Transcript Chapter 12 History of Life

The History of Life
Chapter 12
The Fossil Record
 Fossil Forming
 Perminerilization
 Natural Casts
 Trace Fossils
 Amber preserved
fossils
 Preserved remains
 Most fossils form in
sedimentary rock
The Fossil Record
The Fossil Record
 Relative Dating
 Estimates the time
an organism was
alive based upon it’s
placement in rock
layers
 Allows for inferences
of species origin
 Does not provide
actual age dating of
fossil
The Fossil Record
 Radiometric Dating
 Estimates actual or
absolute age
 Calculation of the age of
a sample based upon
the amount of remaining
radioactive isotopes
 Half life
 The amount of time it
takes for half of the
iostopes in a sample to
decay into another
element

Different items have different
half lives
The Fossil Record
 Carbon-14 Dating
 Good for recent remains
 Carbon-14-taken up by organisms while
they are alive
 C-14 begins to break down when organism
dies
 Researchers compare the amount of
Carbon-14 to Carbon-12 or Nitrogen-14
• The larger the ratio of C-14 to C-12 (or N-14),
the older the organism
The Geologic Time Scale
 Index Fossils

Easily recognized and
the species must have
existed for a short period,
but have a wide
geographic range
 It will only be found in a
few layers, but they will
be specific and in
different locations

Trilobite
Geologic Time Scale
 Evolutionary time is
represented by the
Geologic Time
Scale

This orders rock by
age
 Divided into units
based on order
rocks and fossils
were formed
Geologic Time Scale
 Time between the
Precambrian period
and now is divided
by eras
Paleozoic
 Mesozoic
 Cenozoic

 These divisions are
defined somewhat
by the organisms
present
Geologic Time Scale
 To further define
time, eras are
divided into periods
 The Cambrian
period is important
to biology due to the
huge explosion of
organisms
 Epochs

Smallest unit of time;
several million years
Origin of Life
 Earth is about 4.6 billion
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

year old
How did the earth get
here?
Formed by a
condensing nebula
Material pulled together
Collisions caused the
formation of planets
Origin of Life
 Earth was very hot, violent first 700 million
years
 Many objects struck Earth releasing heat –
kept Earth in a molten state

Objects eventually separated into layers
 Hydrogen, carbon monoxide, water vapor,
methane, and carbon dioxide released

Oxygen not released until about 2 billion years
ago
Origin of Life
 Miller-Urey
Experiment
Lightning strikes
caused inorganic
molecules to form
organic molecules
 Electricity applied to
these inorganic
molecules led to the
production of amino
acids

Origin of Life
 Meteorite
Hypothesis
Amino acids have
been found in
meteorites
 Suggests that amino
acids could have
been present when
Earth formed

Origin of Life
 Iron Sulfide
Hypothesis
Iron sulfide from
deep sea vents form
chimneys
 Compartments in
these chimneys
acted as pockets for
biological molecules
 The walls of these
compartments acted
as the first cell
membranes

Origin of Life
 Lipid Membrane
Hypothesis
Lipids tend to form
spheres –
liposomes
 These spheres could
enclose organic
molecules
 Give rise to cells

Origin of Life
 RNA – Early Genetic
Material
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Ribozymes – RNA
molecules that can
catalyze chemical
reactions
Can make enzymes that
would cut itself, copy
itself, and make more of
itself
Short chains of RNA can
form from inorganic
molecules
Early Single-Celled Organisms
 Early microbes changed
the Earth
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Deposited minerals, gave
off oxygen
Cyanobacteria –
bacteria that carry out
photosynthesis
• Stromatolites –
colonies of
cyanobacteria

Release of oxygen
allowed for aerobic
organisms
Early Single-Celled Organisms
 Early prokaryotes are
considered the
ancestors of eukaryotes
 Early on some smaller
prokaryotes began to
enter into other
prokaryotes
 Endosymbiotic Theory

