LECTURES FOR ZOO 1010—CHAPTER 1
SCIENCE OF ZOOLOGY AND EVOLUTION OF ANIMAL DIVERSITY
BASED ON HICKMAN ET AL. ANIMAL DIVERSITY
3rd Edition
Chapter Prologue—A Legacy of Change: The major feature of life’s history is a legacy
of perpetual change.
Chapter Introduction:
Zoology—the scientific study of animals.
Animal—eukaryotic, multicellular, ingestive heterotrophic organism.
Evolution—study of changes that have produced the diversity of life throughout its
history on Earth.
Phylogeny—evolutionary history of the origin and diversification of any taxon.
Goals of study of animal diversity—(1) reconstruct phylogeny of animal life; (2)
understand historical processes that generate and maintain diverse species and
adaptations throughout evolutionary history.
Principles of Science:
Science has several essential characteristics—(1) it is guided by natural law; (2) it has
to be explanatory by reference to natural law; (3) it is testable against the
empirical world; (4) its conclusions are tentative; (5) it is falsifiable.
Scientific Method—it is a hypothetico-deductive method; a scientist must be able to
say “If my hypothesis is a valid explanation of past observations, then future
observations ought to have certain characteristics.” A hypothesis is an if…then
statement. If a hypothesis is very powerful in explaining a large variety of related
phenomena, it attains the status of a theory.
Experimental and Evolutionary Sciences—questions asked about animal life either
seek to understand proximate causes or ultimate causes. Proximate causes are
investigated using the experimental method and are called experimental sciences.
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Ultimate causes are addressed by the evolutionary sciences using the comparative
method.
Origins of Darwinian Evolutionary Theory:
Darwin and Wallace were first to establish evolution as a powerful scientific theory.
They were not the first, however, to consider the idea of organic evolution.
Pre-Darwinian Evolutionary Ideas—idea of life having had a long history o perpetual
and irreversible change was developed by early Greek philosophers. Christian
teachings established evolutionary views as rebellious and heretical. Buffon,
however, stressed environmental influences on modifications of animal types.
Lamarckism: The First Scientific Explanation of Evolution—established convincing
case for fossils as remains of extinct animals and originated the idea of an
evolutionary mechanism called inheritance of acquired characteristics (1809). It
was a transformational concept, as opposed to Darwin’s variational concept.
Charles Lyell and Uniformitarianism—idea (1) that laws of physics and chemistry
remain consistent throughout the earth’s history; (2) that past geological events
occurred by natural processes similar to those that we observe in action today.
Darwin’s Great Voyage of Discovery—Darwin derived much of the material used to
construct his theory from his experiences on a five-year voyage around the world
aboard the H.M.S. Beagle. Darwin returned to England in 1836, but did not
publish On the Origin of Species until 1859.
Darwin’s Theory of Evolution:
Darwinism—encompasses five major theories, viz. (1) perpetual change; (2) common
descent; (3) multiplication of species; (4) gradualism; (5) natural selection.
Natural selection—consists of a series of five observations and three inferences from
them. Observation 1—Organisms have great potential fertility. Observation 2—
Natural populations normally remain constant in size, except for minor
fluctuations. Observation 3—Natural resources are limited. Inference 1—A
continuing struggle for existence occurs among members of a population.
Observation 4—All organisms show variation. Observation 5—Variation is
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heritable. Inference 2—Differential survival and reproduction occur among
varying organisms in a population. Inference 3—Over many generations,
differential survival and reproduction generate new adaptations and new species.
Evidence for Darwin’s Five Theories of Evolution:
Perpetual change—fossils, radiometric dating, and study of evolutionary trends.
Common descent—homology and reconstruction of phylogeny, and ontogeny,
phylogeny, and recapituation.
Multiplication of species—speciation, reproductive barriers, allopatric speciation, and
adaptive radiation.
Graduation—phenotypic gradualism and phyletic gradualism vs. punctuated
equilibrium.
Natural selection—
Revisions of Darwinian Evolutionary Theory:
Neo-Darwinism—Darwinian evolutionary theory as revised by Weismann, who
experimentally rejected Lamarckian inheritance.
Emergence of modern Darwinism: A synthetic theory—population genetics,
microevolution and macroevolution.
Microevolution: Genetic Variation and Change within Species:
Alleles, polymorphism, gene pool, allelic frequency, genotype, heterozygosity.
Genetic equilibrium—Hardy-Weinberg equilibrium.
Processes of evolution: How genetic equilibrium is upset—genetic drift, nonrandom
mating, migration, natural selection (stabilizing, directional, and disruptive
selection), interactions of selection, drift, and migration.
Macroevolution: Major Evolutionary Events:
Speciation and extinction through geological time—species selection.
Mass extinctions—Permian and Cretaceous extinctions, catastrophic species
selection.
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