Cells are the basic unit of life, with trillions in the human body divided into various types such as brain and muscle cells. The cell theory, formulated in 1839, states that cells contain DNA, energy flows within them, and their activities depend on subcellular structures, distinguishing prokaryotic cells that lack a nucleus from more complex eukaryotic cells. Understanding unicellular versus multicellular organisms includes comparing their characteristics, structure, and how they obtain nutrients and reproduce.

2. THE CELL: THE BASIC UNIT OF LIFE
Cells are microscopic units that collectively carry out
the processes that make an organism a living entity.
Your body is composed of trillions of cells around
200 different types. Your brain is made up of brain
cells, your skeleton of bone cells, and your heart is
cardiac muscle cells.

3. The Cell Theory
- 1839, German botanist Matthias Schlieden,
German physician Theodor Schwann, and German
physician Rudolf Virchow formulated the cell theory.
Modern molecular biology has added many principles
to cell theory. These are:
1. Energy flows within cells.
2. Cells contain deoxyribonucleic acid (DNA), which
passed on from parent cell to the daughter cells
during cell divisio

4. 3. All cells have the same composition and metabolic
activities
4. Cell activity depends on the activities of subcellular
structures within the cell

5. Prokaryotic cells lack nucleus and
membrane-bound organelle
Ex. Bacterium
Bacteria are among the earliest life forms to
appear on Earth and are present in most of
its habitats

6. Eukaryotic cells have both a nucleus and
membrane-bound organelles, more complex
rather than prokaryotic cell
Eukaryotic cells can be found in unicellular
organisms like protozoa and multicellular
organisms made up of many cells which include
some examples of fungi, protists, plants and
animals

9. Unicellular versus Multicellular Organism
Unicellular Organisms have “one-cell-one-organism”
which means they are made up of only single-cell.
They can be prokaryote-like bacteria or eukaryotes
like some protists
Multicellular Organisms are made up of more than
one cell. The cell’s function must be interconnected
with the other cell.
Ex. Plants, some Fungi and animals

10. Unicellular
Prokaryotic

11. Unicellular
Eukaryotic

12. Unicellular and Multicellular T-Chart: The students
will create a T-Chart about unicellular
vs multicellular organisms and prokaryotic vs
eukaryotic cells based on:
• Number of Cells
• Examples
• Size
• Complexity
• How they obtain nutrients
• How they reproduce
• How they respond to the environment

14. Read

15. Which characteristic is unique to prokaryotic
cells? (contains a nucleoid)
Eukaryotic and prokaryotic cells share what
component? (DNA)
Which of the following is not a uniform feature
of cellular life? (nucleus)
Dogs and mushrooms are examples of what
type of organism? (eukaryotic
organisms)
Overall cell size is restricted by the need to
________. (transport materials inside the cell)

17. 1. Formative Assessment
A. Multiple Choice. Write the letter that corresponds to the
correct answer.
________ 1. Which of the following is a characteristic of
multicellular organisms?
a) Composed of a single cell b) Lack specialized cells
c) Can only reproduce asexually
d) Made up of many specialized cells
________ 2. What is a defining feature of unicellular organisms?
a) They have complex structures and systems
b) They reproduce sexually
c) They consist of a single cell
d) They are unable to adapt to different environments

18. ___ 3. What enables multicellular organisms to have longer lifespans than
most unicellular organisms?
a) Ability to hibernate b) Specialized cells
c) Ability to reproduce sexually
d) Capacity to replace or repair damaged cells
________ 4. Why do multicellular organisms have increased complexity
compared to unicellular organisms?
a) They have more DNA b) They lack cell specialization
c) They have a larger surface area-to-volume ratio
d) They consist of many specialized cells working together
________ 5. What is the primary advantage of unicellular organisms?
a) Ability to perform specialized functions
b) Adaptability to different environments
c) Larger size
d) Ability to reproduce asexually

19. B. Venn Diagram: Create a Venn Diagram identifying
the similarities and differences of unicellular and
multicellular organisms.