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History of Life and Evolution
How Life Began (Blue Book, Ch.12, p. 252)
Conditions on Earth were very different from today – no oxygen in the
atmosphere, but did contain carbon dioxide, water vapor, methane
and ammonia gases.
Formation of the basic (organic) chemicals of life from non-living
(inorganic) molecules.
Several different hypotheses:
a. Primordial soup model (scientists Oparin, Miller, Urey) – inorganic
molecules chemically reacted with each other to form organic
molecules, including amino acids, with the input of energy from solar
radiation, volcanic eruptions and lightening.
b. The Bubble Model (Lerman)
Gases from undersea volcanic eruptions were trapped in bubbles
where, protected from damaging ultraviolet radiation, chemical
reactions took place that formed simple organic molecules. When
bubbles rose to the surface and burst, these chemicals were released
into the atmosphere. The energy from lightening and ultraviolet
radiation caused more chemical reactions that formed more complex
organic chemicals which fell into the ocean, starting another cycle.
c. Meteorite hypothesis
Organic molecules have been found on meteorites and asteroids and
may have arrived on Earth with impacts.
How the first cells formed
a. Iron –sulfide bubble hypothesis (Martin and Russell) explains how cell
membranes may have formed
b. Lipid membrane hypothesis (Morowitz) proposes that lipid molecules
spontaneously formed a bi-layer lipid membrane that could protect
organic molecules such as amino acids fatty acids, sugars and
nucleotides from the environment.
Formation of the first genetic material
Cech and Altman proposed that RNA, not DNA, first stored genetic
information. RNA can copy itself and make more RNA, without the
enzymes that DNA needs for these functions.
Other scientists who contributed to origin of life hypotheses
 Louis Pasteur – refuted the concept of spontaneous generation
(organisms arising out of nothing). Showed that sterile broth will not
grow bacteria, only contaminated broth.
 Lynn Margulis – found evidence that supports the endosymbiotic
theory (Mitochondria are the descendants of symbiotic, aerobic
eubacteria and Chloroplasts are the descendants of symbiotic,
photosynthetic eubacteria)
 Sydney Fox – suggested that first amino acids were formed due to
high temperatures near undersea volcanic vents (has since been
refuted)
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How long ago (years)
4.5 bill
4 bill
3.5 bill
3.8 bill
3 bill
1,8 bill
800 mill
Around 700 mill
600 mill
420 mill
370 mill
360 mill
340 mill
230 mill
195 mill
65 million – present
7-5 million
3-2 million
190,000-160,000
40,000
What happened
Earth formed; was a ball of molten rock
Earth began to cool; oceans formed
First bacteria
Primitive prokaryotic cells
Photosynthetic bacteria produce oxygen
Eukaryotic cells appear
First multicellular organisms appear
“Snowball Earth”
Formation of ozone layer; “explosion” of life
Plants on land
Amphibians
Insects
Reptiles
Dinosaurs and Mammals
Birds
The Age of Mammals
First hominids (walking upright, hand-graspers)
First homo species (Homo habilis, homo erectus)
First humans like us
First humans like us outside of Africa
Vocabulary terms (Blue Book Ch.12, sec.1)
Term
Definition
Radiometric
Estimating the age of an object by measuring its content
dating
of certain radioactive isotypes. Radioisotopes decay
(break up) and give off energy over a known period of
time.
Fossil
Remnant of living organism
Creation of life
Most scientists believe that the basic chemicals of life
(organic chemicals) developed from inorganic chemicals
(the newly formed earth contained chemicals in its crust
and its gas atmosphere). No one knows yet exactly how
that happened
Prokaryotes
Single cell organisms without organelles or a nucleus
Eukaryotes
Cells of these organisms have a nucleus and organelles;
include fungi, plants and animals
First living
Prokaryotes (eubacteria and archaebacteria see p.1038)
organisms
Cyanobacteria
The first bacteria on earth; were photosynthetic; over
hundreds of million years they put oxygen into atmosphere
Fossil
Preserved or mineralized remains (bone, tooth, shell) or
imprint of an organism that lived long ago
Most likely found in rock/sediment layers. In amber, tar,
frozen or mummified is not as common
Protists
The first eukaryotic organisms; today’s algae
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Evolution - Ch.13, Section 1
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Who was Charles Darwin and around what time did he live?
o A British naturalist; around the middle of the 19h century
What did most people in Darwin’s time believe about the creation of
species?
o That god put all species into the world and they exist unchanging
Why was Darwin afraid to share his ideas?
o His ideas were contrary to those of the Christian church and the
common beliefs of his time.
