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

 

 

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!!!!

 

 

(1) Chapter title: Descent with Modification: A Darwinian View of Life

(a)                    Major Goal of this Chapter:

(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. Darwin addressed the sweeping issues of biology: the great diversity of organisms, their origins and relationships, their similarities and differences, their geographical distribution, and their adaptations to the surrounding environment. Thus, evolution is the most pervasive principle in biology... (This) chapter defines the Darwinian view of life and traces its historical development."

(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' (Darwin, 1859)." David Roche (2001). A Bit Confused: Creationism and Information Theory. Skeptical Inquirerer March/April:40-42]

(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). Darwin in Mind: 'Intelligent Design' Meets Artificial Intelligence, Skeptical Inquirerer March/April:35-39]

(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)]

(2) Evolution (see also evolution)

(a)                    ["In the broadest sense, evolution is merely change, and so is all-pervasive; galaxies, languages, and political systems all evolve. Biological evolution ... is change in the properties of populations of organisms that transcend the lifetime of a single individual. The ontogeny of an individual is not considered evolution; individual organisms do not evolve. The changes in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the successive alterations that led from the earliest protoorganism to snails, bees, giraffes, and dandelions." Douglas J. Futuyama (What is Evolution?) (Talk.Origins)]

(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 overall is 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) Darwin, Charles (1809-1882)

(a)                    Darwin, of course, gave us Darwinism, a collection of concepts that we will be studying essentially for the entire quarter

(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 Obama

(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 U.S., and, these days, as observed on the internet (e.g., see in particular the rantings of Philip Johnson)

(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 (see also Darwinism)

(a)                    Darwinism is a robust hypothesis that seeks to explain how life on Earth came to acquire its current forms and diversity

(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)                    Together the tenets of Darwinism serve as the foundation of our understanding of life

(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

(i)                     Linnaeus

(ii)                   Lyell

(iii)                 Lamarck

(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 Darwin was certainly not the world's first evolutionist; instead, his contribution was to propose a highly robust and plausible explanation of how organisms adapt to their environment and thereby evolve

(e)                    See Figure, The historical context of Darwin's life and ideas

(f)                     However, "The Origin of Species convinced most biologists that species are products of evolution, but Darwin was not nearly as successful (in his day) in gaining acceptance for natural selection as the mechanism of evolution." (p. 416)

(i)                     The popularity of this latter aspect of Darwin's theories has, of course, dramatically changed with natural selection today serving essentially as the foundation of a biologist's understanding of the natural world

(ii)                   In Darwin's day, however, there were major problems with the concept of natural selection, not least of which was a nearly complete misunderstanding of the mechanisms of genetics

(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) Linnaeus, Carolus (1707-1778)

(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 Darwin, the natural hierarchy of the Linnaen scheme reflected the branching genealogy of the tree of life, with organisms at the different taxonomic levels related through descent from common ancestors. If we acknowledge that lions and tigers are more closely related than are lions and horses, then we have recognized that evolution has left signs in the form of different degrees of kinship among modern species." (p. 420, Campbell et al., 1999)

(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)

(a)                    Lyell was a geologist

(b)                    The arguments of Lyell employed by Darwin basically consist of the following ideas

(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, 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, 6^th 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)                  [Jean Baptiste Lamarck, Lamarckism (Google Search)] [index]

(11) Wallace, Alfred (1823-1913)

(a)                    Wallace independently derived Darwinism

(b)                    Darwin's and Wallace's theories were first presented to the public more or less simultaneously in 1858

(c)                    Darwin's name is better recalled than Wallace's as a consequence of Darwin's extremely robust support and further development of the theory (besides, Darwin had and then sat on the idea long before Wallace derived his very similar ideas)

(d)                   [Alfred Russel Wallace (Google Search)] [index]

(12) Malthus, Thomas (1766-1834)

(a)                    Malthus proposed the idea of limits on population growth

(b)                    Essentially all populations are capable of growing exponentially to an infinite size but don't only because of environmental limits

(c)                    These limits include such things as food supply, supply of fresh water, supply of breathable air, etc.

(d)                   Any species will eventually reach the limits of its environment and then stop growing in numbers

(e)                    This implies that the intrinsic ability of organisms to grow typically exceeds their observed rate of growth

(f)                     In other words, in a world of limits, organisms typically either die before their time or don't make as many babies as they otherwise may be genetically capable of producing

(g)                    [Note that there are a number of individuals around who claim that Malthus was wrong and that, therefore, populations (particularly human) can continue to grow because limits may always be overcome, given sufficient evolutionary or cultural progress--don't believe these zealots: they are radical non-biologists who seek to screw, typically for personal gain, you and your descendants out of an earthly future!]

(h)                    [Thomas Malthus (Google Search)] [An Essay on the Principle of Population (Mathus' essay on population) (Ed Stephan)] [index]

 

SELECTION (AND DARWINISM CONTINUED)

 

(13) Descent with modification (see also descent with modification)

(a)                    Darwinism encompasses the idea that organisms change with time, diverging from a common form (i.e., they evolve)

(b)                    Darwinism additionally argues that many of the changes that occur do so for specific reasons; that is, modification over time is not necessarily completely random

(c)                    If we divide organisms into species, we can follow the evolution of species through time such that multiple, related species collapse into individual ancestral species as we go back in time (the ancestral dog, the ancestral horse, the ancestral ape, etc.)

(d)                   Ultimately, if we go back far enough in time, all living (i.e., extant) species may be collapsed into a single, universal ancestral species (which in all likelihood was a bacterium)

(e)                    Thus, the relationships between species may be visualized as a tree which progressively branches with time, with the tree growing taller but more and more diverse (bushier) with time

(f)                     Typically branches end in extinction, but all living (i.e., extant) organisms can trace their descent (ascent if we use the tree analogy) through branches, none of which ended solely in extinction

(g)                    Note, however, that: "Evolution is not progress. Populations simply adapt to their current surroundings. They do not necessarily become better in any absolute sense over time. A trait or strategy that is successful at one time may be unsuccessful at another." (Talk.Origins)

(h)                    [descent with modification (Google Search)] [index]

(14) Natural selection (see also natural selection)

"What if you could travel in time and visit with Darwin? What would you ask him? First, I'd be so overawed that I wouldn't know quite what to say. But I think maybe if I were really forced to ask him one question it would be, 'Why did you wait so long after you had this brilliantly simple yet powerful idea? Didn't it seem to you so fantastically simple yet so fantastically powerful that if you didn't write it down quickly, somebody else would?' I'm genuinely baffled about that because it's as though Darwin thought he had all the time in the world, and pretty nearly he did. I mean Wallace did get there, but still Darwin had about 20 years before that. What I find remarkable is that Aristotle didn't get it and Plato didn't get it, nor did Pythagorous, Archimedes, Newton, even though you don't need any technical know-how to get the idea. Natural selection is a bewilderingly simple idea. And yet what it explains is the whole of life, the diversity of life, the complexity of life, the apparent design of life. It all flows from this one remarkably simple idea." (p. 413, Campbell et al., 1999, emphasis mine, from a conversation with Richard Dawkins)

