Ch 16 The Origin of Life Flashcards
what is the theory of spontaneous generation
The hypothesis that life regularly arises from non-life
how did three scientists disprove spontaneous generation
- Francesco Redi sealed pieces of meat off from the outside to prove that maggots didn’t generate into existence on the meat, but hatched from eggs
- Lazzaro Spallanzani redid an experiment failed by John Needham that involved gravy and brought a similar result to Francesco Redi
- Louis Pasture isolated a broth from a year to show the same results
what environment did the first life forms develop in
- About 4 billion years ago, after the earth has cooled it was still a hostile place
- Eventually the atmosphere formed a mixture of gases, H2O, CO, CO2, H2, N2, and maybe NH3 and CH4, a primordial soup
- Eventually oceans formed and ~3.5 billion years ago fossil microbes show up, the first record of life
what did Stanley miller and Harold Urey do
- Stanley Miller and Harold Urey experimented by creating a synthetic atmosphere similar to that of early earth and subjected it to energy through sparks to simulate lightening, sun, etcetera
- Their Experiments produced several biological molecules like urea, lactic acid, and amino acids
- These experiments show how the building blocks of life can form on early earht
what did Alexander opaline and Sidney fox do
The formation of complex molecules would be necessary for life to occur
- Alexander Oparin and Sidney Fox have shown that simple molecules can link together to form complex ones in the absence of oxygen
- Sometimes these molecules gather into droplets that demonstrate some qualities similar to life (though they are not alive)
what are some thoughts on the first organism
- it is still a mystery how life started as it is truly complex
- One theory is that RNA was the first code used and evolved to produce certain enzymes
- Life is believed to have started by hydrothermal vents
what were the first true cells like
- Prokaryotic
- Heterotrophic
- Anaerobic
why and how did photosynthesis evolve
- As certain complex molecules were depleted organisms would need a way to synthesize them from similar ones
- For this, outside energy would be very helpful
- early photosynthesis eventually evolved, though were very different and probably used H2S instead of H2O, and were very successful
why can’t life begin again on earth
Life cannot arise again as the presence of oxygen and bacteria would prevent the required molecules from forming
what happened around 2.2 billion yrs ago
- around 2.2 billion years ago, photosynthesis using H2O evolved, they produced O2 into the air
- O2 was initially very deadly to organism
- O2 eventually reformed into O3 at the upper atmosphere making the ozone layer protecting the earth from the sun
how did aerobic metabolism evolve
- Eventually organism adapted to use O2 in their metabolism
- This made them way more effective in acquiring energy from sugars
when did eukaryotes evolve
- happened around 1.4-1.6 billion years ago
- organelles formed
what did the evolution of sexual reproduction do
- increased the speed of evolution
- asexual reproduction leads to clones with little variation
- sexual reproduction shuffles genes between the parents
when did the first multicellular organisms evolve
a few million years after sexual reproduction evolved, the first multicellular organisms arose
