Transcript Evolution

Evolution
I. History of Life on Earth
I. History of Life
A. Early History of Earth
I. Early earth was inhospitable
•
•
•
hot, with many volcanoes
little free oxygen and lots of carbon dioxide
other gases present: nitrogen, methane, ammonia,
hydrogen and water vapor
I. History of Life
B. History in Rocks
•
Fossils are clues to the past
•
•
•
Any trace of a species that once lived
can infer the structure of the organisms, what they
ate, what ate them, and the environment that they
lived in
Paleontologists- detectives to the past
•
scientists who collect, study and classify fossils
I. History of Life
• Fossils occur in sedimentary rock
• sedimentary rock is formed when exposure to
rain, heat, wind and cold breaks down existing
rock into small particles of sand, silt and clay.
• The particles are carried by streams and rivers
into lakes or seas where they eventually settle to
the bottom.
• As layers of sediment build up over time, dead
organism may also sink to the bottom and
become buried.
• The weight of layers of sediment gradually
compresses the lower layers and along with
chemical activity, turns into rock
I. History of Life
• Non-rock fossils
• Fossils can be found in ice
• Ex. Woolly Mammoth preserved in ice
• Fossils can be found in amber
• Organisms preserved in amber
• Amber is a form of tree resin—exuded as a
protective mechanism against disease and insect
infestation—that has hardened and been
preserved in the earth’s crust for millions of
years
I. History of Life
C. Age of a fossil
•
Relative Dating
• oldest fossils are in
deepest layers
• paleontologists can
compare fossils with
that of older fossils
I. History of Life
C. Age of a Fossil
• Radiometric Dating
• Use of radioactive isotopes in rocks to date
fossils
• The technology of radiometric dating
provides evidence that the earth is at least
4.5 billion years old
• Certain elements convert to other elements at
known rates, which can be measured, thus
revealing the age of the specimen
• One half Potassium40 decays to Argon40 in
about 1.3 billion years
• Carbon 14 decays to half of its original
amount in 5730 years
Common Isotopes used to date Geologic Materials
Parent Daughter T (1/2)
Useful
range
Type of
material
>10 millions
Igneous &
sometimes
metamorphic
rocks and
minerals
238 U
206 Pb
4.47 b.y
235 U
207 Pb
707 m.y
232Th
208Pb
14 b.y
40 K
40Ar & 40Ca
1.28 b.y
>10,000
years
87 Rb
87Sr
48 b.y
>10 million
years
147Sm
143Nd
106 b.y
14 C
14 N
5,730 y
100-70,000
years
Organic
material
Bacteria were the earliest life
Formed colonies called stromatolites
(age 3.5 billion years old)
Best colonies in Australia
Era
Period
Precambrian
Paleozoic
Mesozoic
Cenozoic
Million
Years Ago
Major Events
3500
Life evolves
Major Life Forms
Photosynthetic bacteria
3000
Prokaryotes
2000
Eukaryotes
Cambrian
540
Invertebrates
Ordovician
510
First Invertebrates
Silurian
439
First land plants
Devonian
408
First Amphibians
Carbonifero
us
362
First reptile
Permian
290
Conifers dominant
Triassic
245
First dinosaurs
First mammals
Jurassic
208
First birds
First flowering plants
Cretaceous
146
Tertiary
66
Quaternary
1.8
Dominant flowering plants
Humans
II. Origins of Life
II. Origins of Life
A. Origins: The Early Ideas
•
•
Spontaneous generation—non-living material can
produce life
Disproved by Redi experiment meat and maggots
II. Origins of Life
• Disproved by Pasteur—S flask experiment
•
•
•
•
boils broth in S flask
broth is free of microorganisms for a year
removes curved neck
broth is “teeming” with microorganisms
• Biogenesis—living comes from living things.
II. Origins of Life
B. Modern Ideas
•
Oparin—suggested sun, lightning, and
molecules such as water vapor, carbon
dioxide, nitrogen, methane and
ammonia formed a “primordial soup”
that was the beginning of simple
organic molecules
II. Origins of Life
• Miller and Urey—1953-1954
• Tried to answer the question by simulating
conditions on the early Earth
• Filled flask with hydrogen, ammonia, methane,
and water = atmosphere
• They passed electric sparks through the mixture
to simulate lightning
• Within a few days amino acids were present—the
building blocks of protein
II. Origins of Life
II. Origins of Life
• Sidney Fox—showed how sort chains of
amino acids could cluster to form protocells
• Experiments like Miller and Urey’s are
currently studied at major universities (i.e.
