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Chapter 1

Unit 0 - Chapter 1 Bio 1M03 .docx

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James S Quinn

Bio 1A03 Chapter 1: Biology and the Tree of Life Key Concepts  Biological science was founded with these Key Developments: o Cell Theory – proposes that all organisms are made of cells and that all cells come for preexisting cells o The Theory of Evolution by Natural Selection – maintains that species change through time because individuals with certain heritable traits produce more offspring than other individuals do  These developments are unified by the concepts of ancestry and descent o A phylogenic tree is a graphical representation of the evolutionary relationships among species  These relationships can be estimated by analyzing similarities and differences in traits  Species that share distinctive traits are closely related and are placed close to each other on the tree of life  Evolutionary relationships among species (and cells) can be represented by phylogenic trees  How does one “do biology” (ask questions, generate hypotheses and predictions, and conduct experiments to test them)  Theory: An explanation for a very general class of phenomena or observations 1.1 The Cell Theory  Cell – a highly organized compartment bounded by a plasma membrane that contains concentrated chemicals in an aqueous solution o Chemical reactions that sustain life occur in the cell  Cell Theory – states that all organisms are made of cells and all cells come from pre-existing cells o Challenged the hypothesis of spontaneous generation  Within a multicellular individual, all cells are descended from a progenitor cell – the zygote  Hypothesis – a proposed explanation  Prediction – something that can be measured and must be correct if a hypothesis is valid  Louis Pasteur designed an experiment to test whether cells arise from other cells or by spontaneous generation Bio 1A03  Implications of the Cell Theory o Because all cells come from preexisting cells, all individuals in a population of single-celled organisms are related by common ancestry o In a multicellular organism, all of the cells are preexisting cells and are also related by common ancestry 1.2 The Theory of Evolution by Natural Selection  In 1858, Darwin and Wallace proposed that all species are related by common ancestry  Darwin and Wallace also proposed that the characteristics of species can be modified from generation to generation Key Terms  Evolution postulates that o Species are related to one another o Can change through time  Natural Selection – a process that explains how evolution occurs  Fitness – the ability of an individual to produce offspring  Adaptation – a trait that increases the fitness of an individual in a particular environment; the process of a species acquiring fitness-improving traits over time Natural Selection  In order for natural selection to occur you need o Variation o Heritable – traits that can be passed onto offspring o Influences Fitness  Fitness – the ability of an individual to produce offspring  Adaptation – a trait that increases the fitness of an individual in a particular environment  If certain heritable characteristics lead to increased success in producing offspring, the these traits become more common in the population over time  Natural selection acts on individuals, but evolutionary change affects only populations  Evolution occurs when heritable variation leads to differential success in reproduction Artificial Selection  Artificial Selection – individuals in a population are selected for mating bases on particular traits Bio 1A03  Repeating this process over generations results in changes in the characteristics of a domesticated popul
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