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BILD 3 Lecture Notes 4

BILD 3 Lecture Notes 4 - BILD 3 Lecture Notes 4 Eukaryotes...

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BILD 3 Lecture Notes 4 Eukaryotes: general Derived character states of eukaryotes - Presence of a cytoskeleton - Nucleus and organelles are bound by membranes - Chromosomes are linear, multiple Age: at least 2.1 bya Endosymbiotic theory - mitochondria and the chloroplast were originally small prokaryotes, engulf by larger host cells (eukaryotes) o an example of massive horizontal gene transfer - mitochondrion: in plants and animals o heterotrophic prokaryote engulfed now responsible for respiration - chloroplasts: in all plants, algae o a photosynthetic prokaryote (a cyanobacterium ) engulfed now responsible for photosynthesis - all eukaryotes have mitochondria, but not all have chloroplasts o mitochondrial endosymbiosis happened first, THEN this cell engulfed a cyanobacterium to produce the photosynthetic eukaryote lineage (plants and algae) o see below: - evidence o similarity in structure between inner mitochondrial/chloroplast membranes and bacterial membranes o they have their own DNA, and it is circularized (like prokaryotes) o gene similarity between the mitochondrial/chloroplast genome and bacteria - secondary endosymbiosis: engulfment of a eukaryote with a chloroplast by ANOTHER eukaryote
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o responsible for the birth of many algal lineages o you can see extra sets of membranes in these cases Protists Important: the group “protists” is defined as mostly-unicellular eukaryotes that are not animals/plants/fungi therefore this group is PARAPHYLETIC - meaning it contains the common ancestor of eukaryotes, but only some of its descendants (excluding animals, plants, fungi) Examples of protists: - Giardia, responsible for intestinal disorders (giardiasis) - Trypanosoma, responsible for sleeping sickness o Carried by the Tsetse fly vector - Dinoflagellates, members of the phytoplankton (photosynthetic aquatic free-living cells) o Can cause red tides o Can be bioluminescent - Diatoms, also part of the phytoplankton o Have cool silica shells -
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