origin and diversification of eukaryotes: protists
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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 635-535 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