NOTE: The links to the names on this page are just for your further interest. You will not be held responsible for information on these pages. I. Ancient Beliefs A. Plato (428-348 BC) 1. idealism a. the "idea" is an eternal, unchanging essence b. variation has no meaning, only essence matters B. Aristotle (384-322 BC) 1. Scala Naturae or scale of nature 2. from inanimate to plants to animals to man a. permanent, unchanging b. everything fixed in place according to God's plan C. The views of these two early Greeks prevailed for almost 2000 years. II. Beginning of Modern Scientific Methods and Thoughts (Fig 22.1) A. Traditional beliefs 1. all organisms resulted from direct actions of a creator 2. role of natural science was to catalogue the organisms and appreciate God's great wisdom - natural theology 3. earth was about 6,000 years old B. Carolus Linnaeus (1707-1778) 1. father of taxonomy 2. defined fundamentals of biology in terms of nomenclature and classification 3. clustering groups into a hierarchy of increasingly general categories. Fig 25.7. 4. done for the greater glory of god - "God's Registrar" C. Buffon (1701-1788) 1. French naturalist 2. large inheritance freed him from having to earn a living 3. suggested in 1779 that the earth might be very old (very heretical at the time) 4. forced to recant D. Cuvier (1769-1832) Image 1. founder of paleontology (studied fossils - Fig 22.2) - anatomist 2. observed that different strata of sedimentary layers contained different fossils. Fig. 22.3. 3. catastrophism--explained changes in animal world in terms of catastrophes that had destroyed whole populations of living things in prehistoric times (floods etc.) E. Hutton (1726-1797) and Lyell (1797-1875) 1. both were influential geologists 2. Hutton a. same processes are responsible for both past and present events - gradualism - Fig 22.4 and movie b. one of first to imply great age of the earth 3. Lyell Image a. great champion of Hutton's work b. historical and physical continuity of nature c. Principles of Geology (1830)--greatly influenced Darwin even though he himself did not admit biological evolution d. small forces acting over long periods of time can result in major changes e.g. destruction of mountains. Theory of uniformitarianism G. Lamarck (1744-1829) Image 1. the first uncompromising advocate of evolution, attempted to provide a mechanism to explain evolution 2. argued that lowly forms of life arise continually from inanimate matter by spontaneous generation, and progress inevitably toward greater complexity and perfection -- an inherent tendency toward complexity 3. particular path of progression taken is guided by environment 4. changing environment alters the needs of the organisms 5. use and disuse alter morphology and is transmitted to subsequent generations inheritance of acquired characteristics 7. emphasized great age of earth 8. Ideas were almost universially rejected, particularly by Cuvier and Lyell III. Charles Darwin (1809-1882) Darwin in 1874 A. Early life 1. born in 1809 in Shrewsbury, England--the son of a physician 2. studied medicine in Edinburgh 3. studied theology in Cambridge--was very religious 4. at both places he pursued an interest in natural science B. Voyage of the H. M. S. Beagle (1831-1836) Fig 22.5. 1. served as unpaid naturalist - paid his own way 2. made stops along coasts and islands of the southern hemisphere 3. noted how plant and animal forms differed with geographical location 4. Observations in Galapagos Islands and South America. Movie of Galapagos Islands! 5. Read Lyell's Principles of Geology on the voyage - true age of earth much greater than 6000 years C. Return to England after voyage 1. did not accept notion of evolution until it was pointed out that his specimens of finches from Galapagos were so distinct as to represent different species. Fig 22.6. 2. this revelation led him to doubt the fixity of species 3. first published several volumes on geology and the voyage of the Beagle IV. Darwin's Evidence A. Hutton and Lyell's evidence supporting geological events. B. Observations 1. extinct species related to living (extant) organisms a. observations of the fossil record b. e. g. armadillos and glyptodont--found fossil species similar to extant species c. both limited to one geographical area d. if both were created at the same time, and if they were so much alike, why was only one of them alive in 1850? 