How to be successful in this course! Things you can do to help you comprehend and understand the content of this course.

• Attend class lectures!!!!  Regular attendance is a must!  
• Ask questions in class and/or by email, chances are you're not alone.
• I am accessible - contact or stop by to speak with me.  If you are have difficulties with the course material, you have a right to contact me during my office hours.  If the posted office hours are not convenient to discuss course matters with me, then arrange an appointment with me that better fits your school/work schedule.   
• Read the reading assignments in the textbook!
• As you read the sections from the textbook, note words that are in bold print.  Look up meanings in book glossary or a dictionary.  
• As you read the sections from the textbook, review chapter overviews and summaries.
• Study as we cover the material.  Waiting until the last minute to review material for exams is conducive to stress and less so to learning.  

BIOLOGY IS A SCIENTIFIC DISCIPLINE THAT STUDIES LIFE

Think of a name of a living organism (e.g., lion, cactus, whale, bear).  Where do they live (savanna, desert, ocean, forest)?  Animals, bacteria, plants and fungi have adapted to a wide variety of habitats, possess different ways of making a living (acquiring the stuff they need to stay alive) and methods of reproducing and dispersing themselves.

• Currently there are over 1,413,000 species of plants, animals, bacteria, protozoa, fungi, etc. that have been described.

• BIOLOGICAL DIVERSITY is divided into 6 Kingdoms (Refer to Figure 1-5, page 10) - these include:  Eubacteria, Archaea, Protista, Fungi, Plantae, Animalia

What characteristics do all these organisms share? All living organisms share certain characteristics or activities that separate them from non-living matter. What are some of these?

• Structure/organization, which arise from the basic properties of matter and energy.
• Metabolism - "energy transfers".
• Homeostasis - Maintain a livable internal environment.
• Reproduction
• Response to stimuli (e.g., temperature, injury, light, gravity, etc.).
• Movement.
• Mutations or changes in form are possible.
• Adaptation to the environment.
• Interdependence with other organisms.
• Blueprint of life is coded by nucleic acid.
• Growth and development.

 Science is an organized system of knowledge^a obtained by a special method^b, the "scientific method", of research and aimed at explaining the causes and behavior of the natural universe^c.

^aThere are different kinds of knowledge^a:  e.g., knowledge of a language, literature, automotive mechanics, cooking, law, philosophy, the meaning of words.

^bSCIENTIFIC METHOD

Science is not about proof or absolute truth.  Science is more about reducing uncertainty then stating things as hard cold fact.

  1.  Problem or question based on observation.
  2.  Hypothesis - "education guess" to answer or explain the question.
  3.  Experimentation (to determine if the hypothesis is valid or not).
            A. Prediction
            B. The test
  4.  Conclusion

^cNatural universe - Science can say how a guitar string creates sound when plucked, but it can say little about the aesthetic value of music.  Science can say nothing outside it's realm of expertise, in regard to ethics, morality, and the supernatural.

EXAMPLE #1: Falling bodies

Observation: Objects fall under the influence of gravity.

1. Question: Objects fall toward the ground when dropped. What happens if two objects of different mass are dropped simultaneously from the same height? Will they fall at the same speed or at different speeds?

2. Hypothesis: The two balls will hit the floor at the same time.

3. Alternate hypotheses:

• The heavier ball will hit the floor before the lighter ball.
• The lighter ball will hit the floor before the heavier ball.

5. Conclusion: The speed of a falling object is independent of mass.

OBSERVATION: Zebras live on the African savanna.  Zebras have stripes.

QUESTION: Why are zebras striped?

First thing you do is look at the literature to see if this question has been asked by others.  Look at their hypotheses and experimental data.  Are you satisfied that their conclusions are reasonable.  If not, proceed to next step.

Potential or Alternative Hypotheses:

1.  Stripes in zebras is a warning display.  Warning Displays in Animals (i.e., skunks, bees, hornets, poisonous arrow frogs, rattlesnakes, monarch butterflies).  These animals go out of their way to make themselves look conspicuous, to ward off potential predators.

2.  Zebras with stripes are more difficult for predators to capture.  The silhouette of their bodies are broken up when a group of animals are arranged in a herd.  Harder to distinguish one animal from another and therefore pick out a potential prey item to take down in the confusion created for the predator.

3.  Zebras have stripes for no particular reason.  No adaptive value.

4.  Stripes on a zebra are a sexual display for attracting mates.

5.  Stripes assist the zebra in thermoregulation when exposed to the heat of living life on the savanna.

6.  Others hypotheses?

EXPERIMENTATION:  Prediction/test.

If it is a warning display, then you would predict that other animals will avoid zebras.  So you go to Africa to a savanna and you watch how predators react to zebras.  If its a warning display, maybe they stay clear of zebras.  Unfortunately you find that lions love to eat any zebra they come across.  They aren't avoiding them at all!

