Transcript Evolution - sciencebruemmer

Problem Solving
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Cheetahs are the world’s fastest land mammal.
They have the ability to run almost 70 mph in
pursuit of prey. All other big cats can only run
about 35 mph over very short distances
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Do you think the cheetah’s speed is important to its
survival? Why or why not?
How do you think a biologist would explain the
cheetah’s speed, based on the fact that their
ancestors (and all other cats) only run 35 mph
Remember, you are trying to think of a way that all
cheetahs got faster over time
Evolution
Microevolution
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Microevolution is the occurrence of small-scale
changes in allele frequencies in a population,
over a few generations. Therefore, species can
still breed.
These changes may be due to several
processes:
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Mutation: structural changes
natural selection/artificial selection: selection of
certain allele for favorable characteristics
gene flow: transfer of genes from one generation to
next
genetic drift: random accumulation of genes in a
population; some genes may be removed.
http://www.wadsworthmedia.com/biology/049511
l
Genetic Drift
Population
Selection
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Directional
selection:
Stabilizing
selection:
Disruptive
selection:
http://bcs.whfre
eman.com/thelif
ewire/content/c
hp23/2302001.
html
Gradualism vs punctuated
equilibrium
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Gradualism - evolution proceeds at a
steady pace, without the sudden
development of new species or biological
features
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Punctuated equilibrium
species will experience little evolutionary
change for most of their geological history
 evolution occurs in localized rare, rapid
events of branching speciation (called
cladogenesis)
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Cladogenesis - the process by which species
split into two distinct species, rather than one
species gradually transforming into another
•What caused these ancestral related owls to evolve?
•What is the process called?
Speciation
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Making of a new
species over time
Sexual dimorphism
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http://www.pbs.org/wg
bh/evolution/library/05/
2/l_052_04.html
Example:Geographic
isolation
Jean-Baptiste Lamark
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3 basic ideas:
A change in the environment causes a resulting change
in the org. behavior
2. The behavior change causes the org. to use or not use
various organs
3. The added use of an organ will cause it to grow &
become more complex, the disuse of an organ will
cause it to atrophy or waste away
1.
For Example, Lamarck thought that giraffes got longer necks by
stretching to reach food. By using all of the muscles in the neck,
their necks got longer. The giraffes would then pass on the extra
height to their offspring, who would be born just as tall as their
parents.
“Use it or lose it”
Charles Darwin
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A religious, naturalist who put
together evidence from his
voyage to theorize “decent
with modification”. (common
ancestor)
He reluctantly published On
the Origin of Species in 1859
after pressure from A.
Wallace.
Macroevolution
Darwin’s idea
4 Basic Ideas:
1.
2.
3.
4.
There are variations w/in populations of organisms
and these variations can be passed to offspring
Each generation produces more offspring than survive
to adulthood = Overproduction
The organism must struggle to exist.
The organism with the favorable characteristics
survive better and reproduce more often, thus
transmitting their traits to the next generation “Survival
of the fittest” = adaptation
Evolution by Natural Selection
http://www.teachersdomain.org/resource/tdc02.sci.life.evo.howreally/
Selection
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Artificial Selection:
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Nature provides
variation, and humans
selected useful
variations.
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Example: dog
breeding
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G. Mendel's work on
genetics supported
Darwin’s ideas.
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Natural Selection:
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In nature variations
are selected for to
change the species
“fitness”.
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Example: giraffe neck
Does nature always select
best?
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Antibiotic resistance
http://nortonbooks.com/college/biology/animatio
ns/ch17a04.htm
Evidence supporting Evolution
Fossil
 Biogeography
 Anatomy
 Developmental
 Biochemical
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Time scale
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http://www.johnkyrk.com/evolution.html
Nature of Fossils
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A fossil is a trace of longdead organisms.
Fossils are often found in
layers of sedimentary
rock, which is formed
when sediment, such as
dust, sand, or mud is
deposited by wind and
water.
Usually develop from the
hard body parts which are
replaced by minerals over
time
Distribution of Fossils
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The lowest stratum, or layer, in a cross section
of Earth is oldest, while the top stratum is the
most recent.
Fossils found within a single stratum are of the
same approximate age.
Relative age of a fossil says that a given fossil
is younger or older than another based on what
stratum it is found
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Fossil Activity
Absolute age could be estimated from
radioactive dating
Radioactive
dating
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http://www.teachersdomain.org/resource/tdc02.sc
i.life.evo.radiodating/
The Fossil Record
Fossil evidence shows a long history of life
on Earth.
 The history of life is one of constant change
and a tremendous diversity of life-forms
 We can trace how organisms have changed
over time by comparing fossil remains from
different eras
 Lyell: “Principals of geology”; explained that
the geological features of the earth occurred
over long periods of time.
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Transitional fossils:
How did all these flightless
end up on different contents?
birds, who are related,
Biogeography Evidence
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Biogeographical: is the study of the geological
distribution of fossils and of living organisms.
A comparison of recently formed fossil types with
types of living organisms in the same geographic area
shows that new organisms arise in areas where similar
forms already lived.
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http://www.exploratorium.edu/origins/antarctica/ideas/g
ondwana2.html
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How does Biogeography support evolution?
Anatomical Evidence
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Homologous Structures – similar features
originated in shared ancestor.
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i.e. beaks of birds, forelimbs
Analogous Structures – same function & look
alike, but developed independently
Vestigial Structures – Useful to ancestors but
not to modern organism.
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i.e. Whales evolved from land animals (hind legs
Homologous Structures
Analogous
Structures
Analogous Structures
Vestigial
Structures
Developmental Biology
Embryology: in early stages of life
embryos are all similar, suggesting
common ancestry.
 What do evolutionary scientist think when
the embryos all appear similar in early
development?
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Biochemical Evidence
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Molecular: DNA is more similar than
different among most species.
Human DNA is 99.9% alike
 What does that suggest about Humans?
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Patterns of Evolution
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Convergent Evolution – Look similar, but
not related at all.
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i.e. Shark & porpoise
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Divergent
Evolution – 2 or
more related
populations or
species
become more &
more dissimilar
(Can result in
new species)
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i.e. Galapagos
Finches, dogs
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Coevolution – change of 2 or more
species in close association w/ each other.
Newts produce a potent nerve toxin that
concentrates in their skin.
 Garter snakes have evolved resistance to this
toxin.
 The relationship between these animals has
resulted in an evolutionary arms race that has
driven toxin levels in the newt to extreme
levels.
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What is a Primate?
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A primate is a member of the biological
order Primates, the group that contains
lemurs, lorisids, galagos, tarsiers,
monkeys, and apes (including great apes
and humans).
Primate
classification
Mountain gorilla
Spends more time on the ground more
than any other non-human primate
 Feet most resemble those of humans
 Found in Uganda and Rwanda
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Australopithecus afarensis
Australopithecus afarensis
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Lived between 3.9 and 2.9 million years ago
“Lucy” was discovered in 1974
Bipedal = walks on 2 legs
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Before the discoveries of A. afarensis in the 1970s, it
was widely thought that an increase in brain size
preceded the shift to bipedal locomotion.
“Selam”
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3 year old female A. afarensis discovered in Ethiopia
2006
Comparing
skulls
LUCY