Important words and concepts from Chapter 22,
Campbell & Reece, 2002 (3/25/2005):
by Stephen T. Abedon (abedon.1@osu.edu)
for Biology 113 at the Ohio State University
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Course-external links are
in brackets Click [index] to access site index Click here to
access text’s website Vocabulary
words
are found below |
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IT CANNOT BE STATED TOO
STRONGLY THAT THE SIMPLEST THING THAT YOU CAN DO TO BETTER UNDERSTAND THE MATERIAL
PRESENTED IN THIS COURSE IS TO READ YOUR TEXTBOOK
IT ALSO CANNOT BE STATED TOO
STRONGLY THAT YOU WILL BE HELD RESPONSIBLE PRIMARILY FOR THESE NOTES ON EXAMS
THE ABOVE IS NOT A
CONTRADICTION—EXCELLENCE IS NOT ACHIEVED THROUGH A MINIMIZING EFFORT
SUCCESS IN BIOLOGY REQUIRES
MAXIMAL DEDICATION—DEDICATED STUDENTS READ THEIR TEXT BOOKS!!!!
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The material we will
cover in Biology 114 is very much different from that covered in Biology 113,
particularly in terms of the perspective and approach of those who engage in
these difference aspects of biology. It is almost as though biology consists
of two very different sciences, a reductionist science that seeks to emulate
chemistry or physics (113), and a much more philosophical science that is
interested as much in the subtleties of history as it is in rigors of the
more exact physical sciences (114). This is not to say that we will not be
learning real science in Biology 114, but instead that the general approach
of learning that we will employ in Biology 114 will be different from that of
Biology 113. In Biology 113, basically, you sought to understand how a cell
works. Here we will deal with such squishy topics as why it is the cells that
we observe exist at all. Keep an open mind and study hard. By the end of this
term you will have gained an appreciation of the most important concept in
Biology: Darwinian evolution. |
(1)
Chapter title: Descent with Modification: A Darwinian View of Life
(a)
(i)
Get a feel for what it means for two organisms to be evolutionarily
related
(ii)
What do you think that means?
(b)
"The process of evolution
can be summarized in three sentences: Genes mutate. [gene: a hereditary unit]
Individuals are selected. Populations evolve." (Talk.Origins)
(c)
"Evolution refers to the processes that have transformed life on
Earth from its earliest forms to the vast diversity that characterizes it
today.
(d)
“Darwinism remains one of the most successful scientific theories ever
promulgated. There is hardly an element of humanity – not capitalism, not
gender relations, certainly not biology – that can be fully understood without
its help.” (Anonymous, Iconoclast of the Century. Charles Darwin (1809-1882) Time December 31, 1999, p. 186)
(e)
["Evolution is the
cornerstone of modern biology. It unites all the fields of biology under one
theoretical umbrella. It is not a difficult concept, but very few people -- the
majority of biologists included -- have a satisfactory grasp of it…
Misunderstandings about evolution are damaging to the study of evolution and
biology as a whole. People who have a general interest in science are likely to
dismiss evolution as a soft science after absorbing the pop science nonsense
that abounds. The impression of it being a soft science is reinforced when
biologists in unrelated fields speculate publicly about evolution."
(Talk.Origins)]
(f)
[“Mutation is a random process, and random processes do not, at least
on their own, generate complexity. Natural selection, however, is not a random
process. It is an ordering process, creating structure from noise and
increasing the degree of regularity in the biological system. Since complexity
is simply the length of a concise description of all the regularities in such a
system, natural selection, in conjunction with random mutation, can tend to
increase in complexity… The achievement of Darwinism is not that it explains
the origins of information, but that is explains the origins of complexity. And
it does so in terms of a completely natural process: random mutation
followed by non-random selection. Via such a process, the simple can
give rise to the complex: ‘from so simple a beginning endless forms most
beautiful and most wonderful have been, and are being, evolved’ (
(g)
[“Darwinian thinking is not confined to biology; it anchors a
naturalistic understanding of all complex order, even including our own
intelligence. Hence today, Darwinism is central to a thoroughly naturalistic
picture of the world.” Taner Edis (2001).
