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		Quiz Me!	Introduction to Biology 107
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Last revised: Thursday, September 2, 1999
Reading: Ch. 1 in text

Note: These notes are provided as a guide to topics the instructor hopes to cover during lecture. Actual coverage will always differ somewhat from what is printed here. These notes are not a substitute for the actual lecture!

Copyright 1999. Thomas M. Terry

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What is Biology?

"Biology" is not one science -- it is dozens of different sciences, each with its own set of tools and techniques, theories and questions, puzzles and paradigms. Here are some examples of biological sciences:

• Biochemistry: biological molecules and their interactions; metabolism
• Microbiology: bacteria, viruses, and other microscopic organisms, and their interactions with other organisms
• Botany: plant structure and functions
• Cytology: cell structures and their functions
• Physiology: functions of tissues, organs and organ systems, such as the muscular system, the nervous system, etc.
• Genetics: the mechanisms of heredity, including its molecular machinery (DNA) and its observable consequences (e.g., genetic diseases).
• Evolution: the mechanisms by which populations change over time
• Ecology: the interactions of organisms with each other and their environments.

What is studied in this course, Biology 107?

• First half of the semester: focus in on The Life of the Cell, including introduction to biochemistry and cytology.
• Second half the semester: focus is on Animal Physiology and Anatomy, including dissection of fetal pig (lab) and thorough study of human organ systems.
• Biology 108 surveys Botany, Genetics, Evolution, and Ecology.

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Cells have evolved two basic architectural plans

1. Cells without a nucleus = Prokaryotes (procaryotes)
   • include the Bacteria and Archaea [Image: electron micrograph of E. coli bacteria]
   • generally unicellular
   • the earliest and still most abundant life forms; evolved ~ 4 billion years ago
   • generally very small
   • some species highly evolved pathogens: e.g. Yersinia bacteria (cause of bubonic plague, the "Black Death"
   
   Image drawn by Thomas M. Terry for The Biology Place. Used with permission.
   
2. Cells with a nucleus = Eukaryotes (eucaryotes)
   • include the Animals, Plants, Fungi, and Protists
   • some unicellular, some multicellular forms
   • evolved ~ 1 billion years ago
   • size ranges from tiny yeasts to giant sequoias, dinosaurs [Image: electron micrograph of yeast cells, 84,000x]

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Cellular Basis of Human Life

Each adult human consist of about 10¹³ (10,000,000,000,000) cells. These cells live in a gigantic "commune".

The human body contains over 150 different types of cells. Each cell has a very specialized role. Some examples:

• Unicellular blood cells:
  1. Erythrocytes: red blood cells, RBCs, transport oxygen and carbon dioxide. [Image: electron micrograph]
  2. Phagocytic white blood cells, clean subcellular "garbage" from body.
  3. Lymphocytes: immune system white blood cells responsible for antibody synthesis, "policing" the immune systerm and more. [Image: electron micrograph]
  4. Killer T-cells: a type of lymphocyte involved in destroying "foreign" cells. [Movie: 640K 'mov.' file, from Cells Alive! Web site]
• Multicellular tissue cells:
  1. Liver cells are often used in textbooks as examples of "typical" cells, because they lack specialized structures that make other cells so distinctively recognizable. Actually, liver cells are biochemical specialists, converting thousands of chemicals into other chemicals so that your body can either digest or excrete them. Think "detoxification center" and you'll have a good image of a liver cell.
  2. Fibroblasts: cells that make collagen, the most abundant protein in the body, making up connective tissue. [Image: electron micrograph showing collagen fibers; small spherical shapes are fibroblast cells that produce these fibers]
  3. Neurons: cells responsible for communicating and regulating activities of other cells and tissues. [Image: scanning electron micrograph.]
  4. Striated muscle cells [Image: electron micrograph showing striated muscle fibers; no distinct cells are visible. This tissue is coenocytic = components of many indivual cells are fused together.]
  5. Cardiac muscle cells. These cells, like striated muscle, have distinctive banding patterns of muscle. Unlike striated muscle, cardiac muscle cells contract spontaneously without needing an external nerve signal to initiate contraction. The pacemaker coordinates, but does not cause, these contractions.
  6. Cancer cells. These brain cells have lost their characteristic specialized shapes and functions, the result of cumulative mutations that destroy control of cell division. They have become cancerous, and may continue to grow, producing a tumor and possibly killing their host.

Each cell type has a characteristic lifetime, after which it commits suicide (Apoptosis). Some examples:

1. Neutrophils live about 1 day. [Image: light micrographs, including animation]
2. Intestinal epithelial cells live about 3 days.
3. Red blood cells live about 90 days
4. Neurons live as long as 90 years

Each cell is totally responsible for it's own "housekeeping" duties:

1. maintance and repair
2. acquiring food from blood or lymph
3. disposal of wastes into blood or lymph
4. synthesis and regulation of all its large biomolecules
5. dividing (when allowed to do so), and not dividing unless properly signalled (the alternative is CANCER).
6. carrying out its own specialized tasks, such as: contracting, making antibodies, firing nerve impulses, secreting digestive enzymes, etc.

Each cell must be able to communicate with other cells and respond appropriately to signals that regulate its activity.

Certain specialized cells must undergo a meiotic (sexual) cell division, produce eggs or sperm, and at least one such cell must find a partner if cellular life is to survive this particular individual.

• Egg and attached sperm cells. [Image: electron micrograph]

Each cell must differentiate from one common ancestral cell, the fertilized egg, by a complex process of differentiation and development.

• Initial fertilization events. [Image: light micrographs]
• Developing Human Embryo. [Image: photograph]

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