EvolutionEvolutionLesson 1: Lesson 1:
An Introduction to Charles Darwin An Introduction to Charles Darwin and the Nature of Scienceand the Nature of Science
““A scientist, however, gifted, can be A scientist, however, gifted, can be compared with a fly crawling on the inside compared with a fly crawling on the inside wall of a cathedral; if it could draw what it wall of a cathedral; if it could draw what it sees, the fly’s picture of the cathedral would sees, the fly’s picture of the cathedral would be as crude as early maps of the world; if it be as crude as early maps of the world; if it could voice its speculations about the size, could voice its speculations about the size, appearance, and purpose of the cathedral, the appearance, and purpose of the cathedral, the fly’s opinions would be received even more fly’s opinions would be received even more guardedly.”guardedly.”
-- Frederick Aicken, The Nature of Science , pp.29-30
Evolution As An IdeaEvolution As An Idea“ If I were to give an award for the single best idea anyone has ever
had, I’d give it to Darwin, ahead of Newton and Einstein and everyone else. In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning and purpose with the
realm of space and time, cause and effect, mechanism, and physical law. But it is not just a wonderful idea. It is a dangerous idea.”
Daniel Dennet
Evolution as an IdeaEvolution as an Idea“Evolution is one of the most powerful ideas ever to emerge from science. It is the very foundation of biology and the key to understanding our own human origins. The mechanism of evolution helps determine who lives, who dies, and who gets the opportunity to pass on traits to the next generation. At the same time, evolution ranks as one of the most widely misunderstood scientific principles in America today.”
Richard Hutton, Executive Producer, Evolution WGBHJody Patton, Executive in Charge, Clear Blue Sky
productions
Darwin and the GalapagosDarwin and the Galapagos
Consider the following:Consider the following:
1. How did the Galapagos Islands get there?2. How did the first plants get there?3. How did the first animals get there?4. What is ecological succession?
Ecological SuccessionEcological Succession
• process in which communities of plants and animal species in a particular area are replaced over time by a series of different and often more complex communities.
• Two stages– Primary succession– Secondary succession
Primary SuccessionPrimary Succession
succession in a bare area (no mature soil) that has never been occupied before
Secondary SuccessionSecondary Succession
succession in an area in which natural vegetation has been removed or destroyed but the soil remains
Darwin’s Theory of Natural Selection1. Variations exist2. These variations are heritable3. Some variations are advantageous and some are
disadvantageous4. Organisms compete for limited resources5. Organisms with advantageous variations survive and
reproduce most successfully, leafing more organisms like them in the next generation
6. Over time, the population changes to become more like the organisms with advantageous variations
7. Today’s species have descended from past species8. All organisms are related and are members of a single tree
of life
Darwin’s Theory of Natural Selection• Individual organisms differ; variation is
heritable• Organisms produce more offspring than can
survive; they compete for limited resources• Some variations are advantageous; individuals
best suited to their environment survive and reproduce successfully
• Species alive today descended with modification from ancestral species that lived in the past
Evolutionary Classification Using Cladograms• Cladogram – diagram used to show the evolutionary
relationship between organisms• Cladograms are constructed using derived
characteristics– Derived characteristics - characteristics that appear in
recent parts of the lineage but not in older members; new characteristics that evolve over time
– Each branch or junction shows the appearance of a new trait
– Cladograms demonstrate when characteristics first appeared