Georgia Tech, U Michigan
II. Origins of Life
C. Evolution of Cells (based on fossil
record)
•
First true cells—were probably
prokaryotic, heterotrophic and anaerobic
•
•
•
•
•
•
single celled—no nucleus
consumed food for energy
did not need oxygen to survive
Then came chemosynthetic organisms
Then autotrophs—were probably
archaebacteria that live in harsh
environments
Next came photosynthetic prokaryotes—
releases oxygen into atmosphere
II. Origins of Life
•
Endosymbiotic theory
• Proposes that eukaryotic cells arose from
living communities formed by prokaryotic
organisms—Lynn Margulis of Boston
University
II. Origins of Life
Endosymbiotic Theory Explained:
• Mitochondria and chloroplasts contain DNA
similar to bacterial DNA.
• Mitochondria and chloroplasts have
ribosomes whose size and structure resemble
those of bacteria
• Like bacteria, mitochondria and chloroplasts
reproduce through binary fission
• Eukaryotic cells evolved from prokaryotic cells
Endosymbiotic Theory
ENDO = Into
Symbiosis =
relationship of two
organisms living
close together
According to the theory of endosymbiosis
eukaryotic cells evolved when aerobic
eubacteria either infected or were engulfed by
a larger host cell and later established a
symbiotic relationship
III. Natural Selection and
Evidence for Evolution
History of
the Theory
of
Evolution
Darwin’s
Role
http://evolution.berkeley.ed
u/evosite/history/index.sht
ml
III. Natural Selection and Evidence for Evolution
A. Charles Darwin—credited with the
Theory of Evolution
•
Scientists, including Darwin, used fossils
to explain that organisms have changed
over time
Darwin and HMS Beagle
•
•
•
At age 22, Darwin sailed around the world, trip
took 5 years
Ship’s naturalist—he collected specimens and
note of the diversity he saw
Galapagos Islands
III. Natural Selection and Evidence for Evolution
•
Darwin in the Galapagos
• Group of islands off the coast of South
America
• Noted that the animals were unique but
similar to the species he had seen elsewhere
• Giant tortoises had differences in shell
depending on which island they inhabited
• Marine iguanas could swim and eat algae
• Finches had many different size beaks
depending on the type of food they ate
III. Natural Selection and Evidence for Evolution
•
Darwin Continues his Studies
• Lamarck proposed a theory about
evolution in the year Darwin was born
called Use and Disuse Theory
• Proposed that by selective use or
disuse of organs, organisms acquired
or lost certain traits during their
lifetime
• These acquired traits then could be
passed on to their offspring
III. Natural Selection and Evidence for Evolution
How do we know Lamarck’s explanation is false?
III. Natural Selection and Evidence for Evolution
• Darwin continued to look for explanations to
evolution for the next 22 years
• He read about Thomas Malthus’ study which
stated that the human population grows faster
than the earth’s food supply—Darwin applied
this idea to all of life
III. Natural Selection and Evidence for Evolution
•
Darwin also gained insight by
breeding pigeons using artificial
selection
• Breeders determine which
individuals to use for breeding
based on the natural variation
• Are able to produce a wide range of
plants and animals that looked very
different from their ancestors
III. Natural Selection and Evidence for Evolution
•
Darwin Explains Natural Selection
• Natural selection is a mechanism that occurs
when organisms with certain variations
survive, reproduce and pass on their variations
to the next generation
• At this time, Wallace also reached similar
conclusion
III. Natural Selection and Evidence for Evolution
• Darwin wrote a book, “On the Origin of
Species” which today is still a unifying
theme of biology
• There is variation among population
• There is an overproduction of
offspring
• Three is a struggle for survival,
competition for food and shelter
• The fittest survive and reproduce
• Heritable variations are passed onto
offspring
• Giving way to “decent with
modification”
III. Natural Selection and Evidence for Evolution
•
Interpreting Evidence After Darwin
• Modern biologists define evolution as any
change in the gene pool of a population
• gene pool is the combined genetic
information of all the members of a
population
III. Natural Selection and Evidence for Evolution
B. Three Types of Natural Selection
•
Directional Selection
• Favors individuals possessing extreme values
of a trait, which causes the population to move
in a particular direction
• If a climate becomes colder, a population
may evolve in a consistent direction in
response—thicker fur
Directional Selection
# of
Individuals
Phenotypic Range
Shift towards ONE extreme
III. Natural Selection and Evidence for Evolution
•
Stabilizing Selection
• Acts against individuals who deviate too
far from the average, favors the average
• Sizes in lizards: large lizards may be
subject to predation; small lizards may
have a hard time defending territories,
natural selection favors the average
Stabilizing Selection
# of
Individuals
Phenotypic Range
Shift towards
middle
III. Natural Selection and Evidence for Evolution
•
Disruptive Selection
• Adapts individuals in a population to
different habitats.
