22.1 – 1 Which of the individuals discussed in this section viewed species as fixed, and which viewed species as being able to change over time? 22.1 – 1 Aristotle, Linnaeus, and Cuvier viewed species as fixed (though Cuvier noted that the species present in a particular location could change over time). Lamarck, Erasmus Darwin, and Charles Darwin thought species could change. 22.1 – 2 What was Lamarck’s theory of evolution? Explain its significance. 22.1 – 2 Lamarck observed evidence of changes in species over time and noted that evolution could result in organisms’ adaptations to their environments, though his theory was based on an incorrect mechanism for evolution: that modifications an organism acquires during its lifetime can be passed to its offspring. 22.2 – 1 Describe how the following concepts relate to Darwin’s theory of evolution by natural selection: overproduction of populations, limited resources, and heritable variation. 22.2 – 1 Species have the potential to produce more offspring than survive (overproduction), leading to a struggle for resources, which are limited. Populations exhibit a range of heritable variations, some of which confer advantages to their bearers that make them more likely to leave more offspring than less well-suited individuals. Over time this natural selection can result in a greater proportion of favorable traits in a population (evolutionary change). 22.2 – 2 Explain why an individual organism cannot be said to evolve. 22.2 – 2 Though an individual may become modified during its lifetime through interactions with its environment, this does not represent evolution. Evolution can be measured only as a change in proportions of heritable variations from generation to generation. 22.3 – 1 Explain why the following statement is inaccurate: “Anti-HIV drugs have created drug resistance in the virus.” 22.3 – 1 An environmental factor such as a drug does not create new traits such as drug resistance, but rather selects for traits among those that are already present in the population. 22.3 – 2 How does Darwin’s theory account for both the similar mammalian forelimbs with different functions of the human, cat, whale, and bat (shown below left) and the similar lifestyles of the Australian sugar glider and the North American flying squirrel (shown below right). 22.3 – 2 Despite their different functions, the forelimbs of different mammals are structurally similar because they all represent modifications of a structure found in the common ancestor. The similarities between the sugar glider and flying squirrel indicate than similar environments selected for similar adaptations despite different ancestry. 22.3 – 3 Explain how the fossil record can be used to test predictions of evolutionary theory. 22.3 – 3 If molecular biology of biogeography indicates a particular branching patter of descent from a single group of ancestral organisms, representatives of the ancestral group should appear earlier in the fossil record than representatives of later organisms. Likewise, the many transitional forms that link ancient organisms to present-day species are evidence of descent with modification.