Another strategy would be to determine if their is something about zebras that another animal would want to avoid.  If it is a warning display, what is it warning against?  You would predict that zebras must possess some characteristic that makes it worth avoiding them.  At the zoo, you notice that the zebras don't spray foul smelling chemicals like skunks, they don't sting (although zebras probably do kick and bite when cornered).  So you think, maybe they taste bad or are poisonous to animals that eat them.  So you test this by seeing how some animal reacts after eating some zebra meat vs. a control (horse meat).

What do you do after exhaustive study, if you find no evidence that stripes on a zebra serve as a warning display?  You abandon the hypothesis that stripes on a zebra serve as a warning display.  Note that experiments did not demonstrate that alternative hypotheses are not true.  Why?  Because the experiments were not designed to do this.

Further experimentation might show that one or more of the alternate hypotheses is not consistent with experimental observation.  You don't prove that one hypothesis is correct, rather you become more certain that with repeated testing your power of prediction will increase.

Prevailing hypotheses as to why zebras are striped include:

• A strategy for avoiding predators.  Up close predators see them just fine.  However at a distance, the striped pattern breaks up their appearance against the background, especially if these are running in different directions, making them harder to follow and chase down!
• A way to avoid being bitten by the tsetse fly (a fly that carries sleeping sickness - caused by a protozoan).   The striped pattern plays havoc on this insect's ability to home in on its next victim.
• A strategy of removing excess heat (common on the open savannas of Africa) by reflecting a portion of it away from the body, especially from the white stripes.
• A means for recognizing different individuals within a herd, as no two zebras have striped patterns exactly like another.

HYPOTHESIS:  a proposed explanation of certain "facts" that must be empirically  testable in some conceivable fashion.

THEORY:  an integrated, comprehensive explanation of many "facts" and an explanation capable of generation additional hypotheses and testable predictions about the way the natural world looks and works.  A generally accepted scientific theory is a well-tested hypothesis supported by a great deal of evidence.  The scientific definition of theory is different then what is used by the lay person -  like a guess.  "Oh well, it's only a theory".  In fact a theory is well tested, and if consistent with the data, possesses a high degree of certainty (although not equivalent to proof). 

ATOMS ===> MOLECULES ===> ORGANIC MACROMOLECULES===>CELLULAR COMPONENTS ===> CELLS ===> TISSUES ===> ORGANS ===> ORGAN SYSTEM ===> ORGANISM ===> POPULATION (SAME SPECIES) ===> COMMUNITY (DIFFERENT SPECIES) ===> ECOSYSTEM (COMMUNITIES AND THEIR ENVIRONMENT) ===> BIOSPHERE (ALL LIFE ON EARTH)

Does life evolve (change over time)?  Do species give rise over time to new species?
What is a species?

• Concept of species is pre-dates the birth of the Greek philosopher, Aristotle.
• Basic unit of classifying different organisms, whether you use scientific or common names.  The Latin word specere, from which our word "species" is derived, means "to look at."  The word originally referred to the outward appearance of an organism.
• Examples of different species that the average person recognizes include cardinals, bluebirds, snow geese, cats, dogs, petunias, roses, and so on.
• Greek species concept.  Aristotle (384-322 B.C.) and Theophrastus (late fourth and early third centuries B.C.) conceived of species as unstable and highly changeable.  Aristotle believed in spontaneous generation of species, and regarded all kinds of crosses between species as feasible, likely, and a means for the creative construction of new species.
  • Rampant hybridization could produce a new species. A camel could hybridize with a panther to produce a giraffe. An Arabian camel crossed with a wild boar produced the two-humped Bactrian camel.  Oppian argued that a camel crossed with a sparrow produced an ostrich.
• Greek view persisted through the Middle Ages, and only in the 18th century did it begin change. In the 1750's, the naturalist Buffon contributed to the idea that species were discrete entities. Theologians and naturalists of the time argued for the fixity of species, the view that each species remained as created by God, according to the accounts given in the Book of Genesis in the Judeo-Christian Bible.
• By the middle of the 18th century, the discreteness and stability of species were generally recognized, setting the scene for Linnaeus and other taxonomists to collect representative members of each species, preserve these in collections as the representative or type specimen of that species, provide it with a Latin binomial (two word, i.e., genus and specific epithet) species name, and describe its physical appearance in Latin. Thus, developed the typological species concept in which all members of a species were of one basic type.  This type did not vary significantly from place to place or through time.
• Another prevailing idea of the time - Great Chain of Being - species were fixed into place by God (each species being created separately).  Taxonomists during the 18th through the first part of the 19th century worked to pigeon-hole all species, because it was thought that this would give them insight into the Mind of the Creator.

