Protists The first Eukaryotes

Origin of Eukaryotic Cells Endomembrane system- developed from infolding of plasma membrane. Evolutionary advantage? compartmentalization, microenvironments, increased membrane surface area

Endosymbiotic Theory Inside together living. Plastids and mitochondria are a result of the endocytosis of bacteria by larger cells of the lineage that become eukaryotes. All eukaryotes got mitochondria only some got chloroplasts.

Endosymbiotic Theory Evidence 1) C & M have their own DNA ( circular, no histones) 2) C & M have their own ribosomes (small like bacteria) 3) C & M have 2 membranes (outer like eukaryote, inner like bacteria) (homologous transport proteins) 4) C & M replicate on their own 5) Endosymbiosis observed where prey or parasites become mutualistic symbionts

Secondary endosymbiosis of red or green algae create chloroplasts with 4 membrane layers

Endosymbiotic Algae

Importance of Protists Large component of photosynthetic plankton Diatoms, dinoflagellates, Many are Endosymbionts Cause human disease: Giardia (hikers diarrhea), Trichomonas (STD), Trypanosoma (sleeping sickness), plasmodium (malaria),

Protists = Eukaryotes that are not Plant, Animal or Fungus 1) Most are unicellular 2) None have true tissues (so not plant, animal or fungi) 4) Some animal-like(ingest food), some plant-like(photosynthetic ) some Fungus-like (saprobes) 5) Paraphyletic group so not a kingdom (share a common ancestor but does not include all the descendants of that ancestor)

Proposed ‘Supergroups’ of Eukaryotes

Brown Algae Brown pigments absorb wavelengths of light that reach deeper into the water. Largest multicellular algae Sargassum kelp 

Sargasso Sea

Algae parts…

Oomycotes (egg fungi) Saprobe (absorb food) parasites & decomposers Lost chloroplasts Rusts water molds

Chlorophyta Green algae (chlorophyll) Most similar to plants Unicellular …Desmids Multicellular…filamentous algae & volvox Complex life cycles

Red Algae Red pigments absorb wavelengths of light even deeper in the water. (green & blue) phycobilins Used to make thickeners & agar Multicellular Complex life cycles

amoebozoans Complex life cycles Closest to Animals and Fungi All have pseudopods Free-living Amoeba, slime molds, & parasites Free-living & Slime molds important decomposers

Plasmodial Slime mold

Cellular Slime Molds - cAMP