Evidence for the origin of life Flashcards
Conditions on early Earth
Massive oceans existed
Only small landmasses above the surface of the water
No ozone layer
Large amounts of radiation reached the Earth
No free oxygen in the air (anoxic environment)
Large amounts of volcanic activity; heat, ash, dust and gases into atmosphere
Violent electric storms common
ammonia, water vapour, hydrogen and methane
Gases in the atmosphere
methane
water vapour
hydrogen
ammonia
main organic molecules
water
carbohydrates
lipids
proteins
nucleic acids
the basic organic compounds, water, carbohydrates, lipids, proteins, and nucleic acids, are made up of what?
hydrogen (H), oxygen (O), carbon (C), nitrogen (N) and some other common elements
what provided energy for molecules to be formed
The lack of an ozone layer, the frequent violent electric storms, and the volcanic activity of early Earth
was early Earth oxic or anoxic
anoxic
simple organic molecules contain which elements
carbon hydrogen oxygen nitrogen smaller amounts of phosphorous and sulfur
simple organic molecules are known as the building blocks of life and consist of what?
amino acids
nucleic acid bases
sugars and
phosphoric acid
why are amino acids called the building block of life
because they combine in different arrangements to form different types of proteins
Proteins in turn are responsible for the formation, repair and function of all cells in living organisms
how many types of amino acids are there
20
what is a reducing atmosphere
an atmospheric condition in which oxidation is prevented by removal of oxygen and other oxidizing gases or vapours, and which may contain actively reducing gases such as hydrogen, carbon monoxide and gases, such as hydrogen sulfide, that would be oxidized by any present oxygen
what is ‘primordial soup’
a term coined by biologist Alexander Oparin
the early conditions on earth that had an atmosphere which allowed life to begin
name two theories on the origin of life
There are two possible sources for organic molecules.
They can be:
made on the Earth from simpler molecules (theory of BIOCHEMICAL EVOLUTION) OR (chemosynthetic theory)
arrive from space on meteorites. (theory of PANSPERMIA)
what is the theory of panspermia
the belief that meteorites brought living organisms from space which were then able to initiate life on reaching a suitable environment
evidence of panspermia
Murchinson meteorite (1969) in Victoria Australia, which contained amino acids
what is the theory of biochemical evolution (chemosynthetic theory)
the chemical evolution of cellular life
all the elements were available in the atmosphere and with energy they rearranged into organic molecules
evidence of biochemical evolution (chemosynthetic theory)
Urey and Miller
proved that reactions in a reducing atmosphere could lead to the formation of organic molecules through various experiments (amino acids)
main 4 gases present in early earth
hydrogen
methane
ammonia
water vapour
energy sources on early earth
volcanic activity
lightning
radioactivity from the sun
what did Urey and Miller do
sealed a mixture of water, ammonia, methane and hydrogen in a sterile flask
the mixture was heated to evaporate water to produce water vapour
electric sparks were passed through the mixture of water vapour and gases, simulating lightning
after a week, contents were analysed
amino acids, the building blocks for proteins, were found
what did the Urey and Miller experiment proves
the theory of a ‘primordial soup’, the idea that complex chemicals needed for living things to develop could be produced naturally on the early Earth
if early Earth did contain those chemicals, life could
have formed from inorganic molecules.
(biochemical evolution)
what changes in technology have allowed us to accurately date fossils and identify chemicals and molecular structure this gave evidence to support the action of organic compounds
electron microscopes
spacecraft
deep sea exploration vessels
carbon dating
how have electron microscopes advanced technology and help scientists in identifying fossils
has meant that microfossils within rocks can now be seen
this has extended the evidence of live on Earth and also may identify fossils from other planets
how have spacecraft advanced technology and help scientists in identifying fossils
sending spacecraft to other planets makes it possible to examine conditions on these planets to compare to the conditions on early Earth