• CLASSIFICATION OF LIFE'S BIODIVERSITY

  Over 1.5 million species of organisms have been described by biologists.  Classification of life's diversity contributes to our understanding of biology.  Initially, naturalist's, especially during the 18th and first part of the 19th century, were interested in classifying life's diversity in an effort to gain a broad view of the "Divine Master Plan" (i.e., The Great Chain of Being).  Carl von Linne (AKA, Carolus Linnaeus - 1707-1778) developed criteria and methods for describing and assigning species names to newly discovered group of organisms.  His system of naming was called Binomial Nomenclature, two word naming system, in which each species was assigned a two word name, the genus and specific epithet.  (NOTE: IN REVIEW READING MATERIAL IN THE TEXTBOOK, THE BOOK IS IN ERROR BY SAYING THAT THIS TWO WORD NAME IS COMPRISED OF A GENUS AND SPECIES NAME; THE SPECIES NAME IS ACTUALLY MADE UP OF THE GENUS AND THE SPECIFIC EPITHET - refer to Figure 19-4 on page 401 in the textbook.

  Examples of species include:

  • Escherichia coli  or Escherichia coli or a bacterium found in the gut of mammals
  • Quercus alba or Quercus alba L. or white oak, originally named by Linnaeus, hence the L.; the term alba means "white".
  • Homo sapiens or Homo sapiens or human being; Homo = man, sapiens = wise.  Wise man.
  • Smittium boomerangum or Smittium boomerangum Williams & Lichtwardt 1990, an insect gut fungus with boomerang-shaped spores and first observed and described in Australia.
  • Morchella esculenta or Morchella esculenta or the yellow morel mushroom; the term esculenta means "edible".
  • Zea mays or Zea mays or maize or corn.
   

  Note that in the previous example that the first letter of the genus name is upper case; all other letters are lower case.  The species name is italicized or underlined.  The author(s) name or initials may or may not appear after the species name.  The author(s) are the folks who originally published a written description (in their native language and in latin).  The specific epithet is often descriptive of some aspect of the species.

  Linnaeus and taxonomist describe a species based on one or a few species, which are then store in a museum or herbarium collection.  The specimen used as the basis for a species description is called the type specimen.  A type specimen becomes the archetype for the entire species.
  

  ---

  Species are classified into ever broader encompassing categories.  The broadest category is the domain.  There are three domains:  Archaea, Bacteria, and Eukarya - refer to Figure 1-5 on page 10 in the textbook.  Members of the domains Archaea and Bacteria are prokaryotes  while members of the domain Eukarya are eukaryotes.  The next largest category is the Kingdom level.  Only one kingdom is found in domain Archaea, that is, Archaebacteria.  One kingdom represents the domain Bacteria, that is, Eubacteria (the "true" bacteria - bacteria and cyanobacteria).  In prior classification schemes members of the domains Archaea and Bacteria use to be classified together into a single kingdom called Monera.  The Domain Eukarya contains all types of eukaryotic organisms from single-celled to multicellular forms.  Four kingdoms are found in the domain Eukarya (Kingdoms Protista, Plantae, Fungi, and Animalia).
  

  ---

  Of the various taxonomic categories, it is generally recognized that all levels of organizations are artificial, and the only level that is biologically-significant is the species level. 

  ---

  Classification of Life's Diversity is organized in a Hierarchical Fashion.
  • Kingdom
  • Phylum (botanists use the term Division instead of Phylum)
  • Class
  • Order
  • Family
  • Genus
  • Specific Epithet
  A mnemonic device to help remember the order of the various taxonomic categories from the broadest to the most specific would be to memorize the following statement and let the letter of each word stand for the first letter of each category.  Ken's pants caught on fire, Great Scott!

  This hiearchial system of classification to pigeonhole species is analogous to assigning a location where you might find an individual on the planet Earth.

  • Domain                             Earth
  • Kingdom                           North America
  • Phylum or Division             USA
  • Class                                 Arkansas
  • Order                                Craighead County
  • Family                                Jonesboro
  • Genus                                 Fictitious Street
  • Specific Epithet                   1313

  One final note about modern day classification schemes is an attempt to organize biological diversity according to evolutionary relationships that exist between species.  This is based on the premise that all life on this planet originated from one or a few common ancestors which diverged over long periods of time to produce all the forms of life we currently see on earth.  Taxonomy has given way to Systematics which attempts to reconstruct genealogical relationships among all life forms.  