(a)                    "...frequently, people use the word evolution when they really mean natural selection..." (Talk.Origins)

(b)                    The non-random motivator of evolution we call natural selection

(c)                    Natural selection simply is the idea that when organisms within environmentally limited populations die, or don't make as many babies as they otherwise could, they are dying or not making babies non-randomly

(d)                   Particularly, those organisms that are less able to survive or make babies die at a faster rate or make fewer babies than those organisms that are better able to survive and make babies

(i)                     Note that the key word or phrase here is not "dying" but instead is "making babies"

(ii)                   Though we typically think of natural selection as a mechanisms of selective death, in fact the sole reason that selective death impacts on the evolution of populations is because dead organisms can't make babies

(iii)                 Don't forget this idea; in biology it is the making of babies that is everything and we survive only to maximize our reproductive output thereby maximizing the representation of our alleles within our population

(e)                    In other words, environmental limits cause a lack of population growth, but these limits impact on individuals differently

(f)                     Natural selection is another name for these differential impacts of environmental limits

(g)                    In addition, Darwinism employs the idea that at least some of the differences between individuals, which impact their survival and fertility, are heritable

(h)                    Thus, limits dictate that some (typically many) will die (or will make fewer babies) and genetic differences bias these deaths toward genotypes (a very key word) that are less hardy (or fertile) in a given environment

(i)                     Evolutionary change via natural selection: Darwinism

(i)                      Populations are consequently modified over time as those genotypes less capable of surviving or reproducing are culled from these environments (and the alleles underlying these culled genotypes as a result decrease in frequency)

(j)                      "The environment (acts) upon the inherited variations manifest in any population, favoring the survival and reproductive success of some individuals over others. Natural selection edits populations." (p. 409, Campbell, 1996; emphasis mine)

(k)                    ["natural selection" and evolution (Google Search)] [index]

(15) Adaptation (see also adaptation)

(a)                    "The result of natural selection is evolutionary adaptation, a prevalence of inherited characteristics that enhance organisms' survival and reproduction in specific environments." (p. 428, Campbell & Reece, 2002)

(b)                    Adaptation can have physiological/morphological as well as evolutionary meanings

(c)                    Natural selection assures that populations adapt to their environment by culling those individuals who are phenotypically less-well suited to surviving and reproducing in that environment

(d)                   Thus, because many phenotypes reflect underlying genotypic differences, over time populations typically become overall better at surviving and reproducing in a given, unchanging environment (i.e., better adapted genotypes preferentially survive)

(e)                    We describe this process as adaptation (in particular, evolutionary adaptation)

(f)                     We describe those heritable phenotypes associated with increasing survival or reproductive potential as adaptations

(g)                    Darwinism thus involves an adaptation by populations to local environments via the process of natural selection

(h)                    Nevertheless, keep in mind that "natural selection is situational: What works best in one environmental context may be less suitable in some other situation." (p. 409, Campbell, 1996)

(i)                      "We must distinguish between adaptations an organism acquires by its own actions, and inherited adaptations that evolve in a population over many generations as a result of natural selection." (p. 444, Campbell et al., 1999); the former is physiological adaptation or morphological adaptation while the latter is evolutionary adaptation and only the latter involves changes in allele frequencies

(i)                     (though note that this is confusing because the ability of an organism to physiologically adapt is, in fact, itself a product of natural selection, i.e., is itself an evolutionary adaptation--get it? if no, press here for further discussion of this concept)

(j)                      ["A trait's current utility is not always indicative of its past utility. It can evolve for one purpose, and be used later for another. A trait evolved for its current utility is an adaptation; one that evolved for another utility is an exaptation. An example of an exaptation is a penguin's wing. Penguins evolved from flying ancestors; now they are flightless and use their wings for swimming." (Talk.Origins)]

(k)                    [adaptation and evolution (Google Search)] [the evolution of improved fitness by random mutation plus selection (The Talk.Origins)] [index]

(16) Artificial selection (see also artificial selection)

(a)                    Selection may be somewhat "artificially" divided into two types

(i)                     Natural selection

(ii)                   Artificial selection

(b)                    Natural selection is where environmental limits are defined by nature

(c)                    Artificial selection is where environmental limits are defined by man; that is, artificial selection is selection imposed by man rather than by nature

(d)                   Otherwise there exist no fundamental difference between the two processes

(e)                    Artificial selection is responsible for the phenotypic diversity and change from ancestral, wild populations observed in domesticated organisms

(f)                     Note that in addition to purposefully applied artificial selection, much domestication actually occurs via a process of natural selection inadvertently imposed by man, e.g.,

(i)                     Guinea pigs sure look cute, but they also don't bite; a possible explanation for the latter is because guinea pigs that bite became dinner at a higher rate than guinea pigs that don't bite (yes, guinea pigs apparently were initially domesticated as a source of food)

(ii)                   Domestic animals (such as guinea pigs) tend to have huge litters, presumably because man has eliminated many of the environmental limits that prevent wild populations from raising large numbers of offspring simultaneously

(iii)                 Again guinea pigs, they are not terribly good at escaping from pens/cages, presumably because those that were good at escaping were lost from the domesticated populations (i.e., the escapees took their escape-motivating alleles with them)

(iv)                 Etc.

(g)                    See Figure, Artificial selection

(h)                    Thus, again, there exists no fundamental difference between natural selection and artificial selection: both involve differential survival (or reproductive success) based on genotypic differences, between individuals, that impact on phenotypes; the major difference is that when humans are attempting to modify a character via a breeding program, that selection is termed artificial selection whereas all other examples of selection are termed natural selection (though note that artificial selection regimens also typically involve selective matings (i.e., non-random mating), which explains in part why artificial selection appears to operate so much more rapidly than natural selection)

(i)                      [artificial selection, domestication (Google Search)] [index]

(17) The logic of Darwinism

(a)                    Ernst Mayr has collected a series of observations and inferences that he used to dissect Darwinism into component parts that summarizes many of our above discussions:

(i)                     Observation 1: high reproductive potential

(ii)                   Observation 2: stable population sizes

(iii)                 Observation 3: resource limits

(iv)                 Inference 1: struggle for existence

(v)                   Observation 4: variation within populations

(vi)                 Observation 5: variation is heritable

(vii)               Inference 2: differential reproductive success

(viii)             Inference 3: evolution

(b)                   See this dissection on page 420-421 (reproduced below and in outline above--you should understand this logic)

 

Logic of Darwinism (supplemental discussion)
Observation 1	Populations tend to have high reproductive potentials
Observation 2	Populations tend to be stable in size
Observation 3	Environments tend to possess limited resources
Inference 1	There exists a struggle for existence
Observation 4	There exists phenotypic variation within populations
Observation 5	Some phenotypic variation is heritable
Inference 2	Within populations there is differential reproductive success that is influenced by phenotypic differences between individuals
Inference 3	Differential reproductive success leads to a decline in frequency genotypes that underlie phenotypes that are less fit to the environment and a corresponding increase in frequency of genotypes that underlie phenotypes that are more fit to the environment: Darwinian Evolution

 

(c)                    You should know and understand this dissection "of the logic of Darwin's theory of natural selection"

(d)                   "Summarizing Darwin's main ideas:

(i)                     Natural selection is differential success in reproduction (unequal ability of individuals to survive and reproduce).

