Transcript HISTORY OF LIFE Evolution part 1

• The Earth’s age is estimated at about
4.6 billion years old
• Early History of Earth (atmosphere):
–Was very hot, bombarded by
meteorites
–Volcanic action with lava gases,
water vapor, carbon dioxide and
nitrogen
3.9 billion years Earth began to cool
and first organisms appeared
Fossils
–99 percent of all species are
extinct
–Fossils give evidence of
organisms existence
–Most fossils are found in
sedimentary rock and often
destroyed ducts change in the
earth’s crust
Types of fossils
–Trace – markings
left behind
–Casts – minerals fill
in space left by
organism
–Petrified – minerals
penetrate and
replace organism
• Molds – empty
space left in
sedimentary rock
• Imprints –
impression left in
sedimentary rock
• Amber –
preserves
organisms intact
Age of Fossil
Relative dating –
geologic law says
oldest organism
are on the
bottom layer
• Hutton and Lyelle
helped scientists
recognize that
Earth is millions
of years old and
that the
processes that
changes Earth in
the past are the
same processes
that operate in
the present
Age of Fossils
Radiometric dating – radioactive isotopes
break down into new substances
–Half-life – decay rate of radioactive
isotopes
– Ex: Potassium – 40
– Ex: Carbon – 14
Argon – 40
1.3 million years
Nitrogen – 40
5730 years
PRECAMBRIAN
Origin: the Early Ideas
• Spontaneous
Generation
(abiogenesis) – the
idea that nonliving
material can
produce life
Experiments:
• Fransico Redi –
controlled
experiments that
tested the
spontaneous
generation of
maggots from
decaying meat
• Spallanzani –
showed that
microorganisms
would not grow in
boiled and sealed
gravy (similar to
Redi – still did not
receive credit)
Redi
Spallanzani
•Many scientists still
thought that
microorganisms were so
numerous and widespread
that they must still arise
spontaneously from a
vital force in air
Spontaneous Generation
disproved
• Louis Pasteur – showed that
microorganisms do not simply
arise in broth, even in the
presence of vital force
• Biogenesis – the idea that living
organisms come from only other
living organisms – now the
cornerstone of biology
Origin: Modern Ideas
• Simple Organic Molecules
Formed:
–Alexander Oparin
(Russian) –
hypothesized that life
formed on early earth.
• Primordial soup – The sun’s energy, lighting,
and heat triggered chemical reactions to
produce small organic molecules (ex: amino
acids) from substances present in the
atmosphere; rain molecules into the oceans
• Miller and Urey
(Americans)
supported
Oparin’s
hypothesis by
simulating the
conditions of
early earth
(primitive earth)
Formation of Protocells
• Sidney Fox showed how the
first cells might have occurred
as protocells (large, ordered
structures enclosed by a
membrane that could carry out
some life activities) ex: growth,
division
Formation of True cells
–Thought to have been
mostly prokaryotes
(w/o nucleus),
anaerobic (w/o
oxygen) and were
heterotrophs
(obtained food rather
than making their own
food)
• The first autotrophs (make their own
food) are thought to have evolved
later and were probably similar to
Archaebacteria that live in harsh
environments and make own food
buy chemosynthesis rather than
photosynthesis
• Endosymbiont Theory – was proposed by Lynn
Margulis; she proposed that eukaryotes
evolved through a mutualistic relationship
between ancient prokaryotes
• Evidence: mitochondria & chloroplast
contain structures similar to prokaryotes
& unlike DNA in eukaryotic nuclei; they
also have ribosomes & reproduce
independently of cells they are in.
Endosymbiont
Theory
• Ideas of Evolution –
first published by
Charles Darwin and
now the basis of
the Modern
Evolution Theory.
• HMS Beagle an
English Ship – at the
age of 21 Darwin
took a job as a
naturalist.
• It was a 5 year
journey where
collected biological
specimens at every
port
• Galapagos Islands a group of small islands
that was of great interest to Darwin.
• He made observations of many species of
animals and plants that lead to the
possibility that species can change over
time
• Next 22 yrs – Darwin worked to
find an explanation for how
species could change over time.
He modified the ideas of
Thomas Mathus (who was
studying how human
population was growing faster
than Earth’s food supply).
Darwin & 2Types of Selection:
• Artificial Selection: nature provides the
variation but humans select those
variations that they found useful
• Natural Selection: when organisms with
certain variations survive, reproduce, and
pass variations to the next generation
“Survival of the Fittest.”
3 Types of Natural Selection
• Stabilizing: favors
average individuals in a
population;
• ex: spiders with average
size are more likely to
survive
• Directional: favors one of the
extreme variations of a trait; ex:
woodpeckers with long becks feed
on insect under bark
• Disruptive: favors
individuals with both
extremes of trait ex:
light colored and
dark colored limpets
blend in with light
and dark rock
2 Types of Adaptation:
• Structural Adaptations: Arise over
time
• ex: teeth, claws, thorns
–Mimicry – enables one species to
resemble another
–Camouflage – enables species to
blend with their surrounding
“Batesian Mimicry”
• The viceroy (right) and monarch butterflies look very
similar but monarch is poisonous to predators
• Physiological Adaptations: can
develop rapidly; changes
metabolic processes (DNA) ex:
Bacterial Resistance to Penicillin –
DIRECT EXAMPLE
Evidence for Evolution
•Fossils – provide a
record of early life and
evolutionary history
Anatomy – structural adaptations
• Homologous Structures:
similarities in arrangement (look
alike, different functions)
• ex: forelimbs of animals
• Analogous Structures: similarities in
function (look different; same function)
• ex: wings of butterfly and bird
• Vestigial Structures:
body structures that
have no function in
present-day organism;
probably used by
ancestors.
