SH1: Origins and diversity Flashcards
How was oxygen brought into the early atmosphere?
Evolution occurred and photosynthetic bacteria arose which developed a form of photosynthesis which gives out oxygen. Atmosphere oxygen levels increased, then eukaryotes appeared.
Describe the Miller-urey experiment.
Shows ammonia, water and hydrogen form hydrocarbon chains which go onto make amino acids, nucleotides and more complex molecules which was said to form in the air and accumulate in the ocean.
The experiment mimics the conditions of early earth and saw what chemicals might form. Experiment contained water mimicking sea water- the water was heated to evaporate to represent the atmosphere in a separate compartment (this compartment held gases thought to be present in early earth), induce electrical discharge to mimic lightning, condense gas back into water, and run this over weeks.
Analysed in the water and found amino acids, nucleotides and other complicated organic molecules- these molecules are called geochemicals.
Since then scientists have done more experiments to find plausible synthetic routes that other organic molecules would have been made in the early earth.
How do you get from chemical complexity to life?
- You need to combine processes that make energy (metabolism and respiration) with the ability to have and replicate genomes. This happens independently in living systems.
- Cell formation (compartmentalisation) in order to contain molecules.
- Redox couples to power metabolism as it makes energy.
What are RNA’s with catalytic activity called?
Ribozymes
What catalytic activity does Ribozymes have?
Intrinsic catalytic activity- one of its activity’s is polymerase activity as it has the ability to copy.
What needed to go into a cell to give us LUCA?
Metabolism and respiration and nucleic acid replication and macromolecules and selection evolution and time
What is panspermia ?
Another explanation for life on earth which is the theory that life did not originate on earth but from elsewhere in the universe. The problem with this is that we still need to explain how life originated.
Characteristics of current terrestrial life (life on the planet):
- All cells are bound by a lipoprotein membrane/ phospholipid membrane this controls what goes in and out of the cell
- ATP is made from ion (proton) gradients
- There are common biomolecules within cells (RNA, DNA and common metabolism)
- All cells are either single cells or multicellular
- Either reproduced individually (asexual) or in pairs (sexual)
The fact that all cells are very common means:
- They all share a common ancestor (complex organism called LUCA)
- LUCA had all the biochemistry that is now universal
Describe the 5 kingdom classifications and its limitations.
Plants, fungi, animals, single celled eukaryotes and monera (prokaryotes). This system suggests that animals’ plants and fungi are more evolved than the other groups which is not true.
Describe how the 3 domain classification was thought of.
Based on ribosomal RNA sequencing. To come up with this system, the ribosomes (present in every cell on earth) of every cell were studied by looking at RNA is 30th subunits. Based on the similarities and differences, the tree of life was formed, which gave us our 3 domains. It shows that all 3 domains are equally evolved.
Describe the 3 domain classification.
Bacteria, archaea, eukaryotes. Lines are proportional to the amount of time.
Eukarya and archaea are more closely related in evolutionary terms than bacteria are to archaea- this brings in to question whether we should call bacteria ‘prokaryotes’ as we talk about pro+euk which suggest we are linking them together.
Is the concept of the prokaryote valid and useful?
Prokaryotes fit into 2 domains; archaea and bacteria. However evolutionary and biochemically archaea and more closely related to eukaryotes so there is debate about whether we should talk of prokaryotes.
A more accurate system than the 3 domains would be to use the 2 domains, where archaea and bacteria arose first, and those in the archaea give rise to the eukaryotes. It is thought that the eukaryotes came about from archaea engulfing and not properly digesting bacteria