(ii)                   Natural selection occurs through an interaction between the environment and the variability inherent among the individual organisms making up a population.

(iii)                 The product of natural selection is the adaptation of populations of organisms to their environment.

(e)                    Evolution by natural selection is essentially an interplay of an organism's genotype with an organism's environment whereby the product of this evolution is a phenotype that allows the possessing organisms to more closely "fit" their environment such that these organism's reproductive success is greater than it would have been had natural selection not been operating; this is essentially a feedback loop between a population and its environment that is analogous (same idea, different mechanism) as the feedback loops that we studied in Chapter 18 (i.e., operons)

(f)                     [Ernst Mayr (Google Search)] [index]

 

EVIDENCE OF EVOLUTION AND NATURAL SELECTION

 

(18) Evidence of Darwinism

(a)                    "Scientists do not accept (Darwinism) solely on the face of its logic but because it has been confirmed repeatedly by the hypothetico-deductive approach." (p. 409, Campbell, 1996)

(b)                    Keep in mind as we walk through the evidence for Darwinism that some of the evidence is for the idea of descent with modification (evolution) while other is evidence for the occurrence of natural selection

(c)                    Evidence for Darwinism may be subdivided, for example, into

(i)                     Evidence for the occurrence of evolution in extant populations

(ii)                   Evidence of the occurrence of natural selection in extant populations

(iii)                 Evidence from biogeography

(iv)                 Evidence from the fossil record

(v)                   Evidence from comparative anatomy

(vi)                 Evidence from comparative embryology

(vii)               Evidence from molecular biology

(viii)             Etc.

(d)                   Keep in mind also that though much of this evidence is for the existence of evolution rather than for the existence of natural selection; still the typically most robust way to understand evolution is as mechanisms driven to a considerable extent by the non-random processes of natural selection (that is, to explain adaptation one must come up with some explanation for non-random, particularly directed evolutionary change and natural selection is by far and away the most plausible and robust explanation)

(e)                    ["Microevolution can be studied directly. Macroevolution cannot. Macroevolution is studied by examining patterns in biological populations and groups of related organisms and inferring process from pattern. Given the observation of microevolution and the knowledge that the earth is billions of years old -- macroevolution could be postulated. But this extrapolation, in and of itself, does not provide a compelling explanation of the patterns of biological diversity we see today. Evidence for macroevolution, or common ancestry and modification with descent, comes from several other fields of study. These include: comparative biochemical and genetic studies, comparative developmental biology, patterns of biogeography, comparative morphology and anatomy and the fossil record." (Talk.Origins)]

(f)                     [Evidence Darwinism (Google Search)] [index]

(19) Extant populations (see also extant)

(a)                    Evolutionary change is easily observed in extant (i.e., currently existing) populations as changes in genotypes that occur over time

(b)                    The hard part is attributing that change to natural selection

(c)                    Your text examines one such attempt on pp. 437-438 (Campbell & Reece, 2002)

(d)                   Other changes that are consistent with a natural selection cause include:

(i)                     The evolution of antibiotic-resistant bacteria

(ii)                   The evolution of antiviral-resistant viruses

(iii)                 The evolution of insecticide-resistant insects

(iv)                 The evolution of toxin-resistant organisms (i.e., about toxic waste dumps)

(v)                   Industrial melanism (the evolution of darker moths in the face of smoke-blackened trees and birds which hunt visually)

(vi)                 Sickle cell anemia (selected for by resistance to malaria)

(vii)               Predator selection on guppies

(viii)             Evolution of sex ratios

(ix)                 Cancer progression

(x)                   Evolution of pathogen virulence

(xi)                 Etc.

(e)                    You will note, of course, that many of these evidences have man at their centers; this is because natural selection is most easily observed in the face of relatively straightforward environmental change and if there is one thing man is good at, it is totally screwing up the environment in relatively straightforward ways

(i)                     (e.g., air pollution, water pollution, deforestation, desertification, improper use of antimicrobials, over-use of pesticides, over-hunting, elimination of species, conversion of complex ecosystems into extremely simple ones, e.g., irreplaceable wet or wood lands into parking lots, etc.)

(f)                     [extant species (Google Search)] [index]

(20) Biogeography (see also biogeography)

(a)                    Biogeography is the study of the geographical distribution of species

(b)                    "Darwin... noted that the pants and animals in temperate regions of South America were more closely related to species living in tropical regions of that continent than to species in temperate regions of Europe." "He then learned that most of the animal species on the Galápagos live nowhere else in the world, although they resemble species living on the South American mainland. It was as though the islands had been colonized by plants and animals that strayed from the South American mainland and then diversified on the different islands." (p. 433, Campbell & Reece, 2002)

(c)                    Species are distributed neither evenly nor randomly across the globe

(d)                   Instead, related species tend to be more geographically closer to one another than are less-related species doing similar jobs in similar environments

(e)                    "...most island species are closely related to species from the nearest mainland or neighboring island. This explains why two islands with similar environments in different parts of the world are populated not by closely related species but by species taxonomically affiliated with the plants and animals of the nearest mainland, where the environment often is quite different." (p. 441, Campbell & Reece, 2002)

(f)                     As one edition of your text has put it (p. 423, not sure which edition)

(i)                     "Why are the tropical animals of South America more closely related to species of South American deserts than to species of the African tropics?"

(ii)                   "Why are two islands with similar environments in different parts of the world not populated by closely related species but by species taxonomically affiliated with the plants and animals of the nearest mainland, where the environment is often quite different?"

(iii)                 Etc.

