Welcome to Earth…4 billion years ago

•sterile

•hot

•volcanicWhen you think about it…these things could be sources of energy.

•UV radiation

•meteorites

•storms & lightning

The origin of lifeFour steps were needed to make the first cell:

1. The first organic (carbon) compounds2. Joining of these small molecules into macromolecules3. Packaging of molecules into membrane-bound structures4. Origin of heredity (genetic material)

This soon led to the first text message:

OMMG it’s alive!

Look, it’s the first CELL!

The first organic compounds: 3 hypotheses

1) Gases in early Earth’s atmosphere reacted to form simple organic compounds (Oparin/Miller/Urey)

2) They were made in deep sea vents (Wächtershäuser)

3) They came…from outer space!!! (panspermia)

The Oparin-Haldane hypothesis• Early atmosphere came from volcanoes• WHAM!

• Water• Hydrogen• Ammonia• Methane

Aleksandr Oparin and J. B. S. Haldane suggested in the 1920s that these small molecules could have formed more complex molecules under early Earth conditions.

NO OXYGEN!

The Oparin-Haldane hypothesis

Remember, to go from small molecules to large ones, you need to make bonds…

which means you must PUT IN ENERGY somehow!

small small BIG

(photosynthesis is one example of this)

Animationhttp://www.youtube.com/watch?v=iahBQolXQH8&safe=active

The Miller-Urey experiment (1953) tested the Oparin-Haldane hypothesis.

Start: small, simple molecules

End: big, complex molecules

Results:

• Many scientists are not convinced that the early atmosphere was like the Miller-Urey experiment

• Still important—showed that simple gases can make organic compounds on their own

Deep sea vents?• Many deep sea

hydrothermal vents (underwater hot springs) have chemistry similar to WHAM

• Günter Wächtershäuser proposed in 1988 that organic compounds could be made there

• This one called the

“Lost City” is of particular interest to scientists

From outer space?• Organic compounds came to Earth on a meteorite• This hypothesis has less support than the first two• It is possible, though…in 1970 a meteorite containing

amino acids and nitrogenous bases landed in Murchison, Australia

Macromolecules and Membranes• Macromolecules are polymers of simpler molecules• Clay mineral hypothesis:

• Molecules bind to surface of clay minerals• Water evaporates, concentrating organic molecules• High concentration forces molecules polymers

Macromolecules and Membranes• Microspheres and coacervates: basic membrane-bound

chemical systems• Simple reproduction and metabolism; membrane provides

stable internal environment• Experiments show these could have formed spontaneously

from simpler organic compounds

Genetics: the “RNA World” hypothesis• RNA carried out the basic functions of pre-living

systems (this is widely accepted by scientists)• Evidence:

• RNA can store genetic information in bases• Ribozymes (RNA enzymes) can catalyze some

biochemical reactions (discovered by Tom Cech)• RNA can (under certain conditions) make copies of

itself, or of other RNA molecules• Ribosomes are made of RNA

• Sustained abiotic RNA synthesis not shown…yet

Genetics: the “RNA World” hypothesis• RNA can do all this because it is single-stranded,

able to base pair with itself to make different structures (and structure function)

• Example: tRNA

Fig. 25-7

Animals

Colonizationof land

Paleozoic

Meso-

zoic

Humans

Ceno-zoic

Origin of solarsystem andEarth

ProkaryotesBillions of years ago

1 4

32

Multicellulareukaryotes

Single-celledeukaryotes

Atmosphericoxygen

The first cells• Inferred* characteristics:

• Used anaerobic respiration (because atmosphere had no O2)• Prokaryotic (because earliest fossil cells are prokaryotes)• Heterotrophic* (because the early environment had lots of

organic molecules just floating around)

* to infer is to make a logical conclusion based on observations

* Heterotrophs do not make their own food

Chemosynthesis (Cs)• Early cells got energy from chemicals in the environment

(chemosynthesis); Ps evolved later• Cs is widely used by modern archaea• Archaea are prokaryotic, single-celled organisms that often

live in extreme environments (hot, salty, corrosive, etc.)

