Protists
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Transcript of Protists
Protists
Survey of Chapter 25
What is a Protist?
• Eukaryotic organisms that do not fit into any other category are usually called protists
• Most protists are microscopic, but some are multicellular (like algae)
• We determine that an organism is a protist using EXCLUSION: it cannot be classified as a fungus, plant or animal
• Protists are a very diverse group and it’s thought that they were the first eukaryotes
Classification
• Protists are classified by what they resemble• Animal-like protists:– heterotrophic, move around environment
• Funguslike protists:– slime molds and water molds
• Plantlike protists:– can do photosynthesis
Characteristics
• There are only a few general characteristics of protists
• But most are characterized by body plan, how they obtain food, and motility– Unicellular or multicellular– Nutrition: can be autotrophic or heterotrophic– Motility: some move with cilia, flagella or
pseudopodia
Reproduction
• Most protists reproduce asexually using binary fission
• Sometimes protists reproduce by multiple fission where one cell division produces more than two offspring
• Protists that reproduce sexually via conjugation:– two cells join and exchange genetic material
Animal-Like Protists
• These protists are divided into several Phyla:– Protozoa– Ciliophora– Sarcomastigophora– Apicomplexa
• All of these protists are heterotrophic• They move around their environments and
“capture” prey
Phylum Protozoa
• Protozoa are single-celled protists that can move without cilia or flagella
• There are more than 40,000 species of Protozoa
• Most protozoa can form pseudopodia: large, rounded cytoplasmic extensions that function for movement and feeding
• This movement is called ameoboid movement
http://www.youtube.com/watch?v=7pR7TNzJ_pA
Phylum Ciliophora
• All ciliophora have cilia for movement• Cilia: short, hair-like projections that stick out
of the cell membrane• This group includes the genus Paramecium,
which are found in ponds and slow-moving streams
• Ciliophora reproduces asexually and usually have two nucleii
http://www.youtube.com/watch?v=a4aZE5FQ284
Phylums Sarcomastigophora
• All members of this phylum have one or more flagella
• Flagella – long, whiplike structures that are made of microtubules and used for movement
• Flagella help to move the protist rapidly through water
• Many of these members are free-living in lakes and ponds
• Some of these are parasites: Trypanosoma
Phylum Apicomplexa
• Includes 4000 species whose adult forms cannot move
• ALL apicomplexa are animal parasites:– Toxoplasma gondii– Plasmodium spp.– Cryptosporidium spp.
• All apicomplexa have complex life cycle; most require two or more hosts to complete their life cycle
Plantlike and Funguslike Protists
• Plantlike protists includes algae and diatoms• These protists are autotrophic and have
chloroplasts• Funguslike protists include slime molds and
water molds• Like fungi, these protists have a stationary,
spore bearing reproductive stage
Algae Phyla• Chlorophyta (green) – – More than 17,000 species, have chlorophyll/chloroplasts– Most are aquatic, can be unicellular or multicellular
• Phaeophyta (brown) – – Mostly marine, includes seaweed and kelp
• Rhodophyta (red) – – Contains chlorophyll a only, can live at deeper depths
than other algea• Chrysophyta (golden) –– Most live in fresh water, have two flagella, have
carotenoids
Diatoms and Dinoflagellates• Bacillariophyta (diatoms) – – 100,000 species are included in this phylum– All are unicellular, with cell walls– They are different shapes and are abundance in freshwater
environments– Produce oxygen through photosynthesis
• Dinoflagellata (dinoflagellates) –– These are small, usually unicelluar protists with two flagella– They are photosynthetic, but a few species are
heterotrophic– Some species of dinoflagellates use bioluminescence
Slime Molds
• Includes about 700 species of plasmodial slime molds
• Many slime molds have two nuclei that are not separated by a cell wall
• Plasmodium reproduce when water is scarce, forming haploid spores by meiosis
• In favorable conditions, two spores come together to form new plasmodium
Water Molds
• Includes some protists that are parasitic (live in fish), also includes aquatic protists
• Can reproduce sexually or asexually through zoospores
• There is a possible link between one of the water mold phyla and fungi due to the amount of similarities
Protist and Human Interactions
• Protists are typically microscopic, but they do play a very important role in the environment
• Photosynthetic protists produce oxygen, some protists are essential parts of aquatic food chains, some protists play a role in the carbon cycle (respiration), and some protists have important symbiotic relationships
• Protist populations can be influenced by temperature and nutrient availability – increase of both can cause algal blooms
Research
• Protists have helped scientists understand fundamental cellular processes like movement
• There have been many experiments about chemotaxis involving protists and their movement toward specific nutrients
• This can help improve the treatment for some cancers and other diseases
http://www.youtube.com/watch?v=8AghW4zzbhU
Industry
• Seaweed is used a food in Japan, Great Britain and some other Asian diets
• We also use protist byproducts like alginate (used in cosmetics, various drugs, etc)
• Carrageenan (red algae) is used in gelatin capsules and some types of cheese
• Diatomaceous earth (from diatoms) is used in detergents, paint removers and some toothpastes
Human Diseases• Malaria – – Caused by Plasmodium spp, trasmitted by mosquitos,
enters blood stream and bursts red blood cells as well as liver cells
• Giardiasis – – Caused by Giardia lamblia, caused severe diarrhea and
intestinal cramps, transmitted through contaminated drinking water
• Toxoplasma – – Caused by Toxoplasma gondii, transmitted through kitty
litter, can be dangerous for developing fetuses and newborn babies
http://www.youtube.com/watch?v=-zsdYOgTbOk