THE ORIGIN OF LIFE
THE FORMATION OF LIFE This is highly theoretical but not a random guess – there has been lots of research We know more about the conditions of early Earth than about how specific organisms evolved
4.5-4.6 BILLION YEARS AGO- THE EARTH FORMS No oxygen! No oceans! No organic molecules No life! The Earth was extremely hot Lots of volcanoes Lots of comets/meteors
THE EARLY ATMOSPHERE Volcanoes spewed gases such as NH3, CH4, H2O (as a gas) and H2 into the air No oxygen About 4 billion years ago the Earth cooled enough for the gases to condense, forming the oceans
THE MILLER-UREY EXPERIMENT Reproduced the conditions of early earth When they heated a flask containing the molecules of Early Earth organic molecules formed within a day Amino acids formed within a week
HOW DID THIS TURN INTO LIFE? Lots of theories! Each group will research 1 theory of their choice and share out
3.5-3.9 BILLION YEARS AGO – LIFE! Simple, single celled organisms that consumed organic molecules Did not use oxygen and built up CO2 in the atmosphere LOTS of competition so they likely evolved quickly
Autotrophic prokaryotes evolved 3.3 BILLION YEARS AGO Autotrophic prokaryotes evolved Bacteria that could photosynthesize Huge survival advantage Produced oxygen which dramatically changed the Earth’s atmosphere
THE OZONE LAYER FORMED O2 from photosynthesis interacts with UV light to form the ozone layer This prevented UV light from damaging living organisms Can also be used for aerobic respiration
AEROBIC RESPIRATION EVOLVED Mitochondria-like bacteria evolved Use O2 in the atmosphere to more efficiently break down molecules This allowed them to get more energy from food – another huge advantage in survival
ABOUT 1.5-2.1 BILLION YEARS AGO The first eukaryotes formed (single celled) Organisms with organelles Endosymbiosis occurred
ABOUT 1 BILLION YEARS AGO The first multi- cellular eukaryotes appear Probably after the evolution of sexual reproduction Thought to have possibly evolved from colonies of single celled organisms
A NOTE ABOUT MULTICELLULARITY It has evolved several (around 13) times in the eukaryotic lineage Plants and animals have different single- celled common ancestors
ABOUT 600 MILLION YEARS AGO The first simple animals evolved in water
ABOUT 475 MILLION YEARS AGO Plants colonized land This paved the way for animals to come ashore It only took insects about 75 million years to do it And vertebrates about 115 million years (So don’t complain about a 40 minute lecture )
ABOUT 200 MILLION YEARS AGO Mammals evolved Came about 160 million years after amphibians and about 100 million years after reptiles But mammals evolved about 50 million years before birds (and 70 million years before flowers) Hadrocodium – the first mammal????
ABOUT 55 MILLION YEARS AGO The first primates evolved They were small, about the size of a squirrel
ABOUT 2.5 MILLION YEARS AGO The first members of the homo genus appeared Thought to be Homo Habilis but there is still a lot of debate about human evolution
ABOUT 200,000 YEARS AGO The first Homo sapiens sapiens (humans) are thought to have evolved Humans have existed for about 0.004% of Earth’s existence And about 0.005% of the time life has existed And 0.03% of the time animals have existed
WE BELIEVE ALL LIFE IS RELATED 1 tree of life Based on: A common genetic code Same basic molecules in all living things (amino acids, proteins etc.) Similar metabolic pathways
WE BELIEVE ALL EUKARYOTES ARE RELATED Based on: Similar membrane-bound organelles A cytoskeleton organizing the cell Linear chromosomes (compared to circular chromosomes of bacteria)
ORIGINS OF LIFE RESEARCH Pick one of the hypotheses/models/theories Create a relatively short presentation focused on: A general description of the model Who proposed it and when? Evidence/support for it Problems or arguments against it
POSSIBLE THEORIES/HYPOTHESES/MODELS RNA world Clay Iron/Sulfide/Zinc Extra-terrestrial Hydrothermal vents Bubbles Metabolism first Panspermia (extraterrestrial) Something else you’ve heard of