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20.1 Eukaryotes Acquired Features from Both Archaea and Bacteria

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What are protists?
eukaryotes that are not plants, animals, or fungi
How is the history of the eukaryotic cell?
eukaryotes are monophyletic and a single eukaryote ancestor diversified into the many protists lineages and gave rise fungi, plants, animals; eukaryotes are more closely related to Archaea and Bacteria
What followed the split of Eukarya from Archaea?
endosymbioses with bacterial lineages that led to the origin of mitochondria and chloroplasts; also the environment changed and caused evolutionary changes
What are the steps that the modern euakaryotes cells arose?
the origin of the flexible cell; the origin of the cytoskeleton; the origin of the nuclear envelope (enclosed a genome organized into chromosomes)l the appearance of digestive vacuoles; and the acquisition of certain organelles via endosymbiosis
What happens to the surface area to volume as the cell grows?
surface area to volume ratio decreases
What happens if the surface area can't be increased?
the cell's volume will reach an upper limit
How would a flexible surface help?
it could fold inward and become more elaborate creating more surface area for gas and nutrient exchange; it will have a faster metabolism; can pinch off bits of environment (bring them into cell by endocytosis)
What were some basic changes in eukaryote cells structure and function that occurs a long time ago?
the formation of ribosome-studded internal membranes (some surrounded by DNA); development of more complex cytoskeleton; evolution of digestive vacuoles
How does the eukaryote cytoskeleton differ from a prokaryote?
its more developed and complex
What does the greater development of microfilaments and microtubules do for the cell?
supports eukaryote cells and allows it to manage changes in shape, distribute daughter chromosomes and move materials from one part of its larger cell to other parts.
Why did the nucleus form?
in prokaryotes, DNA is attached to plasma membrane so it would be folded with cell surface structure
What was the step after creation of nucleus?
phagocytosis (ability to engulf and digest other cells)
Why was early organism photosynthesis an issue for many organisms?
when cyanobacteria started generating O2 from photosynthesis, many organisms could not tolerate the newly oxidized environment.
What is endosymbiosis?
certain organelles are the descendants of prokaryotes engulfed (not digested) by ancient eukaryotic cells
What was the crucial event in the history of eukaryotes?
incorporation of proteobacterium that evolved into mitochondria
What was the first purpose of mitochondria?
to detoxify O2 by reducing it to water
What did the mitochondria evolve to do?
the O2 reduction became coupled with formation of ATP in cellular respiration
What is evidence of chloroplast endosymbiosis?
chloroplasts appear in several distantly related eukaryote clades; some groups differ in chloroplast pigments; some eukaryotes have 3+ chloroplast membranes
What is primary endosymbiosis?
all chloroplasts originated with engulfment of one cyanobacterium by a larger eukaryote cell
What about the cyanobacteria was shown in the original chloroplasts?
cyanobacterium have an inner and outer membrane so the original chloroplasts have two surrounding membranes.
What is secondary endosymbiosis?
occurs when the product of primary endosymbiosis is itself engulfed and retained by another free living eukaryote.
What is tertiary endosymbiosis?
occurs when a secondary endosymbiont is engulfed by a cell, and that engulfed cell becomes symbiotic within the engulfing cell. and reproduces in the body of the engulfing cell and passes to both new cells when there is fission (reproduction)
What are the key events in the evolution of the eukaryotic cell?
-Origin of a flexible cell surface
-Changes in cell structure & function
-Cytoskeleton
-Internal membranes
-Lysosomes
-Endiosymbiosis
What are the specific structual changed in the evolution of eukaryote cell?
-Protective cell wall lost
-Infolding of plasma membrane to increase SA
-Cyotoskeleton formed
-Internal membranes with ribosomes formed
-DNA enclosed in a membrane
-Microtubles form flagella enabling movement
What is the endosymbiotic theory?
-Mitochondria formed through the endosymbiosis of a proteobacteria
-Chloroplast formed from the endosymbiosis of a cyanobacteria
What is the evidence for endosymbiosis?
-New mitochondria & plastids are formed only by a process similar binary fission
-Mitochondria & plastids are surrounded by at least two membranes
-Innermost membrane composition is similar to bacteria cell wall composition
-Mitochondira & plastids contain DNA
Sequence of this DNA is similar to bacteria
-Internal stucture and biochemistry of plastids is similar to cyanobacteria