EvolutionTEK 7A and 7B*" 2000 Steve Hall
([email protected]). Quoted by Permission."
*EvolutionEvolution means change over time. "The theory that all
forms of plant and animal life are descended from earlier and
simpler forms of life whose existence can be explained without
reference to a Supernatural Creator." *5 Evidences of
evolutionFossil RecordsDNA Sequencing Anatomical
similaritiesHomologous structuresAnalogous structuresEmbryonic
developmentConvergent and divergent evolutionPrentice Hall Biology:
Miller and Levine *Evolution through Fossil RecordsFossils were the
remains of ancient life, and the different layers of rock formed at
different times during the earths history.
Darwin proposed that the earth was millions of years old and
later, scientists compared fossils from older rock layers with
fossils from younger layers. Scientists used these comparisons to
prove that life changed over time.*Rebuttal However, there are gaps
in the fossil records of many species because some various
intermediate species are not found.
Rock Layering
*Fossil Layers
*Evolution through DNA sequencingDNA sequence: many major
species have much of their DNA sequence in common.
*Evolution through DNA sequencingFor example: humans and
chickens share 40% of their DNA in commonAll organisms (animals,
plants, insects, bacteria, and fungi) use the same DNA nitrogenous
bases and the same base pairing rules, regardless of size or
species. (AGTC)Scientists believe that species relatedness is based
on the DNA structures found.
*Evolution through DNA sequencingIf a scientist uses comparative
genomics and they find similarities in the segments of two
different species, they infer that the species are conserved
(related) in the last common ancestorIn humans and chimps are most
closely related In humans and mice 40% of the sequence alignsIn
humans and chickens 2% lines up and that percentage actually deals
with embryonic development and the alignment of fetuses.
*Evolution through DNA sequencingChimps share 99% of their DNA
with humans.*Evolution through DNA sequencingEven though we are
only 1% different in the sequencing of our DNA, the genes we share
are expressed completely different.Also, since most of DNA can be
called junk DNA, the sequences used are the most important thingFor
example: why do we share such a large amount of DNA with chimps yet
we can talk, but they cannot.
*Evolution through DNA sequencingBut the big issue is every
nucleotide isnt used in our genes.We have 3 billion bits of DNA
nucleotides written using ATCG.In DNA there are introns and exons.
Introns are DNA that are not involved in the coding for proteins
and surprisingly most of an organisms DNA are introns. About 95% of
the human genome has once been designated as "junk By Jaan Suurkula
M.D.*Evolution through DNA sequencingDNA files: Beyond Human
http://www.dnafiles.org/programs/beyond-human
*Evolution through DNA sequencingIn conclusion: Scientist
believe that an organisms DNA sequence can be used as evidence for
evolution because:All organisms use the same bases: ATGCOrganisms
share DNA sequencing patterns: Human vs. Chicken/Mouse/ChimpJunk
DNA: Intron and exon expression (scientists believe that they might
play a role in evolution)*Evidence of evolution through anatomical
similaritiesAnatomical similarities- many organisms have the same
or similar body structures that are similar only in FUNCTION! For
example our hands as compared to those of a sloth.
*Evidence of evolution through anatomical structuresHomologous
structures- similar body structures from organisms with a common
ancestor. Structures are similar in LOOK! but not necessarily in
function
*Evidence of evolution through anatomical structuresAnalogous
structure- body part in different species that is similar in
function but not in structure that evolved in response to a similar
environmental challenge. These parts came without coming from a
common ancestor. For example: bats and birds.
*Evidence of evolution through anatomical structuresVestigial
structures- organs that no longer have use but resemble homologous
structures.
*Evolution through embryonic similarities-
Embryonic similarities- organisms that look the same during the
early stages of development due to having a common ancestor
*Convergent EvolutionA phenomenon when two species with
differing ancestries display similar physical features. Many times
these changes are due to environmental circumstances that require
similar developmental for the purposes of adaptation
Divergent Evolution Divergent evolution occurs when a group from
a specific population develops into a new species. In order to
adapt to various environmental conditions, the two groups develop
into distinct species due to differences driven by the
environmental circumstances
Evolution
*EvolutionSpeciation- the evolving of a new species. Happens
through natural selection when the frequency of alleles changes,
forming a whole new species that cannot reproduce with the former
species.
http://en.wikipedia.org/wiki/Drosophila*Mechanisms for
speciationReproductive isolation- when members of two populations
cannot interbreed or their offspring is infertile.For example:
horses and donkeys, humans and monkeys
*Mechanisms for speciationBehavioral isolation- when two
populations can breed, but their mating rituals cause them to
either breed at different times, or mate differently. For example:
some species of fire flies
*Mechanisms for speciationGeographic isolation- two populations
are separated by geographical barriers such as rivers, mountains,
etc.
*EvolutionNatural Selection- mechanism for evolution, meaning
that the strongest most fit organisms or structures survive.
*Natural Selection through AdaptationAdaptation-alteration of
body, behavior or function of an organism to make an organism more
successful in surviving or reproducing.
*Natural Selection through Adaptation Mimicry of leaves by
insects is an adaptation for evading predators. This example is a
katydid from Costa Rica.
Natural Selection through DiversityThe creosote bush is a
desert-dwelling plant that produces toxins that prevent other
plants from growing nearby, thus reducing competition for nutrients
and water.
Natural Selection Examples Natural Selection through Extinction
The modification of an organism that is disadvantageous causing the
organism to be susceptible to disease, predators, or environment.
Examples: The monk seal The golden toadThe Tasmanian devil
Natural Selection through PhylogenyNatural Selection through
BehaviorEvolutionAdaptive Radiation (Divergent evolution)- single
species or a small group of species has evolved through natural
selection and other processes into diverse species that live in
different ways For example: Darwins 12 finches came from one
ancestor.
*EvolutionConvergent Radiation- unrelated organisms come to
resemble one another. From adaptive radiation where unrelated
organisms come from a common ancestor.For example:
SHARK-PENGUIN-DOLPHIN- convergent species
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