A.  Terminology
           1.  Abiogenesis - the production of living things from nonliving things

           2.  Spontaneous Generation - another term meaning the ability to produce life from non-life; synonym to abiogenesis

           3.  Biogenesis - the production of living things only from other living things

    B.  Experiments 
          1.  Francisco Redi - 1600s - Conducted an experiment using meat and flies to show that maggots developed from tiny eggs laid by the flies, not by spontaneous generation

       

          2.  John Needham - 1700s - Conducted an experiment with heated gravy and concluded that the microscopic organisms that appeared were the result of spontaneous generation

          3.  Lazzaro Spallanzani - 1700s - Conducted an experiment with Needham's Gravy to show that the microscopic organisms entered from the air, not by means of spontaneous generation

         

          4.  Louis Pasteur - 1864 - Conducted an experiment with nutrient broth in curved-neck flasks to finally disprove spontaneous generation

           

    C.  Geological Eras of Earth
          1.  Azoic - No life during this 1-2 billion year period because the earth was cooling

          2.  Archaezoic - Earliest life forms appear

          3.  Proterozoic - Living organisms can only survive in the water; Algae and Bacteria present

          4.  Paleozoic - Fish, Amphibians, and Reptiles appear; Many fossils from this era

          5.  Mesozoic - Age of the Reptiles; Dinosaurs prevalent

          6.  Cenozoic - Current era; Age of the Mammals

    D.  Heterotroph Hypothesis
           1.  Alexandar Oparin - 1936 - Stated that the earliest living organisms on earth were simple heterotrophs (organisms that cannot make their own food)

           2.  Explanation
                a.  Heterotrophs ate the organic molecules in their environment until the food sources were very scarce
                b.  Organisms needed another source of energy
                c.  Autotrophs evolved (organisms that can make their own food source)
                d.  Oxygen became prevalent in environment
                e.  Cellular Respiration possible
                f.  Eukaryotes evolved

     E.  Evolution
           1.  Theory - an accepted hypothesis that has been tested over and over again without yet being disproven

           2.  Definition - Evolution is the change in the overall genetic makeup of a population over time

           3.  Three Basic Components
                a.  Individuals cannot evolve.  Populations evolve.
                b.  Natural selection is the mechanism of evolution.
                c.  Evolution occurs by chance.

     F.  Evolution Theorists
           1.  Jean Baptiste de Lamarck - French biologist who developed the following theory in 1809
                a.  Theory of Acquired Characteristics - individual organisms acquire (pick up) traits throughout their lives which make them better adapted to their environment; these traits can be passed on to their offspring
                b.  Giraffe Example - Giraffes kept stretching their necks to reach food from higher branches of the trees.  According to 
Lamarck, these longer necks were acquired and passed onto the offspring.

           2.  Charles Darwin - 1858 - Proposed the Theory of Evolution by Natural Selection
                 a.  H.M.S. Beagle - Darwin was a naturalist aboard this ship for several years
                 b.  Galapagos Islands - Islands off the coast of South America  where Darwin collected most of his research necessary to formulate his theory of evolution

           3.  Alfred Russell Wallace - 1858 - Working individually from Darwin, Wallace also formulated his theory of evolution 

           4.  Charles Lyell - Stated that competition between different species leads to a "struggle for existence"

           5.  Thomas Malthus - Stated that organisms over-reproduce; therefore, there is competition between members of the same species

     G.  Evidence for Evolution
           1.  Artificial Selection - Farmers had been conducting this controlled breeding of livestock and crops for years in order to obtain the most milk from cows or the best cobs from corn plants.

           2.  Paleontology - Study of Fossils
                a.  Fossil - any preserved evidence of past life
                b.  Radioactive Dating - method by which fossil age can be determined by the amount of organic matter remaining in the specimen.  This is possible because some substances break down at a known rate (half-life).
                c.  Archaeopteryx - one of the most famous fossils, showing one of the earliest birds known to exist

           

           3.  Comparative Anatomy - Study of the structures from organisms of many different species.
                 a.  Homologous Structures - Structures with the same origin appearing in organisms of different species
                       - Example = Limbs of humans, cats, horses and bats

                 b.  Divergent Evolution - Method of evolution accounting for the presence of homologous structures.  Multiple species of organisms descended from the same common ancestor at some point in the past. (One to Many)

                 c.  Analogous Structures - Structures with similar functions, but their structures are not similar and appear unrelated.
                       - Example = Limbs (fins) of a Dolphin and Shark

                 d.  Convergent Evolution - Method of evolution accounting for the presence of analogous structures.  Organisms of different species often live in similar environments, thus explaining the presence of features with similar functions.  (Many to One)

