Life on the early earth Flashcards
How old is the earth?
4.5 billion years old.
What is data for the age of the earth derived from?
derived from looking at the ratios of radioactive elements - typically by using uranium-lead dating
What do fossil preserve?
Traces or remains of organisms
Why do the most commonly found fossils arise?
due to replacement of organic material after burial by minerals dissolved in water in the ground and recrystallization.
In exceptional circumstances fossilisation reveals…
…fantastic detail
What are microorganisms the key to?
the key to all life.
OUr perception of life tend to be…
anthropocentric - we notice life at our scale.
Why are microorganisms the key to all life?
they lie at the base of food chains and are essential in ensuring elements such as oxygen, carbon, and nitrogen are available to plants and animals.
What is life dominated by?
life is dominated by microorganisms
when was the origin of the earth?
origin of the earth (~ 4.5 billion years ago)
WHen was the origin of life?
origin of life (~ 3.5 billion years ago)
When was the origin of multicellular life?
Origin of multicellular life (~ 1 billion years ago)
When was the origin of humans?
200 thousand years ago
How does complexity change throughout the modern world?
increasing complexity.
What were key moments in evolution?
- the origin of life2. the oxygenation of the atmosphere3. the origin of eukaryotic cells4. the origin of multicellular organisms5. the ‘Cambrian explosion’6. the colonisation of the land by complex organisms
What did Millers experiment aim to do?
to recreate conditions that existed on the primordial earth
What was generated in Millers experiment?
amino acids.
Describe millers experiment.
Miller’s famous experiment used electricity to provide energy to a mixture of gases in a closed system. After incubating the mixture for a period of time he discovered that some of the building blocks of life – amino acids – had been formed.
What was used in Millers experiment?
gases - methane, hydrogen, ammonia, water vapour.energy sourceboiling watertrap to collect products
whats a problem of millers experiment?
it is now thought that the atmosphere of the earth was quite different
Whats a long popular theory of how life arose?
‘primordial soup’
Explain primordial soup theory.
- sea acts as a trap collecting amino acids, nucleotides, and other organic molecules as they form. - these were then thought to have joined up to make macromolecules (protein and DNA) which led to life
WHats a problem with the primordial soup theory?
One problem is that the ‘soup’ was unlikely to have been concentrated enough. More of a ‘weak broth’ really…
Whats a alternative hypothesis more widely accepted than the primordial soup theory?
life arose around hydrothermal vents in the deep oceans.
Explain the hydrothermal vents theory of how life arose.
hydrothermal vents presented a far more concentrated solution of organic molecules. They also give off energy in the form of heat which is essential for life to develop. These ‘black smokers’ are found on the ocean floor now and have ecosystems that are independent of the sun
Describe the earliest cells.
the earliest cells may have been little more than ‘bags’ enabling higher concentrations of nutrients to build uphigh concentration of organic molecules enabling the construction of ‘biologically useful’ molecules
all current life requires…
…cells.
one possibility is that the first cells were…
…lipid vesicles
Why are lipid vesicles formed?
because fatty acids have one end that likes to react with water (hydrophilic) and another that likes to ‘hide’ from water (hydrophobic).This means that fatty acids will aggregate into a sphere in aqueous solution.
Whats the problem with simply invoking lipid vesicles to collapse and form cells?
The problem with simply invoking lipid vesicles to collapse and form cells is that they are unstable and… where do the phospholipids come from?
Whats a more recent suggestion on how lipids form cells?
More recently suggested that early cells were bounded by an amphiphilic protein membrane or by a combination of lipids and amino acids
What was early life dominated by?
early life on earth was dominated by the simplest organisms we know today - prokaryoteson the left are fossil prokaryotes from a rock formation over 2 billion years oldabove are three electron micrographs of prokaryotes all of these prokaryotes are types of bacteria
Prokaryotes are the simplest…
form of cells that we see living today.
What are the important components of the prokaryotic cell which i need to remember?
plasma membraneDNA in the nucleoidRibosomesCytoplasm
function of plasma membrane in prokaryotes?
(made of lipids which encloses the cell)
FUnction of DNA in the nucleoid in prokaryotes?
encodes all the information it needs to make protein
Function of ribosomes
make proteins
function of cytoplasm
where all the chemical reactions necessary for life occur
whats the size of prokaryotes?
1-10 um
Where are the oldest known fossils found?
found in a rock formation called the Apex chert