Biology for Kids
Protists are organisms that are part of the biological kingdom called the protista. These organisms are not plants, animals, bacteria, or fungi. Protists are a very diverse group of organisms. They are basically all the organisms that don't fit into the other groups.
Characteristics of Protists
Protists as a group have very little in common. They are eukaryotic microorganisms with a fairly simple cell structure. Other than this, they are any organism that is not a plant, animal, bacteria, or fungus.
Types of Protists
One way protists can be divided up is according to how they move.
- Cilia - Some protists use microscopic hair called cilia to move. These tiny hairs can flap together to help the organism move through water or other liquid.
- Flagella - Other protists have a long tail called flagella. This tail can move back and forth helping to propel the organism.
- Pseudopodia - This is when the protist extends part of its cell body to scoot or ooze along. Amoebas use this method to move.
Different protists gather energy in different ways. Some eat food and digest it internally. Others digest their food outside of their bodies by secreting enzymes. Then they eat the pre-digested food. Still other protists use photosynthesis like plants. They absorb sunlight and use this energy to make glucose.
One major type of protist is algae. Algae are protists that perform photosynthesis. Algae are very similar to plants. They have chlorophyll and produce food using oxygen and the energy from the Sun. However, they are not considered plants because they do not have specialized organs or tissues like leaves, roots, and stems. Algae are often divided up by their color such as red, brown, and green.
Slime molds are different from the type of molds that are fungi. There are two types of slime molds: cellular and plasmodial.
Plasmodial slime molds are made from one large cell. They are also called acellular. Even though these organisms are just one cell, they can be very large, even up to several feet wide. They also can have many nuclei in their single cell.
Cellular slime molds are small single-celled protists that can join together to work as a single organism. Different cellular slime molds will take on different functions when they work together.
Amoebas are small single-celled organisms that move using pseudopods. Amoebas are shapeless and eat by engulfing their food with their bodies. Amoebas reproduce by splitting in two through the cell division process called mitosis.
Interesting Facts about Protists
- Many protists act as pathogens to humans. This means they cause diseases.
- The disease malaria is caused by the protist Plasmodium falciparum.
- If an amoeba is cut in half, the half with the nucleus will survive, while the other half will die.
- The word "pseudopod" comes from Greek words meaning "false feet."
- Seaweed is a type of algae that grows in the ocean.
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