Eukaryotic cells arose
from living communities
formed by prokaryotic
cells
Eukaryotic Origins
 Evidence of the Endosymbiotic
Theory
 Mitochondria
and chloroplasts:
• Contain DNA similar to bacterial DNA
• Have ribosomes whose structure and size
closely resemble bacterial ribosome
• Reproduce by binary fission
 These three key pieces of evidence
are what give credence to the idea
that eukaryotes formed from
prokaryotes
Reproduction and Multicellularity
 After arrival, eukaryotes
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reproduced sexually
This increased the
speed of evolution
Sexual reproduction
allowed for shuffling of
genes
Offspring never
resembled their parents
exactly
This increased the gene
combinations – So?
Early Single-Celled Organisms
 Sexual
Reproduction vs.
Asexual
reproduction
Asexual – ease, rate
of reproduction,
energy efficient
 Sexual – genetic
diversity, increase in
evolution
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Paleozoic Era
 Fossil evidence shows a very
diverse life during this era
 Was initially thought that much of
this life originated during this era
 Actually came about much earlier
Cambrian Period
 Cambrian
Explosion

The explosion and
diversification of life
during this period
 Organisms had
shells and outer
skeletons
 Common
organisms:
Jellyfish, worms,
sponges
 Brachiopods,
trilobites

Ordovician and Silurian Periods
 Ancestors of
modern octopi and
squid appeared
 Arthropods became
the first land animals
 Jawless fishes
became the first
vertebrates
 Plants evolved from
aquatic ancestors
Devonian Period
 Plants began to adapt
to drier areas
 This allowed for
invasion of new habitats
 “Age of Fishes”

Many groups of fishes
present in the oceans
 Vertebrates began to
also invade land
Carbiniferous and Permian Period
 Reptiles evolved from
amphibians
 Winged insects began
to appear

Dragonflies and
cockroaches
 Plants became
abundant and when
they died, their remains
are now coal
Mesozoic Era
 Lasted approximately
180 million years
 This era is marked by
two main features
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Dinosaurs
Flowering plants
Triassic Period
 Fishes, insects, reptiles,
and cone-bearing plants
were prominent
 “Age of the Reptiles”

Coelophysis – meat eater
 Mammals first appeared
– mouse or shrew style
Jurassic Period
 Dinosaurs the
prominent life form
 Ruled the earth for
about 150 million
years
 Many scientists
think that birds are
close relatives
Cretaceous Period
 Dinosaurs still present
 New life came about:
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Leafy tress
Shrubs
Small flowering plants
 Another mass extinction
brought this period to
and end

More than half the plant
and animal groups wiped
out
Cenozoic Era
 About 65 million years ago
 Mammals evolved
 Could live on land, in water,
and even the air
 Tertiary Period
 Warm and mild climate
 Whales and dolphins
evolved
 Quaternary Period
 Climate cooled – ice ages
 Earth warmed up about
20,000 years ago
 Homo sapiens – 200,000
years ago in Africa
Extinction
 99% of all species that
ever existed are extinct
 Extinctions happen for
reasons


Resources
Environments change
 Each extinction brings
an opportunity for other
species to succeed
Primate Evolution
 Common
Ancestors
Primates are
mammals with
flexible hands and
feet
 Divided into two
groups

• Prosimians
• Anthropoids
Primate Evolution
 Promisians
 Oldest primate group
 Active at night
 Lemurs, tarsiers
 Anthropoids
 Divided into old and
new world monkeys
as wells as
hominoids
 Hominids can be
even further divided
• Lesser apes
(gibbons)
• Greater apes
(gorillas)
• Hominids (humans)
Primate Evolution
 Bipedalism
 Walking upright, on
two legs
 Came before larger
brains and tool
manipulation
 Allowed to reach
higher into trees,
freed the hands
Primate Evolution
 Early Human
Fossils

Two important genus
• Homo
• Australopithecus
Homo habilis
 Homo
neanderthalensis

• Neanderthals

Homo sapiens
• Modern humans
Primate Evolution
 Human Evolution
 Modern humans
came about 100,000
years ago
 Came out of Ethiopia
 Brain was key to
evolution
• Enlarged skull and
brain
Primate Evolution
Australopithecus afarensis
Homo erectus
Homo neanderthalensis
Homo sapiens