Evolution Lecture 8 Flashcards
(30 cards)
Three domains of life?
Bacteria, Archaea, Eukarya.
Bacteria, Archaea & most eukaryote groups are microbial life-forms. Each domain has its own biologically unique characteristics.
Prokaryotic Cells
Bacteria and Archaea. They are singular celled. Have less DNA. To small to see with the naked eye.
Taxis
What 50% of all prokaryotes are capable of doing. A directed movement toward or away a stimulus (eg. nutrients.)
First direct evidence of life came from what?
Fossilized stromatolites.
Stromatolites
Layered rocks that form when certain prokaryotes bind thin films of sediment together.
How do some Bactria move?
Flagella
Importance of Prokaryotes
On Earth for ~3.5 billion years. First cellular life on earth.
Responsible for most of biological activity in
many ecosystems (e.g. Ocean; Soil). Very important for the earth.
More prokaryotes than human cells in body.
Cause many major diseases & infections. They interact with us.
Biotechnology. Used to make pharmaceuticals.
Bacteria
Includes almost all well-known prokaryotes
– e.g. all known disease-causing species. Often the shape is circular or short rods.
How do bacteria reproduce?
Binary fission. One cell pinching to become two cells.
Bacterial cell envelope?
Usually two bounding membranes: Plasma membrane and outer membrane. Peptidoglycan wall between the membranes (complex polymer of sugars and amino acids). It has its own biochemistry.
Gram-postive Bacteria
Have simpler walls with a relatively large amount of peptidoglycan. No outer membrane. Many soil bacteria, also many causes of diseases. Have the ability to make these really resistant cell stages (because of thick peptidoglycan wall).
Gram-negative Bacteria
Has less peptidoglycan and are structurally more complex, with an outer membrane that contains lipopolysaccharides.
What are Gram-negative Bacteria and Gram-postive Bacteria used for?
Used in medicine for treatment implications.
A few types of bacteria?
– Spirochetes
– Gram-positive bacteria
– Cyanobacteria (photoautotrophs)
– Proteobacteria
Spirochetes
Has a distinct shape (long and think spiral structures). They swim rapidly like a corkscrew. They typically cause diseases.
Cyanobacteria (photoautotrophs)
Photosynthesis in ocean is formed by this important photoautotrophs. Perform oxygen photosynthesis.
Proteobacteria
Very diverse, ie. E coli.
Archaea
Some (many) are extremophiles (live under extreme conditions) e.g. Some are extreme thermophiles
(some grow at 110°C). Many are methanogens (live in low oxygen environments) - produce methane as a waste product of energy metabolism. Not as well known.
Archaea cell envelope?
No ‘outer membrane’; no peptidoglycan. Cell membrane lipids are chemically different from those of Bacteria and eukaryotes. They have branched hydrocarbons. This is because the biochemical process that makes them is a different process.
What are most similar?
Archaea and Eukaryotes. The architecture of RNA polymerase in them are very similar.
Polytomy
The point where the relationship amount species is unknown.
Bacterial origins of mitochondria and plastids (chloroplasts)?
Endosymbiosis is where bacterial cell became incorporated into a eukaryotic cell.
The origin of eukaryotic cells?
Endomembrane system, including nuclear envelope
evolves conventionally (not by symbiosis). Endosymbiotic alphaproteobacterium becomes mitochondrion. Endosymbiotic alphaproteobacterium
becomes mitochondrion. It’s likely that a bacterium swallowed by a more complex Archaea- related call eventually evolved into a mitochondrion- a major step in eukaryote evolution. It lost many features of the cell, independent cell organelles.
Ancestors of modern eukaryotes were what?
Very prokaryotic like, with very few internal cell organelles.
