Origin and Diversification of Eukaryotes: Protists

Eukaryotic Cells Nucleus and membrane bound organelles Well developed cytoskeleton – structural support that lends to asymmetric forms May have originated more than 2.7 bya, but 1.8 bya widely accepted

3 stages of diversity documented by fossil records Initial diversification – 1.8 – 1.3 bya Origin of multicellularity 1.3 bya – 635 mya Emergence of large eukaryotes mya

endosymbiosis Symbiotic relationship in which one organism lives inside the bosy or cell of another organism. DNA sequence data suggest that eukaryotes are “combination” organism from Archaea and Bacteria Endosymbiont theory – mitochondria and plastids were formerly small prokaryotes that began living within larger cells. (See page 485)

Multicellularity Colonies – collection of cells that are connected but show little or no cellular differentiation. Multicellular organisms with differentiated cells – Algae, plants, fungi and animals

Characteristics Most diverse kingdom eukaryotic., 1.5 bya Primarily unicellular/multicellular, heterotrophic/autotrophic Usually asexual, some sexual Found in water, damp soil and sand, leaf litter Some are parasitic 14 phyla

Characteristics Characteristics first seen in Protista kingdom Sexual reproduction (varies, mitosis and meiosis – usually in harsh enviro.) Multicellularity (coordination among specialized cells) Complex flagella and cilia (as opposed to simple seen in bacteria)

Protist diversity Heterotrophic protists = protozoans, slime molds, water molds, parasites Photosynthetic protists = Algae Some are classified further by how they move: Amoebas – pseudopodia Ciliates – cilia, ex. paramecium Flagellates – flagella, ex. Euglena

Algae – Green, Red and Brown Strict autotrophs, some multicellular Distinguished by type of pigment they contain Red Multicellular, warm ocean waters Red pigment can absorb light in deep water Brown Multicellular, marine Kelp, grows along coasts, food and shelter Green Most freshwater, uni and multicellular Contains chlorophyll a and b

Green Algae Phylum Chlorophyta Most unicellular, can be filamentous or colonial Chlamydomonas – unicellular green algae Spirogyra – filamentous green algae Ulva – multicellular green algae (sea lettuce) Volvox – colonial (loose association of independent cells) green algae

Red Algae/Brown Algae Phylum Rhodophyta Economically important – Agar Wrappings around sushi Emulsifying agent for production of chocolate Phylum Phaeophyta Contain chlorophylls a and c and carotinoid Kelp, rockweed – grow along shoreline Harvested for human food and fertilizers Algin – pectin-like material added to icecream

Diatoms Phylum Chrysophyta – includes golden-brown algae and yellow-green algae Photosynthetic, significant part of phytoplankton, Important to food chain Double shell made out of silica, like hat box Move by excreting chemicals through Diatomaceous earth – abrasives holes in shell Found in oceans and lakes

Dinoflagellates 2 flagella, cellulose plates Unicellular Most are marine, make up part of the plankton, important food source, producers Some produce powerful toxins – “red tide”

Euglena Freshwater, unicellular with 2 flagella Some photosynthetic with chloroplasts and has ability to ingest food as well Pellicle – protein fiber inside cell membrane, allows for flexibility and shape change Eyespot – light sensitive organ, toward light Contractile vacuole – expels excess water

Zooflagellates Mostly unicellular, hetertrophic protozoans Symbiotic and parasitic forms Trypanosomes – transmitted by tsetse fly Causes African Sleeping Sickness Giardia lamblia – cysts from contaminated water, intestinal wall, severe diarrhea Trichomonas vaginalis – STO, infects vagina and urethra of women, prostate of males

Amoeba Pseudopodia – false foot, cytoplasmic extensions Food vacuole – food enters and moves throughout cell Contractile vacuole – regulates water Entamoeba histolytica – amoebic dysentery

Forams marine protist that lives in sand or attaches to other organisms Tests – porous shells Thin projections of cytoplasm extend through pores and aid in swimming

Paramecium Freshwater streams and ponds Unicellular, heterotrophic Cilia to move Two nucluei Macro – cell activities, includes DNA Micro –cell reproduction, contains chromosomes

Sporozoans – parasitic protists Form spores during their reproductive cycle Nonmotile, spore forming, unicellular parasites Malaria – anopheles mosquito, pg 392 Toxoplasma gondii – toxoplasmosis, during pregnancy, can affect fetus

Slime molds - decomposers Cellular slime mold, small Behave like amoebas Ingest bacteria During stress, form multicellular colonies Plasmodial slime molds Mass of cytoplasm that looks like ooze, colorful Eat bacteria and other organic material, phagocytes

Water Molds Filamentous decomposers Parasitic to plants and animals in ecosystems Cell wall contains cellulose, not chitin Usually have furry growths Responsible for potato famine in Ireland, 1840’s

Beneficial protists Commensal protists that live in digestive tracts of humans and livestock (hay, cellulose) Plankton – food, shelter, producers Largest group of photosynthesizers Abrasives Detritivores – recycle chemicals in environment Symbiotic relationships - coral