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Themes in the Evolution of Protists
Larger Cell Size
• Larger cells make possible the evolution of diverse structuresand functions.
• Compartmentalization increases the available surface area in the interior of cells, easing food & waste transport in & out of the cell.
Paramecium: a unicellular cilliate
Themes in the Evolution of Protists
Locomotion
• Pseudopods
• Protists can be motile by means of cilia or flagella.
2 singlemicrotubules
9 pairedmicrotubules
Flagella Cilia
The structure of eukaryotic flagella and cilia is different than prokaryotic flagella
Themes in the Evolution of Protists
Multicellularity
Volvocales spp. range from unicellular to colonial to multicellular.
Chlamydomonas Gonium Pandorina Volvox
Some protists are clearly multicellular
This green alga, called Coleochaete orbicularis, is multicellular.
Its cells are packed tightly together and are differentiated in form
and function.
Themes in the Evolution of Protists
Meiosis and sexual reproduction
• Meiosis makes eukaryotic sexual reproduction possible.
Meiosis
A1 A2
A1 A2
Parentalgenotype Gametes
A1 or A2
Fertilization
Offspring genotypesA1 A2A1A1
A2A2
Sexual reproduction produces genetic variability
Chlamydomonas
(n)
ASEXUALREPRODUCTION
SEXUALREPRODUCTION
(n)
(n)
(n)
(n)
(2n)
Zygote
Gametes
Maturecell
SYNGAMY
MEIOSIS
(n)
Haploid
Diploid
Some protists may alternate between sexual and asexual reproduction
Giardia lamblia, a diplomonad
Giardiasis is a diarrheal illness sometimes known as “Traveler’s Disease”
Group 2: Euglenozoa
Typically unicellular
Characteristic type of flagella (1-2 flagella)
Autotrophic, heterotrophic, or mixotrophic
Euglena
Group 2: Euglenozoa- Others Trypanosomes- Parasitic
•Trypanosoma brucei- •African Sleeping Sickness•Carried by Tsetse flies
•Trypanosoma cruzii- •Chagas disease•South America
•Leishmania spp. •Worldwide parasites•Transmitted by sandflies
Group 3: Aveolata
Dinoflagellates
Primary producers in coastal areas
Armored cellulose walls
Two whip-like flagella
Gonyaulax – red tide
Group 3: Aveolata
Apicomplexans
All obligate Parasites
• Plasmodium--> malaria
Mass of organelles at one end (penetrate the host)
Spore-forming
Group 3: Aveolata
Ciliates
Cilia- short hair-like flagella used for feeding and moving
Oral groove
Multi-nucleate
Reproduce by fission and conjugation
Paramecium
Stentor
Group 4: Stramenopila
Oomycotes (water molds)
Fungi-like heterotrophs
Most live in fresh water or moist soil where they are important decomposers of plant detritus
Downy mildew
Potato Blight and the Irish
Potato famine
Group 4: Stramenopila Diatoms
Glass cell walls
Major component of marine plankton
Major contributor to marine photosynthesis
Sediment to form diatomaceous earth
Algae: Plant-like Protists Algae are AUTOTROPHIC Protists- they perform
PHOTOSYNTHESIS.
Often called “seaweeds”= brown, red, green algae
Red: chlorophyll a and phycobilins
Brown: chlorophyll aand chlorophyll c
Green: chlorophyll aand chlorophyll b
Algae: Plant-like Protists
Algae are Different from Plants because they LACK Tissue Differentiation and have No True Roots, Leaves or Stems.
Group 5: Rhodophyta
Red Algae
No flagellated stages
Color from phycoerythrin
Often used to make cosmetics, gelatin capsules, agar
Group 6: Chlorophyta
Green Algae
Not monophyletic
Closely related to plants
common ancestor of green algae and plants--> chloroplasts through endosymbiosis of cyanobacteria
mostly freshwater
Unicellular, colonial, multicellular
Group 8: ????
Hodge-podge of organisms with unknown phylogeny
Use pseudopods for moving and feeding
Rhizopods (Amoeba)
Actinopods
Foraminifera Phagocytosis in Amoeba