Transcript Diversity of Life

Diversity of Life - Early Beliefs
It was believed that the earth was young.
Bishop James Ussher (1581-1656) – using
references from scripture – determined that
the 1st day of creation was October 23,
4004 B.C.
His work was incorporated into an
authorized version of the Bible in 1701.
Diversity of Life – Early Beliefs
All organisms on Earth were created at
once, in a center of creation.
All organisms were created perfectly, welldesigned for the environment they lived in.
Organisms shared no common ancestors.
Scientific evidence began to show
that this explanation was not
completely accurate:
Evidence showed that Earth is very old.
Evidence showed that Earth has
changed a great deal over time.
Diversity
Evolution: Genetic changes in a species
over time.
These changes produce new phenotypes
within a species and lead to the formation
of new species from ancestral forms.
Jean-Baptist de Lamarck
(1744-1829)
Law of Use and Disuse: organisms
become suited to their environment by
creating adaptations within their lifetime.
Inheritance of Acquired Characteristics:
Those acquired traits are then passed on
to future offspring.
Charles Darwin
Darwin’s Journey
The Galapagos Islands are volcanic islands located
500 miles west of Ecuador. The organisms Darwin
observed there were all descendants of those
brought by wind or currents.
Galapagos Islands
A Galapagos tortoise and one of the thirteen finch
species found among the islands.
Charles Darwin
(1809-1892)
Recognized the vast biological diversity
found on Earth.
The earth is very old and has changed a
great deal over time.
Organisms have traits that make them
well-suited to a particular environment.
Applied the ideas of Malthus to all
organisms.
Charles Darwin
Variation exists in a population.
Populations tend to over-produce. This
creates a struggle for survival.
Those members of a population with
variations well-suited to the environment will
survive and pass their traits to future
offspring.
Over time – due to environmental changes,
some populations will change, leading to the
formation of new species.
Species
A group of organisms that naturally
interbreed to produce fertile offspring.
Organisms that are of different species will
not interbreed, or if they do their offspring
typically are not fertile.
Natural Selection
A mechanism where those organisms with
features best suited to an environment will
survive and reproduce.
The result of natural selection is a
population with phenotypes suited to a
local environment.
Wallace
Alfred Wallace, who independently developed
the same theory as Darwin.
Evidence for Evolution
Radiometric Dating
Fossil Evidence
Comparative Morphology and Embryology
Gene Modification Evidence
Experimental Evidence
Radiometric Evidence
How do we know how old the earth really is?
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A technique for determining the age of objects
by measuring the decay of the radioactive
elements they contain
Uraium-238 vs Lead-206
The transformation proceeds at a fixed rate.
The John Day beds of central Oregon. Sedimentary
rocks are formed as layers, one atop another. The
oldest rock is deepest and the newest layers are
closest to the surface.
Fossil Evidence
Compare fossils from the same geologic
layers of sediment , scientists expect to
find similar types of fossils.
When we compare fossil placement with
the dates we get from radiometric dating,
they are very close to being the same.
Fossils
Bird Fossils
Homology
Homologous – the same in structure owing to
inheritance from a common ancestor. It is believed that
all four groups of mammals descended from the same
ancestor.
Comparative Morphology
Morphology is the study of physical forms.
Forelimbs of a diverse group of mammals
are homologous.

The 1-2-5 structure has been adapted by the
four different groups of mammals in
accordance with their varying needs.
Whale, Cat, Bat, Gorilla
The bones in the forearm are similar in structure
despite their variable actions.
Comparative morphology
Python bones corresponding to the bones of the pelvic
girdle in humans. In most vertebrates, the pelvic girdle is
attached to the hind limbs but pythons don't have limbs.
Comparative Embryology
Embryology is the study of how animals
develop from fertilization to birth.
At a certain point in their development,
diverse species all have structures known
as pharyngeal slits.
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In fish these become gills, in humans they
become the Eustachian tubes.
All of these animals shared a common
ancestor.
Comparative embryology
Gene modification Evidence
Evolutionary theory predicts that there
should be fewer DNA base-pair
differences between the genes of similar
organisms as compared to those of very
different organisms.
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Human vs. yeast
Human vs. pig
Many diverse
organisms have
the same enzyme.
Over time the
genetic sequence
of the enzyme has
been altered.
This chart is a
measure of the
amount of
difference
between the
enzymes of these
organisms.
Experimental evidence
Evolutionary change takes place over long
periods of time but a carefully planned
experiment can provide evidence.
Sex and the Male guppy
In the absence predators,
male guppies grow larger in
size and more brightly colored.
Female guppies prefer to mate
with brightly colored males but
these males are more visible
to predators.
In the presence of predators,
the male guppy was smaller
and drab in color. These
males live longer and produce
more offspring because they
live longer.