Mikrobiologi 5
When was earth formed and how do we know that?
About 4,54 billion years ago. It is based on slowly decayign radioactive isotopes
When did water come and how? How can we "know" that water existed at this time?
4.3 billion years ago, either by volcanos or by astreoids and comets from space. We did an analysis of ancient zircon crystals
Describe the evidence that microbial life existed early in earth’s history
We have found stromatolite fossils layerd sedimentary formations created by microorgansims
Atmosphere before life
It had no ozone layer and had a hot sterile environment due to the UV light. The atmosphere consisted of water, methane, carbon dioxide, nitrogen and ammonia.
Experiments show that biomolecules can form spontaneously, describe these experiments. Experiments show that biomolecules can form spontaneously, describe these experiments.
Miller- Urey- experiment. They used a mixture of gases methane CH4, ammonia NH3, hydrogen H2 and water H2O and exposed it to an electric arc/ simulated lightning. After a few days they analyzed the solution and found amino acids and other organic molecules. They didnt degrade because Lack of oxygen, protective environment, they self-assembled into stable structures and no enzyme existed to degrade them
How and where was life formed
RNA world is the hypothesis, the life began with a simple RNA molecule that was self-replicating and could store genetic information and catalyze biochemical reaction. They think they were formed in hypothermaal vents where the condition is good from RNA formation and stability.
How did the first cells look like
It resembeld modern prokaryotes and were single celled. They lacked a defined nucleus and membrane bound organelles and had a simple internal structure
Why did DNA- based cells arise
DNA is more stable and have a lower mutation rate than RNA and it become a template for RNA synthesis
What happened with the atmosphere during the time from when the cyanobacteria evolved approximately 2.7 billion years ago and 2 million years ago?
The great oxidation event
anoxygenic vs oxygenic photosynthesis.
Oxygenic O2 is produced and anoxygenic O2 is not produced
Stromatotile fossils
Layered sedimentary formations creates by microorganism
Evolutionary chronometer
Its a nucleotide sequence that can be used to measure the evolutionary seperations of two organisms. It must have a functionally homologous in each organism studied, it must have conserved regions for alignments of adequate length and they must change/mutate at a sufficient rate.
Mechansims for microbial evolution
Substitution- one nucleotide is replaced by a different nucleotide.
Deletions- the loss of one or more nucleotides.
Insertion- addition of more nucleotides
Duplication- one ore more copies of DNA segment is produed
Bacterial conjugation
The transfer of bacterial material between bacterial cells by direct cell to cell contact or a bridge like connection between two cells.
Bacterial transformation
A recipient cell takes up DNA from the environment such as DNA from a dead organism
Bacterial transduction
DNA from a donor is transferred to a recipients cell via replicating virus.
Selection
A process that results in a change in allele frequencies in a population when individuals that are favoured are able to produce more offspring. Bacteria with beneficial genes surive.
Genetic drift
Results in a change in the allele frequencies as a result of random changes in the number of offspring from each individual over time