38
Introduction to Darwinian Evolution Moises Von Rosauro R. De Gracia BSE - III
| Date post: | 08-Jul-2015 |
| Category: |
Spiritual |
| Upload: | aces-rosario |
| View: | 114 times |
| Download: | 3 times |
Introduction to Darwinian Evolution
Moises Von Rosauro R. De Gracia
BSE - III
What is Evolution?O Evolution is the accumulation of genetic
changes within populations over time.
O The term evolution does not refer to changes
that occur in an individual within its lifetime.
Instead, it refers to the changes in the
characteristics of population over the course
of generation.
Ideas About Evolution
O427-347 B.C. Plato’s divinelyinspired “ideal form”
O384-322 B.C. Aristotle’s “Ladder ofNature”O Aristotle visualized organisms as being
imperfect “moving toward a more perfectstate”
O1700s CreationismO Each species was created individually
by GodO Earth was the center of the universeO Man stood atop creation
O Leonardo Da Vinci (1452 – 1519)O The first to interpret the unusual finding
of animals in the rocks high onmountain.
O 1707-1788 George LeClerc (Comte of Buffon)O creation provided a relatively small number
of founding species that evolved through natural processes
O Idea was not acceptedO Did not provide a mechanism for evolutionO Earth was not old enough to allow time for
the process of evolution
O Jean Baptisté de Lamarck (1744-
1829)
O He was the first to propose that
organisms undergo change over time
as a result of some natural
phenomenon rather than divine
intervention.
O 1769-1832 G. Cuvier
O Theory of catastrophism (creationist
w/extinction)
O 1726-1797 James Hutton
O developed uniformitarianism –
gradual change
O 1797-1875 Charles Lyell’s
O “Old Earth Hypothesis” supported
Hutton, gave time for gradual
change
O 1809-1882 Charles Darwin
O Developed the theory of evolutionO Species evolved through natural selection;
O Adaptation to their ever-changing environment
O 1823-1913 Alfred Wallace
O supported Darwin's theory (workedseparately, came up with sameconclusion, came in “2nd”)
EVOLUTION:The genetic makeup of the population changes over time, driven by natural selection
NATURAL SELECTIONOn average, the fittestorganisms leavethe most offspring
Competition for survival and reproduction
Potential forrapid reproduction
Relatively constantresources andpopulation over time
Variability instructures and behaviors
Some variability is inherited
(observations)
(conclusions)
Darwin’s Theory of Evolution
O Darwin’s Idea of Common Descent
O Darwin’s Idea of Gradualism
O Darwin’s Idea of Multiplication of
Species
O Darwin’s Idea of Natural Selection
Idea of Common Descent
• Evolution = descent with modification
• All organisms are related through descent
from some unknown ancestor that lived in
the distant past.
• As the descendants spilled into various
habitats over time, they accumulated
diverse modifications (adaptations) that fit
them to specific ways of life.
• The history of life is like a tree.
• The Linneanclassificationschemereflected thebranchinggenealogy of thetree of life, withorganisms at thedifferent levelsrelated throughdescent fromcommonancestors.
Idea of Gradualism
• The origin of new species and adaptation
are closely related processes.
• A new species would arise from an
ancestral form by the gradual accumulation
of adaptations to a different environment.
• e.g. Darwin’s finches ADAPTIVE
RADIATION
Idea of Multiplication of Species
O The existence of an enormous number of
species
some species are very similar (not as
distinct from each other!)
gradual changes in various characteristics
as organisms became modified according to
the conditions in which they lived
Idea of Natural Selection
O Overproduction
O All species have a tendency and the potential
to increase at a geometric rate.
O Competition
O The conditions supporting life are limited.
O Only a fraction of the offspring in a population
will live to produce offspring, so that the number
of individuals in a population remains fairly
constant.
O Variation
O Individuals in a population vary greatly in their
characteristics.
O Adaptation
O Some variations enable individuals to produce
more offspring than other individuals.
O Natural Selection
O Individuals having favorable traits will produce
more offspring, and those with unfavorable
traits will produce fewer offspring.
• Speciation
O Given time, natural selection leads
to the accumulation of changes that
differentiate groups from one
another, such that a new species
may arise
Darwin’s Postulates on Natural Selection
O Postulate 1
O Individual members of a population differ from
one another in many respects
O Variations arise purely by chance resulting from
random mutations in DNA
O Differences are obvious in many physical
characteristics and extend to molecular level
O POSTULATE 2
O At least some of the differences among
members of a population are due to
characteristics that may be passed from
parent to offspring
O However, the mechanism of inheritance
was not understood at this point in time
(Mendel was working at about the same
time…and was ignored until someone saw
that Mendel and Darwin/Wallace
supported each other.)
O POSTULATE 3
O In each generation, some individuals in a
population survive and reproduce successfully
but others do not
O Darwin observed that many more
individuals are born than survive
O Some individuals have more offspring
than others
O POSTULATE 4
O Individuals with advantageous traits survive
longest and leave the most offspring, a process
known as natural selection
O Natural selection acts on individuals within
a population; however, it is the population
that changes over time
Patterns of Evolution
O Divergent evolution – from one species to
several different forms; adaptive radiation
O Convergent evolution – results in increased
resemblance between unrelated species
O Coevolution – occurs when two or more
species evolve in response to each other
Evidences of Evolution
O Fossils
O Comparative Anatomy
O Comparative Embryology
O Comparative Biochemistry
Fossils
O Transitional forms are evidence ofevolutionary change
O Fossils of ancient species tend to besimpler in form than modern species
O Several series of fossils have beenfound that exhibit the evolution ofbody structures over time
Interpretation of fossil data controversial
ODating of fossils
ODo fossils really show transitional forms?
Information about Fossils
Fossils of Extinct Organisms
Comparative Anatomy
O Homologous structuresO structures that have the same evolutionary
origin despite their current appearance or function
O Analogous structuresO structures that are outwardly similar in
appearance, but differ in their evolutionary origin
O Vestigial structuresO remnants of structures that are inherited from
ancestorsO Had important functions in ancestorsO Serve no obvious purpose in present day
organism
Analogous Structure
Not homologous;
not analogous
Homologous;
not analogous
Not homologous;
analogous
Homologous;
analogous
Homologous Structure
Flying Swimming Running Grasping
Vestigial Structure
Comparative Emryology
O Early vertebrate embryos
similar
O Tail and gill arches
Comparative Embryology
Comparative Biochemistry
O All have DNA, RNA, ribosomes, ATP,
etc.
O DNA similarities
