17-2 E ARTH ’ S E ARLY H ISTORY

I. F ORMATION OF THE E ARTH

1.
2.
Based on geologic evidence Earth was formed 4.6 billon years ago (bya)
Pieces of debris were attracted to each other based on their chemical bonding over 100 million years.

3.
4.
A large object hit the earth, resulting in the production of so much heat that the earth melted.
The elements on the now melted earth rearranged themselves according to density.

5.
6.
7.
The most dense elements are in the middle, forming
Earth’s core.
The less dense elements formed the top forming earth’s surface.
The surface cooled and formed a solid crust

8.
9.
10.
The early atmosphere contained hydrogen cyanide , carbon dioxide, carbon monoxide, hydrogen sulfide (all poisonous gases), nitrogen & water.
4 bya the Earth cooled & solid rocks formed
Millions of years of volacanic activity shook the Earth’s crust

11.
12.
3.8 bya the Earth cooled enough to allow liquid water to form which formed the oceans
The oceans were brown due to high amounts of iron in the water.

D ISCUSS W / P ARTNER :
1.
2.
3.
What features can you see on Earth’s surface in the photograph and in the drawing?
What are the basic requirements for human life that re found on Earth today?
Which basic requirements were present on early
Earth?

II . T HE FIRST ORGANIC
MOLECULES

1.
2.
3.
In the 1950s, Stanley
Miller and Harold Urey wanted to find out if organic molecules could have evolved under conditions on early Earth
Amino acids were produced from inorganic compounds in the apparatus
Their experiment suggest how life could have arisen from a few chemicals in the ocean.

D ISCUSS W / P ARTNER :

Pg. 424 Figure 17-8
1.
2.
3.
4.
Why did Miller & Urey use a mixture nitrogen, hydrogen, methane, and ammonia in their apparatus?
Why did they boil water to produce water vapor?
What was the purpose of the electric sparks?
Does the Miller-Urey experiment show what actually happened on early Earth?

1.
2.
3.
4.
A NSWERS : methane, and ammonia in their apparatus? B/c this mixture of gases resembles Earth’s early atmospheres.
Why did they boil water to produce water vapor?
To prevent oxygen from entering, b/c Earth’s early atmosphere had no oxygen, & to prevent contamination by modern bacteria or fungi.
What was the purpose of the electric sparks?
To simulate lightning & provide energy for the chemical reactions.
Does the Miller-Urey experiment show what actually happened on early Earth?
No, it is only a model showing how organic molecules could have been produced from inorganic components.

III. T HE PUZZLE OF LIFE ’ S
ORIGINS

3.
4.
1.
2.
Proteinoid Microspherestiny bubbles of organic molecules
Hypothesis suggest that structures like p.m. become more & more like living organisms.
Are NOT cells a) b)
Like cells proteinoid microspheres: selectively permeable membranes can store and release energy
Proteinoid microspheres magnification about 10,000x)

5.
6.
Scientist are not sure how RNA and DNA evolved.
a)
Scientist think RNA evolved before DNA because some RNA sequences can:
Help DNA replicate b) c) d)
Process mRNA
Catalyze chemical reactions
Grow & duplicate themselves

RNA & THE O RIGIN OF L IFE

RNA and the Origin of Life
RNA nucleotides
Proteins build cell structures and catalyze chemical reactions
Abiotic “stew” of inorganic matter
Simple organic molecules
RNA helps in protein synthesis
RNA able to replicate itself, synthesize proteins, and function in information storage
DNA functions in information storage and retrieval

IV. F REE O XYGEN

1.
2.
3.
3.5 bya photosynthetic bacteria was common in the oceans a)
These bacteria absorbed CO released O
2
2
&
2.2 bya the O
2 released from the bacteria started to build up in the atmosphere
Increased O
2 levels caused a mass extinction of some species but generated the evolution of many other species.
Ancient photosynthetic organisms produced a rise in oxygen in Earth’s atmosphere. These
Rocklike formations are called stromatolites, were made by cyanobacteria, which were
Probably among the earliest organisms to
Evolve on earth

V. O RIGIN OF EUKARYOTIC
CELLS

1.
2.
The endosymbiotic theory explores how eukaryotic cells evoled from prokarytotic cells
Endosymbiotic
Theory- eukarytoic cells formed from living together with prokaryotic organisms


Endosymbiotic Theory
Aerobic bacteria
Ancient Prokaryotes
Nuclear envelope evolving
Photosynthetic bacteria
Mitochondrion
Ancient Anaerobic
Prokaryote
Chloroplast
Plants and plantlike protists
Primitive Aerobic
Eukaryote
Primitive Photosynthetic
Eukaryote
Animals, fungi, and nonplantlike protists

O RIGIN OF E UKARYOTIC C ELLS
Aerobic bacteria
Ancient Prokaryotes
Nuclear envelope evolving
Ancient Anaerobic Prokaryote

O RIGIN OF E UKARYOTIC C ELLS oxygen to generate energy-rich molecules of ATP evolved into mitochondria.
Mitochondrion
Primitive Aerobic Eukaryote

O RIGIN OF E UKARYOTIC photosynthesis evolved into chloroplasts.
C ELLS
Chloroplast
Photosynthetic bacteria
Primitive Photosynthetic Eukaryote

VI. S EXUAL R EPRODUCTION &
M ULTICELLULARITY

1.
Most prokaryotes reproduce asexually.
Asexual reproduction: a) Results in daughter cells that are exact copies of the parent cell. b) restricts genetic variation to mutations in DNA.

2.
3.
Sexual reproduction shuffles genes in each generation.
In sexual reproduction: a) offspring never resemble parents exactly b) c) there is an increased probability that favorable combinations will be produced there is an increased chance of evolutionary change due to natural selection