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BIO152H5 (140)
Chapter 1

Chapter 1 Textbook Notes - Biology and the Tree of LIfe

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University of Toronto Mississauga
Fiona Rawle

Notes From Reading CHAPTER 1:B IOLOGY AND THE T REE OFLIFE PGS .1-18) Key Concepts - Biological science was founded with the development of (1) the cell theory, and (2) the theory of evolution by natural selection. - A phylogenetic tree is a graphical representation of the evolutionary relationships among species. Phylogenies can be established by analyzing similarities and differences in traits. - Biologists ask questions, generate hypotheses to answer them, and design experiments that test the predictions made by competing hypotheses. 1.1 The Cell Theory Where Do Cells Come From? - In the late 1660s, Robert Hooke and Anton van Leeuwenhoek were the first to observe cells Are All Organisms Made of Cells? - A cell is a highly organized compartment bounded by a plasma membrane that contains concentrated chemicals in an aqueous solutions Where do Cells Come From? - The cell theory states that all organisms are made of cells and all cells comes from pre-existing cells - A hypothesis is a proposed explanation - A predication is something that can be measured and must be correct if a hypothesis is valid - Louis Pasteur proved that cells arise from cells and not by spontaneous generation - Because all cells come from pre-existing cells, all individuals in a population of single-celled organisms are related by common ancestry - In a multicellular organism all of the cells present descent from pre-existing cells and are connected 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 What is Evolution? - Evolution means that species are related to one another and can change through time What is Natural Selection? - Natural selection explains how evolution occurs - A groups of individuals of the same species living in the same area at the same time constitute a population Notes From Reading CHAPTER 1:B IOLOGY AND THE TREE OF LIFE(PGS.1-18) - Two conditions must be met for natural selection to occur in a population (1) individuals in the population vary in characteristics that are heritable (2) in a particular environment, certain version of these heritable traits help individuals survive better or reproduce more than do other versions - If certain heritable traits lead to increased success in producing offspring, 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 - In artificial selection, individuals in a population are selected for mating based on particular traits. Repeating this process over generations results in changes in the characteristics of a domesticated population over time - Fitness is the ability of an individual to produce offspring - Adaptation is a trait that increases the fitness of an individual in a particular environment 1.3 The Tree of Life - The cell theory and the theory of evolution by natural selection imply that all species come from preexisting species and that all species, past and present, trace their ancestry back to a single common ancestor. - Speciation is a divergence process in which natural selection has caused populations of one species to diverge to form new species - The tree of life is a family tree of organisms that describes the genealogical relationships among species with a single ancestral species at its base. Linnaean Taxonomy - Taxonomy is the effort to name and classify organisms. - In Linnaeus’ taxonomic system for classifying organisms, each organism is given a unique two- part scientific name consisting of the genus and the species. (1) A genus is made up of a closely related group of species. (2) A species is made up of individuals that regularly breed together or have characteristics that are distinct from those of other species. Taxonomic Levels - Linnaeus’ system is hierarchical with ne
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