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Chapter 1- Biology and the Tree of Life

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Boston College
BIOL 2000

Stephen Cheng Professor Danielle Taghian Molecules&Cells 4 September 2013 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. 5 Fundamental Characteristics of Organisms: 1. Energy: organisms have to acquire & use energy 2. Cells: a membrane-bound units, which organisms are made up of 3. Information: organisms process hereditary/genetic information, encoded in genes (along with info they acquire from environment). a. Genetic info make molecules that keep you alive 4. Replication: ultimate goal of organism is to replicate itself 5. Evolution: organisms are product of evolution, population continues to evolve 1.2 The Cell Theory Theory – explanation for a very general class of phenomena/observations Robert Hooke (1665) – Used a crude microscope examine cork and gave the pore-like compartments the name cell. Anton van Leeuwenhoek – developed more powerful microscope, and looked at blood cells, sperm cells. *By early 1800s enough data had accumulate for biologist to claim that all organism consist of cells. Hooke and Leeuwenhoek saw this pattern where all organisms had cells. a. Are All Organisms Made of Cells? Cell – highly organized compartment that is bound by a plasma membrane and contains concentrated chemicals in aqueous solution Scientific Theories – have 2 compartments 1. Describes a pattern in natural world 2. Identifies mechanism/process responsible for creating that pattern Rudolph Virchow – said all cells arise from preexisting cells Cell Theory –All organisms are made of cells, and all cells come from preexisting cells. i. Two Hypotheses Spontaneous Generation – organisms arise spontaneous under certain conditions. -(this was the prevailing explanation of where cell come from) Hypothesis – a proposed explanation. -Used to refer to explanation for more tightly focused questions. Theory – refer to proposed explanation for broad patterns in nature. ii. An Experiment to Settle the Question Louis Pasteur – created an experiment to prove all-cells-from-cells hypothesis. -Abroth no exposed to preexisting cells and a broth that was. Prediction – something that can be measured & must be correct if hypothesis valid. iii. One Hypothesis Supported Chemical Evolution – life did arise from nonlife early in Earth’s history *All cells in multicellular organism are connected by common ancestry. Charles Darwin &Alfred Russel Wallace – all species connected by common ancestry. 1.3 The Theory of Evolution by Natural Selection a. What is Evolution? Theory of Evolution by Natural Selection – 2 parts 1. Species are related by common ancestry 2. Characteristics of species can be modified from generations to generations a. By the process “descent with modification” (Darwin) Evolution – a change in the characteristics of a population over time b. What is Natural Selection? Natural Selection –
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