(g)                    The answer is that environments are not necessarily populated by the organisms best suited to those environments because organisms are typically limited in their ability to traverse geographical barriers including great distances

(h)                    Instead, new environments tend to be inhabited by less well-adapted organisms coming from geographically close environments, and then natural selection in time assures an evolution of organisms better adapted to what had been new environments

(i)                      "Although such biogeographical patterns are incongruous if one imagines that species were individually placed in suitable environments, they make sense in the historical context of evolution. In the evolutionary view, we find modern species where they are because they evolved from ancestors that inhabited those regions." (p. 423, Campbell et al., 1999)

(j)                     See Figure, Different geographic regions, different mammalian "brands"

(k)                   See Figure, The evolution of fruit fly (Drosophila) species on the Hawaiian archipelago

(l)                      [biogeography (Google Search)] [index]

(21) The fossil record (see also fossil record)

(a)                    The fossil record records a very evolutionary view of life complete with the descent of modern forms from archaic forms via numerous evolutionary transitions

(b)                    Note that the fossil record is much less able to confirm the existence of natural selection

(c)                    However, the fossil record is perfectly consistent with an evolutionary interpretation of life (note that this statement is somewhat tautological since evolutionary theory was developed in part as an explanation for what we observe in the fossil record)

(d)                   See Figure, Decent with modification

(e)                    See Figure, A transitional fossil linking past and present

(f)                     [fossil record (Google Search)] [index]

 

HOMOLOGIES

 

(22) Phenotype comparison

(a)                    The more closely related two organisms are, the more similar tend to be their phenotypes (this too is a somewhat tautological statement since degrees of evolutionary relationships are often determined via phenotypic comparisons)

(b)                    More interestingly, seemingly unrelated organisms often show underlying phenotypic similarities that suggest evolutionary relatedness

(c)                    Phenotype comparisons can be grouped under a number of headings including

(i)                     Comparative anatomy

(ii)                   Comparative embryology

(iii)                 Molecular evolution

(d)                   Concepts relevant to such comparisons include

(i)                     Homology

(ii)                   Homologous structures

(iii)                 Vestigial organs

(e)                    [phenotypic similarity (Google Search)] [index]

(23) Homology (see also homology)

(a)                    A homology is a characteristic of two organisms which are similar as a consequence of shared ancestry (i.e., the characteristic is also found in the common ancestor)

(b)                    The wings of birds are homologous structures among birds because the common ancestral bird presumably had wings

(c)                    The wings of birds and bats are not a homology because the common ancestor to birds and bats (a very early reptile) lacked wings (though, it should be pointed out that much of the underlying anatomy of bird and bat wings consist of numerous homologies since the common ancestor to birds and bats had reptilian forelimbs, and wings in both taxa evolved as modified reptilian forelimbs, though modified in different ways)

(d)                   "Surely, the best way to construct the infrastructure of a bat's wing is not also the best way to build a whale's flipper. Such anatomical peculiarities make no sense if the structures are uniquely engineered and unrelated... Such anatomical signs of evolution are called homologous structures... For example, the human knee joint and spine were derived from ancestral structures that supported four-legged mammals. Almost none of us will reach old age without experiencing knee or back problems. If these structures had first taken form specifically to support our bipedal posture, we would expect them to be less subject to injury. The anatomical remodeling that stood us up was apparently constrained by our evolutionary history." (p. 439, Campbell & Reece, 2002)

(e)                    The near-universal commonality of the genetic code (i.e., codon designations) is a homology, one presumably consistent with the existence of an extinct universal ancestor

(f)                     So, in short, a homology is a trait (i.e., a variation on a character) that is shared by two organisms particularly because the common ancestor of those two organisms also possessed this trait

(g)                    Homologies tend to be associated with additional homologies (the existence of a homology predicts additional homologies)

(h)                    "Homologies form a layered pattern, with all life sharing the deepest layer and each smaller group adding fresh homologies to those they share with larger groups." (p. 439, Campbell & Reece, 2002)

(i)                      Analogies (i.e., products of convergent evolution), by contrast, tend to predict only additional functional similarities (i.e., additional analogies; e.g., flippers predict streamlining) and not similarities between underlying structures only tangentially related to function

(j)                      [homology, homology -jonathan -wells (Google Search)] [index]

(24) Homologous structure (see also homologous structure)

(a)                    A homologous structure is simply an anatomical (i.e., structural) characteristic that serves as a homology

(b)                    [Body parts in different organisms that have similar bones and similar arrangements of muscles, blood vessels, and nerves and undergo similar embryological development, but do not necessarily serve the same function; e.g., the flipper of a whale and the forelimb of a horse (OnLine Biology Book)]

(c)                    Wings can be homologous structures (e.g., among birds)

(d)                   Nucleotide sequences, which can also be similar due to descent and thereby homologies, are not anatomical structures and therefore are not called homologous structures (which, however, doesn't mean that nucleotide sequences cannot be examples of homologies)

(e)                    Proteins, on the other hand, can possess homologous structures

(f)                     See Figure, Homologous structures: anatomical signs of decent with modification

(g)                     http://faculty.uca.edu/ben.waggoner/biol1400/

(h)                    [homologous structures, homologous structures -jonathan -wells -denton -god (Google Search)] [index]

(25) Comparative anatomy

(a)                    In comparing the anatomy of organisms, one typically compares these organisms in terms of their similarities and differences

(b)                    "Descent with modification is evident in anatomical similarities between species grouped in the same taxonomic category. For example, many of the same skeletal elements make up the forelimbs of humans, cats, whales, bats, and all other mammals, although these appendages have very different functions. Surely, the best way to construct the infrastructure of a bat's wing is not also the best way to build a whale's flipper. Such anatomical peculiarities make no sense if the structures are uniquely engineered and unrelated. A more likely explanation is that the basic similarity of these forelimbs is the consequence of the descent of all mammals from a common ancestor." (p. 424, Campbell et al., 1999)

(c)                    See Figure, Homologous structures: anatomical signs of decent with modification

(d)                   See also Figure (on p. 477), A range of eye complexity among mollusks

(e)                    Of particular interest when attempting to determine evolutionary relationships are similarities known as homologies

(f)                     ["Groups of related organisms are 'variations on a theme' -- the same set of bones are used to construct all vertebrates. The bones of the human hand grow out of the same tissue as the bones of a bat's wing or a whale's flipper; and, they share many identifying features such as muscle insertion points and ridges. The only difference is that they are scaled differently. Evolutionary biologists say this indicates that all mammals are modified descendants of a common ancestor which had the same set of bones." (Talk.Origins)]

(g)                    [comparative anatomy (Google Search)] [index]

(26) Vestigial structures (see also vestigial structure)

(a)                    Homologous structures are not necessarily useful to a recipient organism

(b)                    A structure that is expensive to make or to sustain, but which truly makes no positive impact on survival or reproductive success will not be selected for (indeed, may be selected against) and therefore will ultimately may be lost via evolution (i.e., via natural selection or via genetic drift)

(c)                    In the mean time, the structure is retained as a vestigial, constituting for us a example of structural evidence of shared ancestry

(d)                   For example, vestigial rear legs in some snakes and in transitional whale ancestors are homologies shared with more-fully legged ancestral species

(e)                    It is very important to keep in mind and then remember that vestigial structures are homologous structures, i.e., structures that are no longer used and have degenerated but nevertheless are similar to structures possessed by other organisms particularly because a shared ancestor possessed these structures

(f)                     The important question, then, is why would an organism possess a useless structure? The answer is that vestigial structures represent evidence for the occurrence of decent with modification, i.e., the utilization of a structure by an ancestor that is no longer utilized by a descendant