(h)
External links: [index]
(i)
[descent with modification: a
Darwinian view of life, Darwinism, evolutionary biology,
descent with modification
(Google Search)]
(ii)
[Teaching About Evolution and
the Nature of Science (National Academy Press)]
(iii)
[biology and evolutionary
theory (Talk.Origins)]
(iv)
[introduction to evolutionary
biology (Talk.Origins)]
(a)
(b)
Evolution, in its most general sense, is simply successive
change that occurs over time
(c)
In biology this change, ultimately, is that which occurs
within the collective genotypes found within a population of organisms
(d)
We observe this change as a change in the collective
phenotypes associated with a population of organisms
(e)
These changes can represent a change in the proportions of
existing variation within a population (due to natural selection, genetic
drift, or migration)
(f)
Or these changes can represent the introduction of new
variation into a population (mutation, migration, recombination)
(g)
For the most part, evolution is overall a destabilizing
process unless some mechanism exists whereby destabilizing influences are discarded;
that stabilizing influence, in biological systems, we call natural selection
(h)
[evolution (417,000
hits on April 1, 2000!) (Google Search)] [evolution is a fact and a
theory (Talk.Origins)] [evidence for evolution: an eclectic
survey (Talk.Origins)] [index]
DARWINISM
(3)
(a)
(b)
[Charles Darwin (Google Search)] [index]
(4)
The Darwinian “Controversy”
(a)
Darwinism is, of course, just about the most controversial subject
among non-biologists short of abortion, easy sex, and the morality of President
Clinton Bush
(i)
(one should, of course, qualify the above statement by noting that
these observations apply to the good ol’ enlightened U.S.A. while the rest of
the world finds threats of apoplectic extinction due to environmental
degradation or in the course of a hot war a tad more troubling than these other
issues, including any so-called controversy over the validity of Darwinian
evolution)
(ii)
I note this for the sake of
warning you about the lack of evolutionary sophistication presented by the
popular media, particularly in the
(iii)
If you’re into anti-intellectualism, you’re gonna love
anti-evolutionism
(b)
[“Scientists such as myself
must share the blame for the lack of public understanding of science. We need
to work harder to convey the correct information. Sometimes we don't succeed
very well but that does not mean that we are dishonest. On the other hand, the
general public, and creationists in particular, need to also work a little
harder in order to understand science. Reading a textbook would help.” (What is Evolution?)
(Talk.Origins)]
(c)
[Darwinism and God (Google Search)] [index]
(5) Darwinism encompasses two ideas, one explaining the other
(a)
(b)
Darwinism encompasses two distinct ideas
(i)
The origin of biological diversity via evolution
(ii)
The mechanisms of evolutionary change (specifically via Natural Selection)
(c)
By far and away, the majority of evidence for Darwinism supports the
former assertion (the existence of evolution, i.e., the origin of biological
diversity via evolution); an assertion which, in fact, predates Darwin
(d)
The latter tenet (ii) is less well-supported than the former (i), but
nevertheless is sufficiently robustly supported to be considered a scientific theory---a hypothesis that explains broad arrays of
data with exceptional clarity
(e)
[origin of biological diversity,
evolution and "scientific
theory" (Google Search)] [index]
(6) Darwinism as the foundation of biology
(a)
(b)
Any time you generalize from one organism to another (e.g., from a fetal
pig to a human) you are assuming evolutionary relationships
(c)
Any time you speculate on the function of a biological structure, you
are speculating on natural selection (otherwise you would
have to assume lack of function, in which case you would not be able to
speculate on function)
(d)
It is difficult to imagine biology as a coherent discipline absent
Darwinism and, in fact, biology did not exist as a coherent discipline prior to
the advent of Darwinism
(e)
[Darwinism as the foundation of
biology (Google Search)] [what is Darwinism?
