lecture 7

Question 1

eukaryotes four groups

Answer 1

protists: mainly uncellular, some mulitcellular
plants: multicellular only
fungi: multicellular only
animals: multicellular only

Question 2

Protists

Answer 2

• these are eukayotes
• mostly of the unicellular variety
• some multicellular protists occur

Question 3

protists are nutritionally diverse group

Answer 3

• 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)

Question 4

protists habitat

Answer 4

-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

Question 5

protists vs prokaryotes

Answer 5

• 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

Question 6

evidence indicates that protest phylogeny is best organized into 5 super groups

Answer 6

1. chromaleveolata
2. rhizaria
3. excavata
4. unikonta
5. archaeplastida

Question 7

how is protists originate

Answer 7

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

Question 8

how did protists orignate part 2

Answer 8

• 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

Question 9

how did protists evolve part 3

Answer 9

• 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