BIO 172January 9, 2019Intro and Scope of BiologyReadings 1.1-1.41. The scientific method is a deliberate way of asking and answering questions about the natural world.2. Life works according to fundamental principles of chemistry and physics.3. The fundamental unit of life is the cell.4. Evolution explains the features that organisms share and those that set them apart.5. Organisms interact with one another and with their physical environment, shaping ecological systems that sustain life.6. In the 21st century, humans have become major agents in ecology and evolution. Biology: The science of how life works Biologists: Scientists who study life 1.1 The Scientific Method Observation: the act of viewing the world around us.  Allows us to draw tentative explanations called hypotheses.- Hypothesis: A tentative explanation for one or more observations that makes predictions that can be tested by experiments or additional observations. Experimentation: is a disciplined and controlled way of asking and answering questions about the world in an unbiased manner. Variable: The feature of an experiment that is changed by the experimenter from one treatment to the next. Test Group: The experimental group that is exposed to the variable in an experiment. Control Group: The group that is not exposed to the variable in an experiment. Scientific Method: A deliberate, careful, and unbiased way of learning about the natural world (Observations, Hypothesis, Predictions, Experiments or New Observations, Theory) Theory: A general explanation of a natural phenomenon supported by a large body of experiments and observations (ex: Evolution). 1.2 Chemical and Physical Principles Four key characteristics of living organisms:  (1) complexity, with precise spatial organization on several scales (2) the ability to change in response to the environment (3) the ability to reproduce (4) the capacity to evolve. The living and nonliving worlds share an important attribute:  Both are subject to the basic laws of chemistry and physics. But the relative abundances of elements in organisms differ greatly from those in the nonliving world.- Universe: hydrogen and helium make up more than 99% of known matter, while Earth’s crust contains mostly oxygen and silicon, with significant amounts of aluminum, iron, and calcium.- In organisms, by contrast, oxygen, carbon, and hydrogen are by far the most abundant elements - Carbon = backbone of life First Law of Thermodynamics The law of conservation of energy: Energy can neither be created nor destroyed—it can only be transformed from one form into another. Second Law of Thermodynamics The principle that the transformation of energy is associated with an increase in the degree of disorder in the universe. Entropy (S) The degree of disorder in a system. Heat corresponds to the motion of small molecules:- The greater the heat, the greater the motion, and the greater the motion, the greater the degree of disorder. - Therefore, the release of heat as organisms harness energy means that the total entropy for the combination of the cell and its surroundings increases, in keeping with the second law. Can living organisms arise from nonliving organisms? Background: Until the 1600s, many people believed that rotting meat spontaneously generates maggots (fly larvae). Hypothesis: Francesco Redi hypothesized that maggots come only from flies and are not spontaneously generated. Conclusion: The presence of maggots in the open jar and the absence of maggots in the gauze-covered and sealed jars supported the hypothesis that maggots come from flies and allowed Redi to reject the hypothesis that maggots are spontaneously generated. Can microscopic life arise from nonliving organisms? Background: Educated people in Pasteur’s time knew that microbes grow well in nutrient-rich liquids like broth. It was also known that boiling would sterilize the broth, killing the microbes. Hypothesis: Pasteur hypothesized that if microbes were generated spontaneously fromnonliving matter, they should reappear in sterilized broth without the addition of microbes. Conclusion: The presence of microbes in the straight-neck flask and the absence of microbes in the swan-neck flask supported the hypothesis that microbes come from other microbes and are not spontaneously generated. Redi’s and Pasteur’s experiments demonstrated that living organisms come from other living organisms and are not generated spontaneously from chemical components. 1.3 The Cell The simplest self-replicating entity that can exist as an independent unit of life. All contain a stable blueprint of information in molecular form. - Nucleic acids store and transmit information needed for growth, function, and reproduction. Deoxyribonucleic Acid (DNA): A linear polymer of four subunits; the information archive in all organisms. The information encoded in DNA directs the formation of proteins: The key structural and functional molecules that do the work of the cell, providing structural support and catalyzing chemical reactions. The term “protein” is often used as a synonym for “polypeptide.”- How does the information stored in DNA direct the synthesis of proteins?  First, existing proteins create a copy of the DNA’s information in the form of aclosely related molecule called ribonucleic acid, or RNA (A molecule chemically related to DNA that is synthesized by proteins from a DNA template).  The synthesis of RNA from a DNA template is called transcription, a term that describes the copying of information from one form into another.  Specialized molecular structures within the cell then “read” the RNA molecule to determine what building blocks to use to create a protein.  This process, called translation (synthesis of a polypeptide chain corresponding to the coding sequence present in a molecule of messenger RNA), converts information stored in the language of nucleic acids to information in the language of proteins.- The pathway from DNA to RNA (specifically to a form of RNA called messenger RNA, or mRNA) to protein is known as the central dogma of molecular biology.- Gene: The unit of heredity; the stretch of DNA that affects one or more traits in anorganism, usually through an encoded protein or noncoding RNA.- Replication: The process of copying DNA so genetic information can be passed