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Topic: Evidence for Macroevolution
Macroevolution = evolutionary changes over long time
spans involving many traits and large genetic changes.
The derivation of a new group above the species level
(ex., genera or family)
In contrast to Microevolution ~ Evolution at the
population level up to the level of species that occurs
through changes in allele frequencies (and likely
genotypes) within a population over time ~ across
generations.
Topic: Evidence for Macroevolution
A. Biogeography
Biogeography = patterns of species distribution.
Taxa on islands more similar to nearest continent.
Example: Galapagos finches
Continental Drift - time of separation between land
masses linked to species similarities.
Figure Biogeographical areas
Figure The history of continental drift
B. Taxonomy
Carl Linneaus recognized the organism diversity
could be organized into groups depending on the
traits expressed.
Kingdom, Phylum, Class, Order, Family Genus,
species
Darwin ‘s interpretation?
Figure Classifying life
C. Fossil Record
Fossils = transformed remains of organisms.
More fossil evidence today.
Radioisotope dating provides age of fossil.
Evidence exists for progressive evolutionary
change.
Fossils are not equally present for all groups of
organisms.
Half-life = length of time required for 50% of the
parent material to decay into daughter product.
• Uranium 235 to Lead 207 (half-life = 710,000,000 years)
• Uranium 238 to Lead 206 (half-life = 4,500,000,000 years)
• Thorium 232 to Lead 208 (half-life = 14,000,000,000
years)
• Rubidium 87 to Strontium 87 (half-life = 47,000,000,000
years) - most common system used for dating rocks older
than 100 million years.
• Potassium 40 to Argon 40 (half-life = 1,300,000,000 years)
- this method is very often used to date rock less than 60
million years old.
Carbon 14 dating:
• Carbon 14 to Nitrogen 14 (half-life = 5,570 years)--• There are 3 forms (isotopes) of carbon occuring in nature: Carbon 12
(accounts for 99%)
• Carbon 13 (accounts for 1%)
• Carbon 14 (accounts for less than 1%).
• While alive, plants and animals incorporate these isotopes of carbon into
their tissues at the ratio found in the atmosphere.
• Upon death, the Carbon 14 in their tissues begins to decay. By
measuring the remaining amount of Carbon 14, the age of the fossil can
be determined. This method can be used to date material ranging in age
from a few hundred years to about 50,000 years. The use of Carbon 14
permits the determination of age directly a fossil. For fossils greater than
50,000 years old, the age of the fossil is found indirectly by determining
the age of the rock associated with the fossil. Carbon 14 dating has a
dating range of several hundred years before present to 50,000 years
before present.
http://snakefly.tripod.com/Date.html
Figure The fossil record is one type of historical documentation that chronicles evolution: Archeopterex
Figure Fossil of a fish: perch
Figure A gallery of fossils
Figure Earth’s crustal plates and plate tectonics (geologic processes resulting from plate movements)
D. Homologous Structures
Homologous = traits developed from a common
ancestor.
Environment-genotype interactions ~ adaptations
Thus homologous traits may function differently.
Example: Mammalian forelimbs
Figure Homologous structures: anatomical signs of evolution
Figure Transitional fossils linking past and present
E. Development
von Baer noted: related species most resemble
each other in the juvenile stage.
Hackel noted:
“Ontogeny recapitulates Phylogeny”
Ontogeny= embryonic development
Phylogeny= evolutionary history
~Successive stages of individual’s development
corresponds with successive adult ancestors.
Ex.’s
Developmental embryology
Developmental Embryology
Humans repeat evolutionary history in utero:
-Possess tail ~ fish, it develops into our tail bone
-Possess fine fur from about 5 mo. Gestation
-Gill like stage in early gestation
Human tail in utero
http://embryology.med.unsw.edu.au/wwwhuman/stages/Images/CSt15.gif
http://www.palaeos.com/Vertebrates/Bones/Gill_Arches/Images/Meckel4.jpg
Figure Some properties of life: Development: tad pole – frog metamorphosis
Timing of development is important:
• Heterochrony = a change in timing of trait
development.
• Ex., bones of forelimb
• Allometric Growth:
• same character either grows faster OR for a
longer period of time and this changes its
shape.
• Change in duration OR rate of development of
a trait.
Figure Homologous structures: anatomical signs of evolution
Timing of developmental change:
Peramorphosis = adult trait expressed in juvenile
(ontogeny does recapitulate)
Two ways:
a) acceleration of development
b) increased duration of development
Ex.,
Hypermorphosis ~ gigantism
Timing of developmental change:
Paedomorphosis = juvenile traits expressed in mature
reproducing adult
Two ways:
a) retardation of development
b) decreased duration of development
Ex., neotonic salamanders
domesticated animal playfulness
***Large changes in morphology can occur through relatively
simple changes in rates or timing of development***
F. Vestigial Structures
Vestigial = structures with no apparent current
function, resembling presumed ancestors.
Consistent with predictions from Natural Selection,
that leftovers of change can be found.
Ex.’s
http://www.gutenberg.org/files/20417/20417-h/images/image258.jpg
G. Molecular Record
Natural Selection results in the accumulation
of genetic changes, reflected in the DNA.
Compare degree of similarity in DNA
sequences among organisms.
Example: human hemoglobin peptide
Figure Molecular data and the evolutionary relationships of vertebrates
Now onto Systematics and Phylogenies