Protists
that are classified as animal-like are called protozoans and they share some
common traits with animals. All
animal-like protists are heterotrophs and they are able to move around in their
environment in order to find food.
Animal-like protists are unicellular and they are divided into four
basic groups based on how they move and live. Some are also parasites that can
cause diseases. The Protozoa is often divided into 4 groups: Protists with
pseudopods, flagellates, ciliates, and Sporozoan (form spores- a unit of
asexual reproduction that may be adapted for dispersal and survival)
Protists with Pseudopods: These protists move by extending their bodies forward and then pulling the rest of their bodies with them. The finger-like structures that they project forward are called pseudopods, which are also used to catch food. Ex. Amoeba; A protist with a transient Pseudopod that extend out to form feet-like structures that propel the cell forward. Many of the amoeba species are found in freshwater, mud, or in rotten vegetation. Amoebas are heterotrophs meaning they eat other organisms. They generally do this by "engulfing" or swarming around their prey until the prey is inside them. The food vacuole is actually bound by a cell membrane. The lysosomes put some digestive enzymes into the vacuole and once the food is digested, they absorb the digested food into their cytoplasm. This whole process of transporting nutrients is known as phagocytosis. Protozoans such as an amoeba lack a supporting cell wall and instead have a contractile vacuole that pumps out excess water that enters the cell by osmosis, this helps the cell maintain homeostasis.
Ciliates: These protists move by using their tiny hair-like structures called cilia. The cilia acts as tiny oars that allow the protists to move through watery environments. The cilia also helps the protists to capture its food. Ex. Paramecium have cilia. They feed on microorganisms like bacteria, algae, and yeasts. To gather its food, the paramecium uses its cilia to sweep the food into the oral groove of the cell. The food goes through the cell mouth into the gullet, which is like the stomach. When enough food has accumulated at the gullet base, it is folded and turned onto itself there to form a food vacuole in the cytoplasm. As it moves along, enzymes from the cytoplasm enter the vacuole to digest the contents, digested nutrients then go into the cytoplasm and the vacuole shrinks. When the vacuole reaches the anal pore, it ruptures and expels its waste contents outside of the cell.
Flagellates: These protists move by using their flagella. They can have one or more of the whip-like structure that allows the cell to move (flagella). Many of these protists live in the bodies of other organisms. They could harm their host by having a parasitic relationship or at other times they are mutualistic with their host. Ex. Zoo-flagellates use their flagella to move around. They mostly live in lakes and streams in which they absorb nutrients from decaying organic material in through their cell membranes. They reproduce asexually by mitosis and cytokineses. During this reproduction, two cells are formed that are genetically identical. Some zoo-flagellates have a sexual life cycle as well. During sexual reproduction gamete cells are produced by meiosis (a type of cell division that results in four daughter cells each with half of the chromosomes of the parent cell, as in the production of gametes and spores). , when gamete from two organisms fuse, an organism with a new combination of genetic information is formed.
Sporozoan: These are parasitic spore-forming protists. They absorb nutrients from their hosts and they do not have a cilia or flagella, so they cannot move on their own. Plasmodium is an example of this type of animal-like protest. Plasmodium, commonly known as the malaria parasite, is a large genus of parasitic protozoa. Infection with plasmodia is known as malaria, a deadly disease widespread in the tropics.
Protists with Pseudopods: These protists move by extending their bodies forward and then pulling the rest of their bodies with them. The finger-like structures that they project forward are called pseudopods, which are also used to catch food. Ex. Amoeba; A protist with a transient Pseudopod that extend out to form feet-like structures that propel the cell forward. Many of the amoeba species are found in freshwater, mud, or in rotten vegetation. Amoebas are heterotrophs meaning they eat other organisms. They generally do this by "engulfing" or swarming around their prey until the prey is inside them. The food vacuole is actually bound by a cell membrane. The lysosomes put some digestive enzymes into the vacuole and once the food is digested, they absorb the digested food into their cytoplasm. This whole process of transporting nutrients is known as phagocytosis. Protozoans such as an amoeba lack a supporting cell wall and instead have a contractile vacuole that pumps out excess water that enters the cell by osmosis, this helps the cell maintain homeostasis.
Ciliates: These protists move by using their tiny hair-like structures called cilia. The cilia acts as tiny oars that allow the protists to move through watery environments. The cilia also helps the protists to capture its food. Ex. Paramecium have cilia. They feed on microorganisms like bacteria, algae, and yeasts. To gather its food, the paramecium uses its cilia to sweep the food into the oral groove of the cell. The food goes through the cell mouth into the gullet, which is like the stomach. When enough food has accumulated at the gullet base, it is folded and turned onto itself there to form a food vacuole in the cytoplasm. As it moves along, enzymes from the cytoplasm enter the vacuole to digest the contents, digested nutrients then go into the cytoplasm and the vacuole shrinks. When the vacuole reaches the anal pore, it ruptures and expels its waste contents outside of the cell.
Flagellates: These protists move by using their flagella. They can have one or more of the whip-like structure that allows the cell to move (flagella). Many of these protists live in the bodies of other organisms. They could harm their host by having a parasitic relationship or at other times they are mutualistic with their host. Ex. Zoo-flagellates use their flagella to move around. They mostly live in lakes and streams in which they absorb nutrients from decaying organic material in through their cell membranes. They reproduce asexually by mitosis and cytokineses. During this reproduction, two cells are formed that are genetically identical. Some zoo-flagellates have a sexual life cycle as well. During sexual reproduction gamete cells are produced by meiosis (a type of cell division that results in four daughter cells each with half of the chromosomes of the parent cell, as in the production of gametes and spores). , when gamete from two organisms fuse, an organism with a new combination of genetic information is formed.
Sporozoan: These are parasitic spore-forming protists. They absorb nutrients from their hosts and they do not have a cilia or flagella, so they cannot move on their own. Plasmodium is an example of this type of animal-like protest. Plasmodium, commonly known as the malaria parasite, is a large genus of parasitic protozoa. Infection with plasmodia is known as malaria, a deadly disease widespread in the tropics.