LIFE ON EARTH
Chapter 10
Origins

Early Earth
 Oldest
rocks suggest Earth is 4.5 billion yrs old
 Condensed gases and dust
 Very hot initially, but outer surface cooled
 Heat is still produced by inner core of Earth
 Location just right from Sun – liquid water
 Large oceans formed, atmosphere from volcanic activity
 Oxygen was not present in the atmosphere
Origins con’t
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Volcanic activity would have triggered large
thunderstorms with lightening
Atmosphere would have had water vapor, methane
gas, carbon dioxide nitrogen, hydrogen, hydrogen
sulfide and ammonia.
From this mix arose organic molecules and the
building blocks of nucleic acids and proteins
Cooled “atmosphere” so
what formed would
“rain” down into the
“ocean”
First cells



Replicating molecules – simple molecules that could
make more copies of themselves, would have
become more common. Probably RNA.
RNA can function like a protein enzyme, so alone
RNA molecules might have been able to self
replicate
Sealed self from external environment in a
membrane
First cells con’t

3.4 billion (3400 million) year old cells
 Rocks
they are in are dated accurately
 Size = modern bacteria
 C12/C13 isotopes indicate fossilized organism, not
rock without fossils


DNA is more stable than
RNA
Cell Membrane critical
Cell membrane



If place phospholipids in salt solution, they will form
spheres spontaneously
Such microspheres will even create new
microspheres – but not replication as such
A combination of RNA or DNA with microsphere
would give all of the components needed to call it
life.
First Prokaryotic Life


3.5 billion years ago
2.5 billion years ago,
some prokaryotes
evolved the ability to
capture sunlight
energy to create
molecules.
 Waste
= Oxygen
 Cyanobacteria
Oxygen Accumulates




Oxygen in atmosphere
Many prokaryotes
survive in places that
lack oxygen – there
today
Larger cells possible
First Eukaryotes 1.9
bya
Paleozoic Era (600-250 mya)

Multicellular organisms
 Soft

bodied (5-600 mya)
First aquatic plants
 1st
vascular plants &
terrestrial invertebrates
(400 mya)



Age of fishes (400-360
mya)
First Reptiles (300 mya)
Mass extinction – cooling
due to formation of
Pangaea
Continental Drift

Evidence:
 Shape
USGS website
of Continents
 As lava cools, metal elements
freeze according to their
position relative to the Earth’s
magnetic field
 Continental drift is measured
today
 Fossil record indicates
changing locations
Mesozoic Era (250-65 mya)

Pangaea starts to
break up and a warm
shallow sea forms in
the center
 Temperatures




rise
Age of dinosaurs
First mammals (mouse
sized)
First birds
First flowering plants
Mesozoic Era con’t



Largest dinosaurs
dominated during the
Jurassic Period (200140 mya)
2 large land masses
formed
Mesozoic ended with
impact of a large
asteroid that cooled
Earth rapidly

Mass extinction of most
dinosaurs, others
Cenozoic Era (65 mya-present)



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
New species of
mammals evolved
Flowering plants
radiated
Grasslands arise
Continents move to
modern locations
Hominidae evolve
about 5 mya
Human roots
365 day perspective


1 picture taken each
year, run film at 144
frames/ sec
Run projector
continuously for 24
hr/day for 365 days

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
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
Jan, Feb, Mar, and most of
April – blank screen
April 12 – oldest rocks
April 20 – 1st prokaryotes
May, June, July & Aug no
change
Sept & Oct – Eukaryotes,
multi-cellular organisms
Nov 16 = 600 mya
365 day perspective con’t



Nov 16 Paleozoic Era
begins
Dec 1 age of fishes
begins
Dec 14 age of reptiles
(Mesozoic) begins and
lasts 12.5 days
 Dinosaurs
and large
reptiles dominate




Dec 26 at 11 PM mass
extinction
Dec 31 4:45 PM = first
species of Homo
11:37 PM Homo sapiens
first seen
11:59 PM to midnight =
entire history of human
civilization since the start
of agriculture
The age of fishes occurred during:
A) The Cenozoic Era
B) The Paleozoic Era
C) The Mesozoic Era
D) The Pre-cambrian Era
The classic experiments performed in the 1950s
by Harold Urey and Stanley Miller were the first
to show that:
A) simple organic molecules, such as amino acids, could form
spontaneously in the laboratory under chemical conditions
mimicking those of primitive earth.
B) water (H2O) could be separated into atmospheric
oxygen
and H2 gas.
C) cosmic microwave background radiation (CMB), a type
of electromagnetic radiation, fills the entire universe and
provides support for the “big bang” model of the origin of the
universe.
D) naturally occurring antibiotics, such as penicillin, could be used
to treat bacterial diseases.
E) the average bill size of a population of Darwin’s finches
changed with environmental conditions, proving that
microevolution can occur within a human lifetime.
Phase 1 of the creation of life on earth was
_____________________. Phase 2 was the
formation of self-replicating, information-containing
molecules. Phase 3 was the development of a
membrane, which enabled metabolism and created
the first cells.
A) the formation of small molecules containing
carbon and hydrogen
B) the formation of DNA
C) the development of a nucleus, which enabled
metabolism and created the first cells
D) the increase in the amount of atmospheric
oxygen
E) the formation of RNA
What is a species?

