Download Chapter 22 - Bio-Guru

Mechanisms of Evolution
Chapter 22
Descent with Modification
A Darwinian View of Life
Chapter 22
History of Evolution Science
Ancient Beliefs
A.
Plato (428-348 BC) idealism
a.
b.
the "idea" is an eternal, unchanging essence
variation has no meaning only essence matters
(VARIATION IS HUGE IN EVOLUTION!)
B. Aristotle (384-322 BC)
1.
2.
Scala Naturae or scale of nature
All things - from inanimate objects to plants to animals to man
a. fixed in place according to God's plan
b. permanent, unchanging
The views of these two early Greeks prevailed for almost
2000 years.
The Old Testament
C. Traditional Christian beliefs
state that all organisms resulted from the
direct actions of a creator
1.Each organism has a specific role to play
2.Each was individually created by God
3.Each organism is such a perfect fit in its environment
because it was “hand-crafted” for that environment.
4.The earth is about 6,000 years old
5.The universe is about 13,000 years old
Beginning of Modern Scientific Methods
and Thoughts
D. Carolus Linnaeus (1707-1778)
1. father of taxonomy
2. defined fundamentals of biology in terms
of nomenclature and classification
3. clustering groups into a hierarchy of
increasingly general categories.
4. done for the greater glory of god - "God's
Registrar"
Invented Binomial nomenclature
E. Cuvier (1769-1832)
1. founder of paleontology (studied fossils –
anatomist)
2. observed that different strata of
sedimentary layers contained
different
fossils.
3. catastrophism--explained changes in
animal world in terms of
catastrophes
that had destroyed whole populations of living
things in prehistoric times (floods etc.)
Hutton (1726-1797) and Lyell (1797-1875)
both were influential geologists
F. Hutton
a. gradualism - same processes are responsible for both
past and present events
b. one of first to imply great age of the earth (not what the
Bible says)
G. Lyell
a. Theory of uniformitarianism small forces acting over long periods of
time can result in major changes e.g. destruction of mountains.
b. great champion of Hutton's work
c. historical and physical continuity of nature
d. Principles of Geology (1830)--greatly influenced Darwin even
though he himself did not admit biological evolution
A COMBINATION OF LYELL’S AND HUTTON’S
IDEAS IS EMPLOYED TODAY
Lamarck (1744-1829)
1. the first uncompromising advocate of evolution, attempted
to provide a mechanism to explain evolution
2. argued that lowly forms of life arise continually from
inanimate matter by spontaneous generation, and
progress inevitably toward greater complexity and
perfection -- an inherent tendency toward complexity
3. particular path of progression taken is guided by
environment
4. changing environment alters the needs of the organisms
5. use and disuse alter morphology and is transmitted to
subsequent generations (inheritance of acquired
characteristics)
7. emphasized great age of earth
8. Ideas were almost universally rejected, particularly by
Cuvier and Lyell
Charles Darwin (1809-1882)
A. Early life
1. born in 1809 in Shrewsbury, England--the son of a physician
2. studied medicine in Edinburgh
3. studied theology in Cambridge--was very religious
4. at both places he pursued an interest in natural science
B. Voyage of the H. M. S. Beagle (1831-1836)
1. served as unpaid naturalist - paid his own way
2. made stops along coasts and islands of the southern hemisphere
3. noted how plant and animal forms differed with geographical location
4. Observations in Galapagos Islands and South America.
5. Read Lyell's Principles of Geology on the voyage - true age of earth much
greater than 6000 years
C. Return to England after voyage
1. did not accept notion of evolution until it was pointed out that his
specimens of finches from Galapagos were so distinct as to
represent different species.
2. this revelation led him to doubt the fixity of species
3. first published several volumes on geology and the voyage of the Beagle
Darwin's Evidence
A. Hutton and Lyell's evidence supporting geological events.
B. Observations
1. extinct species related to living (extant) organisms
a. observations of the fossil record
b. e. g. armadillos and glyptodont--found fossil species similar
to extant species
c. both limited to one geographical area
d. if both were created at the same time, and if they were so much
alike, why was only one of them alive in 1850?
2. characteristics of species varied from place to place
a. appearance of tortoises dependent on location
b. slight changes in appearance after island isolation
3. great variety of organisms on young volcanic islands, e.g., finches
4. resembled forms on mainland, not distant places *organisms in forests of
S. America more similar to organisms of grasslands of S. America
than to organisms in forests of Europe *this would not be so if were
created all at once to be perfectly adapted for that environment.