• Similar to directional selection—but it
favors either extreme
• May occur in an area that provides very
different resources
III. Natural Selection and Evidence for Evolution
•
Galapagos finches had a variety of food choices:
smaller birds fed on small seeds, larger birds feed
on large seeds. Natural selection favors both but
not the average who would compete for both
resources.
Disruptive Selection
# of
Individuals
Phenotypic Range
Shift towards
both extremes
III. Natural Selection and Evidence for Evolution
C. EVIDENCE FOR EVOLUTION
III. Natural Selection and Evidence for Evolution
•
Fossil evidence
•
•
•
Not all species existed at the same time
Fossil record is fully consistent with the
prediction that more “derived” groups
should appear over time in the fossil record
There has not been a single case of a
species out of order—no mammals mixed in
the rock with early fish
III. Natural Selection and Evidence for Evolution
III. Natural Selection and Evidence for Evolution
• Fossil evidence
• Life began in the sea. The oldest fossils are
marine
Burgess Shale: 505 Million Year Old Coral Reef
III. Natural Selection and Evidence for Evolution
• Fossil Evidence
• Transitions between major groups (classes) of
species
• Fish amphibians (transition from ray-finned fish to
tetrapods (vertebrate with 4 limbs)).
• Reptiles birds (Archaeopteryx)
• Reptiles  mammals (synapsid reptiles (therapsids)
have very mammalian characteristics
The London Specimen and a
reconstruction of Archaeopteryx
(from Levin, 1996)
III. Natural Selection and Evidence for Evolution
• Fossil Evidence
• Transitions between classes (ex. Orders of
mammals)
Gradual loss of legs
Leg bones become
smaller and smaller
in more recent
whales
Modern whales
have remnants of
their ancestral
hind legs
III. Natural Selection and Evidence for Evolution
• Fossil Evidence
• Well preserved family groups (horse
family)
III. Natural Selection and Evidence for Evolution
• Fossil Evidence
• Well preserved communities of species
that no longer exist but resemble modern
species. (Rancha LeBrea Tar Pits, Los
Angeles 25,000 years ago)
III. Natural Selection and Evidence for Evolution
• Biogeographical
• Species that existed in the past are fossilized
in areas where species that resemble them are
living now
• Geographic Distribution
• organisms that live under similar
ecological conditions are exposed to
similar pressures of natural selection
• Because of similar selection pressures,
different animals end up evolving certain
striking features in common
III. Natural Selection and Evidence for Evolution
• Adaptations: gradual change in an
organism that enables it to survive in a
particular environment.
• Types
• Structural
• Behavioral
• Physiological
III. Natural Selection and Evidence for Evolution
• Structural
• Structural adaptations are physical features of
an organism like the bill on a bird, the fur on a
bear, stinging cells of jellyfish or sticky tongue
of an anteater
III. Natural Selection and Evidence for Evolution
Structural adaptations
• homologous structures (HSS)
• structures that have different mature
forms in different organisms but
develop from the same embryonic
tissue
• exist among related groups,
providing support for having a
common ancestor
Highly complex anatomical structures have evolved from simple
structures that served the same purpose:
ex: different kinds of eyes
III. Natural Selection and Evidence for Evolution
Structural Adaptations:
• analogous structures (ASF)
• outwardly similar structures
III. Natural Selection and Evidence for Evolution
Structural Adaptations:
•vestigial structures (NF)
structure that serves no useful
function in an organism
(A) Whales have
pelvic bones
floating in their
abdominal cavity
Vestigial Structures
(B) Pelvic bones in
pythons are
unused remnants
from their common
ancestor shared
with lizards
We would not expect to see these structures if snakes had an
origin separate from other vertebrate animals.
(c) Blind salamanders
have eyes with retinas and
lenses, yet the eyelids grow
over the eye, sealing them from
outside light
Vestigial Structures
(D) Flightless Cormorant
Wings: Cormoront lives on
Galapagos Islands, & has wings
too small for flight
(E) Legless Skinks a type of
lizard. In some species the legs
have become vestigial. (so
reduced that they no longer
function)
Human Vestigial Structures
•Humans have > 100 vestigial structures.
•90% develop wisdom teeth (molars used for
chewing & grinding plant material) which usually don’t
erupt from gums, can be malformed and cause pain.
•Tailbone (Coccyx) fused vertebrae that in other
vertebrates are tails. It serves no purpose.
