Chapter 1 - Variation in Populations

Notes for Understanding Evolution - Chapter 1

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The following lecture notes will use the following conventions:
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Objectives:

a) What is distinction between environmental and genetic basis of observed phenotypic variation in population (Multi-leg bullfrog example)
b) How does one test for this difference?
c) In cases with genetic basis, what is expected phenotypic expression (i.e., for case of simple Mendelian recessive allele)

Introduction

I. Environmental Modification

Key Terms: teratogens (various substances that can cause environmental modification, not due to genetic makeup of the individual), expression of a gene vs. the gene itself

RQ1.1: Explain why a cross of two multilegged bullfrogs might provide valuable insight as to why such deformaties might exist.

II. Lamarckism

Featured Scientist: Jean Baptiste de Lamarck

source of image

Links: 1 - 2 - 3 - and especially 4 (Michael Ghiselin's excellent account of textbook falacies about what Lamarck said)

PBS Website Link

RQ1.2: Why does evolution depend on heritable variation?

III. Heritable Variation

Key Terms: allele, recessive vs. dominant allele, carrier (heterozygous for recessive deleterious allele, e.g., the one that when homozygous causes Ellis-van Creveld syndrome, due to a faulty protein produced by a gene on the short arm of human chromosome 4)

RQ1.3: In the bullfrog example, if the multi-leg condition did have a heritable component, why is it potentially significant that the multilegged frogs did not survive long enough to reproduce?

IV. Hypothetico-Deductive Reasoning

Key Terms: hypothesis, deduction, hypothetico-deductive style of reasoning, theory vs. "truth"

RQ1.4: Why do you think that, unlike physics, biology doesn't seem to have much in the way of laws?

Click link to return to Biology 409 Schedule
or ahead to Chapter 2