EVOLUTION
Nancy G. Morris
Volunteer State Community College
Theory of Evolution
The theory of evolution states that:
life arose from random non-living
chemical processes that took place in
the ancient oceans.
mutations and natural selection have
brought great change in organisms.
Life has become more diverse and
complex.
THE ORIGIN OF LIFE
Life on earth originated
approximately 3.5 billion
years ago.
THE ORIGIN OF LIFE
The theory states that abiotic
chemical processes occurring on the
early earth produced basic
precursors leading to the building
blocks of life.
In 1953, Miller and Urey achieved
synthesis of small organic molecules
from abiotic compounds like those
thought to exist on the early earth.
THE ORIGIN OF LIFE
They produced amino acids and
other building blocks by
electrically sparking atmospheric
gases that probably existed on the
early earth.
Comparative Anatomy
The bone types in the limbs of
amphibians, reptiles, birds, and
mammals is very similar.
This suggests common ancestry.
THE ORIGIN OF LIFE
An organic soup -- a mixture of all
sorts of carbohydrate, amino acids,
nucleotide, and lipid molecules --
accumulated in the early oceans as
atmospheric gases reacted.
Energy was supplied by lightning
and UV radiation from the sun.
THE ORIGIN OF LIFE
Laboratory simulations of early earth
conditions have produced organic
polymers such as polypeptides.
Amino acids form polypeptides
abiotically when water with amino
acids drys on hot clay.
THE ORIGIN OF LIFE
Heterotrophic protocells
probably came next.
It is thought that these
protocells had a cell membrane.
THE ORIGIN OF LIFE
Protocells must have fed on
the organic soup of the early
oceans.
Since there was no oxygen,
we assume that the first
cells were anaerobic
fermenters.
THE ORIGIN OF LIFE
Once the protocell was capable of
reproduction, it became a true cell,
and biological evolution began.
Many scientists think that these
ancient cells had RNA for their
genetic code and later cells had
DNA.
Classification: 3 Domains
Bacteria Archaea Eukaryotes
Anaerobic Heterotrophs
capable of division
Anaerobic Heterotrophic Protocells
Organic Soup
Current Classification Schemes
HISTORY OF THE
EVOLUTION CONCEPT
The concept of evolution was
formulated by Greek philosophers over
2000 years age.
LeMarck (a French biologist; early
1800s) proposed a theory of evolution
based on acquired characteristics.
Charles Darwin (1860s) published his
theory of evolution based on natural
selection.
Mechanisms of Evolution
– Natural selection
– Mutation
– Isolation of
Populations
– Mass Extinctions
Natural Selection
Darwin and Wallace’s Theory
Natural Selection means “Survival of the best
adapted.”
Nature is prolific. More individuals are
produced than the environment can support --
thus competition.
Individuals with mutations which are beneficial
(cause better adaptation to the environment)
have a better chance of surviving.
ISOLATION OF POPULATIONS
Darwin’s observations occurred on
the Galapagos Islands
When a small population becomes
geographically isolated from the main
population, the small population tends
to evolve into a separate species
(speciation) because gene flow has
been cut off from the main
population.
Continental
Drift
MASS EXTINCTIONS
The fossil record shows that speciation
(evolution) is most rapid following a
mass extinction.
Mammals and birds evolved rapidly into
many different species after the
dinosaurs were wiped out 65 million
years ago.
Humankind might not be here today had
the dinosaurs not become extinct.
THE PACE OF EVOLUTION
Darwin thought evolution proceeded gradually.
Stephen Gould and some other modern
paleontologists think that evolution tends to
occur in spurts -- especially after a mass
extinction.
Gould believes that evolution is often rapid,
then a new species remains constant for long
periods until the next major environmental
change spurs another burst of evolution.
THE PACE OF EVOLUTION
Biologists know of some species
that have changed very little over
many millions of years because they
are so well adapted to their niche
or their way of life.
Evolutionary Evidences
Artificial selection
Fossil record
Comparative anatomy
Comparative embryology
Comparison of DNA
Vestigial structures
Artificial Selection
All breeds of dog have evolved from
a wolf ancestor through artificial
selection by humankind over the last
10,000 years.
Cabbage, broccoli, cauliflower,
brussel sprouts all have been derived
from a common ancestor by
humankind in just a few thousand
years.
FOSSIL RECORD
Fossils of the simplest organisms are
the oldest.
Fossil evidence for the evolution of
vertebrates is more complete than
for soft-bodied animals.
Fossil evidence for transitional forms
like Archaeopteryx is strong.
Fossil evidence for human evolution is
compelling.
Comparative Anatomy
The bone types in the limbs of
amphibians, reptiles, birds, and
mammals is very similar.
This suggests common ancestry.
COMPARATIVE EMBRYOLOGY
All vertebrate animals are similar in
their early embryonic development.
They all have a notochord, tail, and gill
pouches in their early development.
In humans, the notochord is replaced by
backbone, the tail degenerates, and gill
pouches become the Eustachian tube,
tonsils, and glands in the neck region.
COMPARISON OF DNA
Chimpanzees and humans have a DNA
similarity of 99%.
Humans and cows would have less DNA
similarity.
Humans and jellyfish would have still
fewer genes in common.
The degree of DNA similarity between
two organisms indicates how closely
related they are.
VESTIGAL STRUCTURES
The appendix, coccyx, and
embryonic tail are vestigal
structures in humans.
Nonfunctional eyes in cave fish are
vestigal.
Vestigial pelvic bones are present in
the body of the python.
VERTEBRATE EVOLUTION
The ancestor of the vertebrates
was a small fishlike animal with a
notochord that lived in the seas
about 500 million years ago.
The first fishes were jawless.
Today the only surviving jawless
fishes are lamprey.
VERTEBRATE EVOLUTION
Some of the jawless fishes
evolved into jawed fishes .
The early jawed fishes evolved
into:
– cartilaginous fishes
– bony fishes
VERTEBRATE EVOLUTION
Today there are many bony
fishes.
Cartilaginous fishes include
sharks, skates, and rays.
Some of the early lobe-finned
fishes evolved into the first
amphibians.
VERTEBRATE EVOLUTION
Amphibians today include frogs,
toads, and salamanders.
Some of the early amphibians
evolved into the first reptiles.
Today reptiles include: snakes,
lizards, turtles, crocodiles, and
alligators.
VERTEBRATE EVOLUTION
The reptiles are better adapted to
dry land living because of their
waste-proof eggs and scaly skin.
Some of the early reptiles evolved
into the first birds and mammals.
VERTEBRATE EVOLUTION
Archaeopteryx was the first bird
according to the fossil record.
It had these reptilian features:
– teeth in beak
– claws
– long reptilian tail vertebrae
VERTEBRATE EVOLUTION
Archaeopteryx was a bird
because it had feathers.
Early mammals were shrew-like
animals.
When dinosaurs became extinct,
birds and mammals expanded into
many diverse species.
HOMINID EVOLUTION
– Hominids are primates which
walk upright.
– The first hominid we have fossils
of is “Lucy” Australopithecus
afarensis from Africa.
Hominid Evolution
Homo habilis used stone tools.
Homo erecutus used fire.
Homo sapiens neanderthalensis lived
during the Ice Age. They were
hardy, muscular hunters who buried
their dead.
Major
episodes
Earth’s
Inhabitants