BIO153H5 Lecture Notes - Lecture 19: Protist, Prokaryote, Archaea
Protists
- Foraminifera make up the material that comprise the Egyptian pyramids and the statue(s) sculpted by
Michelangelo. Their shells are made of calcium carbonate. Fora – “window”, and fera – “carries something”
- Diatoms live in glass houses; their shells are made out of silicate and they make intricate structures that come in
numerous shapes, forms, and sizes.
What are Protists?
- Any taxon underlain by the yellow is considered a Protist
- Protists are a…paraphyletic group (a group that includes a common ancestor and some, but not all descendants)
• There is one common ancestor of protists at the very bottom of the tree, but not all of the species in the
diagram are highlighted in yellow, meaning that despite the fact that they are all rooted to one common
ancestor, there are some descendants missing, so it’s paraphyletic
• This diagram is not monophyletic, so it probably doesn’t represent the true evolutionary relationships
together (we need more data to resolve the relationships to result in a monophyletic tree)
- Protists are all Eukaryotes, minus land plants, animals, and fungi
Eukaryotes Have a Membrane-Bound Nucleus
- Contrasted to bacteria and Archaea which lack a membrane-bound nucleus
- When does the membrane-bound nucleus come from? Where did it evolve from?
- The plasma membrane folded from the outside of the cells towards the interior of the cell, eventually forming the
endoplasmic reticulum and the nuclear envelope of the cell
- What’s the big deal of having a membrane-bound nucleus?
• If you have compartments that contain genetic material, you can do things more effectively, as well as some
things bacteria and Archaea can’t do)
This Offers Several Advantages
- Transcription and translation:
• Archaea and bacteria: transcription and translation occur in the same area
• Eukaryotes: transcription and translation are separated
- Different forms of RNA processing
- Gene expression could be better controlled
- Nuclei in eukaryotes are very diverse
Eukaryotes Also Have Organelles
- Organelles are membrane enclosed structures with specialized structures
- One of the reasons bacteria and Archaea haven’t grown very large is because they lack organelles
- Where did they come from?
Lynn Margulis has an Outrageous Idea
- 1970: the origin of Eukaryotic cells
- Originated from ancestral eukaryote cells ingesting bacteria (they engulfed prokaryote cells, and instead of
digesting them, they kept these cells). Over the next evolutionary steps, they become useful eukaryotic organelles
- Proposed the endosymbiosis hypothesis
- Proposed that a eukaryotic ancestor ingested some kind of bacteria, and they don’t inject it or destroy it. Instead,
these cells develop into plasmids as well as mitochondria
(Most) Everybody Thought Margulis was out to Lunch
1. It was so simple, that everybody in biology thought it couldn’t be that
Document Summary
Foraminifera make up the material that comprise the egyptian pyramids and the statue(s) sculpted by. Fora (cid:862)(cid:449)i(cid:374)do(cid:449)(cid:863), a(cid:374)d fera (cid:862)(cid:272)a(cid:396)(cid:396)ies so(cid:373)ethi(cid:374)g(cid:863) Diatoms live in glass houses; their shells are made out of silicate and they make intricate structures that come in numerous shapes, forms, and sizes. Any taxon underlain by the yellow is considered a protist. Protists are a paraphyletic group (a group that includes a common ancestor and some, but not all descendants) This diag(cid:396)a(cid:373) is (cid:374)ot (cid:373)o(cid:374)oph(cid:455)leti(cid:272), so it p(cid:396)o(cid:271)a(cid:271)l(cid:455) does(cid:374)"t (cid:396)ep(cid:396)ese(cid:374)t the t(cid:396)ue e(cid:448)olutio(cid:374)a(cid:396)(cid:455) (cid:396)elatio(cid:374)ships together (we need more data to resolve the relationships to result in a monophyletic tree) Protists are all eukaryotes, minus land plants, animals, and fungi. Contrasted to bacteria and archaea which lack a membrane-bound nucleus. The plasma membrane folded from the outside of the cells towards the interior of the cell, eventually forming the endoplasmic reticulum and the nuclear envelope of the cell.