(g)                   

(h)                    [vestigial structures (Google Search)] [a wonderful debate on the illogic of a creationists position on vestigial structures (Darwin Campfire Chat)] [index]

(27) Comparative embryology

(a)                    The embryos of organisms are loaded with homologous structures and, of even greater interest (since we would expect similar adults to have similar embryonic features), embryos are loaded (at least superficially) with vestigial structures, e.g., gills on human fetuses

(b)                    Thus, even when adult organisms are superficially very different, loads of homologies can still be located in embryos via comparative embryology (i.e., by comparing embryos)

(c)                    "Comparative embryology often establishes homology among structures, such as the gill pouches, that become so altered in later development that their common origin is not apparent by comparing their fully developed forms." (p. 425, Campbell et al., 1999)

(a)                    See also Figure, Allometric growth, Comparison of chimpanzee and human skull growth

(b)                    ["Closely related organisms share similar developmental pathways. The differences in development are most evident at the end. As organisms evolve, their developmental pathway gets modified. An alteration near the end of a developmental pathway is less likely to be deleterious than changes in early development. Changes early on may have a cascading effect. Thus most evolutionary changes in development are expected to take place at the periphery of development, or in early aspects of development that have no later repercussions. For a change in early development to be propagated, the benefit of the early alteration must outweigh the consequences to later development. ¶ Because they have evolved this way, organisms pass through the early stages of development that their ancestors passed through up to the point of divergence. So, an organism's development mimics its ancestors although it doesn't recreate it exactly... ¶ Natural selection can modify any stage of a life cycle, so some differences are seen in early development... There are differences in the appearance of early vertebrate embryos. Amphibians rapidly form a ball of cells in early development. Birds, reptiles and mammals form a disk. The shape of the early embryo is a result of different yolk concentrations in the eggs. Birds' and reptiles' eggs are heavily yolked. Their eggs develop similarly to amphibians except the yolk has deformed the shape of the embryo. The ball is stretched out and lying atop the yolk. Mammals have no yolk, but still form a disk early. This is because they have descended from reptiles. Mammals lost their yolky eggs, but retained the early pattern of development. In all these vertebrates, the pattern of cell movements is similar despite superficial differences in appearance. In addition, all types quickly converge upon a primitive, fish-like stage within a few days. From there, development diverges." (Talk.Origins)]

(c)                    [comparative embryology (Google Search)] [index]

(28) Molecular evolution (see also molecular evolution)

(a)                    Much inference of evolutionary relatedness these days is done, when possible, via comparisons of nucleotide (or amino acids) sequences

(b)                    The use of these techniques are very common and can be found in such areas as

(i)                     The designation of the mitochondrial Eve

(ii)                   Tracking the AIDS epidemic

(iii)                 The relationship between humans and apes

(iv)                 Etc.

(c)                    "If two species have libraries of genes and proteins with sequences of monomers that match closely, the sequence must have been copied from a common ancestor. If two long paragraphs are identical except for the substitution of a letter here and there, we would surely attribute them both to a single source." (p. 425, Campbell et al., 1999)

(d)                   See Table 22.1, Molecular data and the evolutionary relationships of vertebrates

(e)                    [molecular evolution (Google Search)] [index]

 

VOCABULARY

 

(29) Vocabulary [index]

(a)                    Adaptation

(b)                    Artificial selection

(c)                    Biogeography

(d)                   Comparative anatomy

(e)                    Comparative embryology

(f)                     Darwin, Charles

(g)                    Darwinism as the foundation of biology

(h)                    Darwinism encompasses two ideas, one explaining the other

(i)                      Darwinism's historical context

(j)                      Descent with modification

(k)                    Evidence of Darwinism

(l)                      Extant populations

(m)                  The fossil record

(n)                    Homologous structure

(o)                    Homology

(p)                    Lamarck, Jean Baptiste

(q)                    Linnaeus, Carolus

(r)                     The logic of Darwinism

(s)                     Lyell, Charles

(t)                     Malthus, Thomas

(u)                    Molecular evolution

(v)                    Natural selection

(w)                  Origin of Species

(x)                    Phenotype comparison

(y)                    Vestigial structures

(z)                    Wallace, Alfred

(30) Practice Questions [index]

(a)                    In Ernst Mayr's view, what did Darwin logically infer from the following three observations:

(i)                     All species have such great potential fertility that their population size would increase exponentially if all individuals that are born reproduced successfully

(ii)                   Most populations are normally stable in size, except for seasonal fluctuations.

(iii)                 Natural resources are limited.

(b)                    Another word for evolutionarily (i.e., natural selection)-generated changes in "phenotypes associated with increasing survival or reproductive potential" is __________.

(c)                    What are the two major ideas embodied in the concept known as Darwinism?

(d)                   Name two examples of natural selection that have occurred within natural (i.e., not purposefully domesticated) species (note: examples of purposefully domesticated populations/species might include domesticated dogs, domesticated guinea pigs, and the yeasts used to make bread).

(e)                    (bonus) Lamarck's theory of evolution was quite similar to that of Darwin with the prominent exception that Lamarckism lacked Darwin's (and Wallace's) concept of natural selection. Nevertheless, unlike Darwinism, Lamarck's theory of evolution contained a second truly fatal flaw stemming from a lack of compatibility with what more recently described characteristic of plants and animals?

(f)                     On the Origin of Species by Means of Natural Selection, or The preservation of Favored Races in the Struggle for Life was published what year?

(i)                     1811

(ii)                   1812

(iii)                 1850

(iv)                 1859

(v)                   1918

(vi)                 1928

(g)                    __________ was Darwin's contemporary and is credited as the co-discoverer of "Darwinian" evolution.

(i)                     Jean Baptiste Lamarck

(ii)                   Carolus Linnaeus

(iii)                 Charles Lyell

(iv)                 Thomas Malthus

(v)                   Alfred Wallace

(h)                    Beyond the idea that populations possess more potential for growth than environments typically will allow (i.e., population sizes are stable and natural resources limited), what two observations is the following inference (codified by Ernst Mayr) based upon? "Survival in the struggle for existence is not random, but depends in part on the hereditary constitution of the surviving individuals. Those individuals whose inherited characteristics fit them best to their environment are likely to leave more offspring than less fit individuals."

(i)                      Distinguish (mechanistically) artificial selection from natural selection.

(j)                      Distinguish the term homology from vestigial structure.

(k)                    Matching: (a) geologist, (b) not evolutionist, (c) acquired characteristics, (d) Darwin contemporary.

(i)                     Linnaeus:            __________

(ii)                   Lyell:                  __________

(iii)                 Lamarck:            __________

(iv)                 Wallace:             __________

(l)                      What evolutionary process is most closely associated with the concept of Darwinian evolution?

(i)                     Genetic drift

(ii)                   Natural selection

(iii)                 Migration

(iv)                 Mutation

(v)                   Allopatric speciation

(m)                  What is the Darwinian explanation for Linnaeus' grouping of organisms into like groups (taxa) according to phenotypic similarities?

