1 CHAPTER 1 AN INTRODUCTION TO BIOLOGY

2 Properties of Life Unity  All modern forms of life display a common set of characteristics  Based on biological evolution Diversity  Many types of environments with diverse organisms

3 Seven Characteristics of Life 1. Cells and organization 2. Energy use and metabolism 3. Response to environmental changes 4. Regulation and homeostasis 5. Growth and development 6. Reproduction 7. Biological evolution

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6 Levels of Organization 1. Atoms 2. Molecules and macromolecules 3. Cells 4. Tissues 5. Organs 6. Organism 7. Population 8. Community 9. Ecosystem 10. Biosphere

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8 Evolutionary History Life began on Earth as primitive cells bya Those primitive cells underwent evolutionary changes that gave rise to the species we see today Understanding evolutionary history helps us understand the structure and function of an organism’s body

9 Example Evolutionary change involves modifications of existing structures Structures may be modified to serve new purposes Legs used for walking were modified into a dolphin’s flipper or a bat’s wing

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11 Two mechanisms of evolutionary change 1. Vertical descent with modification  Progression of changes in a lineage  New species evolve from pre-existing species by the accumulation of mutations  Natural selection takes advantage of beneficial mutations

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13 2. Horizontal gene transfer  Genetic exchange between different species  Relatively rare  Genes that confer antibiotic resistance are sometimes transferred between different bacteria species

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15 Tree or web of life? Horizontal gene transfer was an important part of the process that gave rise to modern species Tree of life focuses on vertical evolution Web of life includes the contribution of horizontal gene transfer

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17 Classification Taxonomy is the grouping of species based on common ancestry 3 domains  Bacteria- unicellular prokaryote  Archaea- unicellular prokaryote  Eucarya- unicellular to multicellular eukaryotes 4 kingdoms  Protista, fungi, plantae and animalia

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19 A species is placed into progressively smaller groups that are more closely related evolutionarily Approach emphasizes the unity and diversity of different species Jaguar example

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21 Genomes and Proteomes Genome  The complete genetic makeup of an organism Evolutionary history and relatedness of all living organisms can be illuminated by genome analysis Genomics  Techniques used to analyze DNA sequences in genomes

22 Proteomes  The complete complement of proteins that a cell or organism can make The genome carries the information to make its proteome Proteomics  Techniques used to analyze the proteome of a single species and the comparison of proteomes of different species

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25 Biology as a scientific discipline Science is the observation, identification, experimental investigation, and theoretical explanation of natural phenomena The scientific method is used to test theories Some scientists also gather information

26 Investigate life at different levels Different branches of biology study life at different levels using a variety of tools. As new tools become available, they allow scientists to ask new questions

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29 Hypothesis or theory? Hypothesis  Proposed explanation for a natural phenomenon  Educated guess based on previous observations or experimental studies Example  Maple trees drop their leaves in autumn because of shortened amount of sunlight

30 Hypothesis must make predictions that can shown to be correct or incorrect Additional observations or experiments support or reject a hypothesis A hypothesis is never really proven  We may not have found the true explanation for a phenomenon

31 Theory  Broad explanation of some aspect of the natural world that is substantiated by a large body of evidence  Allows us to make many predictions  Also can never be proved true Due to overwhelming evidence, extremely likely to be true Example  The theory that DNA is the genetic material  Overwhelming body of evidence supports this theory

32 Two key attributes of a theory 1. Consistency with a vast amount of known data 2. Ability to make many correct predictions

33 Understanding biology Curiosity is the key Not a rigid set of steps 2 general approaches 1. Discovery-based science 2. Hypothesis testing

34 Discovery-based science Collection and analysis of data without the need for a preconceived hypothesis Goal is to gather information  Test drugs to look for action against disease  Sequence genomes and proteomes Often leads to hypothesis testing

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36 Hypothesis Testing/Scientific Method Five stages 1. Observations are made regarding natural phenomena. 2. These observations lead to a hypothesis that tries to explain the phenomena. As mentioned, a useful hypothesis is one that is testable because it makes specific predictions. 3. Experimentation is conducted to determine if the predictions are correct. 4. The data from the experiment are analyzed. 5. The hypothesis is accepted or rejected.

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38 Common features Data are often collected in two parallel manners  Control and experimental sample  Differ by only one factor Data analysis  Statistically significant differences  Apply statistical analyses to determine if the control and experimental samples are likely to be different from each other because of the single variable that is different between the two samples

39 If the two sets of data are found not to be significantly different, we would reject our hypothesis. Alternatively, if the differences between the two sets of data are significant, we would accept our hypothesis, though it is not proven

40 Cystic Fibrosis Affects about 1 in every 3,500 Americans Persons with CF produce abnormally thick and sticky mucus that obstructs the lungs and pancreas Average lifespan for people with CF is currently in their mid- to late 30s

, Dorothy Anderson determined that cystic fibrosis is a genetic disorder Discovery-based sciences used to find CF gene 1989, research groups headed by Lap-Chi Tsui, Francis Collins, and John Riordan identified the CF gene

42 CF Gene and Hypothesis Researchers hypothesize that the CF gene encodes a protein that transports chloride ions (Cl - ) across the membrane of cells Led to experiments to test normal cells and cells from CF patients for their ability to transport Cl -  CF cells were found to be defective in chloride transport  Transferring a normal CF gene into cells in the lab corrects this defect

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44 Results support the hypothesis that the CF gene encodes a protein that transports Cl - across the plasma membrane A mutation in this gene causes it to encode a defective transporter protein, leading to a salt imbalance This imbalance affects water levels outside the cell, which explains the thick and sticky mucus in CF patients In this example, hypothesis testing has provided a way to accept or reject an idea regarding how a disease is caused by a genetic change