Transcript Document 7115132

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change that occurs over time
it is NOT how life originated on Earth
it is a scientific theory, which means it is
supported by scientific evidence
MICROEVOLUTION refers to smaller scale
evolutionary changes within a species; can be
seen in a lifetime
◦ Example: bacteria changes
MACROEVOLUTION refers to large scale
evolutionary changes; cannot be seen in a
lifetime
◦ Example: formation of new species
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Divergent Evolution
Convergent Evolution
Coevolution
Divergent Evolution
related species becoming more dissimilar
Spontaneous Generation* (life can arise from
nonliving things) was being replaced by Biogenesis
(life arising from life).
◦ *Disproved by Redi (meat experiment) and Pasteur (broth
experiment)
Earth was…
 a few thousand years old
 populated by unchanging life forms - made during a single
week in which the creator also formed the entire universe
Neither the planet nor its inhabitants had changed since creation
Rocks and major geological features were produced suddenly
by catastrophic events – floods, earthquakes, …
Darwin - NOT the first to suggest evolution
several Greek philosophers (Plato & Aristotle)
believed in a “gradual evolution of life”
Linnaeus
◦ Father of Taxonomy (the science of
classification) grouped similar species into
categories
◦ devised system of
binomial nomenclature
Cuvier - developed the science of Paleontology
He said…
each layer (stratum) of rock has unique fossil species
the deeper the stratum, the more different the fossils
are from modern life due to relative age
Hutton and Lyell - said that the
Earth is millions of years old
◦ changes in Earth result over a long
period of time
◦ geological processes continue to
“shape” the Earth today
Darwin was especially influenced by the work of
Hutton and Lyell because…
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He reasoned that if Earth could change, so could its living
inhabitants
Lamarck
◦ Wasthe first to suggest how evolution might occur
Proposed 2 main ideas:
1. Use and Disuse - parts of the body used extensively become
larger and stronger (Example: blacksmith’s arm)
2. Inheritance of Acquired Characteristics - modifications an
organism acquires during its lifetime can be passed to offspring
According to Lamarck,
the giraffe’s long neck
was acquired by
stretching to get to the
highest leaves.
Slightly longer necks
were passed on to the
young and so on…
and so on….
1809-1882
British
Naturalist
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proposed the idea of evolution by natural
selection
collected LOTS of evidence to support his
ideas
GREAT BRITIAN includes England, Sotland, and Wales
UNITED KINGDOM includes - England, Scotland, Wales & Northern Ireland
1831- 1836
Darwin
served as the
ship’s naturalist
HMS Beagle traveled around the world –
main purpose was to chart the coast of South
America
Darwin…made observations, collected flora and
fauna and
studied geological features and land forms
Figure 22.5 The Voyage of HMS Beagle
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relatively recent volcanic
origin
most animal species live
nowhere else
BUT they DO resemble
species living on the
mainland of South
America
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Observed 13 types of finches
Although similar, they seemed to be different species
◦ some were unique to individual islands
◦ some were distributed on 2+ islands
Beaks were different
He hypothesized that the beaks of the finches were evolutionary
adaptations to different food sources
It occurred to Darwin that a new species
could arise from a ancestral form by the
gradual accumulation of adaptations
(good traits) to a different environment.
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early1840’s, Darwin had his major features
of his theory of evolution by natural selection
he did not rush out to publish his beliefs
because his “ideas challenged fundamental
scientific beliefs of his day”
“Darwin was not only stunned by his
discoveries, he was disturbed by them.”
1858 Darwin received a manuscript from Wallace
who had come up with a theory of natural selection
that was very similar to his own
in 1859, Darwin published his book, The Origin of Species.
natural variation -
differences among
members of a species
are due to genetic
variations
genetic variation -
variations in the
genetic makeup of the
members of a
species
1. MUTATION….
a change in the DNA
2. GENE SHUFFLING….
the rearrangement of genetic
information
process by which organisms with favorable
traits survive and reproduce at higher rates
today, we use
the phrase…
“survival of
the fittest”
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variation must exist among members of a species
many more individuals are produced each generation
than will survive – “struggle for existence”
some individuals are better adapted so they survive
and reproduce – “survival of the fittest”
fitness – the ability of an organism to survive
and reproduce – is the result of adaptations
adaptation – any inherited characteristics that
increases an organism’s chance of survival
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members of a species compete for food, space,
mates, and other resources - competition
according to Darwin, natural selection led to
speciation….the development of a new
species
SPECIATION
These are all the same species of beetle.
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dramatic color variations exist
color variations are inheritable and are passed on
those with coloration that best allows them to blend
with their environment will survive, reproduce and
pass on their coloration genes to their offspring
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Darwin found evidence that natural selection might
work by studying artificial selection
Artificial Selection…
the breeding of domesticated plants and
animals
All domestic dogs were originally bred from
wolves.
Insecticide Resistance
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works much like antibiotic
resistance in bacteria
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bugs susceptible to the
insecticide die
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any bug that has a
“resistance gene” will
survive and reproduce
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Darwin perceived unity in life with all
organisms related through descent
from some unknown ancestor that lived in
the remote past.
