Fossils As Evidence for Evolution

Paleontologists have long thought that
Archaeopteryx fossils, including this one
discovered in Germany, placed the dinosaur at
the base of the bird evolutionary tree; evidence
suggests the beast may have been a birdlike
CREDIT: Humboldt Museum für Naturkunde
Evolution Continued: Evidence &
Other Concepts
 Summary
color is
orange; vocabulary is
 Hyperlinks are in
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to you videos and
Unit #12
Evolution Continued
 Today,
most of the evidence for evolution is grouped into these
main categories:
◦ Fossil Record
◦ Biogeography
◦ Homologies
◦ Observable Events
The Evidence of Evolution
Use the information on the following slides to complete your “Matching Notes” student sheet.
 Most
fossils are found in layered
sedimentary rock
 Older fossils = lowest layers
 Comparing fossils from different
layers shows:
◦ Life on Earth has changed
◦ Increased biodiversity
Textbook Reference pg. 399-400
Watch “Fossils As Evidence for Evolution”
 Paleontology
– study of fossils
 Types of Fossils:
◦ Remains: EX bone, tooth, or shell
◦ Traces: EX burrow, footprint, or imprint
Dinosaur fossil searcher Ray
Stanford discovered a large
fossil of a Nodosaur just a few
feet from this spot.
Tracy A. Woodward / THE
Fossils Cont.
 Biogeography:
the geographic
distribution of organisms
◦ organisms living widely
apart (even different
continents), may be similar
because they share a
common ancestor
2 – Biogeography
Watch “Biogeography As Evidence for Evolution”
Beaver and
Coypu and
3 - Homologies: Anatomy
Watch “Anatomical Development and Homologies as Evidence for Evolution”
Textbook Reference pg. 400-402
similar structure, but different
function show an evolutionary relationship
◦ EX limbs of vertebrates (turtle, alligator vs. mammal)
 Homologous structures: w/
Anatomy Cont.
Vestigial structures: reduced in size, are nonfunctioning remnants of
similar structures in ancestral species
◦ Show an organism’s
evolutionary past
◦ Ancestral species would have
similar structures that are still
 EX human tailbone,
appendix, whale
Anatomy Cont.
Can you spot the vestigial limbs?
(Photo Credit: Marc Mythos)
of different species may
appear similar in early stages of
◦ Can show developmental
 Embryos
4 - Homologies: Developmental
Textbook Reference pg. 402
 Hox
genes: found in animals,
determine the pattern of the
body during development
◦ Control transcription
◦ Can show genetic
4 - Homologies: Developmental
(Homeobox/Hox Genes)
 The
genetic code [GCAT] is the
same in all organisms
◦ Triplets (or codons) of DNA bases
code for specific amino acids to
build proteins
5 – Homologies: Biochemistry
Textbook Reference pg. 402-403
 Sequence
of amino acids in a particular protein is compared
between organisms
 AA Sequencing is probably the strongest evidence for
relationships among organisms
Biochemistry Cont.
Cladogram: diagram that
shows the evolutionary
relationship among a group
of organisms.
 Some
changes in species have been observed and studied in
recent times
P. & R. Grant’s Study of Beak Size
Shift in Darwin’s Finches
 Observable
H. Kettlewell’s Study of Peppered
Moth Color Shifts
events show that evolution is an ongoing process
Observable Events
 Species:
a group of organisms that breed
with one another and produce fertile
◦ Speciation: the formation of a new
species as a result of evolutionary
change caused by certain isolating
◦ Isolating Mechanism Animation
Textbook Reference pg. 409
 Two
populations become
reproductively isolated from
each other
◦ Members cannot
interbreed because of
genetic material is too
Spotted owl subspecies living in different geographic
locations show some genetic and morphological differences.
Isolating Mechanism: Reproductive
Textbook Reference pg. 410
Photo Credit, Mike Eggett
 Two
populations are capable of
interbreeding, but have differences in
courtship rituals, etc that involve behavior.
◦ EX two different species of cricket that
would be indistinguishable unless you
heard their mating songs, a noticeably
different pitch
Isolating Mechanism: Behavioral
 Two
populations are
separated by geographic
◦ EX rivers, mountains,
or bodies of water
Isolating Mechanism: Geographic
 Two
species reproduce at different times.
Photo Credit, Christian Ziegler
Populations may mate or
flower at different seasons
or different times of day.
Three tropical orchid species
of the
genus Dendrobium each
flower for a single day; the
flowers open at dawn and
wither by nightfall.
Isolation Mechanism: Temporal
 Do
a population’s genes (or gene pool) change over time?
◦ % of an allele in a gene pool = allelic frequency
◦ Genetic equilibrium: frequency of alleles remains the
 A population in equilibrium is NOT evolving
 Influenced by
◦ environment, mutations
◦ Genetic drift
Genetic Equilibrium
 Adaptive
radiation: type
of divergent evolution;
ancestral species evolve
into an array of species to
fit diverse habitats
◦ EX Galápagos Finches
Types of Evolution:
Divergent Evolution
Textbook Reference pg. 412-13
True or False?
The shark and the dolphin are closely related?
evolution: when unrelated
species occupy similar environments,
evolving similar traits, but are NOT
closely related
◦ Convergent evolution results in
analogous structures
◦ EX Bat wing vs. butterfly wing
Types of Evolution: Convergent
 Convergent

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