A science-fiction tale describes an artificial planet in theform of a band completely encircling a sun (Fig. 6-31). Theinhabitants live on the inside surface (where it is alwaysnoon). Imagine that this sun is exactly like our own, that thedistance to the band is the same as the Earth-Sun distance(to make the climate temperate), and that the ring rotatesquickly enough to produce an apparent gravity of g as onEarth. What will bethe period of revolution,this planetsyear, in Earth days?
Julia Delaluz BIOL 120 Week 6 Notes 3/2125 Diversity of Life There are many different kinds of living things on the planet Some are very different from one another, but some are very similar Why The Unity of Life Today scientists agree that all living things on earth share a common ancestor All existing types of life today developed from said common ancestor The differences arose from differences in environments, and by chance These ideas form the basis of evolutionary theory The Tree of Life The common ancestor is like a tree trunk Current species = top branches Major groupings correspond to more recent divergences The closer the branches = the more two species are related Lower branches = diverged long ago, Higher branches = more recent DNA comparison is one way to determine species’ relatedness Theory of Common Descent^ Universal Tree of Life Biological classification scientists attempt to organize biodiversity into discrete and logical categories Living organisms represent a small remnant of all the species that have appeared over Earth’s history History of Systematics Aristotle 2000 years ago Classify as plant or animal Linnaeus- early 1700s 2 Kingdoms: animalia, vegetabilia KPCOFGS Based on shared physical similarities Binomial nomenclature Kindgom, Phylom, Class, Order, Family, Genus Species- scientific name Taxonomy is based on: DNA: the more closely related the DNA, the more closesly realted the organisms Julia Delaluz BIOL 120 Week 6 Notes 3/2125 Homology: common structures in differing organisms that may result from common ancestry The Classification of Life (table) Cladogram: Linnaean Classification of Humans: What is Evolution A process of change in the characteristic of a population of organisms over the course of generations An organizing theory: o all species present today are descendants of a common ancestry and represent millions of years of microevolution through natural selection Evolutionary Theory Changes in organisms over time Collectively- all the change that transform life on earth Producing diversity of organisms A genetically based phenotypic chance in population of organisms over successive generations Evidence for Evolution Fossils Comparative anatomy Julia Delaluz BIOL 120 Week 6 Notes 3/2125 Comparative embryology Biogeography Molecular biology Together = all evidence supports theory of evolution Evidence from the Fossil Record Over time, the organic material in living things that have been buried Evidence of Homology Homology: the similarity in characteristics that have resulted from common ancestry Test can help determine if Linnaean classifications are correct about similarities between organisms o Behavior, DNA, and physical structure (anatomy) can be observed and tested Divergence: comparable body parts became modified in different ways in different lines of descent from a common ancestor o Same structure, looks different b/c different function o Ex: sea lion flipper bones, human arm bones Convergence: different structure, but looks similar b/c same function o Ex: bat wings, eagle wings Vestigial traits: useful in other animals, useless in others (used to be useful) o Ex: tailbone- useful in primates, useless in humans, goosebumps useful for birds, useless for humans Evidence from Biogeography Pattern of distribution of species on the continents is called biogeography Biogeographic patterns support common descent Species do not develop separately, each in the best way for that environment. o Species more closely match those that are geographically nearby, even when the environments for the two differ a good deal Using Molecules to Track Evolution Homology in Biochemistry o A comparison of the sequences of dozens of genes that are fund in humans and other primates demonstrates the same pattern of relationship Julia Delaluz BIOL 120 Week 6 Notes 3/2125 Molecular Clock o Used to calculate the time of origin on one lineage relative to others, assuming that the lineage accumulates neutral mutations at predictable rates o The molecular clock hypothesis states that the rate of change in some DNA sequences seems to be relatively constant o One application suggests that a 1% difference in overall DNA sequence is generated in about 5 to 6 million years “The Great Chain of Being”- Aristotle o Puts forth that the universe is perfect and there is no change. All species are in order, from the “lowest” (worms) to “highest” (humans) Linnaeus “Father of Taxonomy” o Classified species, believed in unchanging order of life created by God Jean-Baptiste Lamarck o Wrote “Philosophie Zoologique” 1809 o Stated that animals evolved from simpler forms o Saw evolution as a goal-oriented process striving towards perfection o Believed in the inheritance of acquired traits o First to use the terms: invertebrate & biology Charles Darwin o Promoted theory of evolution in mid-1800s, went on ship voyage- o 1859 “On the Origin of Species”- how does evolution occur Answered o Charles Lyell- 1830 “Principles of Geography” Tortoises long neck short neck different islands (Galapagos) o After voyage, Darwin concluded that different subspecies on different islands must have evolved form a single ancestral population Hypothesis of common descent- all modern organisms are descendent from a single common ancestor