PROTISTS

ARRANGED BY : FAJAR BAGAS SAPUTRA

KELAS : XJNO : 15

A. INTRODUCTION

In five kingdom classification system designed by Whittaker. Protist are put in a sepparate kingdom. Protozoa, the animal like protist, are also put in this kingdom and separated from its usual place in the animal kingdom. The same goes for plant like protist. The term Protist was first used by Ernest Haeckel.

B. PROTIST CHARACTERISTIC

Protist are a group of eukaryotic organism, either unicelluler or multicellular and have not yet shown real tissue differentiation.

The characteristics of protists are :1. Most are one-celled, but some have many cells.2. Cells have a membrane arround the nucleus (eukaryotic).3. Some get nutrients and energy by eating other organisms.4. Some get energy from the sun, and nutrients from the water.5. Most reproduce by splitting in two6. Examples are paramecium, amoeba, and kelp

C. THE MEMBER OF PROTIST

The members differ from one another in morphology and how they live. There are those with fungi , animal, or plant characteristic.

1. Fungus-like Protists Fungus like protist consist of water molds and slime molds. Fungus-like protist characteristics have structure to

produce spore, heterotrophic. Characteristic Fungus-like Protist :

Live in water or moist environments Look like tini threads with a fuzzy covering Attack food such as potatoes, cabbage, and corn and

can destroy whole crops Live in moist soil and on decaying plants and trees Very colorful Move by forming pseudopods

   Fungus-like protists are heterotrophic, they cannot make their own food, and thus they must be able to move at some point in their lives. These protists contain long hyphae-like strands thus they contain the physical appearance of fungi. The difference lies in that the hyphae of fungi are white while the hyphae of protists are usually bright in color.    The fungus-like protists can act as decomposers. They break down dead organisms by releasing digestive enzymes into the dead organism. In the end materials useful to other living organisms are released into the surrounding environment.

Water Molds (oomycota)

    

Water molds are fungus-like protists that live in moist environments. They look like tiny threads with a hazy covering (when in a damp environment). Most water molds are decomposers, breaking down dead organisms; few water molds are parasites, living in or on other organisms.      

Water molds attack foods such as potatoes, cabbage, and corn. They are capable of completely destroying crops. An example of the devastation a water mold is capable of doing happened between the years of 1845 and 1860. The growing seasons at this time was a cold and damp one; these are conditions that encourage the spread of the water mold Phytophthora infestans. This water mold is the cause of rotting potato plants (late blight). It infested all of the potato crops in Ireland. During this period one third of Irelands population died; they either starved to death or were killed by the infested potatoes.

Slime molds (Myxomycota)

Gb. Dictyostellium discoideum

Slime molds are a fungus-like protist that lives in moist soil, decaying plants, and trees. They have a very bright appearance.    Slime molds are single celled organisms. When conditions become unfavorable the single celled organisms join together and act like a "multi-cellular" organism.  The protists will then form a sporangia-a cluster of cells on top of a stalk. The sporangia consist of living cells in a dormant stage, while the stalk consists of dead cells that act as a foot and push the cells to favorable conditions. When conditions become favorable the "multi-cellular" organism separates itself back into the single celled organisms.

 

The new communal structure produces a slimy covering and is called a slug because it so closely resembles the animal you sometimes see gliding across sidewalks. The slug oozes toward light. When the communal cells sense that they've come across more food or better conditions, the slug stops. An example : Dictyostellium discoideum

3. Animal-like protist

Animal-like protists are called protozoans ("first animals") because it is thought that they are the evolutionary history of animals. They share many common traits with animals. All of the animal-like protists are heterotrophs; they are unable to make their own food. But unlike animals, they are unicellular. Since they can’t make their own food they must be able to move through their environment and catch their food.

    The animal-like protists are divided into four groups based upon their means of mobility and manners for catching their food. They are divided into: protists with pseudopods, protists with cilia, protists with flagella, and parasitic protists.

