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Chapter 22
Natural selection: process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are organisms with other characteristics
Evolution: “descent with modification”; living species descend from ancestral species that differed from those that currently exist; change in genetic composition
Taxonomy: a scientific discipline concerned with naming and classifying the diverse forms of life
Fossils: preserved remains/impressions of an organism that existed in the past
Sedimentary rock: (strata) superimposed layers of rock that often times carry fossils.
Paleontology: the study of fossils
Catastrophism: principle that events in the past occurred suddenly and were caused by different mechanisms than those today
Uniformitarianism: principle stating that mechanisms of change are constant over time
Descent with modification: Darwin’s way of saying “evolution” without upsetting people of is era
Artificial selection: selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits
Homology: similarity in characteristics resulting from a shared ancestry
Homologous structures: structures in different species that are similar because of a common ancestor
Vestigial organs: organs that do not serve a purpose any more but did years ago
Biogeography: study of the past and present distribution of species
Endemic: species that is confined to a specific, super small geographic area
The Historical Context for Evolutionary Theory
1. State the two major points that Charles Darwin made in The Origin of Species concerning Earth’s biota. 1) Species evolved from ancestral species that weren’t “originally” created. 2) Natural selection is a mechanism that could result in this evolutionary change.
2. Compare and contrast Plato’s philosophy of idealism and Aristotle’s scala naturae. Plato: believed there were two coexisting worlds which included an ideal, real world and am illusionary imperfect world that humans are able to perceive with their senses. Aristotle: had beliefs that don’t include evolution. He noticed that organisms vary from super simple to fairly complex and believed that a scale could be made that demonstrated this, hence, scala naturae. He also believed that species stayed the way they were and could not evolve.
3. Describe Carolus Linnaeus’s contribution to Darwin’s theory of evolution. Linnaeus sought order in the diversity of life. He would name and classify organisms (taxonomy) and used it to create a hierarchy of categories. One thing he did not do was purposely imply any form of evolutionary relations because he believed that species were permanent and never changing. The linking of species through categories allowed Darwin a better insight.
4. Describe Georges Cuvier’s contribution to paleontology. Cuvier founded this study by examining strata (superimposed layers of rock) and noticing that the deeper the layers of strata, the more the fossils differed from current species.
5. Explain how Cuvier and his followers used the concept of catastrophism to oppose evolution. Catastrophism is theory that major changes in the earth’s crust are the result of catastrophic events rather than from gradual processes of change. So in place of evolution, he proposed that there were periodic localized catastrophes resulted in mass extinctions that killed off previous organisms.
6. Explain how the principle of gradualism and Charles Lyell’s theory of uniformitarianism influenced Darwin’s ideas of evolution. First off, gradualism is principle that profound change is the cumulative product of slow, continuous processes and uniformitarianism is the theory that geological processes are uniform and have operated from the origin of the earth to the present. Darwin rejected uniformitarianism, but was influenced by that the earth must be ancient and slow and subtle processes persist and cause substantial change which would then lead to a change in the organisms.
7. Describe Jean Baptiste Lamarck’s model for how adaptations evolve. Explain the challenges to Lamarck’s ideas with respect to current understandings of biology. Lamarck had two real explanations: use and disuse, and inheritance of acquired characteristics. Use and disuse: those body organs used extensively to cope with environment become larger and stronger while those not used deteriorate. Inheritance of acquired characteristics: the modifications an organism acquired during its lifetime could be passed along to its offspring. Using specific organs over the rest do not mean that they grow larger. The example typically given would be the giraffe. He states that a giraffe originally had a small neck but stretched it to reach food on top of trees, giving it that long neck we see today. An animal/organism does not see this type of evolution through work like that.
The Darwinian Revolution
8. Describe how Darwin used his observations from the voyage of the HMS Beagle to formulate and support his theory of evolution. Darwin noticed the similarities of finches he found throughout different portions of the Galapagos Islands. He figured that those species were once all the same and had flocked there long ago but the islands “shape” had split many of them up. The geology varied throughout the island and the food available varied as well. The birds began to develop different “structures” in order to get food. This brought Darwin to the idea of adaptations.
9. Describe how Lyell and Alfred Russel Wallace influenced Darwin. Lyell: Darwin agreed that geological change can result in a slow change in an organism. Wallace: made Darwin realize he should have published his ideas as early as possible instead of having this guy come up with theories similar to his and living up what Darwin wished he could.
10. Explain what Darwin meant by “descent with modification”. It was his way of saying evolution without actually saying it. He believed that as descendants of ancestral organisms lived through various habitats, they would begin to modify within time.
11. Explain what evidence convinced Darwin that species change over time. The Galapagos finches led Darwin to believe in a gradual change over time.
12. Describe the three inferences Darwin made from his observations that led him to propose natural selection as a mechanism for evolutionary change. 1. Individuals do not evolve, but rather the population evolves.
2. Natural selection can amplify or diminish only heritable traits. Traits are passed from the organism to the offspring. Although the species may make adaptions during its lifetime, the adaptions will not be passed on to offspring.
3. Environmental factors vary from time to time. Natural selection is always operating, but which traits are favored depends on the environment.
13. Explain how an essay by the Rev. Thomas Malthus influenced Charles Darwin. He began to make connections between natural selection and the capacity of organisms to “overreproduce”.
14. Distinguish between artificial selection and natural selection. Artificial selection: breeding of domesticated plants and animals have modified species Natural selection: variation and overproduction in populations – the most fit individuals pass on their genes; results from environmental editing
15. Explain why the population is the smallest unit that can evolve. An individual cannot evolve. That would be a mutation. The entire population would have to involve which would make it the smallest unit to evolve.
16. Using some contemporary examples, explain how natural selection results in evolutionary change.
Finch beaks on the Galapagos - average beak depth oscillates with rainfall - natural selection is situational
Butterfly reproduction - they choose different plants depending on where they were laid
Antibiotic resistance in bacteria
Body size of guppies exposed to different predators.
17. Describe the research that suggested to David Reznick and John Endler that the life-history traits among guppy populations are correlated with the main type or predator in a steam pool. The predator was attracted to the colorful guppy versus the non-colored ones. Natural selection favored the drab colored ones because they have a better chance of surviving.
18. Explain how homologous structures support Darwin’s theory of natural selection. Explain how biogeography and the fossil record support the evolutionary deductions based on homologies. Homologous structures support Darwin’s theory of natural selection by showing that every species shares commonality. Every species has the human hand structure, but it was changed and morphed to better equip the organism depending on where it lives.
19. Explain the problem with the statement that Darwinism is “just a theory.” Distinguish between the scientific and colloquial use of the word “theory.” The pattern of evolution has been traced and noted and has been given a great deal of evidence. The colloquial “theory” is noted as a hypothesis, meaning that it’s a strong feeling most have but it has yet to be stated as true. The scientific “theory” means that is has had substantial proof to back it up for it to be trustworthy/true.