•Ear muscles used in other vertebrates for twitching
•Appendix part of digestive tract
used to digest tough plant material is
so reduced in humans that it is
dysfunctional
III. Natural Selection and Evidence for Evolution
• Adaptations
• Behavioral
• Behavioral adaptations are the things
organisms do to survive. For example, bird
calls and migration are behavioral
adaptations.
III. Natural Selection and Evidence for Evolution
Adaptations
• Physiological
• A metabolic adjustment within the cell, or tissues
of an organism in response to an environmental
stimulus, resulting in the improved ability of that
organism to cope with its changing environment.
• Physiological adaptations can develop
rapidly
• digestive enzymes
• hemoglobin
• bioluminescence
III. Natural Selection and Evidence for Evolution
• Embryological Evidence
• during the early stages of development
many animals with backbones are so
similar that they can be hard to tell apart
• embryonic development shows that the
same group of embryonic cells develop
in the same order and in similar
patterns to produce tissues and organs
of all vertebrates
III. Natural Selection and Evidence for Evolution
•
Molecular/biochemical evidence
•
•
•
Fields unknown during Darwin’s time
support predictions made from his theory
and provide independent evidence that is
congruent with the fossil record
All organisms share the same genetic
code which code for amino acids that
make up proteins
Ex. DNA, ATP, proteins
III. Natural Selection and Evidence for Evolution
• Molecular/biochemical evidence
• Mutations that help an organism survive
its environment are passed on to the next
generation.
• Species that diverged longer ago have
more differences in their corresponding
proteins. (just like comparing how closely
related two humans are, one can compare
how related different species are.
• Flagella-• http://www.millerandlevine.com/km/e
vol/design2/article.html
IV. Mechanisms of Evolution
IV. Mechanisms of Evolution
•
A. Population Genetics
•
POPULATIONS, not individuals, EVOLVE
• Gene pool—all of alleles of population’s
genes
• Allelic (gene) frequency--% of specific allele
in gene pool
• Genetic equilibrium—gene frequency
remains constant over many generations (not
evolving)
IV. Mechanisms of Evolution
Changes in Genetic Equilibrium
• Mechanisms for genetic change
1. Mutation—environmental factors or
chance
2. Sexual reproduction
3. Gene flow —when individuals enter
or leave a population
Immigration -individuals moving
INTO a population
Emmigration -individuals moving
OUT of a population
4. Natural selection is the most significant
factor to cause change in a gene pool
IV. Mechanisms of Evolution
Example of Gene Flow
Genetic drift —occurs in small populations that become
isolated like animals in the Galapagos
• In each generation, some individuals may, just by
chance, leave behind a few more descendents (and
genes, of course!) than other individuals.
• The genes of the next generation will be the genes of
the “lucky” individuals, not necessarily the healthier or
“better” individuals.
• It happens to ALL populations—there’s no avoiding the
vagaries of chance.
IV. Mechanisms of Evolution
• Genetic drift can cause big losses of genetic
variation for small populations.
• Examples: Bottleneck Populations and Founder
Effect
Population bottlenecks
occur when a population’s size is reduced for at least one generation.
• Reduced genetic variation means that the
population may not be able to adapt to new
selection pressures, such as climatic change
or a shift in available resources, because the
genetic variation that selection would act on
may have already drifted out of the
population.
An example of a bottleneck
• Northern elephant seals have reduced genetic
variation probably because of a population
bottleneck humans inflicted on them in the
1890s.
• Hunting reduced their population size to as few
as 20 individuals at the end of the 19th century.
• Their population has since rebounded to over
30,000—but their genes still carry the marks of
this bottleneck: they have much less genetic
variation than a population of southern
elephant seals that was not so intensely
hunted.
IV. Mechanisms of Evolution
Founder effect
• A founder effect occurs when a new colony is
started by a few members of the original
population. This small population size means that
the colony may have:
• reduced genetic variation from the original
population.
• a non-random sample of the genes in the
original population.
Example of Founder Effect
• For example, the Afrikaner population of
Dutch settlers in South Africa is descended
mainly from a few colonists.
• Today, the Afrikaner population has an
unusually high frequency of the gene that
causes Huntington’s disease, because those
original Dutch colonists just happened to
carry that gene with unusually high
frequency.
• This effect is easy to recognize in genetic
diseases, but of course, the frequencies of
all sorts of genes are affected by founder
events.
V. Evolution of Species--Speciation
V. Evolution of Species--Speciation
Add this!
