§ The kingdom Protista includes more than 200,000 species.
§ A protist is any organism that is
not a plant, an animal, a fungus, or a prokaryote.
§ Protists are microscopic, unicellular, animallike organisms that carry on all
life sustaining functions.
HOW ARE THEY CLASSIFIED?
§ Based on the way they obtain nutrition.
► Animallike protists - heterotrophs
► Plantlike protists - photosynthesis
► Funguslike protists - decomposers or parasites
ANIMALLIKE PROTISTS: PROTOZOANS
§ Animallike protists were called protozoa, which means "first animals".
§ Four phyla of animallike protists are distinguished from another by their means
► flagella, pseudopods, cilia, no movement
§ phylum Sarcodina, or sarcodines
§ move via temporary cytoplasmic projections known as pseudopods
§ Amoebas are the best known sarcodines.
§ In an amoeba, the cytoplasm is constantly flowing.
§ The streaming cytoplasm pushes against the cell membrane pushing out projections
§ Pseudopod means false feet.
§ This type of locomotion is called amoeboid movement.
§ They are found in the slime at the bottom of streams and ponds, and on water plants.
§ Oxygen and water dif fuse through the cel membrane. Water enters by osmosis and
is always being removed by the contractile vacuole.
§ Amoebas get food by surrounding their food (cells
of algae and other protists) with their pseudopodia. The food is taken in by a food vacuole.
► A food vacuole, is a small cavity in the cytoplasm that temporarily stores
§ Digestion takes place by enzymes produced in the cytoplasm that pass into the
vacuole. Particles that can -not be digested or not used remain in the vacuole and are then released from the cell.
§ Amoebas reproduce by mitosis and cytokinesis.
§ Amoebas are sensitive to light and dark. Also, dryness, cold, or lack of food.
§ If conditions are not correct then they form a cyst until conditions improve and
they become active again.
§ phylum Ciliophora
§ Move by using cilia which are short hairlike projections
§ The cilia beat back and forth like little oars and can beat either forward or
§ Live in both fresh and salt water
§ Paramecium is the best known ciliate.
§ The paramecium does not change shape like anamoeba but has a thick outer membrane
called a pellicle.
§ Trichocysts are their defense mechanism. These fire out when a larger protists
nears. They give the paramecium a bristly or rough appearance.
§ A paramecium possesses two nuclei:
1. Macronucleus - which controls normal cell activity or the "working
library" of genetic information
2. Micronucleus - which aids during cell reproduction or the
"reserve copy" of all the cell's genes.
§ Paramecium sweep in food particles through their oral groove towards the gullet.
There is a front and back to the paramecium. The oral groove runs from front to back.
§ Particles trapped in the gullet are forced into a food vacuole that forms at its
§ The food vacuole breaks away into the cytoplasm and fuses with lysosomes, which
contain digestive enzymes.
§ Food is digested and absorbed with undigested food passing through the
§ Oxygen dissolved in the water diffuses throughthe cell membrane and enters the
cytoplasm. Here it is used for respiration and the carbon dioxide is released back through the cell membrane.
§ Paramecium have a contractile vacuole with canals. The canals fill with water
and then pass it onto the contractile vacuole where excess water is pumped out of the organism.
§ Most other wastes diffuse out of the cell membrane.
§ They move and respond in a "trial and error" fashion. Moving forward until they
bump into something, then they reverse. This is called the avoiding reaction.
§ They are reproduce asexually by mitosis and cytokinesis
§ When placed under stress, they may engage in conjugation.
It is not a form of reproduction but it is a sexual process. The two paramecium meet and exchange micronuclei and then divide
by fission. This adds variation and maintains genetic diversity.
§ phylum Zoomastigina or zooflagellates
§ swim by using flagella which are long, whiplike projections
§ absorb food (decaying organic material) through their cell membrane
§ live in lakes and streams
§ live within the bodies of other organisms
asexually by mitosis and cytokinesis (genetically identical)
§ sexually, gametes are produced by meiosis
§ phylum Euglenophyta or euglenophytes
§ plantlike protists that have two flagella but no cell
§ they move in two ways: one
by twirling the flagellum to push them forward, or two: by inching forward like an inchworm
§ found in ponds and lakes and are excellent swimmers
§ anterior end is rounded, posterior is more pointed
§ the red eyespot
is sensitive to light
§ they seek out bright areas to live which is unlike many other protozoas
§ euglenas have chloroplasts but if sunlight is not available, they live as heterotrophs
absorbing decayed organic material
§ euglena reproduce asexually by binary fission
§ Under good conditions, they can divide once a day. In great numbers, they will
make the water appear green.
§ phylum Sporozon
§ protozoans that do not move on their own and are all
§ live by absorbing food from their host
§ some of the organisms live in one host per lifetime others two.
§ They reproduce by means of sporozoites attaching to
a host cell, penetrating it and living within it as a parasite.
ANIMALLIKE PROTISTS AND DISEASE
§ caused by the sporozoan Plasmodium
which is carried by the female Anopheles mosquito
§ Life Cycle:
1. Transmitted to humans
by the female Anopheles mosquito
2. The mosquito's saliva
contain the sporozoites and enters the human's
3. Once inside, plasmodium
infects liver cells, then red blood cells and
4. Red blood cells burst
releasing parasites into the bloodstream causing
chills and fever
African Sleeping Sickness
§ Trypanosoma, a zooflagellate, is responsible for African sleeping sickness.
§ It is transmitted to humans by the bite of the tsetse fly.
§ symptoms include chills and rashes and can also infect nerve cells.
§ Some individuals lose consciousness, lapsing into a deep and sometimes fatal sleep.
§ characterized by severe diarrhea and is caused by an organism that looks like a harmless ameba.
§ Entamoeba, a parasite spread by contaminated drinking water attacking the walls of the intestine and causing
§ it is most common is areas with poor sanitation.
§ But even crystal-clear mountain streams may be contaminated with a flagellated
pathogen called Giardia that causes severe diarrhea and digestive problems.