As descendants of the first organism spilled
into various habitats over millions of years,
they accumulated diverse modifications
or adaptations that fit them to specific
ways of life.
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variation exists in populations
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more organisms are made than can exist in a population
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(variation is often inherited – genetically based)
(called OVERREPRODUCTION - competition results)
natural selection occurs through
(1) interaction with the environment
(2) variability among individuals in a population
better “fit” individuals produce more offspring
(they pass their “better fit” genes on to their offspring and so on…)
the product of natural selection is….
adaptation of populations to their environment
INDIVIDUALS CANNOT EVOLVE
(1 individual with a new trait does NOT mean a new species has
evolved)
1809
1825
1827
1827
1828
1831
1836
1838
A TIMELINE OF DARWIN’s LIFE
- Charles Robert Darwin born in England
- began pursuit of a medical career at University of Edinburgh in Scotland.
- quit medical school
- attended Christ's College at Cambridge - studying for the clergy
- met Reverend Henslow, Professor of Botany at Cambridge
to 1836 – served as naturalist on board the HMS Beagle
– met geologists Lyell and Owen
- Darwin read a book by economist, Malthus
Malthus put forward the idea that as human populations grow and
resources become scarce the weak die off in a struggle for existence.
Darwin theorized that the same kind of relationship may exist in the wild.
1842 - wrote up a sketch of his ideas about evolution
1844 - wrote an "In the event of my sudden death" letter to his wife
In it he requested that upon his death she promote
the publication of his essay on evolution.
1858 - received a paper from Wallace in which Wallace had come up with a
theory of natural selection that was very similar to his own
1859 - published The Origin of Species
1866 - the phrase, “survival of the fittest," was coined by Spencer and became a
substitute for the phrase “natural selection"
1882 - Darwin died
Chapters 14 & 15
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Fossil Record
Geography
Comparative Anatomy
Comparative Embryology
Comparative Biochemistry
FOSSIL….
 a trace of a long-dead organism
 usually left in sedimentary rock and
can be seen in different layers (strata)
examples: trace (footprints, scat), mold (imprint),
cast (rocklike model), replacement, petrified, amber,
original material (bones, shells, seeds, feathers)
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There are many gaps in the fossil record
Provide for a more detailed pattern of change
There are many of these that share features of
different species.
◦ Derived traits: new traits since ancestor (ex: feathers)
◦ Ancestral traits: retained traits of ancestor (ex: teeth)
The 2 most common ways are…
 Relative Dating: based on law of
superposition (lower fossils are older)
 Radiometric Dating: based on half-life (uses
the decay of radioactive isotopes to measure
the age)
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The study of the geographic distribution of life
forms on Earth.
The existence of similar but unrelated species was
puzzling.
Plate tectonics shifted Pangaea.
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Analogous Structures
Homologous Structures
Vestigial Structures
similarities in the embryological
development of species indicates common
ancestry
similarities in the biochemistry of
species indicates common ancestry
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almost all living organisms have the same
molecules: DNA, RNA, ATP, enzymes, etc.
amino acid sequences are similar
genetic code = A T C G (in ALL living things)
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Gene pool – combined genetic information of all the
members of a particular population – typically
contains 2+ alleles (forms of a gene) for each trait
Due to natural selection – alleles may be “removed”
from the population – thereby changing the genetic
make up of the population
Genetic drift – occurs in small population when
individuals that carry a particular allele may leave
more descendants than other individuals - over time,
can cause an allele to become more common in a
population
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Founder effect: occurs when small samples of
a population settles apart from the
population
◦ Ex: Amish & Mennonite
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Bottleneck: population declines to a very low
number then rebounds
◦ African cheetahs
1. Stabilizing selection: eliminates extremes;
the average expression leads to higher fitness
(most common form)
◦ Baby’s birth weight
2. Directional selection: extreme version of a
trait has more fitness
◦ Galapagos finches; Peppered moths
In the 1800’s many moths in the British Isles began to become
darker in color .
In 1849, a coal-black mutant was found near Manchester, England.
Within a century, this black form had increased to 90% of the
population.
The moth rests by day on tree trunks and is preyed upon by birds.
 In rural areas, the trunks of trees are encrusted with lichens.
 In areas where air pollution is severe, toxic gases and soot has
killed the lichens and blackened the trunks. In these areas, the
darker form of the moth has a much better chance of survival.
PEPPERED
MOTH
3. Disruptive selection: average traits are
removed and extremes are left
Ex: snakes with extreme color will camo
4. Sexual selection: operates in populations
where males and females differ in appearance
Ex: birds
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Two types will prevent gene flow
Prezygotic isolating mechanism – prevent
fertilization from occuring
◦ Behavioral, geographical, ecological
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Postzygotic isolating mechanism - a sterile
offspring is made
◦ Liger
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Allopatric speciation: physical barriers divide
populations (most common)
◦ Mountains, rivers, etc.
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Sympatric speciation: no physical barriers
◦ Insects, plants (polyploids)
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Gradualism: evolution occurs in small,
gradual steps
Punctuated equilibrium: rapid spurts of
genetic change cause quick divergence
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the theory that eukaryotic cells arose from a
symbiotic relationship among different prokaryotic
organisms