Kingdom Protista
· Are simple eukaryotes that have membrane bound organelles and nuclei. They are not, however, organized into complex tissue. They tend to be unicellular.
· Protists are broken into 3 categories:
o Animal-like: unicellular, cell membrane, heterotrophic ex) Protazoan
o Plant-like: chlorophyll, autotrophic ex) Algae
o Fungi-like: different types in life cycle
Animal-Like Protists—The protozoans:
· Rhizopods: Ex. Amoeba Animal-like protist (type of sarcodina) that have no flagella or cilia
o Feeding: heterotrophic—captures other microbes by surrounding them with pseudopodia (phagocytosis)
o Respiration—gases exchange through cell membrane to mitochondria
o Excretion—solid wastes are expelled by exocytosis, liquid wastes are expelled through membrane by contractile vacuole
o Reproduction—Asexual by binary fission (like bacteria)
o Many sarcodina are parasites of intestinal tracks and oral cavities of humans and other vertebrates
o Many sarcodina secrete hard silica or calcium carbonate shells. These have been instrumental in forming many of the world’s limestone deposits
· Ciliates: Move by means of rows of cilia. Ex. Paramecium. Has definite shape (looks like a slipper)
o Feeding: heterotrophic. Cilia wash food continually toward the oral groove. It’s packed in food vacuoles for digestion
o Macronucleus: Maintains cell growth and function by producing mRNA. Controls metabolism
o Micronucleus: Involved in inheritance of genetic material during sexual reproduction
o Respiration: exchange of gases through cell membrane
o Excretion: Solids expelled through anal pore; liquids out by contractile vacuole
o Reproduction: a) Asexual by binary fission. Micronucleus duplicates while macro just splits and becomes smaller OR b) Sexual reproduction by conjugation (no male/female). Purpose is to rejuvenate the macronucleus
· Flagellates: Move by means of flagella. Ex. Trypanosoma. Responsible for the disease African Sleeping Sickness, which is passed to humans by the tsetse fly
o Illness attacks the nervous system which causes weakness and death
o Some flagellates live in salt or fresh water and are free living
o Other flagellates live in digestive tract of termites. They release enzymes that allow termites to digest wood
· Plasmodium: has no means of locomotion. Since they (sporozoans) can’t trap their own food, they live as parasites. Major plasmodiums are transmitted by mosquitoes and cause malaria. Every year 200 million people are infected by malaria.
o Mosquito bites person with malaria and picks up plasmodium with blood
o Plasmodium develops in mosquito’s gut, then mature ones migrate to mosquito’s salivary gland
o Mosquito bites another person, infecting them
o Plasmodium enter victim’s liver, undergo several divisions, the burst liver cell and enter red blood cells
o The plasmodium continually divide asexually in RBC, breaking out of RBC every 48-72 hours—causes chills and fever
o Malaria can hide from the immune system since it’s inside the liver or RBC
o Cycle repeats
Plant-like Protists
· 3 phyla; have both plant and animal-like characteristics
· Mainly comprised of Algae
· Algae are difficult to define; some classifications group Euglena and dinoflagellates with algae, although these are similar to non-photosynthetic protozoa…etc. Algae, however, tend to be unicellular, and even the multicellular algae more closely relates to simple protists than true plants
· Green algae: may be unicellular or multicellular
o Found mostly in fresh water. Some found in marine environments and damp soil. Some land plants evolved from green algae.
o Use chlorophyll a and b in photosynthesis; chloroplasts in double membrane
o Don’t have separate male and female gametes
o Vary in shape
· Golden Algae: have a cell wall
o Colour varies due to pigment they contain
o Have a box-lid-like silica shell; free float in water
o Most common are diatoms
o The shells, when the diatom dies, collect on bottom of the ocean—this produces diatomaceous earth. This can be mined, and is used in cosmetics, toothpaste, and scouring powders. Can also be used to filter fine particles from juice, etc…
o Asexual reproduction
· Brown Algae: Seaweed
o Commercial source of iodine; kelp can be used as a fertilizer and food for humans
o Algin is used to thicken foods like ice cream
· Red Algae: can grow deeper in water than any other algae; some have been found to grow at a depth of 270m.
o Their pigments can trap blue light, which penetrates deeper into water than others, allowing them to grow so deep
o Used commercially as food for humans, makes agar, ice cream, pudding, cake icing
· Euglenoids: both plant and animal characteristics (see diagram p. 401)
o Lack cell walls, used flagellum for movement
o If obstructed, uses euglenoidmovement (inchworm)
o Are photosynthetic. However, if exposed to darkness for an extended period of time, they lose their chloroplasts and become heterotrophic
o Produce asexually by longitudinal fission
o Found in pond water
o Has an eyespot that acts as a light sensor. Result is euglena moves towards light of appropriate intensity, which enhances photosynthesis
· Dinoflagellates: have flagellum for locomotion
o Have cell wall only during part of life cycle
o 2 flagella; one extends behind the cell, the other lies in a groove encircling the cell
o May release toxins that can contaminate shellfish, known as Red Tide (Algal Bloom)
Fungus-like protists
· Heterotrophic
· Slime molds are 1 phylum
· At some stages of life are unicellular, at others is multicellular
· Start are colourful, slimy mass