(i)                     Convergent evolution and sympatry

(ii)                   Phenotypic convergence

(iii)                 Survival of the fittest

(iv)                 Evolutionary relatedness underlies phenotypic similarity

(v)                   Vestigial structure

(n)                    Briefly discuss the key difference between a population that has grown without limits and an otherwise similar population that has grown in the presence of environmental limits on its growth.

(o)                    Another name for the culling of those organisms within a given population that are less able to survive or reproduce is __________.

(i)                     Genetic drift

(ii)                   Natural selection

(iii)                 Migration

(iv)                 Mutation

(v)                   Sympatric speciation

(p)                    Define adaptation in terms of natural selection.

(q)                    Consistent with Ernst Mayr's summation of Darwinism, what three factors (i.e., observations) are necessary before one may infer the existence of a "struggle for existence"?

(r)                     What is biogeography?

(s)                     Two species both exhibit a common structure (e.g., a shell) that we infer represents a homology (i.e., a homologous structure shared by the two species). However, from field observation we deduce that only species A (e.g., a chambered nautilus) employs this structure in the course of its life history whereas in species B (e.g., a squid) the structure has never been observed being used and, in fact, is somewhat underdeveloped compared to the homologous structure in species A. What specific term might we employ to describe the homologous structure as it is displayed by species B?

(t)                     Carolus Linnaeus, though no evolutionist, nevertheless developed the science of taxonomy and invented __________ nomenclature.

(u)                    The evolution of adaptations occurs, in part, as a consequence of differential survival or reproductive success of organisms possessing different phenotypes (phenotypic variation). What must also be present, as a characteristic of organisms, before a mechanism of differential survival/reproductive success may be described as an example of Darwinian evolution?

(v)                    Give three specific examples of situations in which natural selection has been documented within wild populations of organisms. Wild means other than domesticated. Examples of natural selection among domesticated organisms, e.g., guinea pigs, will not be accepted.

(w)                  Molecular evolution in particular involves the comparative study of __________ and is employed toward such pursuits as tracking down the mitochondrial Eve, defining the AIDS pandemic, discovering the evolutionary relationship between humans and non-human primates, etc. (note: "homologies" is not a sufficient answer; I want to know what aspect(s) of organisms molecular evolutionists compare)

(x)                    What was Charles Lyell's profession?

(y)                    How are the definitions of "homologous structure" and "vestigial structure" similar and how do they differ?

(z)                    Darwinism encompasses two ideas. One is the mechanism of evolutionary change (i.e., via natural selection). What is the other idea?

(aa)                 What year was the "Origin of Species" published?

(i)                     1537

(ii)                   1838

(iii)                 1859

(iv)                 1906

(v)                   1937

(bb)                Who defined modern biological diversity according to phenotypic comparisons (and invented binomial nomenclature to boot)?

(i)                     Darwin

(ii)                   Lamarck

(iii)                 Linnaeus

(iv)                 Lyell

(v)                   Wallace

(cc)                 Who was the earlier evolutionist?

(i)                     Darwin

(ii)                   Lamarck

(iii)                 Linnaeus

(iv)                 Mendel

(v)                   Wallace

(dd)               How did Darwin view the Linnaen system of classification (a view not held by Linnaeus)?

(ee)                 What was the profession of Charles Lyell?

(ff)                  The idea that proto-giraffes stretched their necks to reach higher twigs and that this caused their offspring to have longer necks requires which order of information flow?

(i)                     DNA to RNA

(ii)                   Protein to DNA

(iii)                 Protein to protein

(iv)                 RNA to protein

(v)                   RNA to RNA

(gg)                What was Alfred Russel Wallace's contribution to evolutionary theory?

(hh)                What was Thomas Malthus' contribution to evolutionary theory?

(ii)                    The idea that organisms may die non-randomly is one aspect of the concept of __________ which underlies Darwinian evolution.

(i)                     Drift

(ii)                   Migration

(iii)                 Mutation

(iv)                 Non-random mating

(v)                   Selection

(jj)                    Darwinism involves an adaptation by populations to __________ via the process of natural selection.

(kk)                What is the difference between artificial and natural selection?

(ll)                    According to Darwin (via Mayr), what do these observations imply: (1) high reproductive potential, (2) stable population sizes, and (3) resource limits (limitations)?

(mm)            Fundamentally, natural selection reflects a differential success in _________.

(nn)                The evidence from biogeography, the fossil record, comparative anatomy, comparative embryology, and molecular biology supports, particularly, the Darwinian idea of __________.

(i)                     Anagenesis

(ii)                   Descent with modification

(iii)                 Punctual disequilibrium

(iv)                 The importance of convergent evolution

(v)                   The occurrence of natural selection

(oo)                Within extant populations, which is particularly difficult to do?

(i)                     Observe genetic drift as it occurs

(ii)                   Observe migration

(iii)                 Observe natural selection in action

(iv)                 Observe non-random mating

(v)                   Observe the occurrence of evolutionary change

(pp)                What is biogeography?

(qq)                What is a homology?

(rr)                   Give an example of a vestigial structure.

(ss)                  A homologous structure common between two species, but unused and degenerate in one, is described as a(n) __________ particularly in the latter species.

(tt)                   The study of molecular evolution involves the comparison of the sequences of __________, and from these comparisons evolutionary relationships between organisms may be inferred. ("homologous" is not the answer I am looking for... think molecular!)

(uu)                A gill pouch in a human embryo represents all of the following except __________.

(i)                     A homology

(ii)                   A product of artificial selection

(iii)                 A vestigial structure

(iv)                 An anatomical structure shared with an ancestral fish

(v)                   Something observed by a comparative embryologist

(vv)                What was Charles Lyell's contribution to Darwin's development of evolutionary theory?

(ww)            What is the role of environmental limits in the evolution of organisms?

(xx)                What is the contribution of science of biogeography to our understanding of evolution?

(i)                     Ecosystems worldwide possess evolutionarily related species

(ii)                   New environments are populated from adjacent environments

(iii)                 Related species are biogeographically isolated

(iv)                 Species evolve

(v)                   Species live on islands

(yy)                In terms of phenotypic comparisons between organisms, what is a homologous structure?

(zz)                 Comparison of DNA (or RNA) sequences, to infer evolutionary relationship, is most associated with which of following terms?

(i)                     Molecular analogy

(ii)                   Molecular evolution

(iii)                 Molecular homology

(iv)                 Nucleotide homology

(v)                   Species selection

(aaa)             You are studying the evolutionary relationship between two organisms, a barnacle and a lobster. These animals, when sexually mature, display little phenotypic resemblance. Nevertheless, you hypothesize that the two organisms in fact are closely related. Comparing various extant (i.e., not extinct) examples of these two organisms, name two methods, of those that we discussed under the heading of phenotype comparison, that could be effectively employed to suggest that these two species are indeed relatively closely related.

