4.1 Flashcards
For how many years has life existed on earth?
Around 3.5 billion years
What is the oldest fossil and where is it located?
Cyanobacteria (from rocks) found in Western Australia
What are the tree main processes believed to be necessary for life to begin on earth?
- synthesis of simple organic molecules (eg amino acids)
- the origin of molecules that can self replicate (the only molecules known to do this today are RNA and DNA)
- the packaging of molecules into membranes with an internal environment that differs in composition from their surroundings
What makes deep-sea vents (hydrothermal vents) thought to be an ideal environment for life to arise?
- The vents warm ocean water to temperatures conducive to life’s processes
- Release of hydrogen-rich molecules and minerals, which may be used by molecules to obtain energy
What are some characteristics of life forms?
- Consist of cells that include a cell membrane and nucleic acids (eg DNA, RNA)
- Control the internal environment
- Control the exchange of materials
- Remove wastes
- Respond to stimuli
- Utilise energy
- Divide, grow and reproduce
In what year were ribozymes discovered, and what did this shift scientists’ attention to?
1986, shifted attention to another nucleic acid - RNA
What does LUCA refer to?
The last universal common ancestor- the most recent common ancestor for all life that exists on Earth today - not a reference to the first life on Earth, but a reference to the population from which all existing life is derived from
What are the three domains of life descending from LUCA?
Archaea, Bacteria and Eukarya.
What is the fossil record referring to?
Generally, the older the fossil, the deeper it will lie in the ground. (see also carbon dating)
What is the oldest eukaryote?
Protozoa
What is the theory of endosymbiosis?
The proposition that chloroplasts and mitochondria were once “free living” prokaryotic organisms which were engulfed by another cell by endocytosis. Opposed to being digested, the prokaryotic evolved within the host cell to have a symbiotic relationship.
What is the evidence supporting endosymbiosis?
- Have inner membranes that resemble the cell membranes of prokaryotes
- Divide by binary fission, similar to prokaryotic cells.
- Have circular DNA similar to prokaryotes
- Have their own protein synthesis system which includes ribosomes that, incidentally are more similar (in size and structure) to prokaryotic cell ribosomes
What is a Stromatolite
Formed from cyanobacteria, and secretes mucus and calcium carbonate
What are three pieces of evidence supporting prokaryotes evolving before eukaryotes?
- Fossil record
- Geo-chemical evidence
- Endosymbiosis