(Talk.Origins)] [index]
HISTORY OF DARWINISM (AND
EVOLUTIONARY THINKING)
(7) Darwinism's
historical context (Origin of Species)
(a)
The advent of Darwinism is
typically traced to 1859, the year of the publication of Charles Darwin's The Origin of Species
(i)
(the full title of this text, by the way, is On the Origin of Species by Means of Natural Selection, or The
Preservation of Favored Races in the Struggle for Life)
(b)
What Darwin did in this text is essentially to synthesize (i) the
then-current understanding of geology, the diversity of life, and the
domestication of plants and animals, with (ii) the contention of Malthus that populations
are limited in size by external factors (e.g., food supply)
(c)
The roots of Darwinism are found
in many individuals. We will limit our discussion to the contributions of
(ii)
Lyell
(iv)
Malthus
(v)
Wallace
|
A Brief
History of Evolutionary Thought – Supplemental Table |
||
|
Person |
Dates |
Concept |
|
Aristotle |
384-322
B.C.E. |
Scala
Naturae
|
|
|
|
Natural
Theology |
Carolus Linnaeus |
1707-1778 |
Taxonomy
(biology) |
|
Georges
Cuvier |
1769-1832 |
Catastrophism
(geology) |
|
James
Hutton |
1729-1797 |
Gradualism
(geology) |
|
Charles
Lyell |
1797-1875 |
Uniformitarianism
(geology) |
|
Jean
Baptiste Lamarck |
1744-1829 |
Adaptation
(biology) |
|
Thomas
Malthus |
1766-1834 |
Limits
(economics/biology) |
|
Charles
Darwin |
1809-1882 |
Natural
Selection (biology) |
|
Alfred
Russel Wallace |
1823-1913 |
Natural
Selection (biology) |
(d)
Generally, it is worth noting that
(e)
See Figure 22.1, The
historical context of
(f)
However, "The Origin of
Species convinced most biologists that species are
products of evolution, but
(i)
The popularity of this latter aspect of
(ii)
In
(g)
[darwinism history (Google Search)] [The Origin of Species
(full text of first edition) (Talk.Origins)] [Darwin's precursors and
influences (Talk.Origins)] [index]
(8)
(a)
Carolus Linnaeus was the developer of the science of taxonomy
(b)
He was the inventor of binomial nomenclature
(e.g., Escherichia coli) and higher
taxonomic descriptors
(c)
He was a grouper of organisms according to phenotypic resemblance (recall that evolution is
typically observed in populations as differences in or changes in phenotypic
resemblance)
(d)
Linnaeus essentially defined modern biological diversity according to
phenotypic relationships
(e)
Linnaeus was not an evolutionist
(f)
However, the explanation that phenotypic relationships exist due to
evolutionary (i.e., "blood") relationships is one of the triumphs of Darwinism
(i)
(this, by the way, is the answer to the question I posed at the top of
this page: Get a feel for what it means for two organisms to be
evolutionarily related. What do you think that means? It means that two
organisms are related by blood, just as you are related by blood to your
parents and siblings or, more distantly, to your first, second, third, etc.
cousins)
(g)
For example, Linnaeus' system would group the various species of dogs into a higher taxonomic category
on the basis of shared phenotypic characteristics
(i)
[that taxon, by the way, is called family Canidae, the canines
(Google Search)]
(h)
Darwinism would argue that dogs share certain phenotypic
characteristics with each other but not with other groups of organisms (e.g.,
horses) due to a closer blood relationship between dogs than between dogs and other
organisms (again, such as horses)
(i)
“To
(i)
[lions and tigers are members of order Carnivora, family Felidae, the
cats (Google Search)]
(ii)
[horses are members of order Perissodactyla,
the odd-toed ungulates, family Equidae (Google Search)]
(j)
[Carolus Linnaeus (Google Search)] [popular groups on the tree
(The Tree of Life)] [index]
(9)
Lyell, Charles (1797-1875)
|
What we see around us
predominantly are those things that are most easily created, given existing
raw materials and processes, and those things that are sufficiently durable
that, once created, they hang around for a while. What we do not see are
things that are rarely created or very fragile. Thus, the world is populated
by relatively inert, readily created chemicals such as water, nitrogen gas,
and carbon dioxide; constantly created but highly reactive chemicals such as
molecular oxygen; rocks due to their durability and abundance; soil (or sand)
due to the propensity for rocks to be converted into smaller rocks; and the
products of both geological processes and natural selection. |
(a)
Lyell was a geologist
(b)
The arguments of Lyell employed by
(i)
Geological processes of the past resemble (in a physical sense) the
geological processes of today
(ii)
These processes would have to have been going on for a very long time
to result in the Earth we observe today
(c)
Thus, the surface of today's earth is the cumulative product of the
gradual expression of the same physical processes we observe today
(d)
See Figure 22.3, Formation
of sedimentary rock and deposition of fossils from different time periods
(e)
This is essentially Darwinism as applied to geology: Long time frames
with net loss of that which is most easily lost and retention of that which is least easily lost
(f)
This is neither the first nor the last time that geology and Darwinism have intercepted
(g)
[Charles Lyell, gradualism and geology,
uniformitarianism (Google Search)] [index]
(10)
Lamarck, Jean Baptiste (1744-1875)
(a)
Lamarckism is a forerunner of Darwinism
(b)
Lamarckism is very similar to Darwinism in terms of the first tenet of Darwinism,
the origin of biological diversity by means of evolution
(c)
