17-2 Earth_s Early History

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17-2 EARTH’S EARLY HISTORY
I. FORMATION OF THE EARTH
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.
DISCUSS W/ PARTNER:
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. THE 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.
DISCUSS W/ PARTNER:

1.
2.
3.
4.
Pg. 424 Figure 17-8
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.
ANSWERS:
Why did Miller & Urey use a mixture nitrogen, hydrogen,
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. THE PUZZLE OF LIFE’S
ORIGINS
1.
2.
3.
4.
Proteinoid Microspherestiny bubbles of organic
molecules
Hypothesis suggest that
structures like p.m.
become more & more like
living organisms.
Are NOT cells
Like cells proteinoid
microspheres:
a)
b)
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.
Scientist think RNA
evolved before DNA
because some RNA
sequences can:
a)
b)
c)
d)
Help DNA replicate
Process mRNA
Catalyze chemical
reactions
Grow & duplicate
themselves
RNA & THE ORIGIN OF LIFE

Proteins build cell
structures and catalyze
chemical reactions
RNA and the Origin of Life
Simple organic
molecules
Abiotic “stew” of
inorganic matter
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RNA nucleotides
RNA helps in
protein synthesis
RNA able to replicate itself,
synthesize proteins, and
DNA functions in
function in information
information storage
storage
and retrieval
IV. FREE OXYGEN
1.
3.5 bya photosynthetic
bacteria was common
in the oceans
a)
2.
3.
These bacteria
absorbed CO2 &
released O2
2.2 bya the O2 released
from the bacteria
started to build up in
the atmosphere
Increased O2 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. The
Rocklike formations are called stromatolites
were made by cyanobacteria, which were
Probably among the earliest organisms to
Evolve on earth
V. ORIGIN 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
Ancient Prokaryotes
Chloroplast
Nuclear
envelope
evolving
Ancient Anaerobic
Prokaryote
Photosynthetic
bacteria
Plants
and
plantlike
protists
Mitochondrion
Primitive Aerobic
Eukaryote
Primitive Photosynthetic
Eukaryote
Animals,
fungi, and
nonplantlike
protists
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Aerobic
bacteria
ORIGIN OF EUKARYOTIC CELLS
Ancient Prokaryotes
Nuclear
envelope
evolving
Ancient Anaerobic Prokaryote
Copyright Pearson Prentice Hall
Aerobic
bacteria
Prokaryotes
that
use
ORIGIN
OF E
UKARYOTIC
CELLSMitochondrion

Copyright Pearson Prentice Hall
oxygen to generate
energy-rich molecules
of ATP evolved into
mitochondria.
Primitive Aerobic Eukaryote
O
E
RIGINthat
OFcarried
UKARYOTIC
Prokaryotes
out
photosynthesis evolved into chloroplasts.
CELLSChloroplast
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Photosynthetic
bacteria
Primitive Photosynthetic Eukaryote
VI. SEXUAL REPRODUCTION &
MULTICELLULARITY
1.
a)
b)
Results in daughter
cells that are exact
copies of the parent
cell.
restricts genetic
variation to
mutations in DNA.
Copyright Pearson Prentice Hall
Most prokaryotes
reproduce asexually.
Asexual
reproduction:
2.
3.
Sexual reproduction
shuffles genes in each
generation.
In sexual reproduction:
b)
c)
offspring never
resemble parents
exactly
there is an increased
probability that
favorable combinations
will be produced
there is an increased
chance of evolutionary
change due to natural
selection
Copyright Pearson Prentice Hall
a)

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