's
development?
- How would you explain the similarities in the embryos
of birds, mammals, and reptiles at early stages of development?
- What directs the sequence of events that turn a blob of
cells into an embryo with specialized tissues and organs?
- How do cells in different parts of the embryo become
different kinds of cells and organs?
- What role does DNA play in the development of the
embryo?
- What kinds of proteins are found in different cells
and organs and how are they produced by cells?
7.
Have students explore the
Gallery of Cells
for similarities and differences in cell structure and function.
Ask them to draw at least three types of specialized cells,
one on each index card, and to label the cell type and any
cell structures. Then have students describe the similarities
and differences among the different cells and
how their structure is related to their function.
8.
Attach the life-size outline drawing of the human on the board and ask
students to tape their cell drawings to the place in the body where
these cells would be found. Afterwards, ask:
- Are all these cells in the correct location?
- Where else might these cells be found?
- How do the cell drawings compare to the actual
size of cells in a human body?
- Where in the body would you expect to find the
greatest number of each kind of cell?
- What other kinds of cells are in the body?
Have students research and draw these other
cells and then add them to the body outline.
9.
Show the Immune Cells in Action video.
Discuss how white blood cells are specialized to fight viruses.
Ask students where they would expect to find white blood cells
in the body and if there might be more of these cells in one
area of the body than in another. Have students explore the
action of immune cells with the
Fighting Back Web activity.
Ask:
- What disease-fighting cells are always present in
the body?
- What cells or parts of cells are produced after the
disease-causing virus enters the body?
- What are some ways in which the body develops
immunity to a disease?
- Must a person have had mumps to be immune to the
mumps virus?
- If the human body can successfully fight off the
mumps virus, why can't it fight off the HIV virus that
causes AIDS?
