Unicellular Vs. Multicellular
Section 2.3 p. 110-114
Learning Outcome
• To recognize similarities and differences
between single celled and multicellular
organisms
Smallest vs. Biggest Organisms
How did Multicellular organisms come about
• Originally it is believed that life developed from a single cell
• Why did this occur?
• Scientist believed that this occurred out of necessity for survival
• Scientist tested this theory by using Chlorella Vugaris cells
• When left alone they developed normally as single celled organisms
• When a predator cell (Ochromonas vallesicia) was introduced, their
population declined rapidly at first
• But then eventually started to repopulate as clumps of around 8 cells
together
• These clumps were to large for the predator to consume and thus they were
left unharmed
Multicellular Organisms
• Made up of numerous cells
• Organisms contains specialized cells to perform certain functions
• Injury or death to some cells does not necessarily affect the
organism since the cells can be replaced
• Can obtain a large size, by increasing the total number of cells
• Longer lifespan
• Individual cells have double responsibility (one to themselves, one
to the organism)
Unicellular Organisms
• Body is made up of a single cell
• A single cell carries out all of life's process’s (i.e. eating, waste
removal, reproduction)
• Cell body is exposed to the environment on all sides
• Usually maintains a very small size to limit surface area exposure
• Life span is short due to heavy workload
Single-Celled
BOTH
Multi-Celled
Protista Celled Organisms
• Two Main types
• Amoeba
• Paramecium
Amoeba
-Lack a particular shape
-Have one or more pseudopod’s that
they control by changing the density
of their cytoplasm
-Feed through phagocytosis
-Have many Nuclei
-Contractile Vacuole helps maintain
balance throughout the cell
-Reproduce asexually using cell
division
Paramecium
-Shape
resembles the sole of a shoe
-Stiff but elastic membrane maintains this
shape
-Move by utilizing their cilia
-They have a mouth located in their cell
-Again use the cilia to help sweep food to
the opening
-Food sources include, bacteria, algae, and
yeast cells