The Protists Chapter 20 https://www.youtube.com/watch?v=Ln69k7LyTsU

What is a protist? A mixed bag of organisms Anything that is not a plant animal fungi prokaryote

General characteristics Eukaryotic Can be single-celled, colonial, or multicellular Some are microscopic but not all Can reproduce sexually and asexually

When did they evolve? Fossils of eukaryote protists date back to about 1.5 billion years ago.

How did they get their organelles? 1)By endosymbiosis (Margulis’s hypothesis) - a prokaryotic cell engulfed another cell that could carry on photosynthesis or aerobic respiration and those became chloroplasts and mitochondria. 2) Infolding of cell membrane (endocytosis) to enclose DNA (nucleus) and make ER and Golgi complexes

endocytosis endosymbiosis

Protists are difficult to classify. Protista is one kingdom in the domain Eukarya.

Protist classification will likely change. Some protists are not closely related. Molecular evidence supports reclassification.

How are they generally classified? By their mode of nutrition This is NOT an evolutionary classification 1) plant-like - autotrophic 2) animal-like - heterotrophic 3) fungi-like - those that live on dead and decaying matter (saprophytic)

Protist Category How they get their food Body Form Animal-like Single-celled, colonial, or multicellular decomposer multicellular

Protist Category How they get their food Body Form Animal-like heterotrophic Single-celled Plant-like Autotrophic photosynthetic Single-celled, colonial, or multicellular Fungi-like Decomposer saprophytic multicellular

Are protists more closely related to animals or to bacteria?

What type of protist is moe closely related to animals?

Animal-like Protists – classified by how they move Generally called Protozoa (proto – first; zoa – animal) Most reproduce asexually by binary fission

Protozoa with Flagella ex Peranema

Some are important disease-causers. Importances: Some live inside of other animals such as in termites to help them digest wood. Some are important disease-causers.

This flagellate Trichonympha – lives in termite guts This flagellate Trichonympha – lives in termite guts. The protist gets food and shelter. The termite has something to digest the wood!

Protozoa with Pseudopodia Pseudopodia (false foot) result from streaming of cytoplasm (amoeboid movement), used for movement and food gathering Ex – amoeba, forams

Amoeba http://biog-101-104.bio.cornell.edu/bioG101_104/tutorials/protista/movies/Amoeba.MOV Exhibition of Movies on Protists

Amoeba capture their food by surrounding it with their pseudopodia.

Forams Foraminiferans (forams) are “shelled” amoebas. They have pores in their shells in which the pseudopodia could stream out for movement.

Forams shells make up beach sand in the Caribbean.

The White Cliffs of Dover Impressive and dramatic, the White Cliffs of Dover keep watch as a citadel over the southern entrance into the Strait of Dover, which separates England from France. They are made of forams in addition to limestone deposits.

Protozoa with Cilia Cilia are short, hair-like structures Unicellular Most are free-living Ex - Paramecium https://www.youtube.com/watch?feature=player_detailpage&v=a4aZE5FQ284

Paramecium diagram. The parts are as follows: 1) food vacuoles 2) micronucleus 3) oral groove 4) gullet 5) anal pore 6) contractile vacuole 7

Structural Features They have contractile vacuoles to pump out excess water. They have two nuclei: micronucleus and macronucleus. Micronuclei are exchanged in conjugation

Conjugation in Paramecium They exchange micronuclei – adds genetic diversity

Animal-like Protists that Cause Disease Trypanosoma – African Sleeping sickness, transmitted by tsetse fly Plasmodium – causes malaria, transmitted by mosquitoes Giardia – causes intestinal problems, found in contaminated water

Trypanosoma Causes African sleeping sickness

Life cycle of a plasmodium in malaria. It moves through a mosquito and then to humans.

Giardia – bad boy in bad water

Plant-like Protists Not like plants – no roots, stems, leaves, or same reproductive structures Make up large part of phytoplankton Photosynthetic, unicellular protists are called algae Larger forms are called seaweeds

In this group are unicellular, colonial, and multicellular organisms

Euglenoids Ex- Euglena Single-celled, have flagella No cell wall, pellicle covering instead Have red eyespot for detecting light Are myxotrophic (can be autotrophic and heterotrophic)

Dinoflagellates Called “fire plants” because some are bioluminescent Unicellular Some are auto, some are heterotrophic Have armor-like cell walls, 2 flagella Cause red tides (algae blooms) that are toxic to fish Some help build coral reefs

Diatoms Unicellular Cell walls made of silicon glass that fit into each other like a petri dish Major part of plankton, produce about ½ of oxygen we breathe Make diatomaceous earth for abrasives cleaners, pesticides, and filters Found in fresh and salt water

Multicellular algae are classified by their pigments. Green algae Brown algae Red algae

Green Algae Found in fresh and salt water and on land Contain pigments chlorophyll a and b and carotenoids Can be unicellular, colonial, or multicellular Share similarities with plants (ancestors) - cellulose cell walls - same chlorophyll pigments - store food as starch Can cause algae blooms http://www.funsci.com/fun3_en/protists/exhibition.htm#amoebae

Unicellular Multicellular Colonial

Volvox A colonial algae Daughter cells

Brown Algae Marine, multicellular Contains chlorophyll c Largest seaweeds (contains the Kelp) Used as food

Red Algae Marine, multicellular Contain red pigments in addition to chlorophyll Seaweeds that live at great depths Have mutualistic symbiotic relationships with coral animals and forams Used commercially in milk products, cosmetics, sushi, ice cream

Reproduction The plant-like protists can reproduce both sexually and asexually with some alternating stages.

Fungi-like Protists Like fungi in that they are decomposers and have similar structures (hairy and produce spores on stalks) Different from fungi since some have cells (spores) that can move Main groups: slime molds water molds

Slime Molds Important decomposers Two types: Plasmodial (large multinucleate mass) Cellular (individual cells congregate to form a mass called a pseudoplasmodium.

A plasmodial slime mold

Forming a pseudoplasmodium from individual cells

Under stressful conditions, they will form stalks with spores Stalk with spores Plasmodium https://www.youtube.com/watch?v=GY_uMH8Xpy0

Water Molds May appear as white fuzz on dead things Fungi-like due to hairy (hyphae) structures Important disease causers Great Potato Famine in Ireland in 1846 - caused mass migration of people to the US

Hyphae

Importances of the Protists Recyclers and decomposers Carry on ½ of world’s photosynthesis Important in symbiotic associations ex – trichonympha in termite guts to help digest cellulose Food supply Homes for organisms (seaweeds) Commercial products Disease causers – infect water supply, also many parasitic diseases such as malaria