Different kinds of
organisms
 Populations
that
interbreed
 Can’t breed with other
organisms under
natural conditions
 Reproductively isolated
Reproductive Isolation
Classification
How do new species evolve?

Process is called speciation
 Requires
populations to become reproductively isolated
 Populations evolve separately
 Both change to the point that when they re-encounter
each other, individuals from the two populations can no
longer interbreed
Forms of Speciation

Allopatric speciation
A
population is split
 Migration
of small group
to an island
 River changes course
 Mountain building

Sympatric speciation
 No
physical barrier
 Something else causes
reproductive isolation
Sympatric Speciation




More rare event
Mostly in plants
Rare in vertebrates
Some insect examples
 If
mate on particular type
of plant
 Mutation causes change in
plant preference
 Populations can be
isolated due to food and
mating location
preference
Apple maggot flies
Sympatric Speciation con’t
Chromosome duplication

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Error during meiosis
Doubled # sets of
chromosomes
Can’t cross with
parents, but can with
self
Apples and bananas
Hybrid allopolypoidy

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Cross between 2 closely
related species
Sterile hybrid
reproduces asexually
Those offspring can
reproduce together
Wheat, bananas,
potatoes, coffee
The biological species concept is
primarily based on:
A) reproductive isolation.
B) phylogenetic history.
C) ecological niche.
D) morphological differentiation.
E) behavioral differentiation.
Horses and donkeys can breed and
produce sterile offspring known as mules.
Horses and donkeys remain separate
species because of this hybrid sterility,
which is:
A) an allopatric barrier to reproduction.
B) a postzygotic barrier to reproduction.
C) a sympatric barrier to reproduction.
D) a prezygotic barrier to reproduction.
E) a good thing.
Plant species A has a diploid chromosome
number of 18. Plant species B has a diploid
chromosome number of 10. A new species, C,
arises as an allopolyploid of species A and B.
What is the most likely diploid chromosome
number of species C?
A) 38
B) 28
C) 10
D) 46
E) 18
Tree of Life

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Evolutionary history can be
visualized as a tree with branches
Branches show relationships among different species
and where speciation occurred
Phylogeny is the study of the evolutionary history of
groups of species
 Based
on structures, development, behavior, and
genetics
Monophyletic groups
For similar species the
number of changes in
DNA can give an
estimate of the time
since they diverged.
For very different
groups it is harder to
make a comparison.
Convergent Evolution
These are
Analogous traits –
similar but do not
share an
evolutionary history
Homologous traits
= jaw of bat and
mouse = share an
evolutionary history
Structures of wings
are very different
Vertebrate eye
and eye of octopus
and squid share
many
characteristics, but
= convergent
evolution
Convergent Evolution con’t
Which of the following BEST explains the finding
that the nuclear DNA of house cats and African
wild cats has a very high degree of similarity?
A) Convergent morphological evolution has occurred.
B) Convergent molecular evolution has occurred.
C) House cats and African wild cats are both
members of the family Felidae.
D) Divergent morphological evolution has occurred.
E) House cats and African wild cats share a recent
common ancestor.
Sequencing DNA from different organisms has
been a breakthrough for phylogenetics because:
A) we can now build heat-tolerant animals.
B) we now have a method to determine the
relatedness of organisms that leave no fossils.
C) it has reduced the impact of antibiotic
resistance in bacteria.
D) we can now recreate genomes from the past.
E) All of the above are correct.
Macroevolution vs Microevolution
1 of over 400 species of Anolis
Macro- versus Microevolution
Rate of Evolutionary Change
Adaptive radiations

Times of rapid species
formation
 There
has been an
extinction event that
opened up niches for
those who survived
 New habitat is
available
 New innovation that
opens new niches
Extinction


Extinction of species has
occurred regularly
though time
Mass extinctions are
dramatically larger
events that have
occurred periodically

Humans are causing
another right now –
doesn’t show yet, but the
present rate of extinction
is very high
The ___________________ propelled
flowering plants to an explosive
adaptive radiation.
A) colonization of land
B) mass extinction of fern-like plants
C) colonization of the Galápagos Islands
D) evolutionary innovation of the flower
E) evolutionary innovation of the leaf
_________________ produces new species and
_________________ takes them away.
A) Speciation; extinction
B) Extinction; speciation
C) Convergent evolution; extinction
D) gradual change; punctuated equilibrium
E) Background extinction; mass extinction
Read chapter 13 Microbes