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AP Biology Evolution Unit

AP Biology Evolution Unit. Mechanisms of Evolution. Descent with Modification. Traditional views: Aristotle 384-322 BC – Scala naturae , life-forms could be arranged on a scale of increasing complexity. Old Testament- perfect species were individually designed by God.

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AP Biology Evolution Unit

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  1. AP Biology Evolution Unit Mechanisms of Evolution

  2. Descent with Modification • Traditional views: • Aristotle 384-322 BC – Scalanaturae, life-forms could be arranged on a scale of increasing complexity. • Old Testament- perfect species were individually designed by God. • Carolus Linnaeus (1707-1778) grouped similar species into increasingly general categories reflecting what he considered the pattern of their creation. • Developed taxonomy, branch of biology dedicated to the naming and classification of organisms. • Developed binomial nomenclature, a two-part naming system that includes both genus and species

  3. Descent with Modification • Traditional view cont’d • Georges Cuvier (1769- 1832) geologist who advocated catasrophism, the principle that events in the past occurred suddenly and by different mechanisms than those occurring today. • He opposed evolution using his theories on catastrophism to explain boundaries between strata and location of different species (fossils included) • Charles Lyell (1797-1875) geologist who developed the principle of uniformitarianism, the idea that the geological processes shaping the planet are the same as they have always been. • His book Principles of Geology argued that the Earth was much older than once believed, Darwin read this book during his journey on the HMS Beagle

  4. Descent with Modification • Traditional view cont’d • Jean-Baptiste de Lamark (1744- 1829) developed an early theory of evolution based on two principles • Use and disuse • Inheritance of acquired characteristics • Importance: Lamark recognized species evolved he though he lacked the evidence to support his mechanisms These traditional views paved the way for Darwin’s work

  5. Descent with modification • What were some events that led to the development of Darwin’s theory of evolution? • Lamark- inheritance of acquired traits through use and disuse, 1st theory of evolution • Malthus- wrote an essay “Principles of Population” the idea that people compete for a limited number of resources, and population growth rates depend on this flux in resources • Lyell- wrote “Principles of Geology” established that the Earth has undergone tremendous changes, making it much older than once believed • Wallace- through his own research came to the same conclusion as Darwin about Natural selection • Who was Charles Darwin? • Lived from 1809-1882 • Developed the theory of evolution by means of natural selection

  6. Descent with Modification • Charles Darwin Journey: He 1st started collecting evidence for his theory while traveling on the HMS Beagle from 1831-1836. Darwin’s mechanism for evolution was natural selection. Natural selection explains how adaptations arise.

  7. Descent with modification Adaptations are characteristics that enhance organisms’ ability to survive and reproduce in specific environments. Ex. Desert foxes have large ears which radiate heat. Arctic foxes have small ears which conserve body heat. Natural selection is a process in which individuals that have certain heritable characteristics survive and reproduce at a higher rate than other individuals *Over time, natural selection can increase the match between organisms and their environment. *If the environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process.

  8. Descent with modification What support/evidence do we have that evolution has/is occurring? The theory of evolution is supported with the following evidence • Fossil record- using relative dating and carbon-14 dating to determine age of extinct and extant groups of organisms. • Biogeography- comparing differences in groups of organisms in line with the migration of continents and other changes in geography • Comparative Anatomy- looking at common anatomical structures (homologous or vestigial features) • Comparative Embryology- looking at common tissue development • Molecular Biology- comparing the DNA and protein sequencing of extant organisms and determining the accumulation of mutations since they shared a common ancestor (phylogeny- an evolutionary tree)

  9. Descent with modification • Natural selection results in alleles being passed to the next generation in different proportions from their relative frequencies in the previous generation. • These selective pressures come from changes in the environment and can be classified as one of three modes of natural selection: • 1. stabilizing • 2. directional • 3. disruptive

  10. Number of Individuals Small Large Size of individuals 1. Stabilizing Selection • Acts upon extremes and favors the intermediate.

  11. Number of Individuals Small Large Size of individuals 2. Directional Selection • Favors variants of one extreme.

  12. Number of Individuals Small Large Size of individuals 3. Diversifying Selection • Favors variants of opposite extremes.

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