jimtrue.com : school : BSC2010 : CH 01: Intro - 10 Themes in the Study of Life

Posted by Jim True on February 1, 2004 1:44 AM. Last Updated October 22, 2006 9:23 PM

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CH 01: Intro - 10 Themes in the Study of Life

What is Science?

• From the latin "scientia", meaning "having knowledge" or "to know".
• In modern use, we define science as a branch of knowledge.
• Specifically, science is the branch of knowledge that attempts to determine the truth about what makes up our universe and how our universe works. It's a dynamic knowlege -- "always changing based on evidence".
• The level of the universe we wish to study ranges from the galactic to the subatomic.
• In this course we will focus mainly at the cellular and subcellular (molecular) levels.

What is Biology

• the word comes from the Greek root words bios- "life" and ology- "the science of" or "the study of".
• Biology is literally the "science of life".
• Biology involves the study of structures, types and processes of all living things.
• Biology is strongly integrated w/Chemistry and Physics (thermodynamics). The other sciences are direct applications as they relate to Biology.
• Biology is a huge field of study with numerous subdisciplines within it. Biology --> Zoology --> Ichthyology

10 Unifying Themes

• Chapter 1 provides an overview of 10 interconnected themes that unify biological concepts.
• We'll deal with 4 of these in varying degrees in lectures and 5th in the laboratory. The text refers to these as:
  1. Emergent Properties
  2. Cell Structure
  3. Heredity
  4. Regulation and Energy
  5. Scientific Inquiry

Emergent Properties

• Every organism has some level of structural complexity.
• There is a hierarchy, which are levels of organization increasing in complexity.
• At each new level (step) of complexity, new characteristics are exhibited ("emerge") that were not present in the higher level.
• In this course, we will remain at the lower levels of complexity.
• Molecule -- group of atoms that together form a single particle.
• Organelle -- subcellular components that perform specific functions for cells.
• Cell -- Organized assembly of molecules that forms the basic unit of life.
• Tissue -- aggregation of similar cells that together form a specific function (Biology II) Figure 1.2, p.3

Properties of Life

• The cell is the basic unit of life, possessing all or many of the basic characteristics of life, including:
  • Order, arises from the complex organization that is a cell
  • Presence of one or more cells. Viruses are "not living"; they have no cellular structure. They do not grow or metabolize; they do reproduce, but only by changing another cell to make copies of themselves.
  • Reproduction and heredity -- each cell or organism produces its own kind from a master set of organic "blueprints" (DNA)
  • Growth and Development -- (these are not the same) Increase in the size of the cell &/or the overall organism (Growth), accompanied by changes in structure and function (Development) Figure 1.3, p.5
  • Use of Energy -- Metabolism (major theme); physical use of energy. All metabolic activities require continuous input of energy. Metabolism is the subtotal of collective chemical/physical processes that provide or use energy. To be alive, we require continuous input of energy.
  • Response to environment -- Environment is the aspects of the surrounding of an organism, both internal and external. Responses vary in their rapidity and also the structural level at which they occur.
  • Homeostatis (homeo -- like or resembing, stasis -- standing) -- ability to regulate internal conditions within a narrow range. (ie Shivering or sweating are examples of Thermal Regulations). The more advanced the organism, the more numerous and complex the homeostatic mechanisms. eg thermal regulation in mammals.
  • Evolution (via ("by way of") adaptation -- changes in organisms in response to environmental changes (adaptation) cause them to change into new and different types of organisms (evolution) [Will primarily discuss in Biology II]

Cell Theory and Structure

• Cells were first described and named by Robert Hooke in 1665.
• He examined a slice of tree bark containing cork cells, which look very much like little open boxes. He termed the structures cellulare, Latin for "little rooms".
• It was not until the late 1830's that cells were considered to be the fundamental unit of life.
• Since then, this finding and two others have been combined to form modern cell theory, which includes the following concepts:
  1. Cells are the basic unit of life,. At least one cell must be present in order for the organism to be considered alive.
  2. All cells arise from pre-existing cells.
  3. All cells arose from a common ancestral type.
• Even though life on this planet is diverse, all life forms are based on just two cell types.
• the simplest cell type is the prokaryotic cell, which is small and lacks much internal structure. The DNA molecule is present, but does not have its own membrane separating it from the rest of the cell. In other words, prokaryotic cells lack a nucleus. Figure 1.4, p.6 Tidbit: 70% of what you eliminate as solid waste is bacteria.
• All organisms with prokaryotic cells are unicellular ("uni" -- one). We refer to these as bacteria. The cell IS the organism.
• The second cell type is the eukaryotic cell.
  • Much more internally complex.
  • Separate membrance around the DNA, called the Nucleus
• Eukaryotes include both uni-- and multicellular forms. Our largest and most familiar organisms, animals and plants, have eukaryotic cells.
• We'll deal with cell structure in chapters 7 & 8.

Heredity

• regardless of cell type, all living organisms have a fairly simple but quite large molecule present in each cell. It is deoxyribonucleic acid or DNA.
• the overall size and number of DNA in a cell depends on the organism.
• Its function is to act as a "blueprint" of life that provides instructions for each cell tell the cell:
  • What is is
  • How it functions
  • when and how to reproduce itself
• Heredity refers to the transmission of this information from one individual to the next individual in a generation; the transmission of the "blueprints" to each new cell. Figure 1.5, p.6
• We will examine the concepts of cell replication and reproduction in chapters 12 & 13, heredity and genetics in Chapters 14 & 15, and DNA structure and function in Chapters 16 & 17.

Regulation and Energy

• Metabolism in living things involves billions of different chemical reactions taking place at different rates and in different locations.
• All are regulated to some degree by special proteins called enzymes through a series of feedback mechanisms.
• Feedback means that the product of a reaction controls:
  • whether the reaction is accelerated (positive feedback)
  • or slowed/stopped (negative feedback) Figure 1.8, p.9
• We will examine basic metabolic and energy related concepts in Chapter 6.
• We will then relate it to two of the most significant metabolic processes or energy conversion (Cellular Respiration and Photosynthesis) in Chapters 9 & 10. Animals perform Cellular Respiration; plants perform Photosynthesis.

Scientific Inquiry

• We will cover this mainly in the laboratory, but Scientific Inquiry refers to the way in which scientists attempt to answer questions about all aspects of our universe.
• This is an outgrowth of our insatiable curiosity. We all want to know how and why things are the way they are. Figure 1.19, p.17

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