  ---

• During the 18th and 19th century, species were thought to be immutable, unchanging, and fixed.   Species don't mix, and when they do hybridize, the progeny are usually sterile - HYBRID STERILITY (fertile donkey and fertile horse = sterile mule; fertile horse and fertile zebra produce a sterile zebroid - refer to Figure 16-2 on page 326 in the textbook.).
  • Check out the link to zebroids (i.e., sterile hybrids of a horse and zebra.
    • Herd of zebroids
    • More zonkeys, zoneys, and zebroids
  • Check out the link to ligers and tigons (i.e., sterile hybrids of a lion and tiger).
    • liger #1
    • liger #2
    • liger#3
  • Check out the link to other REAL HYBRID ANIMALS at http://www.greenapple.com/~jorp/amzanim/crossesa.htm.
• Mind set of people prior and early into the 19th century - species do not evolve, they are static or constant.  A dog is always a dog, a cat is always a cat ...........

Biogeography - study of the world distribution of plants, animals, and other organisms.

• Biodiversity is high! According to E. O. Wilson, there are currently over 1,413,000 species of plants, animals, bacteria, protozoa, fungi, etc. that have been described - refer to Figure 17-2 on page 350 in the textbook.

• 751,000 species of insects
• 281,000 species of all other animals
• 248,400 species of higher plants (ferns, flowering plants, gymnosperms)
• 69,000 species of fungi
• 26,900 species of algae
• 30,800 species of protozoa
• 4,800 bacteria and related forms
• 1,000 types of viruses (alive?)

• Distribution of species varied from place to place.  Many places contained unique or endemic species!  Example:  The mammals in Australia:

• Placental mammals - fetus attached to uterus by placenta.
• Marsupial mammals - short gestation period, young raised in pouches - refer to Figures 15-2A and 17-16 on pages 302 and 360 in the textbook.
• Why are some species only found in certain parts of the world?
• Why are different kinds of organism similar in some respects, but obviously different?
• Examples:  Tasmanian wolf (tiger) vs. gray wolf; sharks (a cartilaginous fish) and dolphins (a mammal), American cactus vs. African Euphorbs (spurge).

Comparative Anatomy

• Homologous structures - same structures are modified for different functions.

• Example:  Bones in vertebrate forelimbs (humerus, radius, ulna, carpals, metacarpal, phalanges) are found in limbs of seals (flippers), wing (bat and bird), human arm, animal leg (carnivore paw) - refer to Figure 15-9 on page 315 in the textbook.
• Why are there the same number of vertebrate in the neck of a human and a giraffe?  Is it just a coincidence?

• Vestigial structures - structures that are present but serve no discernible purpose.

• Examples:  pelvic bones in boa constrictors, wings and feathers in flightless birds (e.g., ostriches, emus); blind eyes in cave-dwelling fish species - refer to Figure 15-13 on page 318 in the textbook.

• Embryology- presence of a structures that suggest a relatedness to other life forms.

• Example:  human embryos have pharyngeal arches, a two-chambered heart, and a tail which disappears before birth!  Pharyngeal arches in fish develop into the gills and the jaw.  In humans, pharyngeal arches do not develop into gills, but into the lower jaw, hyoid bone, and larynx - refer to Figures 15-14 and 15-15 on pages 318-319 in the textbook..
• Karl Ernst Von Baer in 1828 noted that the earlier stages of embryos of more advanced species resembled the earlier stages of development in more primative species.
• Ernst Heinrich Haeckel in 1867 formulated the "biogenetic law", that is, ontogeny recapitualtes phylogeny, or in other words, embryological development retraces ancestory.
• Although in a strict sense, an embryo does not retrace it's ancestory as it develops, the physical evidence does suggest that developmental pathways appear to be constrained along certain avenues of development.  This probably goes hand-in-hand with the conservative nature of the genes which govern this process and the need to insure that embryological development concludes itself in the production of a viable offspring.

• Nicolaus Steno - Anatomist and geologist published a work in 1669 dealing with the the question of "Why is a solid in a solid?"  He was puzzled by the existence of 'tongue stones' which were found embedded in rock, but which bore a strong resemblance to sharks teeth.  He proposed that some forms of rock (sedimentary rock) were not always hard but were formed by from a slurry of mud, rock, sand, and other materials which had encased teeth from sharks before some geological process had transformed the entire lot into stone. He was one of the first people to recognized that fossils were the castings and/or physical remains of life forms that had existed in the past.
• Fossils are often found layered in sedimentary rock.  Complex fossils are found in newer strata, while simpler forms are found in older layers.   Conditions are not always conducive to fossil formation.  Usually only harder components of an organism are fossilized.  Erosion destroys many fossils and sedimentary layers through the action of wind and rain.  Consequently, the fossil record is not complete but derived from data collected from different parts of the world.  Dating sedimentary layers suggests that these are ancient - refer to Figures 15-6 and 15-7 on page 308-311 in the textbook..
• The fossil record gives evidence of organisms that no longer exist but which appear to be part of sequence of species that lead up to modern day forms (e.g., horseshoe crab - refer to Figure 15-4 on page 305, the horse - refer to Figure 16-15 on 317  in the textbook.).
• Darwin found fossils in the Andes mountains suggesting that the land had once be the bed of an ocean.  Geologic forces raised the sea floor up to produce land and mountains.
• Species have gone extinct.  Some people suggested that fossilized creatures had not gone extinct, but that they would be discovered once the Americas was complete.  Generally, this is not so, (dinosaurs and trilobites are dead - refer to Figure 15-2B page 302 in the textbook.). although many extant organisms are found in the fossil record.  On the other hand, ginkgo trees and coelacanths (refer to Figure 16-15 on page 342 in the textbook) are referred to as living fossils, precisely because these were described from fossilized remains before being rediscovered as extant species.
• Dinosaurs with teeth, claws, and feathers?  Is this extinct animal, known as Archaeopteryx, a transitional form between dinosaurs and modern day birds?  Check out the following two figures:

•                      

• Domesticated Plants and Animals have been selected and bred by humans for various characteristics.  Breeds includes, dogs (refer to Figures 15-8  and 15-17 on pages 314 and 321 in the textbook), cats, horses, pigeons, fruits, vegetable, etc..
• Forage kale or wild cabbage (Brassica oleracea) is the ancestor of kohlrabi (expanded just above the roots), cauliflower (abortive flowers, that are kept white by tying the leaves at the base around the inflorescence so chlorophyll won't form), broccoli (fertile flower buds), cabbage (terminal bud), brussels sprouts (axillary buds), and kale (leaves).  All these varieties belong to the same biological scal differences.  You can cross broccoli with cabbage and get fertile offspring (refer to Figure 1-8 on page 12).

•  Comte Georges-Louis de Buffon (French, 1707-1788) was the first modern biologist to discard the concept of special creation.  He believed that animals were plastic, that small variations produced by the environment were accumulated to make larger differences.  Each animal in ascending series of types was transformed from some simpler ancestor.
  • For some fun history, see Jefferson, Buffon, and the Mighty Moose at http://www.monticello.org/press/newsletter/2002/mse.pdf and A Day in the Life of Thomas Jefferson at http://www.monticello.org/jefferson/dayinlife/entrance/fun.html.
• Erasmus Darwin (English 1731-1802), grandfather of Charles Darwin, added the further idea that functional responses to external stimuli were inherited.

  Organic life beneath the shoreless waves
  Was born and nurs'd in ocean's pearly caves;
  First forms minute, unseen by spheric glass,
  Move on the mud, or pierce the watery mass;
  These, as successive generations bloom,
  New powers acquire and larger limbs assume;
  Whence countless groups of vegetation spring,
  And breathing realms of fin and feet and wing.

