eukaryotes four groups
protists: mainly uncellular, some mulitcellular
plants: multicellular only
fungi: multicellular only
animals: multicellular only
Protists
- these are eukayotes
- mostly of the unicellular variety
- some multicellular protists occur
protists are nutritionally diverse group
- some protists are autotrophic, obtaining carbon from Co2 via photosynthesis: these protists are called algae
- some protists are heterotrophic, eating bacteria and other protists to acquire carbon, collectively these protists are referred to as protozoans
- some heterotrophic protists can also obtain nutrients via absorbtion, a feature similar to that of fungi
- some protists may be either autotrophic or heterotrophic depending on the availability of light and nutrients (mixotrophs)
protists habitat
-most protists are aquatic
-can be found almost anywhere that there is water: damp, soil, ponds, ect
-some protists inhabit host organisms
(protist shown lives within the gut of a termite)
-this relationship is referred to as an endosybiosis
- a symbiosis refers to a close relationship between organisms of two or more species
-an endosymbiosis refers to one species referred to as an endosymbioant living within another species
-the termite endosymbiosis digest the tough cellulose in the wood diet of the termite, in exchange the endosymbiont has a place to live
protists vs prokaryotes
- protists are eukaryotes they are more complex than prokaryotes
- membrane bound nucleus and organelles
- because protists are mostly unicellular they are the simplest group of eukaryotes
- they are very elaborate cells still
- the single celled protist must preform the same eukaryotic life functions as the multicellular plants and animals
evidence indicates that protest phylogeny is best organized into 5 super groups
- chromaleveolata
- rhizaria
- excavata
- unikonta
- archaeplastida
how is protists originate
endosymbiosis is the theory for the origin of eukaryotic cells
- this theory suggests that eukaryotes evolved when prokaryotes established residence within other much larger prokaryotes
- evidence fro this theory comes from molecular similarities in between prokaryotic cells and present day mitochondira and chloroplasts
- within the eukaryotic cell, mitochondria and chloroplasts even replicate their own DNA
- reproducing in a process similar to that of prokaryotes
how did protists orignate part 2
- it is believed that heterotrophic eukaryotes evolved first:
- these are eukaryotes with mitochondria and no chloroplats
- they do not preform photosynethesis
- autotrophic eukaryotes with chloroplast and mitochondria
- they preform photosynthesis
- suspected that they originated when an individual engulfed an autotrophic cyanobacterium (photosynethetic bacteria)
- this cyanobacterium- containing heterotroph would have had a steady source of food as by products of photosynthesis were produced
- eventually the cyanobacteria would have evolved into a chloroplast
- this eukaryotic linage later evolved into green red algae
how did protists evolve part 3
- this green and red algae then also became endosymbioants when engulfed by heterotrohpic eukaryotes
- the heterotrophic host cells enclosed the algae in food vacuoles but parts of the algae survived digestion and became ceullar organelles
- these endosymbioants which also has the ability to self-replicate provided the host a selective advantage
- this process by which an autotrohpic eykaryotic protist became endosybiotic in a heterotropic eukaryotic protists is called a secondary endosymbiosis
