Botany: Chapter 20 Notes
Evolution of Eukaryotes
 Protist = “very first”
 Protists were the 1st Eukaryotic Cells to evolve from
Prokaryotic Cells
 First to have nuclei
 1st 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 – Funguslike 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?