2. characteristics of species varied from place to place a. appearance of tortoises dependent on location b. slight changes in appearance after island isolation 3. great variety of organisms on young volcanic islands, e.g., finches 4. resembled forms on mainland, not distant places *organisms in forests of S. America more similar to organisms of grasslands of S. America than to organisms in forests of Europe *this would not be so if were created all at once to be perfectly adapted for that environment. C. Darwin and Malthus 1. Malthus wrote Essay on the Principle of Population (1798) a. argued that unchecked growth of the human population must lead to famine *populations increase geometrically - Fig. 22.8. *food supplies increase arithmetically b. nature acts to check population growth via death *in humans this is famine, war, and disease 2. Led Darwin to his idea of natural selection 3. Ernst Mayr summed it - see page 435. D. Natural Selection (Fig 22.10) and artificial selection (Fig 22.11b) 1. the differential reproduction of individuals that differ in one or more hereditary characterisitics - Fig 22.9. a. difference in survival and/or reproduction not due to chance b. has the potential consequence of altering the proportions of different characters 3. changes the nature of the population as a whole. Descent with modification - Fig 22.7. 4. natural selection in action - pesticide resistance in insects - Fig 22.12. and drug resistance in HIV. Fig 22.13. V. Publication of Darwin's Theory A. First draft completed in 1844, but was not published B. Began work on Natural Selection in 1856, was to be a 20 volume set C. Alfred Russel Wallace Also see info on Wallace here. 1. was a British army surgeon stationed in Malaysia who studied insects 2. wrote Darwin a letter in which he stated his theory of evolution by natural selection and told Darwin he thought he knew how evolution worked 3. this resulted in Darwin publishing The Origin of Species (1859) rather than the 20 volume set he was contemplating. Darwin in 1859. Also see: On The Origin Of Species By Means of Natural Selection, Or The Preservation of Favoured Races In The Struggle For Life. By CHARLES DARWIN, M.A., Fellow of the Royal, Geological, Linnaean, etc, Societies; author of Journal of Researches During H.M.S. Beagle's Voyage Round the World. London: John Murray, Albemarle Street, 1859. D. First edition said descent with modification--did not use term evolution until the last paragraph.
I. Comparative anatomy
A. Homologous structures Fig 22.14.
B. Homoplastic (analogous) structures result from convergent evolution. Fig 22.15.
III. The Molecular Record
A. Universal genetic code - all consist of nucleotide
B. Comparison of DNA sequences or amino acid sequences of proteins between organisms - Table 22.1
C. Can use this data to construct phylogenetic trees.
IV. Patterns of distribution/biogeography
A. Organisms on islands most closely resemble forms on nearest continent. Hawaiian honeycreepers.
Forms not identical, but diverged over time. Endemic species common on islands.
Example: Hawaiian fruit flies. Fig 22.16
B. earth is 4.6 billion years old
C. Continental drift (plate tectonics) Fig 25.4.
Pangaea, Gondwana, Laurasia
V. Fossils - relics or impressions of organisms from the past, preserved in rock.
Fossils provide the most concrete evidence for evolution.
Transitional fossils abound in the fossil record. Fig 22.17.
Interesting Links:
Evolution is a change in the allele frequency of a population.
TERMS TO REVIEW: gene, chromosome, homologous chromosomes, allele, locus (loci), dominant, recessive, homozygous, heterozygous, haploid, diploid, phenotype, genotype, gene pool
The mechanisms of heredity genes unknown in Darwin's time Mendel's theory rediscovered 1900 at first scientists used Mendel's work to discredit Darwinian evolution later (1920's) determined that laws of inheritance explain genetic variation
Population Genetics
Modern synthesis--forged the contributions of genetics, Darwinism and paleontology. 1. Populations contain genetic variation that arises by random mutation and recombination. 2. Populations evolve by changes in gene frequency brought about by random genetic drift, gene flow and especially natural selection. 3. Most adaptive changes are gradual. 4. Diversification comes about by speciation, which ordinarily entails the gradual evolution of reproductive isolation among populations. 5. These processes, continued for sufficiently long periods, give rise to changes of such great magnitude as to warrant the designation of higher taxonomic levels.
The Hardy-Weinberg Theorem
States that there will be no change in allele frequencies in a population if the following 5 conditions are maintained: (See page 449 in your text also)
In a population meeting all these conditions, no evolution is occurring. It is in Hardy-Weinberg equilibrium.
All these conditions are never met.
The Hardy-Weinberg Equation - Fig 23.3a and Fig 23.3b.
Microevolution: Why Do Allele Frequencies Change?
Genetic variation within populations
Variations between populations
Sources of genetic variation
Diploidy and balanced polymorphism preserve variation
Selection In Action
Forms of Selection - summary of 3 forms from Solomon or Fig 23.12
Natural selection maintains sexual reproduction - Fig 23.15
Natural selection cannot make perfect organisms
