1. Water and Life
Last time we discussed the existence of water on earth between 3.5 and 4.4 billion years ago. This was during the precambrian which was the time the earth was setting the stage for the evolution of advanced forms of life. We also discuss some potential sources of the earth’s water.
But regardless of how it arrived, it is fortunate for us that it did. Water is an essential precursor to life.

2. How large is the earth? 326 million mi3 Radius: 3986 mi (4000 mi)
Diameter:
7973 mi (8000 mi)
Circumference:
25,048 mi (25,000 mi)
That leaves earth as a unique body in the solar system. Let’s look at its dimensions.
400 billion billion gallons
Volume of Water:
326 million mi3

3. Zircon Crystals Earliest Evidence of liquid Water on Earth ~ 4.3 bya
Western Australia, 2001
Zircon crystals (minerals) in rocks found in Western Australia indicate reaction with water based on their oxygen composition. This may indicate the presence of at least ephemeral liquid water and an early earth environment that may not have been as hostile as once believed. A much cooler earth in which a stable crust began to form and the possible existence of liquid water.
Zircon Crystals
Earth’s oldest terrestrial materials

4. Pillow Lavas Basaltic Extrusive Rock 3.5 bya
3.35-billion-year age of the Pilbara pillow lavas. Colonized by ancient microorganisms. The tubules were drilled by microbes seeking vital minerals in the volcanic glass, says geologist Neil Banerjee of the University of Western Ontario, much as they do today in the same sort of basalt lava which squeezes out of the ocean floor in volcanic zones. To back up their claims, the scientists used an x-ray technique and found traces of organic carbon, phosphorous, and nitrogen—chemical signatures of life—in the tiny bacterial burrows but not in the surrounding rock.

5. Sources of Earth’s Water
Earth’s Mantle
Asteroids
Comets
That the Earth’s water originated purely from comets is implausible, as a result of measurements of the isotope ratios of Hydrogen in the three comets Halley, Hyakutake and Hale-Bopp by researchers like David Jewitt, as according to this research the proportions of Deuterium and Protium (D/H – Proportions) of the comets is approximately double that of oceanic water. What is however unclear is whether these comets are representative of those from the Kuiper Belt. According to A. Morbidelli et al. (Meteoritics & Planetary Science 35, 2000, S. 1309–1329) the largest part of today’s water comes from protoplanets formed in the outer Asteroid belt that plunged toward the Earth, as indicated by the D/H proportions in carbon-rich chondrites. The water in carbon-rich Chondrites point to a similar D/H ratio as oceanic water

6. Setting the stage for the evolution of life
Water is an essential precursor to life.

7. The most abundant substance
Water and Life
The most abundant substance
in living systems % 70
About 70% by weight.
Human body = 65%, infants = 75%
Plants = 80%
Fruits and Vegetables=70-80%
Plants ~ 80%
New born baby     ~ 77% Grown man      ~ 65% Grown woman ~ 58% The elderly            ~ 50%

8. Water Loss Average person has about 50 quarts of body water
A loss of just 5 percent of the body's total water will cause the mouth to go dry, the surface of the skin to shrink, and may even cause hallucinations
A loss of more than percent total body fluid would be fatal.
The longest anyone has ever survived without water is _____
12 days
Water Loss
The percentage of water within the human body must be carefully maintained. A loss of just 5 percent of the body's total water will cause the mouth to go dry, the surface of the skin to shrink, and may even cause hallucinations. A loss of more than 15 percent total body fluid would be fatal. And, death by dehydration is one of the most painful experiences imaginable.
About 15 percent of human water loss is through the act of respiration. Another 20 percent is lost through perspiration, and almost. Sweat has been found, through chemical analysis, to be loaded with waste products. Without a sufficient supply of liquid to carry it away, such filth would remain in the body and poison it. The retention of too much water, on the other hand, may cause nausea, tremors, convulsions, disorientation, and even unconsciousness or coma.
The average person has about 50 quarts, nearly 100 pounds or 65 percent of their total weight, of water in their body. A lean, muscular adult's body may be as much as 75 percent water, while an obese adult, with an abundance of water-poor fat tissue, may be only about 50 percent liquid. A young child may be as much as 90 percent water, however, but the total volume diminishes with age.
Mankind, and all other known forms of life, is helpless without water. A person may survive for several weeks without food, but would die a painful death in just a few days without water. In fact, one Indian Fakir lived for almost 81 days with no form of solid nourishment whatsoever. But, without water, however, the longest anyone has ever survived is 12 days.
15 percent of human water loss is through respiration
20 percent is lost through perspiration
65 percent is lost by excretion

9. Water and Life Water is an ideal medium for life processes.:
1. retains heat, moderates temperature
2. excellent solvent: transports nutrients, life compounds
4. Participates in biochemical reactions

10. Water and Life’s Beginnings

11. Water, Carbon, and Life
Living organisms consist of assemblages of similar complex carbon compounds (organic) and require water to develop.
To grow and develop, organisms must
assemble complex carbon compounds
from external sources of carbon.
Assembling complex carbon compounds
requires energy and reaction with water.
One readily apparent commonality is that all living things consist of similar organic (carbon-rich) compounds. Another shared property is that the proteins found in present-day organisms are fashioned from one set of 20 standard amino acids. These proteins include enzymes (biological catalysts) that are essential to development, survival and reproduction.
Proteins are assembled based on instructions carried in our DNA and RNA
Metabolism and reproduction are controlled
by proteins. Protein synthesis requires reaction
with water.

