The Kingdom Protista The catch-all kingdom

What do you mean by catch-all kingdom? In our 5 kingdom paradigm, the Kingdom Protista was the last one to be created. The members of this kingdom were all placed in either the kingdoms Animalia, Plantae or Fungi. Upon further study, taxonomists agreed that they didn’t belong in any of those kingdoms and the Kingdom Protista was born.

So former plants, animals and fungi are all in the same kingdom? That’s correct. So as you may surmise, this kingdom is divided into three different groups. The Protozoans: The animal-like protists The Algae: The plant-like protists The Slime Molds: The fungus-like protists.

So do they have anything common? Almost nothing. There is one thing they all have in common though, which is they all possess eukaryotic cells. That means their cells contain a nucleus and all the other organelles that we learned about when we studied plant and animal cells. Outside of that, they are all quite different from each other.

The Protozoans This phyla represents the animal-like protists. The word protozoa means “first animals”. All members of this phyla are unicellular, heterotrophic eukaryotes. These organisms either feed on decaying matter, devour algae and plants, or feed on each other.

How are they classified? Protozoans are classified by their method of movement. Flagellates: These protozoans move by means of a flagellum. A flagellum is a whip-like appendage that the protozoan swings back and forth for movement. Some have more than one flagellum Flagellate locomotion

Types of flagellate protozoan Euglena is the most well studied of all flagellates. They possess the ability to move around and ingest matter like other protozoans, but some are able to photosynthesize as well. Strange as they are, they are classified as protozoans.

The ciliates The next class of protozoans are the ciliates. These organisms move around by means of thousands of tiny hair-like projections from their cell membrane. These projections are called cilia. Ciliates coordinate the movement of their cilia to navigate their environment. ciliate movement

Example of a ciliate protozoan The paramecium is the most common example of a ciliate. Paramecium use their cilia not just to move around, but to move food into their primitive mouth, called an oral groove. Paramecium contain specialized organelles called contractile vacuoles. These vacuoles are used to remove excess water from it’s cell.

Amoeboid motion The third class of protozoans move by means of psuedopods, or false feet. This type of motion is called amoeboid motion. These protozoans move around by actually projecting their cell membrane outwards, and then pulling themselves along. Amoeboid motion

The Amoeba Possibly the most well known and easily recognized of all protozoans. Amoeba are voracious predators, encircling any food they find with their pseudopods and enclosing it in a vacuole. Some amoeba are large enough to see with the naked eye. Some types of amoeba can make us very sick.

Protozoan reproduction. All protozoans reproduce asexually, meaning that a single cell splits into two. They don’t all use the same type of asexual reproduction. Some paramecium do occasionally share genetic material with each. This is called conjugation, which may represent the first step towards sexual reproduction. conjugation

The Algae This phyla represents the plant-like protists. Algae can be either unicellular or multicellular. All algae are autotrophic, asexual eukaryotes. Algae are classified by their color. There are green, brown and red algae.

Green Algae Like plants, green algae photosynthesize using chloroplasts, and are green because they contain chlorophyll. Green algae are the largest and most diverse group of Algae, and it was from green algae that all plants evolved. Most green algae are aquatic.

Green algae reproduction Some types of green algae undergo alternating cycles of asexual and sexual reproduction. Other types simply reproduce asexually. volvox in motion

Brown algae A large group of mostly marine algae which play a large role in their ecosystems. Sea weed and kelp are both examples of brown algae. Some types of kelp form undersea forests and can be over 60m in length!

Kelp forest Some brown algae reproduce both sexually and asexually. Others are strictly asexual. Some types of brown algae are commercially viable as food.

Red Algae Most red algae are found in the ocean. Very similar to brown algae in appearnce. Two types of red algae are used to make a substance called agar, which is used as a growth medium in petri dishes. Reproduction is both asexual and sexual.

Protozoans and Algae living together. These two phyla are the chief components of plankton. Plankton are free floating protozoan and algae what make up the base of most food chains in the oceans. The oxygen produced by refreshes the atmosphere, and the CO2 taken up by plankton is significant.

Plankton Seasonal blooms of plankton can be seen from outer space. Zooplankton = protozoans and small animals. Phytoplankton = Algae.

Slime molds One of the most bizarre of all life forms on earth. They begin life as single-celled amoeba like creatures. They aggregate into masses and begin to change form. These contain many nuclei without cell membranes between them, which can grow to be meters in size.

Ecology and lifecycle. Slime molds feed on bacteria found in the soil. Often found on dead and decaying matter. Once they aggregate, they form a plant-like body structure which then produces spores, like a fungus. These spores are carried by wind and air. They change into the amoeba like form of slime molds.

Time lapse slime mold and mushrooms. Slimey!