Species: a group of organisms with a
common gene pool that is
reproductively isolated from other
organisms
Isolating mechanism: factors that restrict
gene flow between species and
sometimes different populations within
a species
V. Evolution of Species--Speciation
A. Allopatric Speciation
• geographic barrier physically isolates populations of
a species which blocks gene flow
• once isolated allopatric populations (living in
different places) accumulate genetic differences due
to natural selection, genetic drift, and new mutations
• removing the geographic barrier---the following
could happen:
1. meld together by allele flow and
2. recombination once again to form a single
species;
3. remain reproductively isolated—pre-mating
or post-mating isolating mechanisms-different types of reproductive isolation
Example of Allopatric Speciation
• island chains frequently produce new species;
• provide geographic barriers that facilitate
invasion and re-invasion by different species;
• this is the probable mechanisms for the
proliferation of Darwin's finches on the
Galapagos Islands;
• Hawaiian Islands once supported thousands of
speices of Drosophilia flies that probably evolved
by a similar mechanism
V. Evolution of Species--Speciation
B. Sympatric speciation (does not involve a geographic
barrier)
• results from intrinsic factors such as chromosomal
changes and non-random mating
• become genetically isolated even though their
ranges overlap
ex. polyploidy, non-random mating
• change in Chromosome Numbers and Speciation
Ex. Polyploidy—more than a normal set of
chromosomes.
V. Evolution of Species--Speciation
C. Reproductive Isolation—interbreeding organisms
can no longer mate and produce fertile offspring
• Genetic material very different so fertilization
doesn’t occur
• Behavioral—mating at different times of
day/month/year
• Different pheromones
• Mechanical—physical differences prevent mating
between species
VII. Pacing of Evolution
VII. Pacing of Evolution
Gradualism—fossil evidence shows this
• Explanation that evolution involves a
slow and steady accumulation of
changes over a period of time
Punctuated equilibrium —occurs relatively
quickly, in rapid bursts, with long
periods of genetic equilibrium in
between
• Pattern of long, stable periods of stasis
(no change) interrupted by brief
periods of rapid evolution
VIII. Patterns of Evolution
VIII. Patterns of Evolution
A. Convergent Evolution
•
•
Two different species develop similar
adaptations because they live in similar
environments
For example—ability to move through the
water rapidly—shark (fish), penguin
(bird), and dolphin (mammal)
•Species evolve to fill niches
•Mutations occur randomly in geographically distinct
populations
•Natural selection allows the mutations that “work” to become
adaptations
VIII. Patterns of Evolution
B. Divergent Evolution
• Occurs when a population becomes
isolated from the rest of the species and
begins to follow a different evolutionary
course
• often results in adaptive radiation
• associated with the opening up of a new
biological frontier
• For example—Darwin’s finches which had
different beak lengths
Examples of Divergent Evolution
Example of Adaptive Radiation
(divergence into an abundance of available niches)
VIII. Patterns of Evolution
C. Coevolution
• Two different species evolved at the same
time because of a beneficial relationship
between the two groups
IX. Primate Adaptation and Evolution
•
Primate—a group of mammals that include
lemurs, monkeys, apes and humans
•
•
•
•
•
Most are arboreal (live in trees)
Binocular vision
Opposable thumbs
Flexible joints
Fossils indicate that they appeared on
earth 60-70 million years ago
•
Major trends—increasing brain size and
walking upright
X. Human Ancestry
•
Earliest Hominids
•
•
•
•
Australopithecine fossils from Africa 5-8
million years ago
Bipedal and climbed trees
Brain and body size increased and jaws
and teeth decreased in size
Stone Tools and genus homo
•
•
Appeared 2 million years ago
Use of fire, language, and culture
developed
Embryological
development matches
the progression of
fossils in the fossil
record
Fossil
Record
Vertebrates not only
repeat the development of
ancestral vertebrate but
they have similar bone
structure and unused
remnants of their
structures
Anatomical
Embryological
Present & past distribution
of continents explains the
distribution of fossils
Mutations exhibited
in bacteria provide
concrete evidence
for the changes that
lead to the
branching of species
observed in the
fossil record
Amino acid sequences
are more similar in
species with more
similar bone
structures.
Biogeography
Molecular
Mistakes during
cause
DNA
REPLICATION
MUTATIONS
Add variations to
GENE POOL
NATURAL
SELECTION
ADAPTATIONS
Direct Evidence (microevolution)
Evolution Before Our Very Eyes
1. Selective Breeding
2. Industrial melanism.
3. Antibiotic resistant bacteria
4. Herbicide resistant weeds.
5. Annual changes in influenza viruses
6. Pesticide Resistant Insects
7. Resistance to anti viral medicines (HIV)