12. Water, Life, and the Earliest Organisms

13. Oxygen Early Organisms and Conditions on Earth Ammonium Carbon Dioxide
Hydrogen
Helium
Water Vapor
What’s missing?
Oxygen

14. The Earliest Organisms
Anaerobic
live in low-oxygen environments
or in the absence of oxygen.
Autotrophic
Self-feeding. Cannot consume
other organisms for energy.
Carbs

15. Two Types of Autotrophs
Photoautotroph
Use light energy to assemble complex
carbon compounds (organic) from simpler
carbon-containing molecules (CO2)
Chemoautotroph
Use energy from chemical reactions
to assemble complex carbon
compounds (organic) from simpler
carbon-containing molecules

16. Photoautotroph Photo = light Complex organic compounds
A photoautotroph is an organism that assembles complex
organic compounds from simple carbon-containing molecules
using energy from light.
Photosynthetic Algae
Photo = light
Complex organic compounds
(initially sugars C6H12O6)
Simple carbon molecule:
CO2
Plants
Photosynthetic Bacteria

17. Chemoautotroph Energy from Chemical Reactions Zinc/manganese
A chemoautotroph is an organism that produces complex
organic compounds from simple carbon-containing molecules
using energy from chemical reactions
Energy from Chemical Reactions
Zinc/manganese
Sulfur/potassium nitrate

18. The Earliest Organisms: Chemoautotrophs
A chemoautotroph is an organism that produces complex
organic compounds from simple carbon-containing molecules
using energy from chemical reactions
simple inorganic molecule
Chemical Reactants (energy)
Iron
Sulfur
CO2 
complex
organic compounds

19. Iron Sulfur ~ 3.5 bya Evidence for Earliest Organisms Chemoautotrophs
Embedded in the lava are
numerous tubular structures
left behind by ancient microbes
mineralized tubes that were formed in the pillow lava, suggest microbes colonized basaltic glass of the early oceanic crust, much in the same way as they do modern volcanic glass. The 3.5-billion-year-old tubes contain carbon and traces of carbonates that could represent organic material left behind by the primitive organisms about 3.5 billion years ago.
"On the microscopic level, we see that during metamorphism, the new minerals cross cut the preserved biological features," said Muehlenbachs. "This means that the biological features pre date the metamorphism, leading to the conclusion that the microbes were attacking the glass 3.48 billion years ago-very soon after the glass chilled and lasting a few million years, perhaps until the usual geological processes buried and cooked them."
~ 3.5 bya
tubes contain carbon that represents organic material left behind by early organisms.

20. Photoautotrophs 2.5 – 3.0 bya Cyanobacteria Photosynthetic light
Microscopic
Cyanobacteria
(Blue-green algae)
Photosynthetic
Fix carbon dioxide into
complex organic compounds.
The first photoautotrophs were cyanobacteria and some fossils have been dated to as far back as 3.5 billion years. Cyanobacteria can grow with light as an energy source photosynthesis; carbon dioxide (CO2) is fixed into organic compounds like glucose using same mechanism used in green plants. Thus, all species will grow in the absence of organic nutrients.
One of the important features of the emergence of cyanobacteria is that they remove carbon dioxide from the atmosphere and evolve oxygen.
light
6CO H2O C6H12O6 + 6O2
(Simplified)
- removed carbon dioxide
- production of oxygen

21. Stromatolites turfs Colonies of Photosynthetic Cyanobacteria
The oldest macroscopic evidence of life on Earth, at least 2.5 billion years old
turfs
The oldest macroscopic evidence of life on earth are stromolites, produced by the activity of ancient cyanobacteria. What you see in the picture are called “turfs” or layers of cyanobacteria and calcium carbonate. As the cyanobacteria floursished, the layers comprising the turfs were produced as calcium carbonate precipitated over the growing mat of bacterial filaments.
The calcium carbonate was able to precipitate (form a solid) because photosynthesis in the bacteria depleted carbon dioxide in the surrounding water. Essentially, CO2 is an acid that prevents precipitation of calcium carbonate. The carbonate minerals, along with grains of sediment precipitating from the water, were then trapped within the sticky layer of mucilage that surrounds the bacterial colonies, which then continued to grow upwards through the sediment to form a new layer. As this process occured over and over again and layers of sediment were created. This process still occurs today; Shark Bay in western Australia is well known for the stromatolite "turfs" rising along its beaches
Colonies of Photosynthetic Cyanobacteria

22. Stromatolites sediments Effect? Produced billions of tons of O2
Cyanobacteria colonies
sediments
Cyanobacteria
colonies
Effect?
Produced billions of tons of O2
Increase in atmospheric O2?

