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Chapter 1

Chapter 1 BIOL 1M03 (Textbook Notes)

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Jon Stone

CHAPTER 1 – BIOLOGY AND THE TREE OF LIFE 1.1 WHAT DOES IT MEAN TO SAY THAT SOMETHING IS ALIVE?  Organism: a life form; a living entity made up of one or more cells  Organisms share five fundamental characteristics o Energy: to stay alive and reproduce, organisms have to acquire and use energy o Cells: organisms are made up of cells; cell’s membrane regulates the passage of materials between exterior and interior spaces o Information: organism process hereditary or genetic information, encoded in genes, along with information they acquire from the environment o Replication: almost everything an organism foes contributes to one goal: replicating itself o Evolution: organisms are the product of evolution and their populations continue to evolve 1.2 CELL THEORY  Theory: an explanation for a very general class of phenomena or observations  Cell theory and theory of evolution address fundamental questions: What are organisms made of? Where do they come from? o Established two of the five attributes: organisms are cellular and their populations change over time  Robert Hooke used a crude microscope to inspect the structure of cork; microscope magnified to just 30x but allowed Hooke to see small, pore-like compartments that were invisible to the naked eye; came to be known as cells  Anton can Leeuwenhoek developed a more powerful microscope, magnifying up to 300x; he inspected pond water and made the first observation of human blood cells and of sperm cells  Cell: a highly organized compartment that is bounded in a thin, flexible structure called a plasma membrane and that contains concentrated chemicals in an aqueous solution; chemical reactions that sustain life take place inside cells o Capable of reproducing by dividing  Scientific theories have two compartments o First describes a pattern o Second identifies a mechanism or process that is responsible for creating that pattern  Cell theory: all organism are made of cells, and all cells come from pre-existing cells o Contrary to the prevailing explanation, spontaneous generation hypothesis, that organisms arise spontaneously under certain conditions  Hypothesis: a proposed explanation  All-cells-from-cells hypothesis stated that cells do not spring to life spontaneously but are produced only when pre-existing cells grow and divide  Louis Pasteur conducted an experiment to test which hypothesis was correct, where he created two treatment groups: broth that was not exposed to a source of pre-existing cells and a broth that was o Spontaneous hypothesis stated that cells would appear in both while the all-cells-from- cells stated that cells would only appear in the broth exposed to pre-existing cells (the flask without the swan neck) o Spontaneous hypothesis was rejected while the other was maintained o Effective because there was only one difference between the two treatments  If all cells come from pre-existing cells, all individuals in an isolated population of single-cells organisms are related by common ancestry 1.3 THEORY OF EVOLUTION BY NATURAL SELECTION  Darwin and Wallace made two claims o Species are related by common ancestry (contrasted with the view that species represent independent entities created separately by a divine being) o The characteristics of spe
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