Lamarckism, however, lacks the robust explanation for why evolutionary
change occurs that Darwinism employed (i.e., natural selection)
(d)
Note that this distinction is not terribly large: Lamarckism
essentially employed ideas of adaptation though failed to articulate
that evolutionary adaptation is derived from differential reproductive
success
(e)
Lamarckism is also known for its (now considered to be incorrect) idea
of acquired characteristics: That individuals can acquire characteristics
during their lives that they are then able to pass down to their offspring
(f)
Keep in mind in understanding Darwinism historically
that Darwinism and Lamarckism are not incompatible theories
(g)
Instead, it is Lamarckism and Mendelism that are incompatible, and Darwinism
was derived independent of knowledge of Mendelian genetics
(h)
Though Lamarck, for historical reasons, would not have understood it in
these terms, Lamarck's “inheritance of acquired characteristics idea” posits
essentially protein to DNA information flow; Mendelism, however, is consistent
only with DNA to DNA (or, more generally, nucleic acid to nucleic acid)
information flow along with the nucleic acid to RNA to protein flow of
transcription and translation
(i)
“Even though the Lamarckian theory of evolution is ridiculed by some
today because of its erroneous assumption that acquired characteristics are
inherited, in Lamarck’s time that concept of inheritance was generally accepted
(and, indeed, Darwin could offer no acceptable alternative)… In retrospect,
Lamarck deserves much credit for his theory, which was visionary in many
respects: in its claim that evolution is the best explanation for both the
fossil record and the current diversity of life, in its recognition of the
great age of Earth, and especially in its emphasis on adaptation to the environment as a primary product of evolution.”
(p. 417, Campbell et al., 1999)
(j)
["Biology came of age as a
science when Charles Darwin published "On the Origin of Species."
But, the idea of evolution wasn't new to Darwin. Lamarck published a theory of
evolution in 1809. Lamarck thought that species arose continually from
nonliving sources. These species were initially very primitive, but increased
in complexity over time due to some inherent tendency. This type of evolution
is called orthogenesis. Lamarck proposed that an organism's acclimation to the
environment could be passed on to its offspring. For example, he thought
proto-giraffes stretched their necks to reach higher twigs. This caused their
offspring to be born with longer necks. This proposed mechanism of evolution is
called the inheritance of acquired characteristics. Lamarck also believed
species never went extinct, although they may change into newer forms. All
three of these ideas are now known to be wrong." (Talk.Origins)]
(k)
[“In retrospect, Lamarck deserves much credit for his theory, which was
visionary in many respects: in its claim that evolution is the best explanation
for both the fossil record and the current diversity of life; in its
recognition of the great age of Earth; and especially in its emphasis on adaptation
to the environment as a primary product of evolution.” p. 431, Campbell
& Reece, 6th edition, 2002]
(l)
FAQ: 1. If populations adapt to their environment isn't it the same
as: they become better to fit such environment? Yes, though it could be
that better fit means better able to compete with their ancestral genotypes
rather than translating to an increase in stable population densities. 2.
why is the inheritance of acquired characteristics not true? What is the mechanism?
It would have to be phenotype impacting on genotype specifically so that
physiological or morphological adaptations translate into a genetic
perpetuation of, say, larger muscles on the children of blacksmiths. There just
isn't any sensible way that one could picture information moving about in that
manner. Confusingly, though, it clear that the ability of individual organisms
to adapt physiologically or morphologically to their environments is a product
of natural selection. Furthermore, it is clear that natural selection does
allow phenotype to influence genotype, particularly within populations and
across generations. But inheritance of acquired characteristics would be as
though changing one's hair color resulted in a change in the hair color of
one's offspring. Biological systems just don't work that way. 3. If the
individuals that have the proper trait for certain environment have more
chances to successfully reproduce than those who don’t have that trait, isn't
it the same as 2? Not quite. Only if the trait has an underlying genetic
basis such that possessors of the trait do possess that basis and
non-possessors don't. To a degree, both blacksmiths and non-blacksmiths have
the potential to have the same genetic potential to have well-muscled arms.
Therefore, even if there is selection for well-muscled arms, this does not
necessarily translate into a change in allele frequency (unless, of course,
that people genetically predisposed to having well-muscled arms tend to become
blacksmiths, but that would imply a priori genetic distinctions rather than
physiological adaptation resulting in genetic change). 4. In our notes it
says: at least some of the differences between individuals which impact
survival and fertility are heritable; isn't this the same as characteristics or
traits that are passed from parents to offspring? Yes. But note that not
all phenotypic differences are heritable. Phenotype is more than just a
consequence of underlying genotype.
(m) [