First cells / Early life: expected outcomes, notes

EXPECTED OUTCOMES

Concepts:

The four possibilities as to how life originated on Earth

How the Earth was formed from molten rock to oceans

Miller / Urey experiment

Criteria used to define life

Development of protocells and coacervates

Considerations that enabled life on earth

First autotroph - what it is, how it works, how it became

First heterotroph - what it is, how it works, how it became

What is aerobic photosynthesis, how did the atmosphere change

Time table of events

THE EARTH DURING THE HADEAN EON

NOTES

Characteristics/criteria of life:

made of cells

movement

perform complex chemical activities

metabolism, ingestion, digestion, respiration, excretion

growth and development

respond to stimulus

reproduce

behavior - communication, patterns

change - genetics

death

Needs of organisms:

energy, food and water, oxygen, living space, proper temperature

Life originated on earth 3.5 billion years ago

Earth formed 4.6 billion years ago

Hadean times - name of the first billion years of earth history

Earth began ball hot molten rock - how did it get to what it is today?

Four possibilities as to how life became on earth

unknown(we don't know and never will)

natural outside source - carried here from other place in universe

supernatural - divine entity

evolution - series of random changes becoming more and more complex

Earth formation

ball of molten rock

as earth cooled gases released - nitrogen, hydrogen, water vapor, sulfur, carbon, ammonia methane

lots of energy - solar radiation(UV light), lightning, volcanoes, heat

gases underwent complex chemical reactions forming complex molecules

buildup of water vapor led to years of rain - led to oxidation, erosion, oceans, mineral breakdown

called "primordial soup"

Miller / Urey experiment

wanted to know what kind of molecules could be present early earth

assembled experiment to recreate early conditions

diagram of experiment - one side gases other side water vapor with heat and energy

results - carbon in methane converted to other carbon compounds

formaldehyde(CH2O) and hydrogen cyanide (HCN)

important because these lead to adenine an base of DNA - major important discovery!!

also found formic acid(HCOOH) urea(NH2CONH2) and amino acids(building blocks of protein)

Origin of first cells

many different kinds of similar molecules aggregate(come together) - form clusters big enough to see - Protocells

Coacervates - protocells that randomly formed membrane around cell that enclosed small amounts of water

contain energy processing molecules within, could grow and divide but no DNA

early oceans would have contained billions of coacervates in a single teaspoon

some chance chemical reaction coacervate absorb amino acids

life - grow, divide and pass along DNA, metabolize energy

First Autotrophs - organism produce own energy

Anaerobic photosynthesis - not modern plants

used H2S(hydrogen sulfide) as energy because there is plenty of it(called sulfide repirators)

millions of years taking place

also some aerobic photosynthesizers -used mostly methane(CH4) and carbon dioxide(CO2)

began releasing O2 into atmosphere

First heterotrophs - gets energy from other organisms

Methanogens - uses methane (plenty of it, it is everywhere) as energy instead of carbon dioxide

These three organisms dominated earth for first billion years

Around 2.5 billion years ago, major changes in earth's atmosphere as result of above

also rocks rich in iron dissolving in water releasing O2 through oxidation(breaking down of iron)

lead to a new plentiful energy source CO2

random event led to organism able to use this for energy, replacing diminished H2S

could get needed hydrogen and carbon from these sources

Cyanobacteria - blue green algae

saturated oceans with O2, which is a by product of photosynthesis

caused further change in atmosphere and structure of oceans

dominated earth for another billion years

Eukaryotic cells - single cell life - basis for plants and animals - 1.6 billion years ago make first appearance

bigger, thicker, has nucleus, more complicated

dominated life on earth for one by

led to first life on land - .6 mya

Time table

4.6 to 3.6bya - Hadean times

3.6 to 2.6 bya - methanogens, sulfide breather, anaerobic photosynthesis

2.6 to 1.6 bya - cyanobacteria - modern photosynthesis

1.6 to 560 million - eukaryotic cells

560 mya - first land life to present

Cyanobacteria