Eukaryotes fossil eukaryotes 2 bya “true nucleus” (prokaryote = “before nucleus”) linear chromosomes membrane bound compartments Figs 6.9, 6.6

Eukaryotes distinctive flagella: 9 + 2 microtubules inserted into cytoplasm surrounded by membrane Fig 6.24

Independent origin of flagella Prokaryotes globular protein flagellin attached to outer membrane Fig 27.6 note: singular of flagella is flagellum similar to bacteria & bacterium

Origin of Eukaryotic Cell Fig 25.9

Serial Endosymbiosis Theory explains how eukaryotic cell evolved prokaryotic symbionts evolved into mitochondria & chloroplasts symbiont lives INSIDE host cell (intracellular symbiont) starts as prey (not digested) or parasite (not lethal)

Serial Endosymbiosis Theory symbiont genes move to host nucleus proteins transported to symbiont symbiont & host become dependent new organism has evolved well accepted; lots of evidence:

1. Similarities between bacteria & mitochondria and plastids Size Circular DNA w/out assoc. proteins Binary fission Ribosome size, biochemistry RNA sequence data

2. Eukaryotic cell biology DNA from organelle in host nucleus Some DNA still in organelle Euk. cells deprived of mito & chlplst CANNOT reproduce them

3. Evidence of Past Symbiosis Glaucophytes Chlplst CANNOT live indply Chlplst has small peptidoglycan wall

4. Modern Day Symbiosis Paramecium bursaria Host and symbiont CAN live indply Remove symbionts, host re-acquires

Types of Endosymbiosis Fig 28.2 Primary: symbiont is prok. 2 chlplst membranes Secondary: symbiont is euk. Evidence for 2ndary endosymbiosis: Extra chlplst membranes Remains of nucleus = nucleomorph (in two lineages)

protist = “the very first” Modern relatives of earliest euk. “protists” = eukaryotes that are NOT plants, animals, or fungi 60,000 species known diverse lineages not closely related heterotrophs, autotrophs in same lineage (also mixotrophs) all w/ PS have chlorophyll a; accessory pigments vary between lineages

body forms of “protists” unicells, colonies, multicellular relatives diversity of form within lineages unicellular—>multicellular many times complex unicells: all functions one cell larger multicellular protists provide habitat

ecological roles of “protists” unicellular (chemo)heterotrophs = protozoa Protozoology (photo)autotrophs = algae Phycology or Algology (includes photosynthetic protists & cyanobacteria) primary producers, base of food web small protists are plankton zooplankton & phytoplankton Fig 28.28

role of plankton in C cycle PS: H2O + CO2 --> (CH2O) + O2 die & fall as “marine snow” C sinks resistant compounds degrade slowly CO2 removed from atmosphere

phytoplankton decline water transparency secchi disk since 1899 >100 yrs of data chlorophyll conc. temp increase Nature July 29, 2010 16