  - The Temple of Nature 1802 by Erasmus Darwin

• Prevailing idea of the time - Great Chain of Being - species were fixed into place by God (each species created separately.  Taxonomists worked to pigeon-hole all species, because this would give them insight into the Divine Master plan.
• Jean-Baptiste Lamarck (French, 1744-1829)
  • anatomist/student of classification
  • life created a long time ago in a simple state and changed through time.
  • species had a tendency toward perfection, which allowed for small alterations in morphology, physiology, and behavior to accommodate changes in the environment.
  • Species don't go extinct, they are transmutated into new species.
  • belief in a natural tendency for perfection and Theory of Evolution by Inheritance of Acquired Characteristics (outlined in 1801 and set forth in his Philosophie Zoologique).
  • evolution brought about through internal desires towards perfection.
  • frequent continuous use develops/enlarges an organ, while permanent disuse weakens it until it finally disappears; all acquisitions or losses wrought through influence of the environment and hence through use or disuse.  Giraffe's - short necked animal to long-necked animal; weight lifter analogy.
• Lamarck's major contribution to understanding the mechanism of evolutionary process was:
  • Species change over time, and the environment is a factor in that change.
  • His error wasn't as much the genetics (Darwin made the same mistake) but that he assumed evolution had a goal!!!
  • Trofim Lysenko (1898-1976) - Soviet biologist maintained the possibility of inheriting environmentally acquired traits.  Influential in directing breeding programs for plants in Soviet Union through the first two thirds of the 20th century.  Pseudo-Lamarckism - Lysenkoism (visit http://en.wikipedia.org/wiki/Trofim_Lysenko for more information).
  • Is transmission of human culture from one generation to the next, Lamarckian?
• Charles Darwin (1859) - "On the origin of species by means of natural selection, or the preservation of favored races in the struggle for life" and Alfred Wallace (1858).
  • The Theory of evolution through Natural Selection and Modification with descent.
  • Charles Darwin (1809-1882) - English naturalist
  • From 1831-1835 - naturalist on the H. M. S. Beagle, explored South America, the Galápagos Islands; refer to Figure 17-1 on page 349 in the textbook
  • The facts of animal distribution^A and the relations between living/fossil animals^B learned in his travels led him to consider the origins of species.  The "species problem".
    • ^ASimilar kinds of organisms confined to different geographic regions often showed pronounced differences in some of their traits.
    • ^BNow extinct glyptodonts resembled extant or living armadillos.  If these animals were created at the same time, why were glyptodonts extinct, while armadillos still alive.  Could armadillos have arisen from glyptodonts? 
  • Galápagos Islands were 950 kilometers off the coast of Ecuador.  Every island or island cluster was home to divers species, including birds called finches.
  • Darwin reasoned that all 14 species originated from one common ancestor.  The Galápagos Islands (cluster of 25 separate islands) arose about 5 million years ago.  Species that live there must have colonized these islands from the mainland.
  • Land vertebrates, at least seven species of reptiles (one or more snakes, a huge tortoise, and at least 5 lizards, including two very large iguanas), seven species of mammals (5 rats and two bats), and a limited number of birds (including two species of owls, one hawk, one dove, one cuckoo, one warbler, two flycachters, one marten, mockingbirds, and the famous Darwin's finches.
    • 14 species of Darwin's finches - constitute a separate subfamily found nowhere else in the world.  13 species are thought to have evolved on the Galápagos Islands, and one on Cocos Island (NE of the Galápagos Islands; refer to Figures 17-10, 17-11 17-12 and 17-13 on pages 356-358 in the textbook
    • Click on the following picture to find the original source at http://lhs.lps.org/staff/sputnam/Biology/U6Evolution/finches.png. 
    • 
  • In 1838, Darwin read the essay by Thomas Malthus (refer to text on pages 306-307 in the textbook), "Essay on Population".  Populations increase at geometric ratio^a until checked by limiting factors (e.g., food, shelter, fuel).  He came to the recognition of the struggle for existence within all population and concluded favorable variations would be preserved while unfavorable variations would not.  In 1844, Darwin wrote a summary of theory but continued to gather data.
    • ^aReproductive potential of most species higher than actually possible.  For example:
      • Paramecium (0.25 mm long) can divided about 600 times per year.  If all survived and continued to divide, their bulk would exceed that of the earth after several months.
      • Darwin assumed that elephants breed at 30 years to 100 years, each female producing but 6 young, in 750 years about 19,000,000 would be alive.
      • Puffballs - Giant puffball (7 trillion spores), spores become fruit bodies they would griddle the earth more than 5 times; or fruit bodies would stretch twice to the sun and back, and form a mass eight hundred times the weight of the globe.
  • Alfred Russel Wallace (1823-1913) studying the rich fauna and flora of the Malay Archipelago, independently and rapidly arrived at similar conclusions.  In 1858, he shared his insights to Darwin (refer to Figure 15-5 on page 307 in the textbook).  Wallace's essay and a brief of Darwin's conclusions were published together in the same year.
  • Darwin's and Wallace's theory of descent with modification through variation and natural selection:  Basic Assumptions or tenets of how Darwin and Wallace conceived evolution to occur were as follows:  (Items highlighted in red and italics in the following text came to light during the second half of the 19th century and during the first part of the 20th century).
  1. Many more individuals are born in each generation than will survive and reproduce.
  2. There is variation among individuals; they are not identical in all their characteristics; refer to Figures 2-6 on page 27 and Figure 2-8 on page 29 in the textbook.
     • SOURCE OF VARIATION IS MUTATION: A RANDOM PROCESS.
     • Mutation - any novel genetic change in the gene complement or genotype relative to the parental genotypes, beyond that achieved by genetic recombination during meiosis.
  3. Individuals with certain characteristics have a better chance of surviving and reproducing than individuals with other characteristics.
     • NATURAL SELECTION: A NONRANDOM PROCESS IMPOSED BY THE ENVIRONMENT.
  4. Some of the characteristics resulting in differential survival and reproduction rates are heritable.
     • Darwin assumed this, without knowing whether it was true or not.
     • Darwin was a proponent of pangenesis, which was a good guess but incorrect.
  5. Vast spans of time have been available for change.
     • Darwin was influenced by Lyell's Principles of Geology and Uniformitarionism - enormous time spans involved in geological changes - natural forces persisted over time - current processes of geological activity were sufficient to explain past geological phenomena.
     • Lyell and Darwin were opposed to the concept of catastrophism ==> i.e., different strata of fossil represented devastating extinctions followed by "new creation" and progressionism with each new creation event leading to newer advanced forms - refer to Figure 15-3 page 304 in the textbook.

     For an overall summary of the Theory of Evolution proposed by Darwin and Wallace - click here for an MS Word - DOC.