(bbb)            A homologous structure is an anatomical similarity that is similar as a consequence of __________.

(ccc)             Why are two islands with similar environments in different parts of the world not populated by closely related species but by species taxonomically affiliated with the plants and animals of the nearest mainland, where the environment is often quite different?

(ddd)          Ernst Mayr summarizes the logic of Darwinisn, as presented by your text. Five observations are employed to derive three inferences. The last inference may be summarized with the phrase, Darwinian Evolution (or, simply, evolution). What are the other two inferences (i.e., inferences 1 and 2 in the summary)?

(eee)             From the perspective of affected populations, artificial selection, as an evolutionary mechanism, does not differ conceptually from that of natural selection, but nevertheless is much more readily observed. Darwin consequently (and wisely) employed examples from artificial selection to bolster his arguments for the existence of natural selection. How does artificial selection differ from natural selection?

(fff)               The word adaptation can be confusing because, in biology, it essentially has two different meanings. One meaning--synonymous with the phrase "evolutionary adaptation"--is a description of the phenotypic consequences of natural selection on populations, i.e., evolutionary innovations that allow the possessing organisms to survive and reproduce better within a given environment. What is the other meaning of the term adaptation?

(ggg)            Why are the phrases "survival of the fittest" and "natural selection", as applied to individual organisms, not synonymous? Hint: the answer as nothing to do with the idea that it is populations that evolve rather than individuals.

(hhh)            Who proposed the idea of limits on population growth?

(i)                     Jean Baptiste Lamarck

(ii)                   Carolus Linnaeus

(iii)                 Charles Lyell

(iv)                 Thomas Malthus

(v)                   Alfred Wallace

(iii)                  Who was the earliest evolutionist?

(i)                     Aristotle

(ii)                   Darwin

(iii)                 Lamarck

(iv)                 Lyell

(v)                   Malthus

(jjj)                  What was Linnaeus' contribution to evolutionary thinking (hint, Linnaeus was not an evolutionist)?

(kkk)            Explain the following in terms of Darwinian evolution:

(lll)                  Can an anatomical structure be both vestigial and homologous at the same time? Why or why not?

(mmm)      Darwinism encompasses two distinct ideas, a mechanism of evolutionary change via natural selection and __________. Though both ideas were proposed in Darwin's Origin of Species, it took much longer for scientists to accept natural selection as the primary mechanism of directed evolutionary change.

(nnn)            Matching (a) Darwin, (b) Lamarch, (c) Linnaeus, (d) Lyell (use each only once).

(i)                     Defined modern biological diversity according to phenotypic relationships

(ii)                   Derived ideas without knowledge of Mendelian genetics

(iii)                 Postulated what today could be described protein to DNA information flow

(iv)                 Today's earth is the cumulative product of the gradual expression of the same physical processes we observe today

(ooo)            Darwinism employs the idea that at least some of the selective differences between individuals, which significantly impact their survival and fertility, are __________ and therefore selectable over generations.

(ppp)            In Ernst Mayr's summation of the logic of Darwinism, he cites three observations that give rise to the inference, "Struggle for existence." Those three observations are (i) Environments tend to possess limited resources, (ii) Populations tend to have high reproductive potentials, and (iii) __________.

(qqq)            Most island species are closely related to species from __________. This explains why two islands with similar environments in different parts of the world are populated not by closely related species.

(rrr)                Define the term homology. I am looking for a general definition rather than specific illustrating examples.

(sss)               Define the term vestigial. I am looking for a general definition rather than specific illustrating examples.

(ttt)                Comparative __________ often establishes homology among structures, such as gill pouches that become so altered in later development that their common origin is not apparent by comparing their fully developed forms.

(i)                     Biogeography

(ii)                   Embryology

(iii)                 Evolution

(iv)                 Molecular biology

(v)                   Phenotypy

(uuu)            What is a homology? Note the definitions of homology and synapomorphy are not perfectly synonymous so please do not define the latter for me in place of the former.

(vvv)            True or False, homologies can be more easily identified in embryos than in adult organisms. A: True

(www)      True or False, vestigial structures are present in organisms in part as a consequence of the presence of similar structures in ancestral organisms. A: True

(xxx)            What is the definition of the term homology as employed by evolutionary biologists? A: a homology is a trait (i.e., a variation on a character) that is shared by two organisms particularly because the common ancestor of those two organisms also possessed this trait

(yyy)            True or False, the fossil record tends to be better at confirming the existence of natural selection than it is at indicating an evolutionary interpretation of life. A: False

(zzz)             Given the great diversity of organisms on Earth, and the large number of different types of environments to which individual organism types are well adapted, why is that the introduction of new types of environments into a given region will not necessarily in the short term result in a colonization of those environments with organisms that are highly fit for growth and survival within those environments. A: organisms are limited in their ability to disperse over great distances and consequently migrants to new environments typically come from relatively local environments even though organisms within neighboring environments may not themselves be well adapted survival and reproduction within the new environment (on the other hand, they likely can avoid significant competition by invading these environments to which they are not-yet terribly well adapted)

(aaaa)          Evolution is driven to a considerable extent by the non-random processes of __________. A: Natural selection

(bbbb)        In summarizing Darwinism, what observations did Ernst Mayr provide as evidence for the existence of a Struggle for Existence among organisms? A: high reproductive potential combined with resource limitations and/or observation of stable population sizes

(cccc)          The change of organisms to the domestic varieties with which we are all familiar (e.g., varieties of dogs) is a consequence of an application __________ selection. A: artificial

(dddd)      In an evolutionary sense, what is an adaptation? A: an adaptation is a trait that enhances an organism's survival and/or reproduction (ultimately the latter) and by and large which is a product of natural selection.

(eeee)          Darwinism employs the idea that at least some of the phenotypic differences between individuals, which can differentially impact their survival and fertility, are __________. A: heritable, i.e., passed on from parent to offspring

(31) Practice Question Answers [index]

(a)                    Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of offspring surviving each generation.

(b)                    Adaptation(s)

(c)                    (i) evolutionary relatedness explaining the diversity of life, (ii) non-random survival of variation due to natural selection

(d)                   (i) antimicrobial resistance, (ii) insecticide resistance, (iii) toxic waste resistance, (iv) industrial melanism, (v) sickle cell anemia

(e)                    Mendelian genetics

(f)                     (iv) 1859

(g)                    (v) Alfred Wallace

(h)                    (i) Individuals of a population vary extensively in their characteristics; no two individuals are exactly alike, (ii) much of this variation is heritable

(i)                      There is no difference except that in artificial selection the agent which causes environmental limitations is man while in natural selection it is nature; often natural selection is limited to include only those limitations man puts in place purposefully

(j)                      A homology is a characteristic which is similar due to descent, i.e., is found in the common ancestor; a vestigial structure is a homologous structure which is no longer useful to one of the possessors, but nevertheless exists in both due to common descent

(k)                    (i) (b), (ii) (a), (iii) (c), (iv) (d)

(l)                      (ii) Natural selection

(m)                  (iv) Evolutionary relatedness underlies phenotypic similarity (that is, phenotypically similar organisms are more closely related evolutionarily, i.e., diverged from a common ancestor at a later date than have the common ancestors of less similar organisms).

