Transcript Document 7562882

Chapter 15-Darwin’s theory of
Evolution Evolution
I.
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The Puzzle of Life’s Diversity
___________________-variety of organisms
_________________-change over time
Voyage of the Beagle
–
Charles Darwinsailed____________________(1831) and
collected many scientific observations –
particularly of interest at the area around
S.America and the Galapagos Islands
Biological
Diversity
H.M.S. Beagle
– Darwin collected ___________ remains-some
resembled living organisms and some did not--indicating species had disappeared
.
– Observed great diversity and saw so many
organisms were well suited to their environments
and various patterns ----leaving him w/ many
questions…
Fossilized
– Although the Galapagos Islands were very near
S.America,their climates were different than
S.America and each other.The
_________________ and iguanas varied in
predictable ways from island to island/also many
observations on variations in birds-eg. Size or
shape of beak.
– After returning to England , he began to wonder if
the animals on different islands were once
members of the same species.
tortoises
II. Ideas that shaped Darwin’s thinking
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Predominate thought was that the earth and inhabitants
were only a couple thousand years old.
__________________ published a detailed hypothesis
about the geological forces that have shaped the earthproposing layers of rocks formed slowly and the
physical earth was shaped by a variety of forces..
_____________________________________ wrote
Principles of Geology .---stressed that scientists must
explain past events based on processes they can
actually observe---eg. By volcanoes that we still observe
may we get an idea of how the earth has changed
1795-James
Hutton
Charles Lyell in
1800’s
Lamarck
– _________________(1809)-realized organisms
change over time but he felt that selective use or
disuse of organs caused organisms to acquire or
lose traits
• 1) _____________He said all organisms have a
tendencies towards perfection ..thus
continually acquiring characteristics to
improve themselves----Thus he would say birds
fly because they long ago tried to and their
wings kept developing over the generations to
fly.
Perfection
USE AND DISUSE
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INHERITANCE OF ACQUIRED
CHARACTERISTICS
2) ________________if something is used it is
transformed for that purpose while if it not
used,it would eventually disappear
3)____________________.---If a giraffe
stretched its neck to reach its food,it would
pass that trait on…
4)Evaluating Lamarck- incorrect in many
ways– He did not know an organism’s
experiences or behavior have no effect on
inheritance
Thomas Malthus1798
• Population Growth-_____________-reasoned that if
the human population continued to grow
unchecked,sooner or later there would be
insufficient space & food---war,famine and disease
work against this
• Darwin realized this applied less to humans than
other animals and plants because
_______________________________________
People do not reproduce as
much young
III. Darwin presents his case
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A. publication
• 1858-Alfred Russel Wallace summarized the
thoughts on evolutionary change Darwin had been
looking @ for 25 years…This gave Darwin the
incentive to publish his work
• 1859—Darwin Published “On the origin of
Species…”proposed the mechanism for evolution to
be ______________________________________
Natural selection
B. Inherited Variation and Artificial Selection
• Members of each species vary from one another
• Some variation heritable-passed on
• ______________________selective genetic variation
where nature provides the variation and humans
select to breed for this characteristic
Artificial selection
C. Evolution by Natural Selection
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1)
Struggle for existence
• Applying Malthus’ principles,He realized high
birth rate and shortage of resources
produced _______________________struggle for existence---faster,etc. avoid being
caught
competition
2) Survival of the Fittest
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_____________________=ability of an individual to
survive and reproduce
___________________=any inherited characteristic
that increases an organism’s chance of survival
Organisms w/ low levels of fitness are unlikely to
survive and reproduce
__________________________________=survival
of the fittest….may inherited characteristics of a
population
Natural selection
fitness
adaptation
3) Descent with Modification
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Over long periods ,natural selection produces
organisms that have different structures,establish
different niches,or occupy different habitats---each
species descends ______________________.
– Implies all living organisms are related to each
other
– _____________________________-all speciesliving and extinct were derived from common
ancestors
Modification/changes
Common descent
D.Evidence of Evolution
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1) Fossil Record-record of the history of life on
earth-comparing fossils from different layers
Felt the earth was millions of years old
Since Darwin,people have discovered many
transitional species in fossilized form
Gaps remain—providing some uncertainty
about how some species evolved
2)Geographic Distribution
• With reference to birds he observed,Darwin felt
although they varied,they descended with
modification from common mainland S.American
ancestor
• Animals w/certain similarities between areas
developed this way due to similar ecological
conditions
3)Homologous Body Structures----structures that have
different mature forms but develop from the same
embryonic tissue
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Example:The bones of a bird skeleton
more closely resemble homologous
bones of certain reptiles than that of bats
• ___________________________-traces of
homologous organs….appear to have no function
Vestigial organs
4)Embryological Similarities-many embryos look esp.
similar during certain stages of
development…producing homologous structures
E. Summary of Darwin’s Theory
Inherited
traits
• Individuals differ and some can be
___________________________.
• Organisms produce more offspring that can survive
and many do not _________________________.
