Download What are Algae?

Objective – I can describe characteristics of algae.
What Are Algae?
(source: modified from an article from BioMara)
Algae are organisms that are like plants. They are found living in the sea, rivers, lakes or ponds.
Algae make energy from the Sun. There are two types of algae – macroalgae (large algae) and
microalgae (you need a microscope to see them). We will look at microalgae.
Microalgae are small floating organisms that contain one cell and are called “unicellular” organisms.
The cell is surrounded by a cell wall. Microalgae make their own energy and store it in the cell.
They can either appear blue-green, yellow, brown or orange.
The two main types of microalgae are “diatoms” and “dinoflagellates.”
Diatoms have different shapes. Some are shaped like spheres, elliptical, triangles and a star. They
contain tiny amounts of oil within their cell. The oil helps them move within the water to find their
food and nutrients. They are weak swimmers so the water currents help them to move.
A diatom cell is surrounded by a silica shell which makes the cell wall. The silica looks like glass and
is used to protect the cells. The cell wall within the diatom is like a box with an overlapping lid.
They cannot move themselves so they float free.
Dinoflagellates have two “flagella” which appear like short tails that help them move through the
water. One flagellum is wrapped around the cell. The other is visible and helps the microalgae
move. They can also use the oil within their cell to sink or swim. Dinoflagellates are surrounded by
a tough shell which they use for protection. Certain types of dinoflagellates glow in the dark at
night when disturbed.
Diatoms and dinoflagellates grow very quickly and large amounts are called algal bloom. Algal
blooms can cause problems for the environment. Both of these microalgae have the ability to cause
food poisoning. Shellfish may eat the microalgae as their food. If humans then eat the shellfish they
may get sick. Some algal blooms are beneficial to the environment making huge amounts of food
for fish.
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Objective – I can describe characteristics of algae.
Name ____________________________________________________________
What Are Algae?
1. Select and circle the key words in the box associated with microalgae.
Stem
Phytoplankton
Flower
Microscope
Seaweed
Diatoms
Flagella
Multi-cellular
Oil
Silica
Single-celled
Roots
2. Describe by writing one sentence the differences between macroalgae and
microalgae.
Macroalgae _____________________________________________________
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Microalgae _____________________________________________________
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3. Describe diatoms (include shapes).
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4. Describe dinoflagellates.
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