1. Protists with Pseudopods :

A pseudopod is a "false foot" that slowly moves the protist. These protists move towards their food or prey by extending their cytoplasm into a "false foot". The "false foot" extends from the cytoplasm, attaches to the ground, and pulls the rest of the body toward the food. The pseudopods are not only for the means of locomotion; they also capture the food. They capture the food by wrapping the "false foot" around the prey and bringing it into their bodies. One example of an animal-like protist with pseudopods is the Amoeba (see picture above).

Gb. Amoeba Proteusamoebas are single celled animal-like protists that live in moist soil, freshwater, and salt water. There are different types of Amoeba but they all use pseudopods as means of locomotion and capturing food. Most of the Amoebas are free-living and eat things like other protozoans and bacteria; few Amoebas are parasitic and live on or in other organisms, where they obtain nutrients.

An example of an Amoeba is Entamueba histolytica. This Amoeba is the cause of amoebic dysentery, which is a deadly infectious disease found mostly in tropical areas and usually in areas where sanitation is poor. This disease is the leading cause of death for infants and toddlers; their immune systems are not yet developed, therefore they cannot destroy the disease.

2. Protists with Cilia

Cilia are tiny hair-like structures that surround some protists. The cilia beat back and forth. This movement enables the animal-like protist to move through its aquatic environment. The cilia also help the organism capture food. When the cilia beat, the prey (food) is moved into its body.

    Cilia are composed of ten pairs of microtubules. The microtubules are arranged in what is known as the 9+2 configuration. Of the ten pairs of microtubules nine pairs form a circle. Inside the circle lies the tenth pair; this is how it got the name 9+2 configuration.

   

One example of an animal-like protist with cilia is the Paramecium.

Paramecium is one known ciliated protist. The cilia help the Paramecium push the food and water into the cell body. The food then becomes enclosed in a vesicle filled with enzymes. In this vesicle the enzymes help the organism to digest the food.    The cilia can also helps the protist move towards the food/prey by beating the organism through the aquatic environment. The cilia can become leg-like structures under the Paramecium allowing it to "run.“

3. Protists with Flagella :

Flagella are long whip-like structures that move back and forth allowing the animal-like protist to move. Protists with flagella beat the long whip-like structure to move through their aquatic environments. These organisms can be free-living; some are parasitic, living in moist tissues of plants and animals. Sometimes the parasitic protists help their host, but others are harmful.    Flagella, like cilia, are composed of microtubules. They are arranged in a 9+2 configuration. Nine of the pairs of microtubules form a circle around the tenth pair.    One example of an animal-like protist with flagella is Giardia lamblia.

Parasitic Protists

    The parasitic protists are animal-like protists that live in or on another organism, obtaining all its nutrients from that host organism. Many of these protists are disease causing. These protists go in and out of the active stage and the dormant stage. When conditions are good for them they are active; when conditions are bad they become dormant. One example of this parasitic animal-like protist is Plasmodium, which causes malaria.

Plasmodium

    Plasmodium is a parasitic animal-like protist. It is the cause of malaria. Plasmodium is transported through mosquitoes. While in the mosquito the Plasmodium is in a dormant stage. When it is transported into the human it becomes active. It is mostly found in the red blood cells of humans. The Plasmodium asexually reproduces inside the liver and then enters the red blood cells. The red blood cells are destroyed in massive amounts. Merozoites are produced in some of the red blood cells. These merozoites develop into the male and female gametophytes. The infected gametophytes are taken in through a mosquito and the process begins all over again.   

Below is the life cycle of Plasmodium.

3. Plants-like Protist

plant-like protists are autotrophic; they can make their own foods. They live in soil, on the barks of trees, in fresh water, and in salt water. Plant-like protists are very important to the earth because they produce an abundant amount of oxygen. They are the basis for the aquatic food chain.