• ex: appendix, snakes
with legs
• Embryology – similarities in the earliest
stages of growth and development
• ex: in birds, mammals, fish, reptiles it is
difficult to distinguish embryos
•Biochemistry –
comparison of
the DNA, amino
acids
sequences.
Summary: Evidence for Evolution
1. Fossils
2. Anatomy
3. Embryology
4. Biochemistry
*All evidence only shows common
ancestry
Mechanisms of Evolution
• Populations – consists of all the
members of a species that live in
that area;
• evolution occurs as a population’s
genes change over time not
individuals
• Gene Pool – all the genes in
a population
• Allelic Frequency – percentage of any
specific allele in a gene pool (Hardy
Weinberg Principle = p2+2pq+q2=1)
Genetic Equilibrium – population’s
genes remains the same (not
evolving)
Changes in Genetic Equilibrium:
1. Natural Selection: Survival of
the Fittest – due to variations
2. Mutation: changes in DNA
sequence; many are lethal
3. Genetic Drift: alterations of alleles
by chance events; usually in small
isolated populations ex: Amish
4. Gene flow: movement of individuals
in and out of a population
Evolution of a species?? How??
• Species – organism that look alike;
can interbreed to produce fertile
offspring
• Speciation – evolution of new
species; occurs when members of
similar population no longer
interbreed to produce fertile
offspring
Causes of speciation
• Geographic Isolation
(allopatry) – when two
populations are
separated by
geographic barriers
• ex: river, mountains
• Behavioral
Isolation – when
two populations
are capable of
interbreeding but
have differences in
courtship rituals
• Temporal (Reproductive) Isolation when species reproduce at different
times ex: orchids pollination on
different days
• Polyploidy – multiple sets of
chromosomes
Patterns of Evolution
• Divergent Evolution –
where species that were
once similar become
different
Adaptive Radiation - divergent
evolution that occurs when a
species evolves into an array of
species to fit diverse habitats
ex: Galapagos finches
 Convergent Evolution – when
distantly related organisms
evolve similar traits due to similar
habitats
ex: dolphin and shark
Summary:
Patterns
of
Evolution
Patterns of Evolution
divergent
convergent
• In 1871, Charles Darwin
proposed in his book
“The Decent of Man”
that there might be an
evolutionary link among
monkeys, apes, and
humans.
What is a primate?
• A group of mammals that include
lemurs, monkeys, apes, & humans
6. arboreal
1. Opposable thumbs
2. Large brain
7. Round head, flat face
8. nails, claws
3. Binocular vision
4. Flexible joints
5. Adapted feet
PRIMATE ORIGIN
• Scientists use fossil evidence,
anatomy, embryology and genetics
to propose ideas about how modern
primates evolved
2 MAJOR PRIMATE GROUPS
• Prosimians –
lemurs, ayesayes, tarsiers
• Anthropoids –
human like
primates,
includes
monkeys &
hominoids
Primates
Prosimians
•Live in tress
•Mostly active
at night
•No larger
than a house
New World
cat
Monkeys
•Eat insects,
•Central & South
seeds, fruits
America
•Live in treesarboreal
•Can grab things
with their tails
(prehensile tail)
Anthropoids
•Large brain
•Complex skeleton
Old World
monkeys
•Africa & Asia
•Live in trees
or on ground
•Some live in
cold regions
•Use tails for
balance
Hominoids
•Do not have tail
•Use simple tools
•Humans have
largest brain
capacity
•Classified as apes
or humans
Primates
Anthropoids
Large brain
Complex skeleton
New World
Monkeys
Prosimians
Live in tress
Mostly active at
night
No larger than a
house cat
Eat insects, seeds,
fruits
Hominoids
Central & South
America
Old World
monkeys
Do not have tail
Africa & Asia
Live in treesarboreal
Use simple tools
Live in trees or
on ground
Can grab things
with their tails
(prehensile tail)
Some live in cold
regions
Humans have
largest brain
capacity
Use tails for
balance
Classified as apes
or humans
Human Ancestry
• Hominids are primates that can walk
upright (bipedalism) & include gorillas,
chimpanzees, & humans
• Scientists propose that
between 5 and 8
million years ago in
Africa that hominids
diverged into 2 lines:
1. African Apes – gorillas
and chimpanzees
2. Modern Humans-Evolution of
Homo
Sapiens
Australopithecus
Australopithecus
afarensis (1924)
africanus (1974)
Lucy
4 mya
3 mya
Skills
• Australopithecines climbed trees
• They could also walk upright on the
ground
• They have a foramen magnum opening in
the skull through which the spinal cord
passes
• Possessed ape-like & human-like traits
Homo Habilis (1964) Homo erectus
Leaky
1.5-2 mya
1.6 mya
Skills
•
•
•
•
Homo habilis used simple tools
“Handy Man”
Homo Erectus used large tools
“Upright Man”; more human like
Archaic Homo Sapiens
Neanderthal
Cro-Magnon Homo sapien
3500-100,000 yrs ago
100,000 yrs ago
33-40,000 yrs ago
Skills
• Neanderthals seem to have hatchet,
culture, and spoken language
• Cro-Magnons were talented artists & tool
makers
• Homo sapiens build cities and used
technology
• Brain volume of 1,000 to 1,4000 cm3