           

                 e.  Vestigial Structures - Structures that are useless presently to the organism, but they are homologous with structures that serve important functions in other organisms
                       - Example = Human appendix is homologous to chambers for digesting leaves and grasses in other mammals

                  

          4.  Comparative Biochemistry - Study of the similarities and differences found in DNA, RNA and proteins from organisms of different species
               - Example = Humans and Chimpanzees have proteins that are 99% alike.

          5.  Comparative Embryology - Study of the similarities and differences found in embryos from organisms of different species
                - Example = Similarities amount chicken, pig, fish and human embryos



          6.  Biogeography - Study of the distribution of organisms across the world.

                  a.  Adaptive Radiation - Evolutionary process in which the original species gives rise to many new species, each of which is adapted to a new habitat and a new way of life.
                        - Example = Darwin's Finches 

                   

                  b.  Endemic Species - Species found only in one location in the world.  Darwin found many of these species during his travels to the Galapagos Islands.

     H.  Natural Selection
           1.  Four Components
                a.  Individuals of a species vary.
                b.  Some variations are genetically determined.
                c.  More individuals are produced than live to grow up and reproduce.
                d.  Individuals with certain genetic variations are more likely to survive and reproduce than those with others.

           2.  Conclusion - Those hereditary traits that make their owners more likely to grow up and reproduce will become more common in a population from one generation to the next.

           3.  Peppered Moth Example - Popular example of Natural Selection observed in England from the 1850s to 1950s
                a.  Variants of the Peppered Moth:
                     1)  Black Moths - produce a lot of melanin (pigment)
                     2)  Light Gray Moths - produce much less melanin

                b.  1850s - Before the Industrial Revolution - Many more gray moths than black present because they were better camouflaged by the trees, thus they had a higher survival rate, which led to a higher reproductive rate

 

                c.  1950s - After the Industrial Revolution - Many more black moths than light gray present because they were better camouflaged by the trees (which were now darkened with soot from industry pollution), thus they had a higher survival rate, which led to a higher reproductive rate

   

                d.  Evolution - The peppered moths evolved during this time span due to the change in frequency of the black allele (and the light gray allele) in this population.

                e.  Industrial Melanism - Evolution of darker populations of animals in the presence of industrial pollutants.

           4.  Adaptation - Result of natural selection upon a population determined by the traits that increase an organism's chance of surviving and reproducing in its environment

     I.  Causes of Evolution
          1.  Mutations - random changes in genetic material at the level of the DNA nucleotides or entire chromosomes

          2.  Natural Selection - most important cause of evolution; measured in terms of an organism's fitness, which is its ability to produce surviving offspring
               a.  Stabilizing Selection - average phenotypes have a selective advantage over the extreme phenotypes
               b.  Directional Selection - phenotype at one extreme has a selective advantage over those at the other extreme
               c.  Disruptive Selection - both extreme phenotypes are favored over the intermediate phenotypes

                   

          3.  Mating Preferences - Organisms usually do not choose their mates at random, thus the selection process can cause evolution

          4.  Gene Flow - Transfer of genes between different populations of organisms.  This situation leads to increased similarity between the two populations

          5.  Genetic Drift (Founder Effect) - Situation that results in changes to a population's gene pool caused by random events, not natural selection.  This situation can have drastic effects on small populations of individuals.  Common on islands.

          

     J.  Speciation
           1.  Species Definition - A group of organisms capable of breeding with one another to produce fertile offspring, yet this group is unable to breed successfully with members of other groups.

           2.  Allopatric Speciation - A population becomes physically separated from the rest of the species by a geographical barrier that prevents interbreeding.  Because gene flow is disrupted by this physical barrier, new species will form.

           3.  Sympatric Speciation - Two populations are geographically close to each other, but they are reproductively isolated from each other by different habitats, mating seasons, etc.

           4.  Punctuated Equilibrium - "Fast and Slow" pattern of speciation in which there are long periods of little change followed by short periods of rapid change

To test your knowledge about Evolution, click on the Evolution Questions Link at the top of this page.  After you answer the questions, be sure to check your responses by clicking on the Evolution Answers Link.

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