MICR 2420 Lecture Notes - Lecture 5: Saprotrophic Nutrition, Agarose, Sargassum
27 Jun 2018
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Differences in Eukaryotes, bacteria and Archaea
Eukaryotic Diversity is Profound
Widest diversity in form and size in the tree of life
From blue whales and sequoias to tiny algae such as Ostreococcus tauri (green algae, less
than 2 micron) and structurally beautiful diatoms
How do we classify such a diverse group of organisms?
While the structure and form of eukaryotes is profound, their metabolism is not as
complex as for the prokaryotes
All eukaryotes descended from an ancestral cell that engulfed a bacterial endosymbiont –
which became a mitochondrion
All phototrophic eukaryotes descended from an ancestral cell that additionally engulfed
the bacterial ancestor of chloroplasts
Thus most eukaryotes conduct oxygenic photosynthesis, or heterotrophy, or both
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Where do animals (metazoa) fit into the eukaryotic tree?
Emerging utility of genome sequencing is allowing us to determine this for the first time
For eukaryotes, rRNA genes are ambiguous
oNeed something better
Look for a gene deletion or insertion unique to one clade
Baldauf et al., University of York
oFound a stretch of DNA encoding 12aa – present in animals and fungi but absent
from plants and most protists
oElongation Factor-1α (EF-1α)
Thus animals and fungi fit in one clade – the opisthokonts
Why do we care who our closest non- animal relatives are?
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They can be used as models to answer key questions
oExample: basis of cancer and aging
It is important to define differences clearly
oThey can be exploited, example: treatment of fungal infections
Eukaryotes in a Nutshell
Show greatest range of size and shape of all three domains
Animals and fungi are closely related
The plants and (primary) algae (“macroalgae”) are closely related
The protists are polyphyletic and highly divergent and include secondary algae
Common Features:
Membrane bound organelles
Sexual and asexual reproduction
Multicellular forms are differentiated
Protist: single celled and colonial eukaryotic microbe, usually motile; not a fungus
-includes protozoa & algae
Protozoa: a single celled heterotrophic eukaryotic microbe, usually motile, that is not a
fungus
Algae are two kinds-
Primary algae- derived from single endosymbiotic event and are closely related to green
plants
Secondary algae- various groups of heterotropic protest, in second event of
symbiogenesis
The protozoa are predators of the microbial world (heterotrophs)
The protozoa consume their prey through phagocytosis
The protozoa lack cell walls but live in water
Contractile vacuoles are membrane bound organelles to control the effect of osmosis
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Document Summary
Widest diversity in form and size in the tree of life. From blue whales and sequoias to tiny algae such as ostreococcus tauri (green algae, less than 2 micron) and structurally beautiful diatoms. While the structure and form of eukaryotes is profound, their metabolism is not as complex as for the prokaryotes. All eukaryotes descended from an ancestral cell that engulfed a bacterial endosymbiont which became a mitochondrion. All phototrophic eukaryotes descended from an ancestral cell that additionally engulfed the bacterial ancestor of chloroplasts. Thus most eukaryotes conduct oxygenic photosynthesis, or heterotrophy, or both. Emerging utility of genome sequencing is allowing us to determine this for the first time. For eukaryotes, rrna genes are ambiguous: need something better. Look for a gene deletion or insertion unique to one clade. Baldauf et al. , university of york: found a stretch of dna encoding 12aa present in animals and fungi but absent from plants and most protists, elongation factor-1 (ef-1 )