Conditions on earth, before life began - Refer to Figures 18-6 and 18-7 on pages 380 and 382 in the textbook

Entire universe is thought to have arisen about 15 billion years ago;  the solar system started taking shape about 5 billion years ago; the earth starts to coalesce and cool about 4.5 billion years ago; first protobiont appears about 3.5 billion years ago.  As the earth coalesced, outgassed, and cooled, the early atmosphere, oceans, and crust formed.  Hydrogen and helium being lighter gases escaped the gravitational pull of the planet as energy from the sun swept these gases out into space.  Denser molecules and matter remained behind, held by the gravitational pull of the earth itself.  The early earth was rich in water, silica, metals, heavier molecules, and other rocky components.  Early oceans became salty as carbonates, Mg⁺², K⁺, and other ions accumulated as acids (e.g., H₂CO₃, HNO₃, H₂SO₄) interacted with water and inorganic matter.   Atmosphere arose as the earth formed and as outgassing occurred from within the earth, CO (carbon monoxide), CO₂, H₂S (hydrogen sulfide), CH₄ (methane), and NH₃ (ammonia).  The characteristics of the early atmosphere is based, in part, on what planetary astronomers have discovered from other planets in the solar system.

Primeval Life

In the 1930s, Alexander I. Oparin from Russia and J. B. S. Haldane from England, proposed that life arose under certain conditions that allowed for abiotic formation of organic compounds.  Oparin and Haldane assumed that three conditions had to exist:

• Anoxic atmosphere  (presence of free oxygen would tend to interfere with chemical reactions that transform simple organic molecules into complex ones)
• Precursor molecule supply had to be in abundance
• A source of  Energy to start and keep the process going

Early life forms were probably unicellular and resemble modern day prokaryotes.  After life got started, it probably existed in an anaerobic environment.  As more complex biochemical pathways evolved, such as photosynthesis, waste products produced of such processes (i.e., oxygen) were toxic to existing organisms.

• Geological Evidence
  • uranite - UO₂ precipitates in stream beds.  Early atmosphere was probably < 1% O₂.  Geologic record indicates uranite started to accumulate about 2 billion years ago.
  • iron oxide or rust suddenly starts to accumulate in rock that are 2-3 billion years old
• Biochemical Evidence
  • Early attempts of cellular respiration, early stages of this process do not require oxygen (glycolysis, fermentation), but later stages require oxygen (oxidative respiration).

Lynn Margulis (1967) has been a strong advocate for the Endosymbiont hypothesis  This hypothesis proposes that mitochondria and chloroplasts became incorporated into cytoplasm of eukaryotes through the symbiosis of larger cells with with bacteria (mitochondria and flagella) and cyanobacteria (chloroplasts) - refer to Figure 18-16 on page 392 in the textbook.

• prokaryotes, mitochondria, and chloroplasts possess similar genomes; each type contain a naked circular loop of DNA
• ribosomes produced by prokaryotes, mitochondria, and chloroplasts are similar in size and structure and smaller than those found in the cytoplasm of eukaryotic cells
• inner membranes of mitochondria and chloroplasts are similar to the plasma membranes of bacteria.
• mitochondria, chloroplasts, and prokaryotes reproduce asexually through binary fission.
• antibiotics that inhibit protein synthesis in bacteria also do the same to mitochondria and chloroplasts but not to inhibit protein synthesis mediated by the nucleus

About 2.5 billion years ago, a billion years after the origin of the protobiont, eukaryotes evolved and proliferate.  We would recognize many of these forms as being similar to modern day amoebae, protozoa, and unicellular green algae.  Multicellular forms do not appear in the fossil record until about 0.6 bya during a period of vast change on the face of life.

• evidence of this preserved as fossils in the Burgess Shale
• Animal Phyla in the Burgess Shale include:  Porifera, Brachiopoda, Arthropoda, Echinodermata, Hemichordata, and Chordata (each phylum represents a different body plan).

Major evolutionary trends:

• a transition from being unicellular, filamentous, or forming small colonies of cells toward becoming multicellular
• greater complexity
• development of organs and organ systems
• changes in reproductive strategies
• development of adaptations to exist in and exploit a terrestrial environment
• greater interdependence/more interactions among different species

IF THE HISTORY OF LIFE WERE PLACED ON A 24 HOUR SCALE (Keep in mind that these times are approximate)

• Midnight - first protobiont or life forms come into existence (approx. 3.5 billion years ago) or midnight.  Prokaryotes rule!  Evolution of photosynthesis eventually leads to accumulation of  toxic levels of oxygen -  leads to mass extinction.
• 10:17 a.m. - first eukaryotes (e.g., unicellular organisms - protozoan-like).
• 8:18 p.m. - trilobites and other aquatic multicellular organisms appear in earth's oceans (Cambrian explosion).
• 8:34 p.m. - first vertebrates (e.g., marine and fresh-water fish).
• 9:15 p.m. - land plants first appear.
• 9:36 p.m. - winged insects take to the land and air.
• 10:34 p.m.- mass extinction.
• 11:18 p.m. - dinosaurs rule.
• 11:19 p.m. mass extinction (approximately 75 % of all life goes extinct).
• 11:33 p.m. (approximately 65 mya) - adaptive radiation of birds and mammals.
• 11:59 p.m. - Humans arrive on the scene (200,000 years ago).
• 11:59:56 p.m.- Birth of human civilization.