(n)                    Size, the population that has grown without limits will be larger. An additional difference should be that the population that has grown without limits should display greater genetic variability.

(o)                    (ii) Natural selection

(p)                    With natural selection, those organisms that are less able to adapt to their environment are lost. Consequently, a population is enriched for individuals that are more adapted to their environment. The specific morphological or physiological features that contribute to the survival of these better-adapted organisms are termed adaptations.

(q)                    (i) Unlimited potential for population growth (ii) but observed stable population sizes (iii) given the existence of environmentally imposed limits.

(r)                     Biogeography is the study of the geographical distribution of species.

(s)                     A vestigial structure.

(t)                     Binomial

(u)                    Heritability of the variation upon which natural selection acts

(v)                    The evolution of antibiotic-resistant bacteria, the evolution of antiviral-resistant viruses, the evolution of insecticide-resistant insects, the evolution of toxin-resistant organisms (i.e., about toxic waste dumps), industrial melanism (the evolution of darker moths in the face of smoke-blackened trees and birds that hunt visually), sickle cell anemia (selected for by resistance to malaria), predator selection on guppies, evolution of sex ratios, cancer progression, evolution of pathogen virulence, etc.

(w)                  Nucleotide sequences

(x)                    Geologist

(y)                    A vestigial structure is a homologous structure, i.e., a structure that is in common between two organisms by descent; a vestigial structure, however, has at best a marginal function in the possessing organism whereas homologous structures are simply similar due to common ancestry (i.e., a vestigial structure is no-longer used structure that is similar by descent to a functional structure found in another organism)

(z)                    The evolutionary descent of organisms from common ancestors (origin of biological diversity) and therefore the idea of evolutionary relationship

(aa)                 (iii) 1859

(bb)                (iii) Linnaeus

(cc)                 (ii) Lamarck

(dd)               Darwin viewed the Linnaen system of classification essentially as a map of evolutionary relationships

(ee)                 He was a geologist

(ff)                  (ii) Protein to DNA

(gg)                Wallace was a co-discoverer of Darwinian evolution, particularly of natural selection

(hh)                Malthus argued that there are limits to population growth

(ii)                    (v) Selection

(jj)                    Local environments

(kk)                Fundamentally there is no difference except that in artificial selection the selector is man while in natural selection the selector is nature

(ll)                    These observations imply a struggle for existence

(mm)            Reproduction

(nn)                (ii) Descent with modification

(oo)                (iii) Observe natural selection in action

(pp)                Biogeography is the study of the geographical distribution of organisms

(qq)                A homology is a trait shared by two organisms from two different species that is present in both species because it was also present in the common ancestor to both species

(rr)                   E.g., the vestigial rear limbs in boa constrictors

(ss)                  Vestigial structure

(tt)                   Nucleotides (amino acids, DNA, RNA, protein, and nucleic acid are also reasonable answers)

(uu)                (ii) A product of artificial selection

(vv)                Uniformitarianism/long time frames/gradual processes... even gradualism would be reasonably acceptable as an answer though "geology" alone would not

(ww)            They assure that a populations reproductive potential cannot be realized

(xx)                (ii) New environments are populated from adjacent environments

(yy)                A homologous structure is a characteristic that is similar between two organisms of two different species that is similar as a consequence of both common decent and because the common ancestor to the two organisms also possessed that structure

(zz)                 (ii) Molecular evolution

(aaa)             Molecular evolution/sequence homology/sequence comparison and comparative embryology

(bbb)            Shared ancestry, common decent, evolutionary relatedness

(ccc)             Environments are not necessarily populated by the organisms best suited to those environments because organisms are typically limited in their ability to traverse geographical barriers including great distances

(ddd)          Struggle for existence and differential reproductive success

(eee)             The difference lies in the selector, which is human action for artificial selection but natural phenomenon for natural selection; another way of answering this is that artificial selection is purposefully directed whereas natural selection is not

(fff)               Adaptation is also employed as a synonym for physiological or morphological adaptation, which is a change in an organism brought on by interaction with its environment but which is not heritable

(ggg)            I envisage that this could be answered two ways. First, you could rightly point out that natural selection refers to reproductive success, which is a product of both survival and fecundity, while survival of the fittest singles out survival to the exclusion of reproductive success. In this way the phrase "survival of the fittest" is, in fact, misleading as a synonym of evolution. The second approach comes from a completely different perspective, with survival representing a positive action (the survival of the fittest) while selection represents a negative, editing action (the lack of survival of the not fit). I look forward to reading clever approaches to answering this question. Note that I wrote with the first of the two presented answers in mind--that is, this question was written to test your appreciation of both the multi-facetted nature of the idea of natural selection as well as the greater importance of the idea of reproductive success relative to mere survival

(hhh)            (iv) Thomas Malthus

(iii)                  (iii) Lamarck

(jjj)                  The idea that species may be fairly naturally arranged (be classified) into a hierarchical order "To Darwin, the natural hierarchy of the Linnaen scheme reflected the branching genealogy of the tree of life, with organisms at the different taxonomic levels related through descent from common ancestors. If we acknowledge that lions and tigers are more closely related than are lions and horses, then we have recognized that evolution has left signs in the form of different degrees of kinship among modern species."

(kkk)            These are homologous structures that are similar in underlying structure presumably as a consequence of shared ancestry (and, yes, I use the word "presumably" to avoid sounding dogmatic rather than because I think that I have a better explanation for occurrence of the observed similarities)

(lll)                  Yes. A vestigial structure is simply a homologous structure that is no longer terribly well utilized and consequently is no longer terribly well maintained by natural selection

(mmm)      The evolutionary relatedness of species/the origin of biological diversity via evolution

(nnn)            (i) (c) Linnaeus, (ii) (a) Darwin, (iii) (b) Lamarch, (iv) (d) Lyell

(ooo)            Heritable

(ppp)            Populations tend to be stable in size

(qqq)            The nearest mainland or neighboring island

(rrr)                A homology is a similarity that exists as a consequence of common descent (i.e., the common ancestor also possessed the feature in question)

(sss)               Vestigial refers to absence of current utility resulting in a reduction in size or complexity of a structure (this is what Dictionary.com says: "Occurring or persisting as a rudimentary or degenerate structure"; this is what Google's define function says: "not fully developed in mature animals; 'rudimentary wings'")

(ttt)                (ii) Embryology

(uuu)            A homology is a characteristic of two organisms which are similar as a consequence of shared ancestry; a synapomorphy is a homology is that is unique to an individual taxon