• Studying archaea gives scientists clues about how metabolism might have worked in early cells

• Cs and Ps are the 2 kinds of autotrophy

Photosynthesis and aerobic respiration• Cyanobacteria are photosynthetic bacteria• They grow in colonies and form huge fossils (stromatalites)• Oldest stromatalites are ~3.5 billion years old

Photosynthesis and aerobic respiration• Evolution of Ps added oxygen to atmosphere• O2 allowed the evolution of aerobic respiration; also created

ozone layer (blocks harmful UV) so life could move to land

The first eukaryotes• In 1966, Lynn Margulis proposed endosymbiosis:

mitochondria and chloroplasts evolved from one prokaryote engulfing a second one, which continued to live and reproduce inside• The “engulfed” cell got protection• The “engulfing” cell got energy

• Evidence: mitochondria and chloroplasts have double membranes, divide independently, have their own DNA, DNA is circular

Points:1. Outline the modern scientific understanding of the

formation of Earth2. Summarize the concept of half-life3. Describe the production of organic compounds in

the Miller-Urey apparatus4. Summarize the possible importance of cell-like

structures produced in the laboratory5. Explain the importance of the chemistry of RNA in

relation to the origin of life6. List three inferred characteristics that describe the

first forms of cellular life on Earth7. Compare the two types of autotrophy used by

early cells8. Relate the development of photosynthesis to the

development of aerobic respiration in early cells9. Explain the theory of endosymbiosis

To do:

•Miller Urey Reading•Pick up D1-D2 mastery checklist

Evolution is not goal-orientedAn evolutionary trend does not mean that evolution is goal-oriented.

Surviving species do not represent the peak of perfection. There is compromise & random chance involved as well

Remember that for humans as well!

Evolution is not the survival of the fittest.

Rather it is the survival of the just

good enough.

Speciation in sticklebacks

Finish C1-C3 activities and get stamps

• 2 worksheets

• Comic

• Mass Extinction

Finish B1-B2

• Clay

• Homeobox

•C1-C3 Mingle-Line up by birth city

2007-2008

Mom, Dad…There’s something you need to know…

I’m a MAMMAL!

The Origin of Species

“That mystery of mysteries…”Darwin never actually tackled how new species arose…Darwin never actually tackled how new species arose…

Both in space and time, we seem to be brought

somewhat near to that great fact—that mystery of mysteries—

the first appearance of new beings on this Earth.

• While natural selection explains evolutionary modifications within lineages, speciation explains evolutionary branching and diversification.

• Speciation involves genetic differentiation, ecological differentiation (niche separation) and reproductive isolation.

2007-2008

Any Questions??

5 mass extinctions—take out packet

Mass Extinction 1- Ordovician-Silurian Extinction • The first of the mass extinctions happened 439 million years ago during the Ordovician-

Silurian period. This was the initial phase of the pre-historic era when most of the land masses were still one major continent, which scientists named as Gondwana. Accordingly, it drifted for some time until it settled in the South Pole.

• The movement of several bodies of water later separated these land masses to form the continents we now know of as Africa, South America, Australia, Antarctica and North America, but was completed only in the later pre-historic periods. North America was said to be the first to separate.

Mass Extinction 2- Devonian Extinction

• The second of the five mass extinctions took place 364 million years ago or roughly about 75 million years after the

Ordovician-Silurian period.

• This era was also known to be the Age of Fishes, since marine life spawned numerous varieties of fish. They included species that had powerful jaws and blade-like plates which served as teeth. Based on fossil studies, there were quite a number of ferocious species that measured up to 33 feet and seemed to have the appearance of having heavy protective armor and rounded shields. This was also the period where fossils unearthed from the red rocks in Devon, showed signs that marine life had started to seek life on land. The fossils of the first amphibians had crocodile-like heads, bony fins and short legs. These species were said to have survived up to the last of the mass extinction which was during the Cretaceous period.

Mass Extinction 3 –Permian Triassic Extinction

• However, the worst mass extinction took place in this Permian Triassic period, which wiped out 70% of the land animals and about 90% of marine life. In eliminating the asteroid/comet theory, scientists and scholars presented series of volcanic eruptions as the root causes of the extinction. The continuous flow of hot flaming lava caused large quantities of fumes, ashes and debris to rise up in the air and became part of the atmosphere. This development blocked out the sun’s radiations and prevented plants from their food production processes which involved photosynthesis.