Mammals- share characteristics with other mammals such as:  vertebrate with a spinal chord, skeleton, skull housing a large brain, ability to give birth to live offspring, mammary glands, hair or fur, and common ancestry.

Humans differ from other mammals:

• Teeth
  • canines - for tearing and piercing (most carnivores)
  • incisors - nip and cut food (rodents)
  • premolars with cusps - grinding and crushing (horses)
  • molars with cusps - grinding and crushing (cattle)
  • Early and more primitive mammals have 66 teeth; modern mammals have 44; humans have 32.
  • The incidence of Wisdom teeth appear to be diminishing (natural selection?) in human populations (in Central Europe, one or more wisdom teeth are missing in 19% of population.  Wisdom teeth or third molars are common among Native Americans, but not among Africans).
• Offspring have an extended period of learning.
• Humans have an overall larger brain size.
• Humans possess behavioral flexibility

TRENDS IN PRIMATE EVOLUTION

• Change in overall skeletal structure and mode of locomotion - bipedalism (able to move on 2 appendages for extended periods of time; with minimum energy loss) -refer to Figure 17-21 and 1725 on page 368 and 371 in the textbook .
• Modification of hands - humans can cup hands and possess a opposable thumb - refer to Figure 17-23 on page 370 in the textbook
• Less reliance on sense of smell and more reliance on sense of daytime and color vision, and depth perception.
• Change in dentition - primates moved from eating insects to more fruits and vegetables to becoming omnivorous - adaptation of teeth is probably caused by natural selection, so that the kinds of teeth best able to accommodate a particular diet become enhanced over time - refer to Figure 17-23 on page 369 in the textbook.
• Brain expansion - more elaborate.
  • Gorilla 600 cm³
  • Humans 1350 cm³
• Higher intelligence may have resulted from tool making, need for better memory, or to increase ability to anticipate jumps (from branch to branch) or throws (weapons and spears).  Once you let go of something, you don't have any way to control its motion.
• Behavioral and cultural evolution- ability to learn and mimic behavior.  ex. language.

The movement to different types of environments may have influenced cultural evolution.  The culture tends to be Lamarckian because changes can be acquired and passed on.  Examples are language, tool making, technology, and domestication of plants and animals.  The transition from humans making a living as hunter/gathers to an agriculturally-based civilization started about 12-14,000 years ago, based on archeological evidence.

ANCESTORS OF MODERN HOMO SAPIENS

Mitochondrial "Eve": determined through lineage coalescence; all human descending from a very small population (probably African) @ 200,000 years ago.  These dates are inferred based on the fact that mitochondrial DNA is maternally inherited and on assumption that mutations in this DNA happen at consistent rate.  Thus far the fossil evidence tends to support these findings.

The family tree for primates:

• Prosimians - lemuroids; lemurs, lorises, etc.
• Tarsioids - tarsioids; tarsiers
• Anthropoids - ceboids; new world monkeys
• Cercopithecoids - old world monkeys; prehensile tails
• Hylobatids - gibbons, siamang
• Pongids - orangutan, gorilla, chimps
• Hominids - humans and their most recent ancestors

Morphologically humans and apes are distinct from one another.  Based on molecular data, isozyme polymorphisms and sequences of mitochondrial and genomic DNA, humans and apes, in particular, chimpanzees are quite similar.  Humans and chimpanzees share 52 % of the same alleles.  Nucleic acid differences are even less, 1.1 percent difference.  If humans were more objective, when it came to taxonomic classification, humans and chimpanzees and perhaps even other apes, might be classified in the same genus.  Should humans be classified as Pan sapiens instead of Homo sapiens, or chimpanzees as Homo troglodytes instead of Pan troglodytes?  Was the common ancestor to humans and chimpanzees separated by the Great Rift Valley in Africa, leading to allopatric speciation?  Humans probably evolved in response to changing environmental conditions as forests gave way to savannas.  Some evidence supports this hypothesis, but it is far from conclusive.

PHYLOGENETIC TREES FOR PRIMATES AND HOMINIDS

• Several phylogenetic trees for the primates and hominids have been proposed.
• Refer to Figures 15-1, 17-22 and 7-26 on pages 300, 369 and 373 in the textbook.
• Becoming Human
• Primates and Humans:  Lineages that Share a Common Ancestory

This page is maintained and constructed by Dr. Martin Huss.  Last updated 1-25-2006.