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# Modern Classification Techniques by rsnRgbG5

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```									Modern Classification
Techniques
Taxonomy
   - the science of taxonomy also involves other
biological sciences such as evolution

   - taxonomy also attempts to determine the
evolutionary history of groups of organisms

   - scientists compare characteristics of different
species living today with each other and with
extinct species

   - there are several different types of evidence
that scientists can use to classify organisms and
study evolutionary relationships
Evidence Used

(ii) comparative anatomy ( Structural Info.)
(iii) comparative embryology
(iv) biochemical information ( DNA / Proteins )
(v) cellular structure
(vi) behavior
 fossils are dated either through
determining the relative age or finding an
absolute age.
 relative age - sedimentary rock forms in
layers so the age of each layer can be
determined in relation to each other
 the oldest layers are found at the
bottom, and the younger layers are on
top.
 the age of a fossil can be approximated
by the rocks layer it is found in.
Absolute Age
- The absolute age of a fossil or rock can be
neutrons) breaks down into a new
element at a known rate called a half-life
(a half-life is the time it takes for ½ of a
radioactive sample to break down). Page
113.
Carbon Dating              Half - life Useful range
C14 ----------> C12        5730 yrs     60 000 yrs

note: for fossils too old for carbon dating, an isotope
with a longer half - life must be used:
Isotope                   half - life
U235                        700 million years
K40                         1.25 billion years
U238                        4.5 billion years
Try This

Sample Problem:
If you had a fossil with 2 units of C14 left in it
and you determined that in the living organism
(or one that is similar) has 16 units of C14, you
could use one of the following methods to find
the absolute age of the fossil:
Method 1:
1. Determine amount of C14 left in fossil.
2. Determine amount of C14 in a living organism
of the same size and type living today.
3. Calculate the number of half-lives needed to
reduce the C14 in the living organism to the
amount that is left in the fossil.
4. Multiply by the half - life ( in this case, 5730
years ) to determine the age of the fossil.
“MATH”
Method 2:               where:
 N = No (½) t/H        - N = units in the fossil
2 = 16 (½)t/5730      - No = units in the
living organism
1/8 = (½)t/5730
- H = the half – life
(½)3 = (½)t/5730      - t = time ( this will
most likely be the one
3 = t/5730
you will be finding)
t = 3 x 5730
(ii) comparative anatomy
Comparing the anatomy of organisms indicates a
common ancestry because of:

   homologous structures - structures having a
common ancestry but with different uses in
various species.
 Eg. Similar bone structure of the forelimb of
a bat, whale, horse and human suggests
these different species have a similar
evolutionary origin. Page 113,114 & 664
   - analogous structures - body parts of
organisms that do not have a common
evolutionary origin but perform similar
functions.
 Eg. insect wings and bird wings are
similar in function but not in structure.
Page 665
- vestigial organs - small or incomplete organs ( or bones )
that have no apparent function in one organism but do
have a function in another species. This indicates
evolutionary origin from a common ancestor. Page 665
 Eg. Human ear muscles, Human appendix, Hip bones
in whales, Human tail bone, Leg bones in snakes, and
Forelimbs in the flightless ostrich
iii) Comparative Embryology

   Comparing the embryos of organisms can
indicate a common ancestry with other
types of living organisms because of
similar stages of embryonic development.
   (eg. gill slits and tail in human embryos
indicates humans share common ancestry
with birds, reptiles and fish) Page 665
(iv) biochemical information
( DNA / Proteins )
Comparing the biology of one species with
another at the molecular level (DNA &
Proteins) can indicate a common ancestry. Page
115
- human proteins (amino acid sequences) have
more in common with chimpanzee proteins than
frog proteins.
- pig or beef insulin is similar enough to humans
that it can be used to treat human diabetes.
(v) cellular structure

Studying structures of cells gives clues to their
evolutionary history.
- Remember only two basic types of cells
prokaryotic and eukaryotic (review p. 106)
- fossil evidence has shown the first life forms were
prokaryotic (similar in appearance to bacteria) and existed
approximately 3.5 billion years ago
-eukaryotes appeared only about 1.5 billion years ago
- multicellular organisms only 700 million years ago
(vi) behavior
-   how organisms are adapted in how they respond
to their environment is called behavioral
-   eg. include migration, courtship displays, foraging
behavior
- it is believed that these adaptations have evolved
in response to changes in environmental
conditions as continents formed and moved
millions of years ago
- the favorable adaptations were passed on to the
offspring
- note: Biofact p.706
How have classification systems improved as
a result of these modern techniques?

- through the use of these techniques,
organisms once thought to be closely
related, have been found not to be related
and vise versa.
Phylogeny and Phylogenetic Tree
   A hypotheses about the evolutionary
history of an organism.
   The roots of the phylogenetic tree show
the oldest ancestral species.
   The upper ends of the branches show
current species.
   Each fork represents the adaptation that
changed the common species into two
new species.
   Use the example on page 116.

   Cladistics is a classification scheme based
on phylogeny.
   A Cladogram is similar in design to the
phylogenetic tree, but used to test
hypotheses about how the branches could
have occurred.
   Which of the following 3 cladograms
makes the most sense.
Homework

   PAGE 121:
   1, 2, 5,6, 9 (paragraph), and 12

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