Darwin and Malthus
Malthus wrote Essay on the Principle of Population
(1798)
a. argued that unchecked growth of the human
population must lead to famine
–
–
populations increase geometrically
food supplies increase arithmetically
b. nature acts to check population growth via death
–
in humans this is famine, war, and disease
Malthus’ ideas led Darwin to his idea of natural selection
(competition for resources)
Alfred Russel Wallace
• A contemporary of Darwin, who also came up with
the theory of Natural Selection independently.
• He sent his work to Darwin
• Darwin’s work “THE ORIGIN OF SPECIES” was
published
• Wallace insisted that Darwin get all the credit,
because Darwin had done more extensive work
and research on it than Wallace. (what a decent guy!)
So What is Natural Selection?
5 observations Darwin made
(does not apply to humans!)
1. If all members of a particular species
survived to reproduce successfully, the
population size would grow exponentially.
2. However, population sizes usually stay the
same, except for some seasonal
fluctuations.
3. In any environment, resources are limited
4. Members of a populations vary in their
characteristics – no two are alike
5. These variations are heritable
What Darwin inferred from his observations
1. Overproduction of offspring: When there are more
organisms than an environment’s carrying capacity…
2. Struggle for existence: there will be a struggle for
survival a.k.a COMPETITION
3. Genetic Variation: The organisms that possess a
variation that will help them in this struggle, will
survive to reproduce.
4. Differential survival and reproduction: These
favorable traits will be passed on to their
offspring, giving them the same benefit.
Summing it up
In the end, only those members of the
population that are best adapted to their
environment will be successful.
THIS WAS HIS THEORY OF NATURAL
SELECTION
http://www.pbs.org/wgbh/evolution/library/11/2/e_s_4.html
Some of the 13 finches Darwin studied
Biogeography and Convergent
Evolution
• The geographical distribution of species
• The same type of niche in 2 lands very far
from each other my have different, but
similar looking species
• This is because they share similar
environmental conditions/niches, but
independently, from different ancestors.
Biogeography and Convergent Evolution
The sugar glider is indigenous and
endemic to Australia is a marsupial
mammal, related to the kangaroo
Indigenous – belonging naturally to a
geographic area
Endemic – found nowhere else in the
world
The flying squirrel is indigenous to
North America is a eutherian
(placental) mammal
Lamarck versus Darwin / Wallace
Artificial Selection
• Animal husbandry
• Pet breeding
Evidence of Evolution
•
•
•
•
•
Anatomical Homologies
Embryological Homologies
Molecular Homologies
Vestigial Organs
Fossil Record
Anatomical Homologies
Homologous structures indicate evolutionary ties
Analogy vs. Homology
• Structures that are similar due to
evolutionary origin, such as the forearm
bones of humans, birds, porpoises, and
elephants, are called homologous.
• Structures that evolve separately to
perform a similar function are analogous.
The wings of birds, bats, and insects, for
example, have different embryological
origins but are all designed for flight.
The bones in the three flying animals (not the insect) are homologous, but
the wing structures of all 4 flying animals are analogous
Embryological Homologies
Molecular Homologies
• All life has DNA, RNA and the genetic
code is universal
• So all animals could have descended from
a common ancestor
• Even animals as dissimilar as bacteria and
humans, share common genes inherited
from a distant ancestor.
Vestigial Organs
Adenoids The adenoids are tonsil-like
Tonsils
tissues that are located in the back of
the nose, next to the opening of the
eustachian tube.
Coccyx (tail bone)
Nictitating membrane of eye
Thymus
Appendix
Little toe
Wisdom teeth
Nipples on males
Parathyroid
Nodes on ears "Darwin's points"
Ear muscles for wiggling
Pineal gland The pineal gland is a tiny
structure located at the base of the brain.
Its principal hormone is melatonin, which
regulates our day and night cycles
Body hair
Fossil Record (basically anatomical homology)
• Transitional fossils
that link the past with
the present
Approximately 50 million years ago, this wolf-size
pakicetid—an ancestor of the whale—lived on land but
may have waded into streams to feed on fish.
Read article on origin of whales
END OF CHAPTER 22