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Evolution (Chapter 22) Lecture Overheads (revised).docx

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Natural Science
NATS 1675
Robert Crippen

EVOLUTION OVERHEADS—1675 Evolution comes from the Latin word evolvo = unroll. Evolution in the broadest sense is the “unfolding of a changing continuity”, it is change over time. Organic evolution – the evolution of living organisms—i.e., inheritable change in lines of successive generations. Microevolution—change within a species. Macroevolution—one species changes into another. Evolution is also the concept that there is a kinship among all forms of life because all evolved over time from one common ancestor. Time—The age of the Earth is a bit over 4.6 billion years. If the history is the Earth is compressed into a single year starting 1 January: 20 March (Spring)—first simple cells appeared; 22 July—Atmospheric oxygen becomes abundant; 17 November—multicellular animals appear; 28 November—land plants appear; 21-27 December—Age of the dinosaurs; 31 December (9:07 PM)—ancestral humans of the genus Homo; (11:45 PM)—Homo sapiens (our species) appeared. Genetics comes from the Greek gen = to be born, to become something. Genetics includes the transmission of traits from generation to generation by birth, and it also includes how traits are expressed (our characteristics). Mutation refers to the heritable biological changes in cells and organisms that are the ultimate source for all variations in species. Causes of mutations include: a) accidents of nature; b) exposure to various chemical compounds; and c) radiation including x-rays (mostly from medical sources), natural radiation and ultraviolet light. Genetic engineering refers to the ability to transfer hereditary traits from one organism to another. The Universe is estimated to be about 13.8 billion years old; the Earth about 4.6 billion. Early or Primitive Atmosphere mostly H O vapour, N , CO and small amounts of H & CO (toxic) 2 2 2 2 plus energy sources volcanoes, meteorites, radioactive isotopes, lightening & UV eventually produces NH =3ammonia (toxic) & CH = met4ane (toxic) further produces fatty acids, glucose, nucleotides, amino acids, purines & pyrimidines which leads to proteins eventually coming together to form protocell Both prior to and when life on Earth began, the composition of the atmosphere was very different from its present composition. It contained mostly water vapour (H O), n2trogen (N ) and 2arbon dioxide (CO ), and sm2ll amounts of hydrogen (H ) 2nd carbon monoxide (CO) (toxic). Energy sources included volcanoes, meteorites, radioactive isotopes, lightening and ultraviolet light. The interaction of these energy sources and the components of the early atmosphere eventually led to the production of ammonia (NH ) (toxi3 and inorganic) and methane (CH ) (toxic and4 organic) (Fig. 22.2). Next came more complicated molecules such as fatty acids, glucose, nucleotides, amino acids, purines and pyrimidines à proteins à protocell (TO BE DISCUSSED SHORTLY). The “first great pollution event” occurred about 2.7 billion years ago when photosynthesis first began. Free oxygen was now being released, first into the water and then into the atmosphere. Oxidation began. Oxidation rips cells and molecules apart. No one has any idea of what the first living things were like, but most authorities agree that the first living creatures, protocells, showed at least certain characteristics in common with living organisms today: 1) composed of complicated molecules, 2) separated from the environment by a selective barrier—a membrane; and 3) they must have reproduced themselves in nearly exact copies. Comparative morphology (study of form or structure), from both present day organisms and the fossil record (Palaeontology). Phylogeny—this refers to evolutionary relationships and lines of decent. Cell type—prokaryotic vs. eukaryotic. Embryology—study of development. Radial cleavage is typical of vertebrates; spiral cleavage is typical of invertebrates. Comparative morphology (previously defined) Homology refers to origin. Analogy refers to function. Physiology—study of functions and activities. Biochemistry—study of chemical processes in living organisms. In the sixth century B.C.E., Indian Samkhya philosophers proposed the evolutionary unfolding of the cosmos. th The Greek philosopher Anaximander (also 6 Century B.C.E.) advanced a transmutational account of life, arguing that it emerged from water and that humans descended from fish. Transmutation—this is an early term for “evolution”; it means the act that changes the form or character or substance of something. th The Greek philosopher Thales (also 6 Century B.C.E.) studied life in the Aegean Sea and declared water to be “the mother from which all things arose and out of which they exist”. rd The Greek philosopher and naturalist Aristotle (3 Century B.C.E.) maintained that there was a natural procedure from plants to plant-animals to animals and then by graduated steps to humans. Lucretius, (1 Century B.C.E.) employed a crude version of natural selection to argue that different species have populated the world at different times. He believed that organisms appeared by spontaneous generation, and those not suited for survival perished. Spontaneous generation—the view that new organisms arise directly from nonliving substances rather than from living ancestors. Theories of organic evolution largely fell out of favour and circulation until the time of Galileo and the scientific th th revolution when they began to re-emerge, especially in France in the 17 and 18 centuries, e.g., Jean-Baptiste de Lamarck. In the late 1700’s, Erasmus Darwin, a physician and naturalists – grandfather to Charles Darwin – wrote “would it be too bold to imagine that all warm-blooded animals have arisen from one living filament?”. In 1858-59, Charles Darwin and Alfred R. Wallace independently concluded that evolution by means of natural selection is responsible both for the diversity of living things and for their good fit with the environment. Evolution is a dynamic or active process. Malthus noted that human populations grow geometrically, but the food supply grows more slowly. Therefore, “there is not enough food to go around—so some people survive, but most die”. Darwin “proposed the conditions for—and the mechanism of—evolutionarychange” (Kardong 2008). His explanation for the way in which evolution occurs was based on four observations and three deductions: Observation 1 The numbers of all organisms tend to increase exponentially. Observation 2 Yet on the whole their numbers remain more or less constant. Deduction 1 Therefore there must be a struggle for existence - some organisms survive, others die. Observation 3 Organisms vary - some are better adapted to their environment than others. Deduction 2 Therefore in the struggle for existence it will be these that tend to survive - there is Natural Selection.* Observation 4 Much of this variation is inherited. Deduction 3 Therefore the results of natural selection will accumulate as one generation replaces another - there will be evolutionary change. The modern theory of evolution is often called neo-Darwinian: Darwinian because it uses Darwin’s idea of natural sele
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