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Amoebae can be split into several general groups. However, there is an exception to every rule, and amoebae who appear in several groups. In the A-Z assume that an amoeba has all the traits of its type, unless stated otherwise.
Naked Amoebae (lacking a test)
These types of amoeba all have granular cytoplasm (they appear speckled). They do not any sort of covering or 'shell' (a test).
- Freshwater - One of the main traits seen in
freshwater amoeba, and not others, is the contractile vacuole. This is a
solution to a big problem freshwater amoebae face. Water naturally diffuses
from where it is highly concentrated, to where it is in low concentration.
An amoeba has high concentrations of chemicals inside it, such as salts,
glucose, and waste products, meaning it has less water inside than the
environment it is living in. The effect of this is vast amounts of water
will diffuse into the amoeba. If nothing is done about this, eventually the
amoeba will swell so much, it will burst. The contractile vacuole is a space
in the amoeba, which it fills with chemicals to a higher concentration than
the rest of the cell. This means that water from the cell moves into the
vacuole. When the vacuole is is full, the amoeba quickly reabsorbed the useful
chemicals from the vacuole, and dumps the water in the vacuole back into
the environment. This continual removing of water prevent the amoeba from
bursting.
Freshwater amoeba have crystals in them. These are a crystalline form of urea, a waste product. usually these are bipyrimidal in shape, though some species have different shaped crystals. Other traits of freshwater amoeba are mitochondia, and golgi membranes. - Marine - These have no contractile vacuole. Seawater has a high concentration of chemicals such as salts, so it is easy for the amoeba to keep the same concentration of chemicals in itself. This means there is no net flow of water between the amoeba and its environment. Marine amoeba do not have urea crystals, mitochondria, or golgi membranes.
- Parasitic - Most parasitic amoebae are dependent on their host; they have become so specialized that the only way they can live is as a parasite. If they are separated from the host for too long, they die. They have no mitochondria, golgi membranes, urea crystals, or contractile vacuoles.
- Soil - Soil dwelling.
Testate Amoebae
These amoebae are covered in a test made of silicates. These coverings protect the amoeba, but also restrict its movement to some extent.
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