Chapter 4.1 The origin of life on Earth Flashcards
Evidence shows that life has existed on Earth for around 3.5 billion years, during which time it has diversified. Existing cells are the products of evolution. Membranes may have formed spontaneously and the first simple cells may have used RNA as genetic information. Ribozymes may have played a role in this development. Describe the possible roles of RNA and ribozymes in the first simple cells. There is evidence that prokaryotic cells existed before eukaryotic cells. Describe this evidence
When did earth first form?
Earth formed about 4.5 billion years ago (through big bang theory;hypothesis) where it was very hot and there was no biological moleulces.
When was life first on earth
A billion years after earth formed (3.5 billion years ago) was when we first got life on earth through which is was inhabitable
What is cell thoery?
- All organisms consists of cells or the product of cells
- All cells come from pre-existing cells through cell division
- Cells are the building blocks of life
leaving scientists with the interesting dilemma; if all cells come from pre-existing cells where did the first one come from.
What are the oldest widely accpeted fossils?
Oldest widely accepted fossils are cyanobacteria ( from rocks in Western Australia and are about 3.5 billion years ; traced through carbonate fossils.
What proccesses are thought to be necessary for life to begin on earth?
- Synthesis of simple organic molecules (amino acids)
- Origin of self-replicating molecules (DNA/RNA)
- Packaging of molecules into membranes (different intra and extra cellular
environments)
Whats is the Miller and Urey experiment
The Miller and Urey experiment (sometimes called the primordial soup thoery) was a simulation of early life on earth and demonstrated that organic molecules (amino acids, nucletoides, ATP) can form from inorganic compounds (when put under the right conditions)
Why is the Miller and Urey experiment important?
The Miller–Urey experiment was proof that the building blocks of life could be synthesized abiotically from gases, and introduced a new prebiotic chemistry framework through which to study the origin of life.
Did the first cells have DNA or RNA?
Evidence that RNA arose before DNA in evolution can be found in the chemical differences between them: RNA is self replicating, came about though organic molecules and uses ribozymes (parallel to enzymes in DNA).
Therfore it can be suggested the first cells may have had RNA.
Describe the importance of the emergence of the cell membrane
The cell memebrane is like a barrier that surrounds the cell, seperating the insdie from the outside and is made up of lipids and proteins (fluid mosiac model).
What evidence is there that prokaryotic cells existed before eukaryotic cells?
- prokaryotic cells are much simpler and have no membrane bound organelles
- prokaryotic cells can surive in harsher conditions/environments( early earth vlocanic activity and radiation)
- fossil records (carbonate rocks’cyanobacteria’)
Whats is the process of endosymbiosis?
Endosymbiosis is the process through which a prokayrotic cell gets englulfed by another (due to an evolutionary adavnatge e.g. photosynthesis or respiration) resulting in a mutually benefical relationship.
*played a significant role in the evolution of eukaryotic cells**
What evidence is there of endosymbiosis
- Mitochondria and chlorplast have two membranes (internal): The inner membrane resembles the cell
membrane of prokaryotes. - They contain small amounts of their own
circular DNA: Similar to prokaryotes - They can divide via binary fission and have
their own protein synthesis system
State one piece of physical evidence to support this
hypothesis that prokaryotic cells probably existed before
eukaryotic cells.
Fossil are the physical piece of evidence
State and explain one piece of evidence to support the
hypothesis that the evolution of eukaryotic cells probably
involved endocytosis events.
Double membrane or their circular DNA traces
Name the type of molecule, with the ability to store and
transmit genetic information in the first simple cells.
RNA for simple cells
State how a protein could have been produced in the first simple cells in the absence of DNA
Through ribozymes