• Organisms ______________for limited resources.
• Each unique organism has unique advantages and
disadvantages in struggling for existence---Those
best suited will reproduce,passing on their traits.
• Species alive today descended with modification
from ancestral species…uniting us in a single tree of
life
reproduce
compete
Strengths and Weaknesses
• Continues to change as new data and
technology develop
• Argument about extinction
• Origin of life
Evolution cont’d-pieces of Chapter
16 & 17
• _____________________=all genes,inc. all the
different alleles,that are present in a population
• ______________________of an allele= # times that
the allele occurs in a gene pool,compared with the #
of times other alleles for the same gene occur.(often
a %)
• In genetic terms ,evolution is any change in the
relative frequency of alleles in a population.
Gene pool
Relative
frequency
Sources of genetic Variation– 1)mutations
– 2)gene shuffling
– ----- Natural selection can affect the distribution of
phenotypes in any of the 3 following ways:
• 1) Directional selection-Individuals @ one end
of curve have higher fitness than those @
middle or other end-Example-birds w/
large,wide beaks can crack large seeds….If the
supply of small seeds decreases,they dominate
• 2) ___________________-individuals near center of
curve have higher fitness—example-babies of
average weight survive better than very low or high
birth weights.
Stabilizing
Selection
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3)______________________________-individuals
@ upper and lower end of curve have higher
fitness than individuals near middle-example midsized seeds become less common and large
beaked or small beaked birds both benefit.
Disruptive
selection
_________________________________=
random change in allele frequency
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Genetic Drift
___________________________Principle-allele
frequencies in a population will be constant unless one
or more factors change it.
• 5 conditions for it(GENETIC EQUILIBRIUM) to hold
– 1)genetic equilibrium from generation to
generation
– 2)random mating
– 3)large pop.
– 4)NO emigration or immigration
– 5) no mutations or natural selection
Hardy Weinberg
• ___________________= formation of new
species
• Due to• Isolation-reproductive isolation due to
behavorial,geographic or
______________________isolation(reproduce
@ different times)
speciation
temporal
• ______________________________are
scientists who study fossils
Paleontologists
How fossils form:
• sedimentary rock
• sometimes an imprint and sometimes a preserved
remains
• buried in resin-amber
• tar pits
Dating– compare w/other sediments and fossils
– radioactive dating using half lives-esp. C-14,since its half
life = 5730 years
• Geologic Time scale-see p.421
3 Eras
Mesozoic
• Paleozoic,_______________________ and Cenozoic
– 1) Paleozoic-diversity of marine life
– 2) Mesozoic-increasing dominance of
Dinosaurs,flowering plants appear
– 3) Cenozoic-mammals evolved adaptations to allow
them to live in various environments
periods
_________________-are subdivisions of
eras
• Earth’s early atmosphere probably contained Hcyanide,CO2,CO,N,H2S and H2O
• Miller & Urey’s experiments suggested how mixtures
of the organic compounds necessary for life could
have arisen from simpler compounds.This was not
totally accurate –the experiment-but lead to similar
experiments-even producing nitrogenous bases .
• ~ 200-300 million after earth cooled to carry water,
cells similar to bacteria developed, beginning
w/something similar to a cell membrane
coacervate
Amino acids produced
• Next eukaryotic cells developed
by______________________________as a
symbiosis formed between
prokaryotes….eventually specializing into
organelles like_________________
• Margulis supported this in the 1960’s w/the
following evidence:
– mitochondria and chloroplasts carry DNA
similar to bacterial DNA.
– mitochondria and chloroplasts have ribosomes
similar to that of bacteria
– mitochondria and chloroplasts reproduce by
binary fission a lot like bacteria
mitochondria
Endosymbiotic Theory
Patterns of Evolution• 1)extinction
• 2) ___________________________single species evolve into several different
forms in different ways
Adaptive
radiation
3._______________________________-unrelated
organisms come to resemble one another
• Convergent evolution
4._____________________________-2 species evolve in
response to changes in each other over time
• Coevolution
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5_____________________-long,stable
periods,interrupted by brief periods of more rapid
change
In spurts
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6. __________________--opposite of punctuated
equil.---slowly over a long period of time
Punctuated equilibrium
gradualism