What was Lamarck’s theory?
o Individuals change physical characteristics while alive (example:
giraffe gets longer neck because it keeps stretching upward to eat)
o Individuals pass on these new characteristics to offspring
Which part of Lamarck’s theory is wrong?
o That individuals adapt and change during their lifetime
Who gave Darwin the idea for natural selection?
o English economist, Robert Malthus
What are the four major points of Darwin’s theory of evolution?
o There is variation in the genetic material between individuals
because of random genetic changes (mutations)
o Individuals with better adaptations are more likely to survive and
produce offspring (=natural selection)
o Over time, traits that make individuals of a population better able
to survive and reproduce, tend to spread in that population.
o There is overwhelming evidence for the idea that species evolved
from organisms that are now extinct
Evolution
The same vs. different
species
Population
Descent with
modification
Change over time
Individuals may seem similar but cannot
interbreed with each other unless they have the
same number and kind of chromosomes and live in
the same area
Humans and apes cannot interbreed; donkeys and
horses can (also zebras and horses, lions an tigers)
All the individuals of a species that live in a specific
geographic area, and that can interbreed
Parents pass traits on to offspring but there are
small changes over time
Natural selection
Individuals that are better adapted to their
environment are better able to survive and produce
offspring
Adaptation
Inherited trait that has become common in a
population because it provides a selective
advantage
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Reproductive isolation
Gradualism
Punctuated
equilibrium
Paleontologist
Vestigial structures
Homologous
structures
Divergence
Speciation
Subspecies
Coevolution
Convergent evolution
Adaptive radiation
How do we know that
whales evolved from a
land animal?
Two populations of the same species do not
interbreed because of geographic separation or
another barrier to reproduction
Gradual change over a long period of time leads to
species formation
A model of evolution in which periods of rapid
change in species are separated by periods with
little or no change
Scientist who studies fossils
Structures, usually bones, are considered to be
evidence of an organism’s evolutionary past
“Tail bone” in humans; pelvis in whales
Structures that share a common ancestry
See p. 286
All vertebrates have the same kinds of bones in
their forelimbs even though they now function and
look differently
Accumulation of differences between groups
Process by which new species form
If I built a city right through the middle of a forest,
the frogs on either side would not be able to mate
with each other any longer. Over time they would
become more and more different.
When populations that belong to the same species
start to differ genetically because they have to
adapt to a different environment, they become
subspecies
Back and forth evolutionary adjustments between
interacting members of a community.
Example: If zebras run faster, lions have to run
faster also
Similarities evolve in some organisms not related
to each other because they live in similar
environments. The similar structures are called
analogous.
Example: wings in bats vs wings in butterflies
The diversification, or evolution, of many different
species from one ancestral species
Vestigial evidence: whales have some remnants of
bones no longer needed
Embryological evidence: embryos of whales and
land animals are very similar
Molecular evidence: similar milk protein genes as
in certain land animals
Evidence for evolution (Ch.13, sec.2)
a. Fossil evidence: shows orderly patterns of evolution
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Example: p.284, fig.8
b. Anatomy and development: bone structures are most similar in
organisms that have the most recent common ancestor
Examples:
vestigial structures (p.286)
homologous structures
embryos of all animals look very similar
c. Biological molecules – as species evolve, there should be more and
more changes (mutations) in the species’ DNA
Example: amino acid sequences for hemoglobin (a protein in
the blood that carries oxygen) are most similar for species that
have the most recent common ancestor (p. 287, fig.10)
Darwin’s finches (p.290):
Darwin collected individuals of 9 different finch species in the
Galapagos Islands, all very similar except for their beaks. Darwin suggested
that they all had a common ancestor and developed different beaks in order
to adapt to different food sources (divergence). If species become different
enough they may form a new species (speciation). First they are considered a
subspecies but if they continue to change they become different enough to
form a new species that cannot interbreed with the original species.
Evidence that evolution is occurring right now:
 Bacteria become more resistant to antibiotics over time (blue book, pg.
289)
 The flu virus mutates (evolves) over the course of just a few months and
the flu vaccine must be reformulated every year
 You can get a cold more than once because the virus mutates all the time
Evolution explains unity (similarities between all living things) and
diversity (differences between living things)
Factors in Natural Selection:
 Only individuals who survive can reproduce
 More offspring are born than the environment can support
 Individuals that are better able to cope with their environment are
more likely to leave offspring
Hominid evolution (Green Book p.379)
Hominoids include:
 Lesser apes: Gibbons
 Great apes: orangutans, chimpanzees, gorillas
 Hominids: includes all the species in the human lineage, both modern
and extinct.
Human Family History (includes only the most recent and most well-known)
 Homo habilis- left Africa
 Homo erectus: invented the use of fire and emigrated all over the
world; maybe had language
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Homo neandertalensis: sophisticated humans; buried their dead; may
have had language; became extinct 40,000 years ago, maybe because
of us (homo sapiens); stockier and stronger than us
Homo sapiens: modern humans
Features of hominids:
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walking upright (bipedal);
longer lower limbs than upper limbs,
opposable thumbs,
large brains
Bipedalism predated large brains and tool use; the ability to use hands
for foraging, carrying things and infants, and using tools may have
stimulated brain development.
Jaw development: jaws became smaller as hominids became more
intelligent; the reasons for that are not clear
Brain size: relative size is related to intelligence (as evidenced by
more and more sophisticated tools). Tool use started about 2.5 mill
years ago; largest increase in brain size happened between 800,000
and 200,000 years ago, maybe because frequent climate change made
life more challenging
Once tool use became essential in acquiring food, hands may have
evolved to become more sophisticated
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