1. Descent with Modification: A Darwinian View of Life Chapter 22

2. Pre-Darwin: Scale of Nature and Natural Theology Greek philosophers who influenced Western culture. Plato believed in 2 worlds: real and illusory Aristotle believed all living forms could be arranged on a scale or ladder of increasing complexity (scale of nature); species are perfect and never evolve. Natural theology- philosophy dedicated to discovering the Creator’s plan by studying nature Linnaeus: taxonomy- branch of biology concerned with naming and classifying diverse forms of life; developed 2 part binomial system: according to GENUS and SPECIES. This grouped similar species before Darwin.

3. Cuvier, Fossils, and Catastrophism Fossils- relics or impressions of organisms from the past, mineralized in rock. Most fossils found in sedimentary rocks- sand and mud settle at bottoms of seas, lakes, and marshes. Paleontology- study of fossils Cuvier: noted each stratum in sedimentary rock have unique group of fossil species. Catastrophism-each boundary b/w strata corresponded in time with a catastrophe like a flood or drought, and destroyed species in that time.

4. Gradualism Hutton: proposed it is possible to explain various land forms by looking at mechanisms currently operating the world. Hutton explains Earth’s geological features by gradualism- change is a constant, consistent, slow process. Lyell: incorporated gradualism with Uniformitarianism:-Lyell’s idea that geological processes have not changed throughout Earth’s history. Darwin influenced by Hutton and Lyell observations: 1.If geological change is slow and continuous, then Earth is much older than 6000 years according to biblical refence. 2. Slow and subtle processes persiting over a long period of time can cause substantial change.

5. Lamarck Aristotle saw one ladder of life, while Lamarck saw many. He thought species could move up ladders and reach greater complexity. Species at bottom of ladder are simple, microscopic organisms made from nonliving material, while species at top are complex. Species try to move up ladder and be more complex, attain perfection, and be better adapted to environments. Thus, evolution responds to organism’s “felt needs”. Lamarck proposed 2 ideas of how species evolve to specific adaptations: 1. Use and disuse: parts of body to cope with environment get bigger and better, and parts not used deteriorate. 2. Inheritance of acquired characteristics: modifications organism acquires during its lifetime is passed on to offspring. Lamarck’s theories not accepted because evolution was not yet accepted, and they also thought that certain characteristics cannot simply be passed on.

6. Darwin Collected 13 similar but different species of finches: certain came from certain individual islands, or neighboring islands. It occurred to him that a new species could arise from an ancestor by gradual accumulation of adaptations to a different environment. If geographical barrier isolates two populations of a single species, the populations would change in appearance to adapt to local environment. Hypothesis: over many generations, 2 population can be dissimilar enough to be considered a separate species. Wallace published almost identical theory of natural selection before Darwin, but Darwin’s evidence proved it to be more convincible  evolution accepted within a decade

7. Origin of Species Descent with Modification- Darwin perceived a unity of life, where all organisms related descent from unknown prototype that lived in the past. As the descendents moved into different habitats over millions of years, they underwent adaptations. Linnaeus connected Darwin with idea of “groups subordinate to groups”; major taxonomic categories: KINGDOM, PHYLUM, CLASS, ORDER, FAMILY, GENUS, SPECIES

8. Ernst Mayr: Inferences and Observations Ernst Mayr dissected Darwin’s theory: Observation #1: All species have great chance of fertility that the population would greatly increase if all individuals reproduced successfully. TREMENDOUS FECUNDITY Observation #2: Populations tend to remain stable in size; except for seasonal fluctuations. STABLE POPULATIONS Observation #3: Environmental resources limited. LIMITED ENVIRON. RESOURCES Inference #1: Production of individuals cause struggle in population. Observation #4: No two individuals are exactly alike. VARIATION AMONG INDIVIDUALS Observation #5: Variation is heritable. HERITABILITY Inference #2: Those with best fitting traits likely to have more offspring. Inference #3: Unequal ability of individuals to survive  gradual change in population w/ favorable characteristics accumulating over generations

9. Summarizing Darwin’s Main Ideas 1. Natural selection is differential success in reproduction 2. Natural Selection occurs by interaction b/w environment and individuals in population ability to inherit variables. 3. Product of N.S. is adaptation of populations of organisms in their environments.

10. Malthus Human suffering (disease, famine, homelessness, and war) is the inescapable consequence of potential for human brings to increase faster than supplies and resources; the capacity to overproduce

11. Artificial selection: breeding of plants and animals; can cause substantial change in pop. Two Main features of Darwinian view of life: 1. Diverse forms of life have risen by descent with modification from ancestral species 2. Mechanism of modification is natural selection working over long periods of time

12. Subtleties of Natural Selection Population- group of interbreeding individuals belonging to particular species and sharing common geographic area; smallest unit that can evolve. Individuals to not evolve, POPULATIONS EVOLVE OVER TIME. Evolution can be measured only as changes in relative proportions of variations in a population over many generations. There is no evidence that characteristics acquired during a lifetime can be inherited. * Read exmaple of natural selection in action on pg. 422.

13. Evidence of Evolution Biogeography- geographical distribution of species: Islands have indigenous species (native, found nowhere else), closely related to species of nearest mainland or neighboring islands. Fossil record- In the fossil record, prokaryotes are the ancestors of life and predicts bacteria should precede all eukaryotic life; fossils help link older fossils to modern species. EX: fossilized leg bone of whale Homology- similarity in characteristics resulting from common ancestry. Homologous structures- anatomical signs of evolution. EX: forelimbs of humans, cats, whales, and bats have similar structures but different functions. So they had a common ancestor, which modified characteristics to take on new functions over time. Vestigial organs- parts left in body no longer necessary, but functioned in ancestors. EX: human appendix/ pelvis and leg bones on whales. Vestigial organs represent changes in an organisms’ embryonic development wrought by natural selection.

14. Comparative embryology: Closely related organisms go through similar stages in embryonic development (EX: fish and humans develop gill pouches, and fish develop further into gills, humans further develop Eustachian tubes connecting ear to throat). Ontogeny (development of individual organism) is a replay of phylogeny (evolutionary history of the species). Molecular biology supports Darwin’s speculation that ALL forms of life are related to some extent through branching descent from the earlier organisms, common ancestry connected by comparisons of amino acids.