16 terms

Chapter 27.1 How did the Eukaryotic Cell arise?

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scientists conclude that eukaryotes are monophyletic and that a single eukaryotic ancestor diversified into many different
protist lineages as well as giving rise to the plants, fungi, and animals
mitochondria and chloroplasts of eukaryotes are clearly drive from
bacterial lineages
5 events significant in the origin of eukaryotic cell
1. origin of a flexible cell surface: cell wall was lost
2. the origin of a cytoskeleton
3. the origin of a nuclear envelope, which enclosed a genome organized into chromosomes
4. the appearance of digestive vacuoles
5. the acquisition of mitochondria and chloroplasts via endosymbiosis with cyanobacteria
Flexible cell surface: first step toward the eukaryotic condition was the loss of the cell wall
with out the cell wall, cells can infold and create more surface area for gas and nutrient exchange.
flexible surface can pinch off bits of the environments and bring them into the cell by endocytosis
changes in cell structure and function. three advances
1. formation of ribosome studded internal membrans
2. development of complex cytoskeleton
3. evolution of digestive vacuoles
cytoskeleton is in both
prokaryotes and eukaryotes
but is more complex in the eukaryotes
primary feature of eukaryotic cell is
evolution of a nucleus
Endosymbiosis
cyanobacteria were generating oxygen gas a a product of photosynthesis. Theory of endosymbiosis proposed that certain organelles are the descendants of prokaryotes engulfed, but not digested, by early eukaryotic cells.
crucial event in the history of eukaryotes was the incorporation of the proteobacterium that evolved into the
mitochondria. Initially, the new organelle's function was to detoxify O2 by reducing it to water. Later, this reduction was coupled with ATP in cellular respiration.
photosynthetic eukaryotes are the result of
incorporation of a prokaryotes related to cyanobacteria which became the chloroplast
chloroplasts have been
transferred among eukaryotes several times
all chloroplasts trace their ancestry back to the
engulfment of one cyanobacterium by a larger eukaryotic cell-- known as primary endocymbiosis
the original chloroplasts had two
surrounding membrane.
primary endosymbiosis give rise to the chloroplasts of
red algae, green algae, and land plants.
secondary endosymbiosis
euglenid: their ancestor took up a unicellular green alga, retaining its chloroplasts and eventually losing the rest of the constituents of the alga
tertiary endosymbiosis
dinoflagellate apparently lost its chloroplast and took up another protist that had acquired its chloroplasts through secondary endosymbiosis
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