23. Little Alteration of the Earth’s Atmosphere
Ammonium
Carbon Dioxide
Hydrogen
Helium
Water Vapor
Oxygen = 0.21%
Oxygen
Photosynthesis
6CO H2O C6H12O6 + 6O2
Billions of tons of oxygen

24. Iron
Does not dissolve
in water: insoluble
Iron oxide

25. In the absence of oxygen, iron is easily dissolved in water
Prior to this time oxygen was approximately 1% to 2% of its current level. And there was abundant dissolved iron in the oceans, probably producing a greenish cast.

26. CO2 + H2O C6H12O6 + O2 Between 1.8 – 2.5 bya
When oxygen is present it quickly combines with iron
to form compounds that are not easily dissolved in water.
Photosynthesis produces oxygen
CO2 + H2O C6H12O6 + O2
Dissolved iron oxygen = solid iron
But, as more and more oxygen was produced, most of it, rather than escaping to the atmosphere, combined with iron in earth’s oceans eventually changing it from green to blue.
sinks
Between 1.8 – 2.5 bya

27. Banded Iron Formations
photosynthesis
CO2 + H2O C6H12O6 + O2
Iron + O Fe2O3
Dissolved
in oceans
solid
The conventional concept is that the banded iron layers were formed in sea water as the result of oxygen released by photosynthetic cyanobacteria (bluegreen algae), combining with dissolved iron in Earth's oceans to form insoluble iron oxides, which precipitated out, forming a thin layer on the substrate. The total amount of oxygen locked up in the banded iron beds is estimated to be perhaps twenty times the volume of oxygen present in the modern atmosphere
Evidence can be seen in what are known as banded iron formations indicating reaction of iron with oxygen. Much of the iron ore mined today comes from these formations.
Deposits contain 20 times the
oxygen of the atmosphere.
End ~1.8 bya
The source of all iron that is mined today

28. Oxygen in the Atmosphere/Oceans
Emergence of more complex cells
Multicellular Organisms
Increased complexity/diversity of organisms
Diversification of Aquatic Life
all modern phyla of animals develop
first vertebrates emerge
About 1.5 bya oxygen was about 10%. The increase in oxygen in the earth’s atmosphere coincides well with the emergence of more complex organisms.
All life existed in the oceans at this time because the ozone layer was not developed to withstand ultraviolet rays from the Sun. The most advanced animal of this period was the trilobite. The Cambrian is known as "the age of the trilobites."
fishes diversify
Mya - first land plants and animals arise
Why did it take so long?

29. Water Screens Out Ultraviolet Radiation
~ 500 million years ago
Higher Oxygen Levels
Ozone Layer
3.8 billion years of simple cells (prokaryotes),
3 billion years of photosynthesis,
2 billion years of complex cells (eukaryotes),
1 billion years of multicellular life,
600 million years of simple animals,
570 million years of arthropods (ancestors of insects, arachnids and crustaceans),
550 million years of complex animals,
500 million years of fish and proto-amphibians,
475 million years of land plants,
400 million years of insects and seeds,
360 million years of amphibians,
300 million years of reptiles,
200 million years of mammals,
150 million years of birds,
130 million years of flowers,
65 million years since the non-avian dinosaurs died out,
2.5 million years since the appearance of the genus Homo,
200,000 years since humans started looking like they do today,
25,000 years since Neanderthals died out.
The ozone layer screens
out harmful UV radiation
Terrestrial Life
First land plants ~480 mya

30. About 350 million years ago
Carboniferous Period
About 350 million years ago
First land plants: 480 mya.
First land plants: 480 mya. The Carboniferous Period, also called the Mississippian and Pennsylvanian Periods, lasted for 70 million years. The Carboniferous is often called "the age of swamps and coal." During this time period much of the land was covered by swamps and seas. The climate was extremely warm during this period. Giant insects and plants dominated this period. Much of the coal supplies world-wide originated from this period.
The large coal deposits of the Carboniferous primarily owe their existence to two factors. The first of these is the appearance of bark-bearing trees (and in particular the evolution of the bark fiber lignin). The second is the lower sea levels that occurred during the Carboniferous as compared to the Devonian period. This allowed for the development of extensive lowland swamps and forests in North America and Europe. Some hypothesize that large quantities of wood were buried during this period because animals and decomposing bacteria had not yet evolved that could effectively digest the new lignin
Primitive bark-bearing trees (lignin)
“the age of swamps and coal"

31. 245 mya – 65 mya Age of Reptiles Warm Wet Productive
Ferns, conifers, flowering plants (100mya)

32. Subsequent Timeline Mammals ~65 million years ago
Reptiles ~ 245 million years ago
Mammals ~65 million years ago
Primates ~30 million years ago
Pre-humans ~5-8 million years ago
Monkeys, prosimians, apes.
They were still somewhat squirrel-like in size and appearance, but apparently they had grasping hands and feet that were increasingly more efficient in manipulating objects and climbing trees.  It is likely that they were developing effective stereoscopic vision.  lemurs
Chimps are apes.
Hominidae consisting of orangutans, gorillas, chimpanzees, and humans
200, ,000 years ago humans.
Homo sapiens ~200,000 years ago