Transcript 1. Explain the importance of the fossil record to the study of evolution.

Chapter 25 Reading Quiz
1.
2.
3.
4.
5.
What is the evolutionary history of a
species called?
Which isotope has a half-life of only
5,730 years?
What was the supercontinent called 250
million years ago?
The mass extinction 65 million years ago
marked the end of what era?
All related Orders belong to what
taxonomic grouping?
1. Explain the importance of the fossil record
to the study of evolution.
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Biologists reconstruct evolutionary history
by studying the succession of organisms in
the fossil record
Phylogeny  the evolutionary history of a
species
Fossil record  the ordered array in
which fossils appear within layers of rock
that mark the passing of geological time 
2. Describe how fossils form.

Usually from mineral-rich hard parts of
organisms (bones, teeth, shells of
invertebrates) since most organic
substances usually decay rapidly
 some fossils in layers of sandstone or
shale retain organic material
 other fossils are molds in mud, etc.
 trace fossils like footprints, animal
burrows, etc. can also exist 
3. Distinguish between relative dating and
absolute dating.

Relative dating  this record chronicles
the relative ages of fossils, showing order
of evolution
 “strata” are rock layers from different
time periods; younger strata are on top of
older
 the succession of the fossil species
chronicles phylogeny since fossils in each
layer represent that time period 
#3 continued….

Absolute dating  gives the age of the
fossils in years
 done by radiometric dating, which is the
very next question 
4. Explain how isotopes can be used in
absolute dating.
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Fossils contain isotopes of elements that have
accumulated in the living organisms
Radioactive isotopes have fixed half-lives and
comparing the ratio of isotopes in a fossil a year
can be determined
 this is not affected by temperature, pressure,
etc.
Ex: C14 has a half-life of 5600 years, meaning that
½ of C14 in a specimen will be gone in 5600 years,
etc.
 only useful in dating fossils less than 50, 000
years old. 
5. Explain how continental drift may have
played a role in the history of life.
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Phylogeny has a biogeographical basis in
continental drift  spatial distribution of life
North America and Europe moving apart 2cm/year
 250 mya Pangaea came together
 180 mya Pangaea began breaking up - puzzle is
explained by the pattern of continental
separations
 matching fossils from coastlines (South
America and Africa) 
6. Describe how radiation into new adaptive
zones could result in macroevolutionary
change.
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Intervals of extensive turnover included
explosive adaptive radiation of major taxa
Ex: evolution of wings allow insects to
enter a new adaptive zone
Ex: evolution of shells and skeletons in a
few key taxa led to a large increase in the
diversity of sea animals between the
Precambrian and Paleozoic eras 
7. Explain how mass extinction could occur
and affect evolution of surviving forms.
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Extinctions may be caused by habitat
destruction or by unfavorable
environmental changes
 not only are many species eliminated,
but those that survive are able to undergo
new adaptive radiations into the vacated
adaptive zones and produce new diversity

8. List the taxonomic categories from the
most to the least inclusive.
1.
2.
3.
4.
5.
6.
7.
Kingdom (Ex: Animals)
Phylum / Division
Class
Order
Family
Genus
Species (Ex: Homo sapiens) 
9. Distinguish between homologous and
analogous structures.
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Homology  likeness attributed to shared
ancestry
ex: wings of birds and bats both are modifications
of the vertebrate forelimb and thus are
homologous
Analogy  similarities due to convergent evolution,
not common ancestry
ex: insect wings and bird wings evolved
independently and are constructed from entirely
different structures 
Ocotillo
&
Allauidia
10. Explain why it is important when constructing a
phylogeny to distinguish between homologous and
analogous character traits.
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Generally the greater the amount of
homology, the more closely related the
species
Adaptation and convergence often obscure
homologies, although studies of embryonic
development can expose homology that is
not apparent in mature structures 
11. Describe four techniques used in
molecular systematics and explain what
information each provides.
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2.
Protein comparison  similarities in amino acid sequences
of two proteins from different species indicates that the
genes for those proteins evolved from a common gene
present in a shared ancestor
DNA and RNA comparisons 
a. DNA-DNA hybridization – compares whole genomes by
measuring the degree of H bonds between 2 sources
b. restriction maps – information about the match-up of
specific DNA nucleotide sequences (restriction enzymes)
c. DNA sequence analysis – most precise by comparing
DNA as it determines the actual nucleotide sequence of a
DNA segment 
#11 continued….
3. Identifying and comparing homologous DNA
sequences  comparing corresponding DNA
segments from two species
4. Molecular clocks  different proteins and nucleic
acids evolve at different rates
 the number of amino acid substitutions is
proportional to the elapsed time since divergence

12. Distinguish between a monophyletic and a
polyphyletic group.
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Monophyletic group  single ancestor gave
rise to all species in that taxon and to no
species in any other taxon
Polyphyletic group  members are derived
from two or more ancestral forms not
common to all members 
13. Describe the contributions of phenetics
and cladistics to phylogenetic systematics.
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Phylogenetic systematics = cladistic analysis
Cladistics  produces a cladogram
 the sharing of primitive characters indicates
nothing about the pattern of evolutionary
branching from a common ancestor
Phenetics  comparisons of characters
(anatomical characteristics) without sorting
homology/analogy
 useful for analyzing DNA sequence data and
other molecular comparisons between species 
14. Describe how cladistic analysis uses novel
homologies to define branch points on
phylogenetic trees.
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Cladistics classifies organisms according to
the order in time that branches arise along
a phylogenetic tree 