Chapter 1 Biology and the Tree of Life

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Mark Huyler

Chapter 1: Biology and the Tree of Life  1.1 What Does it Mean to Say That Something is Alive?  Organism: life-form, a living entity made up of one or more cells. Five fundamental characteristics  Energy: To stay alive and reproduce, organisms acquire and use energy  Ex. Plants absorb sunlight; Animals ingest food.  Cells: Made up of membrane-bound cells.  Membrane regulates passage of materials between exterior and interior spaces.  Information: Process hereditary or genetic information, this kind of genetic information is encoded along with the information acquired from the environment in genes.  Replication: everything in organism contribute to replicating itself.  Evolution: Products of evolution, population continues to evolve.  1.2 The Cell Theory  Two fundamentals: Cell Theory and Theory of Evolution  Theory: explanation for a very general phenomena or observations  They explained that organisms are cellular & populations change over time.  Cell Theory:  1665 Robert Hooke examines cork with *30 microscope---cells  200 years of work, cells.  Anton van Leeuwenhoek: 300* microscope  Observed human blood cells and sperm cells.  1670s, researcher conclude large leaves are composed of many individual cells  1800s, enough data: All Organisms Consist Of Cells  Bacteria: smallest organisms  <80 nanometers/ 80 billionths of a meter  Single-celled  Cell: a highly organized compartment that is bounded by a thin, flexible structure called a plasma membrane.  The plasma membrane contains concentrated chemicals in an aqueous solution.  Two components of scientific theories:  1. Describes a pattern in the natural world.  2. Identify a mechanism or process that is responsible for creating that pattern.  All organisms are made of cells, and all cells come from preexisting cells.  Where do cells come from?  Two hypotheses: proposed explanation  1. Spontaneous generation  Bacteria in spoiled food  2. All-cells-from-cells  Prediction: can be measured, must be correct if a hypothesis is valid.  Louis Pasteur:  Two treatment groups:  1. A broth that was not exposed to a source of preexisting cells  2. A broth that was exposed to a source of preexisting cells.  One hypothesis supported: All cells common ancestry  1.3 The Theory of Evolution by Natural Selection  What is Evolution? (act on populations)  Has pattern and process  Pattern: proposed by Darwin and Wallace.  1. Species are related by common ancestry. Unlike what most people believed at that time that species are independent entities created separately by God.  2. Characteristics of species can be modified from generation to generation.  “descent with modification”---Darwin  Evolution is a change in the characteristics of a population over time.  Species are not independent and unchanging entities, but are related to one another and can change through time.  What is Natural Selection? (act on individuals)  Process: natural selection with 2 conditions.  1. Individuals within a population vary in characteristics that are heritable-traits that can be passed on to offspring.  Population: group of individuals of the same species living in the same area at the same time.  2. In a particular environment, certain versions of these heritable traits help individuals survive better or reproduce more than do other versions.  Some heritable traits increased success in producing offspring more common in the population.  Selection on Maize as an Example  Artificial selection: changes in populations that occur when humans select certain individuals to produce the most offspring.  1896, researchers long-term selection experiment on maize.  Individual maize differed in the percentage of protein.  Parents pass the trait of kernel protein to offspring.  Researchers chose the ones with the highest protein contents to be parents
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