Protists Flashcards
Domain and Kingdom?
Domain: Eukarya
Kingdom: “Protista”
What’s special protists?
Not monophyletic. It is paraphyletic (common ancestor and some but not all groups). Kingdom “Protista” is a catch all for eukaryotic cells that do not fall under plants, animals, or fungi.
History of Eukaryotes
Nuclear envelope, mitochondria, endoplasmic reticulum, and other membrane bound structures are present. Oldest unicellular eukaryote is 1.8 billion years old. Red algae is the oldest multicellular specimen at 1.2 billion years old.
About the Kingdom:
Most eukaryotic lineages are protists. Most unicellular, some colonial, and some multicellular. No chemoautotroph or photoheterotroph eukaryotes. Only photoautotrophs, heterotrophs, and mixotrophs (hetero and photoatuo pathways, usually only one used at a time though). Free-living and parasitic heterotrophs.
Photosynthetic protists are called what?
Heterotrophic protists are called what?
Algae
Protozoa
Endosymbiont Theory
Multicellularity evolved multiple times. Mitochondria come from Alpha subgroup of Proteobacteria. Chloroplast as a cyanobacteria to form endosymbiosis with eukaryote. Mitochondria and chloroplast formely small independent prokaryotes that began living as symbionts within larger cells. Discovered in 1910 when chloroplast division was seen to have been similar to that of binary fission.
Steps for Endosymbiosis to Occur
- Prokaryote lost cell wall in order to grow larger and develop infoldings of cell membrane to increase surface area to volume ratio.
- Infolding of cell membrane.
- Pinching off of membrane leads to an internal membrane structure.
- Proteobacterium enters newly formed eukaryote as prey or parasite and avoids digestion and over time becomes mitochondria producing ATP for the cell.
- Some eukaryotes go on to acquire endosymbiosis in the form of cyanobacteria to have chloroplasts.
On the phylogenetic tree of life:
mitochondria at the base of all eukaryotes as derived trait. Chloroplasts occur at the base of Archaeplastida for “Protista”.
Evidence for Endosymbiotic Theory
Mitochondria and chloroplast inner membrane is similar to membrane structure of gram negative bacteria. Cell division of mitochondria and chloroplast looks a lot like binary fission. Transcribe and translate their own DNA. DNA structure is circular just like bacteria.
Supergroups of Kingdom “Protista”:
Excavata
SAR Clade
Archaeplastida
Unikonta
Excavata Supergroup contains:
Diplomonad Clade
Parabasalid Clade
Euglenozoan Clade
-All possess an excavated feeding groove
Euglenozoan Clade
Heterotrophs, autotrophs, mixotrophs, and parasites. Crystalline rod cross section of flagella. Rod is crystalline or spiral in flagella.
2 Phyla in this Clade: Euglenids and Kinetoplastids
Euglenid Phylum
Mixotrophs. 2 flagella running parallel to one another. One long and one short. Pellice (protein band that provides strength and flexibility) present. Allows for scrunch up and burst off movement.
Kinetoplastid Phylum
Large mitochondria contains kinetoplasts (organized mass of DNA). All are heterotrophic (marine, freshwater, and terrestrial). Parasites present in this phylum: Trypanosoma (resposible for African Sleeping Sickness). Has a “bait and switch” immune defense - after a few generations can completely switch its surface proteins.
Diplomonad Clade
“Double cell”. Two nuclei in each cell. Reduced mitochondra called MITOSOMES. Makes them incapable of electron transport and oxygen use. Obligate anaerobes. Multiple flagella. Many are parasites, such as giardia.
Parabasalid Clade
Reduced mitochondria called HYDROGENOSOMES. Even less capable of carrying out cellular respiration. Very limited anaerobic functions. H2 gas as a byproduct. Exist as a symbiont with host or as a parasite. Trichomonas vaginalis is an STD and an example of a parasite. Trychonypha campanula and bacter are a symbiont within termites that allow them to ingest wood.
SAR Clade Sugergroup contains:
Stramenophile Clade
Alveolate Clade
Rhizaria Clade
- No one unique synapomorphy (shared derived trait) for this supergroup.