Botany: Chapter 20 Notes

Evolution of Eukaryotes Protist = “very first” Protists were the 1 st Eukaryotic Cells to evolve from Prokaryotic Cells First to have nuclei 1 st Eukaryotes were zooflagellates ~ 2.2 bya

Protists! “very first” What are they? There is no universal agreement amongst scientists as to what constitutes a protist Diversity Protozoa – Animal-like protists Algae & Seaweeds – Plant-like protists Slime molds & water molds – Fungus- like protists Range in size Microscopic to 250 ft. tall kelp!

Cellular Organization Most Unicellular Some form colonies – an aggregation of loosely organized cells Some are coenocytic – a multinucleated mass Some are simple multicellular (without specialized cells)

Ways of Obtaining Nutrients Autotrophs – Self nurished Photosynthesize like plants Heterotrophs Absorb nutrients like fungi Ingest food like animals Can be a combination of these

Dependency Many are free living Some form symbiotic relationships with other organisms Mutualism – partnership/both benefit Commensalism – 1 partner benefits/other is neither helped nor harmed Parasitism – 1 partner benefits/the other is harmed

Habitat Most are aquatic (water dwelling) Marine = saltwater environments Freshwater = ponds, lakes, streams Some are terrestrial (land dwelling) Restricted to damp places = soil, bark, leaf litter

Reproduction Mostly Asexual Some Sexual Syngamy – union of gametes

Mobility/Locomotion Waving Cilia Lashing Flagella Flexing individual cells Amoeboid – use a “pseudopodia” = false foot Cytoplasmic Streaming By moving organelles around within the cytoplasm, they are able to change their shape, which allows them to move toward nutrients or away from toxins Some use a combination of these

10 Phyla of Protists 1. Euglenophyta – “Euglenoids” Unicellular 2 flagella Autotrophic – Photosynthetic Reproduce asexually by cell division Dwell in Freshwater Have an eyespot – helps perceive the direction of light

10 Phyla of Protists 2. Dinophyta– “Dinoflagellates” Unicellular, some colonial 2 flagella Some Autotrophic – Photosynthetic A part of marine plankton – base of the aquatic food web Form Red Tides – produce a toxin that attacks the nervous systems of fish, leading to massive fish kills; can become airborne Dinos = “whirling” Mainly asexual

10 Phyla of Protists 3. Oomycota– “water molds” Coenocytic mycelium Mycelium is a body form grows over a food source digests it with enzymes that it secretes absorbs the predigested nutrients made up of hyphae (one multinucleated cell) 2 flagella on zoospores Heterotrophic Contain cellulose and/or chitin in cell walls Caused late blight – p. 389

10 Phyla of Protists 4. Bacillariophyta– “Diatoms” Unicellular, some colonial Most nonmotile; some glide over secreted slime Autotrophic – Photosynthetic Contain silica in shell Freshwater & marine Diatomaceous earth p. 391 White Cliffs of Dover in Britain

10 Phyla of Protists 5. Chrysophyta– “Golden Algae” Unicellular or Colonial 2 flagella or none Autotrophic – Photosynthetic May be covered by calcium carbonate or silica scales Make up part of nanoplankton

10 Phyla of Protists 6. Phaeophyta– “Brown algae” All are Multicellular 2 flagella on reproductive cells Autotrophic – Photosynthetic Ex. Kelp

10 Phyla of Protists 7. Rhodophyta– “Red Algae” Most multicellular; some unicellular Nonmotile Autotrophic – Photosynthetic Can use floridean starch from cell walls to make agar!

10 Phyla of Protists 8. Chlorophyta– “Green Algae” Unicellular, colonial, siphonous “tubular” – giant cells, or multicellular Most flagellated at some stage in life; some nonmotile Autotrophic - Photosynthetic

10 Phyla of Protists 9. Myxomycota– “plasmodial slime molds” Multinucleate plasmodium (changes shape as it moves) Cytoplasmic streaming; flagellated or amoeboid reproductive cells Heterotrophic Reproduce by spores

10 Phyla of Protists 10. Dictyosteliomycota– “cellular slime molds” Vegetative form; single cell Reproductive form; multicellular slug Amoeboid (for single cells) Cytoplasmic Streaming (for multicellular) Heterotrophic Terrestrial

Why are Protists Considered Paraphyletic?