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Biology and the Tree of Life

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BIOL 1500
Alexander Mills

Biology 1001 – Textbook Notes # 1 Pages: 12, 13, 40, 41-48 Biology and the Tree of Life Experimental Methods  A good scientific hypothesis makes testable predictions - ^predictions that can be supported or rejected by collecting and analyzing data  It is critical to include control groups - A control checks for factors, other than the one being tested, that might influence the experiment’s outcome  The experimental conditions must be as constant or equivalent as possible  Repeating the test is essential (duplicates and trials)  A good hypothesis is one that is simple, consistent with the available facts  Theory describes some aspect of the natural world with facts using experiments whereas a hypothesis is just a prediction of what you expect to happen in your study Evolution by Natural Selection  The theory of special creation held that: - All species are independent (not related to each other) - Life on Earth is young (6000 years old) - Species are immutable (incapable of change) The Evolution of Evolutionary Thought  The idea that Darwin and Wallace said that species were specially, not naturally created  Typological thinking: is based on the idea that species are unchanging types and that variations within species are unimportant or even misleading Lamarck and the Idea of Evolution  In 1809, he proposed a formal theory of evolution (that species are not static but change through time  Claimed that simply organisms originate at the base of the chain by spontaneous generation and then evolve by moving up the chain over time  Lamarckian Evolution: is progressive in the sense of always producing larger and more complex or “better” species  An individual’s phenotype changes as that individual develop in response to challenges posed by the environment, and these phenotypic changes are passed on to offspring Darwin and Wallace and Evolution by Natural Selection  Process responsible for change through time is evolution - Occurs because traits vary among the individuals in a population, and because individuals with certain traits leave more offspring than others do  Population: consists of individuals of the same species that are living in the same area at the same time  Darwin claimed that instead of being unimportant or an illusion, variation among individuals in a population was the key to understanding the nature of species - ^ called population thinking  The theory of evolution by natural selection was revolutionary for several reasons: - It overturned the idea that species are static and unchanging - It replaced typological thinking with population thinking - It was scientific: it proposed a mechanism that could account for change through time and made predictions that could be tested through observation and experimentation The Pattern of Evolution  Darwin repeatedly described evolution as descent with modification - He meant that species that lived in the past are the ancestors of the species existing today, and that species and their descendant species change through time - ^ Descended species are modified  Theory of evolution: - Species change through time - Species are related by common ancestry Evidence for Change through Time  Fossil: is any trace of an organism that lived in the past - These traces range from bones and branches to shells, tracks or impressions, and dung  Fossil record: consists of all the fossils that have been found and described in the scientific literature  Extant species: those living today  The heat and pressure from being buried in sediment can sometimes cause the tissues of organisms to release hydrogen and oxygen, leaving behind a residue of carbon - This process — which is called carbonization, or distillation — yields a detailed carbon impression of the dead organism in sedimentary rock Geologic Time  Geologic Time Scale: a sequence of named intervals called eons, eras, and periods that represented the major events in Earth’s history  The geologic record indicated that the Earth was much older than 6000 years claimed by advocates of the theory of special creation  Radioactive decay: the steady rate at which unstable or “parent” atoms are converted into more stable “daughter” atoms (furnished a way to assign absolute ages, in years, to the relative ages in the geologic time scale  With information on the decay rate allows researchers to estimate how long ago a rock formed  Earth is about 4.6 billion years old, and the earliest signs of life appear in rocks that formed 3.4-3.8 billion years ago Extinction Changes the Species  Researchers began discovering fossil bones, leaves and shells that were unlike structures from any known animal or plant  Baron Cuvier published a detailed analysis of an extinct species called the Irish elk - Scientists accepted this because this gigantic deer was too large to have escaped discovery  His reasoning was that if species have gone extinct, then the array of species living on Earth has changed through time  Over 99% of species that ever lived are not extinct Transitional Features Link Species  Law of succession: species in the fossil record were succeeded, in the same region, by similar species  Darwin pointed out that it provided strong evidence in favour of the hypothesis that species had changed through time and that they represented ancestors and descendants  Transitional feature: is a trait in a fossil species that is intermediate between those of older and younger species  Evolution of feathers, flight in birds: - Data like these are consistent with predictions from the theory of evolution: if the traits observed in more recent species evolved from traits in more ancient species, then intermediate forms are expected to occur in the appropriate time sequence Vestigial Traits are Evidence  Darwin was the first to provide a widely accepted interpretation of vestigial traits  Vestigial trait: is a reduced or incomple
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