    These protists are similar to plants. Most are photosynthetic. Some have stem-like structures called stipes and anchoring structures called holdfasts, while plants have actual stems and roots. Many of these protists release their eggs into the environment where the sperm will fertilize the egg. Plants on the other hand will retain the egg in the "parent" plant where it will fertilize.

    Some examples of plant-like protists are: Euglenoids, Dinoflagellates, Chrysophytes, Green Algae, Red Algae, and Brown Algae.

1. Euglenoids

Euglenoids are plant-like protists that are usually found in fresh water. During the day these protists are autotrophic; they can make their own foods. When night falls they become heterotrophic; they are unable to make their own foods, and thus they must be able to find it. Some Euglenoids have flagella to help them move during the heterotrophic stage.    The Eugleoid is a single celled organism with an abundance of organelles. They have an "eye spot" which covers a light-sensitive receptor. The cell will move to places where the light suits it best.

2. Dinoflagellates

Dinoflagellates are plant-like protists found in salt water. They are unicellular and have flagella to help them move through the water. The Dinoflagellates are capable of glowing in the dark. They are the cause of Red Tide, when there is an outburst in population and in turn water becomes red/brown in color.    The Dinoflagellates can produce toxins. If a human eats seafood contaminated with the toxins he/she will have memory loss and other impaired brain functions. One dinoflagellate that has gotten out of control is Pfiesteria.  Pfiesteria grows in fertilizer and raw sewage. It has killed a billion fish along the costs of North Carolina, Maryland, and Virginia since 1991.

gb. Pfiesteria piscicida.

3. Chrysophytes

Chrysophytes are plant-like protists found in toothpaste, scouring products, and filters. Chrysophytes have a glasslike cell wall. The Chrysophytes are free-living, photosynthetic, unicellular protists. They consist of diatoms, golden algae, and yellow-green algae. Many Chrysophytes form colonies.    The diatoms are photosynthetic. They contain a shell that is made of silica. The cell has two parts that overlap. Over millions of years the shells become crushed and form the sand found on the bottom of oceans and lakes.    Golden algae have no cell wall. They do have scales made of silica. They also contain chloroplast and they do photosynthesize.    Yellow-green algae also have no cell wall. They are unable to move, but some do have flagella to help assist movement when conditions become harsh. This algae is common in nearly all aquatic environments.

4. Green Algae

Green algae are plant-like protists that are structurally closest to plants. The green algae can be seen in many forms. Most are unicellular, some live in colonies, and few are milticellular. Green algae grows at the surface of the ocean, in marine waters, below the surface of the soil, and in rocks, tree bark, in other organisms, and in snow.

5.  Red Algae

Red algae is a plant-like protist that can be found in aquatic areas; most live in marine waters, but some are found in fresh waters as well. Not all red algae appear red. The color depends on the pigmentation and chlorophyll abundance in the protist. They can appear green, purple, and black. The cell walls of red algae are composed of agar, which gives it a slimy/slippery feeling.    Humans use red algae every day. The red algae Eucheuma is used as thickening agents in such things as paints, dairy products, and hair conditioners.

6. Brown Algae

Brown algae is a plant-like protist found in cool temperature marine waters. They range in colors from dark brown to golden, depending on the amount and arrangement of certain pigments. They range in size from thirty meters, such as giant kelp, to microscopic organisms.    Macrocyctis is giant kelp. It is one of the most complex of all protistans. They are multicellualr and contain stipes (stem-like structures), blades (leaf-like structures), and holdfasts (anchoring structures). Kelp often live in giant colonies, creating a kelp bed. These giant kelp beds act like underwater "forests". Many fish, bacteria, and other protistans live their lives with in the giant kelp "forests."    Brown algae are found in many products such as: ice cream, pudding, jelly beans, salad dressing, canned foods, frozen foods, beer, cough syrup, toothpaste, floor polish, cosmetics, and paper. Many people harvest kelp for food, mineral salt, and fertilizer for crops.