Name:______________________________
Date:_____________ Period:_____
One Becomes Two and One Becomes Two Lab
Background Information
Every living thing begins as a single cell. You might think that when an organism grows,
its cells increase in size. However organisms with many cells, multicellular organisms,
grow by producing new cells with many levels of organization. Each level of organization
is made up of smaller levels that perform a particular function. Where do all these cells
come from to form tissues, organs, organ systems, and multicellular organisms?
Levels of Organization Review
Directions: 1. Match the correct word from the word list below to the drawings 1-5.
2. Color each drawing the CORRECT color noted under the word.
Exponential Growth
One of the basic functions of all living things is the ability to make copies of itself or
reproduce. This includes individual cells because they are the basic units of life. If
cells couldn’t reproduce to make complete new cells, life on Earth would not exist. The
follow adapted excerpt describes what doubling is and why it is necessary to occur1
All cells grow. They double their size by doubling everything that they are made of.
Then they exactly double their DNA and divide in half. Two completely new cells replace
the original parent cell.
We each began as a single cell (our mother’s egg was fertilized by our father’s sperm).
This cell grew and divided, and then divided again, and then again. Doubling over and
over, and over – two producing four, producing eight, etc. – quickly leads to large
numbers. If all these early cells divided at the same rate, it would take only about 30
divisions to make the many billions of cells of a newborn human.
Cell division is essential to produce a complete human being from a fertilized egg. It is
also needed to replace cells lost during an organism’s lifetime by wear and tear and by
cell death and for an organism to grow.
1
Adapted from a reference cited as Hoagland, Mahlon and Bert Dodson. The Way Life Works: Everything You Need to Know About
the Way All Life Grows, Develops, Reproduces, and Gets Along. Time Books. 1998.
Vocabulary Comprehension:
1. What does “essential” mean?
2. What does “wear and tear” mean?
Where Do Cells Come From
Most all cells in your body contain identical sets of chromosomes. The chromosomes are
made up of DNA (deoxyribonucleic acid) and proteins. The instructions for making all of
your different proteins are in the DNA, the hereditary material. The various proteins
produced by DNA are needed for growth, reproduction, and cell functioning2.
Whenever fresh cells are needed a parent cell divides itself into two parts. The process
whereby two new cells are formed is called mitosis. The new cells are called daughter
cells. What a great idea. Parents turn into children again!
Cell division is not easy. The new daughter cells must be more or less identical to the
parent cell. They need the same genes so that they can create the same proteins.
Therefore equal distribution of the DNA is key to cell division. The DNA wrapped up in
the chromosomes must be doubled; each daughter cell can then receive its own copy of
chromosomes.
Vocabulary:
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Gene: a section of DNA on a chromosome that determines a particular inherited characteristic.
Proteins: substances that make up living things and may have enzymatic functions
Distribution: division or “handling” out of something.
Reading Comprehension
Cell Division is called ______________. What are the three reasons why cell division is
necessary?
1. __________________________________________________.
2. __________________________________________________.
3. __________________________________________________.
4. What is the hereditary material in the cell called? ___________________________.
5. What is the function of DNA? ________________________________________.
6. What are the basic units of living things? ________________________________.
7. A person has about 200 different kinds of cells; each specialized to do a particular job.
This means that a person is what type of organism?
8. Each level of organization is made up of smaller levels that do what? ____________
_________________________________________________________________.
2
Adapted from a reference cited as: Baeurele, Patrick, and Norber Landa. The Cell Works: An Expedition Into the Fantastic
World of Cells. Barron’s Education Series. Inc.
One Becomes Two Lab
Question
Your cell divides every hour. Assuming no cells die, how many cells will exist after each hour?
How many cells would exist after 12 hours? After 24 hours?
Hypothesis
I think that there will be ____________ cells after 12 hours and ______________ after 24
hours, because ____________________________________________________________
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Data
Complete the following table
Hour
Number of Cells
Exponents
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Create a graph showing the hours and number of cells for the data collected beginning
at hour zero and ending at hour six.
Analysis
Describe patterns observed in the data.
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Conclusion
Was the hypothesis supported by the data or not, explain using data examples, also summarize
why the replication of cells is necessary and was their any possible source of error?
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