BIOLOGY: The study of life.

What is Biology? Biology is the study of living things. The word comes from two Greek words, bios (meaning life), and logos ( meaning the study of ). Usually we think of Biology as one part of a science curriculum, a course that satisfies one of your science requirements. So that brings up the question, what is science? Science can be defined as a body of knowledge (about anything and everything) and a logical, organized method of study. Biology is one of the two major divisions of science, physical science and biology.

The physical sciences study the non-living world around us. Some typical divisions of the physical sciences include: chemistry, physics, meteorology, astronomy, geology, and oceanography.

Biological sciences include (but are not limited to) such things as:

Click here to Go to quiz 1
 
 

Characteristics of Living Things

What are living things? How do we know if something is alive or not? Let's examine the characteristics of living things.

We use the term organism when describing a complete and entire living thing.

1. Organisms are made of cells. The number of cells may vary greatly, but the size of the cells and types of cells are fairly uniform in all living organisms. Cells are both structural and functional. That means that they are used as building blocks, but also perform other functions as well. Viruses, which have some of the other characteristics of life, are not made of cells, and

2. Organisms are highly organized. They may contain thousands of substances. They manufacture complex chemicals such as proteins, carbohydrates, and fats in their cells.

3. Organisms use energy. We must have a constant supply of energy or we die. This energy is obtained from food molecules that are either made, eaten, or absorbed by the organism and then stored until needed. The chemical processes used in building up and tearing down food molecules to get and use energy are referred to as metabolism.

4. Organisms grow and develop.

  5. Organisms have a lifespan. Typical Lifespans: 6. Organisms reproduce 7. Organisms respond to stimuli. 8. Organisms adjust to their environment. Environment is defined as an organism's surroundings.

An adaptation is a change that makes it better suited to its environment.

• Short term adaptation - fur changes color in the arctic fox during winter.

• Long term adaptation - changes occur over many generations and are inherited.

• Variation - normal differences that exist among individuals.

• Homeostasis - a self-adjusting balance of life functions. (heartbeat, respiration, temperature)
 

Click here to go to Quiz 2



ORGANIZATION OF LIVING THINGS
 

• Atoms - the building blocks of all matter, (the smallest unit of an element.)

• Elements - the simplest form of matter. They cannot be broken down chemically.

• Molecules - two or more atoms combined chemically (the smallest unit of a compound)

• Cells - the smallest unit of a living thing.

• Organelles - structures within cells that perform specific functions.

• Tissues - a group of similar cells that perform a similar function. (muscle tissue, bone tissue, skin tissue)

• Organs - a group of tissues that work together to perform a specific task. (brain, stomach, heart, etc.)

• Systems - a group of organs that work together to perform a specific task. (skeletal system, digestive system, etc.)
  • Organisms- complete, entire living things may exist as single cells, as simple organisms with tissues but no organs, or they may have organs that are not organized into organ systems. However, most organisms are made up of several organ systems.
    •  Some organisms are colonial; they consist of cells that live in groups, but are separate organisms.


    Groups of Organisms:
     

    • Population - a group of organisms of the same species in a particular place at a particular time. (organisms that can interbreed)

    • Communities - different populations that live in the same area. (all the living things)

    • Ecosystems - a community of living things and its non-living environment.

    • Biomes - a large geographic area that has the same major forms of life. (due to geography and climate)

    • Biosphere - all the ecosystems on the earth. (all the life-supporting environments and all the organisms that inhabit them.) Most live on or near the surface of the earth.

         Go to quiz 3 and arrange the items in order.

    Go to the multiple choice quiz 3b

     



    THE SCIENTIFIC METHOD -- a logical, organized method of study

    Steps of the scientific method:

    1. Define the problem - This is usually a question. Example: "Does acid rain affect the development of salamanders?"

    2. Collect and organize information - Research library information on:

    • Salamanders, acid rain, acids and bases, etc.
    • Sources could include: books, journals, internet articles, etc.
          3. Form a Hypothesis (educated guess or tentative explanation)
        The hypothesis is a statement that can be tested. • Example: "Salamanders that develop under acid rain conditions show a greater number of
      developmental abnormalities than salamanders that develop in unpolluted waters."
          4. Test the hypothesis - EXPERIMENT
         Controlled experiment - all the conditions are alike except the condition being tested.  
    • VARIABLE - the one condition that is tested

    • The EXPERIMENTAL GROUP is exposed to the variable.

    • The CONTROL GROUP is raised under normal conditions, without the variable.

    • Only one variable may be tested at a time.
     

     5. Observe and record. Measurements are important. Always rely on facts not comparisons. The scientist may use drawings, tables, graphs, diagrams, photographs, written observations, or sound recordings.

    6. Drawing Conclusions

  • Conclusions are based on DATA (facts)
  • Statistics may be used to evaluate data.
  • If a hypothesis is proven to be true over and over it may be called a law or principle.
  • If a hypothesis seems to be true but is unable to be directly tested, it becomes a theory.
  • Theories and laws may have to be replaced as new evidence becomes available.
    •

    Go to quiz 4 and arrange the items in order.
     
     

    USING THE SCIENTIFIC METHOD:

    We can look back in history to see how controlled experiments were used to prove or disprove theories, hypotheses, and/or superstitions. Let's examine the controversy over spontaneous generation. Spontaneous generation, or abiogenesis, was a belief that living organisms could develop from nonliving materials.

    Examples of Spontaneous generation (or abiogenesis):

      

    Francesco Redi set out to disprove the belief that flies come from decaying meat. He believed that flies developed from eggs laid by other flies that land on the meat.

    • He filled 2 sets of jars with meat (veal, snake, fish, eel).

    • He sealed 1 set (the experimental group), and left other jars open (the control group).

    • As he predicted flies developed in the open set, but not in the sealed jars.

     Supporters of spontaneous generation argued that his experiment was flawed. There were two variables. The sealed jars not only kept out flies, but also oxygen. They claimed that the flies could not develop because of the lack of air.

    So Redi performed his experiment again with screens on one set of jars instead of sealing them. Again the results were the same, the meat in the open jars developed flies, but not the jars with screens.
     
     

    John Needham tried to prove that microorganisms develop from boiled mutton (lamb) broth, and claimed to have succeeded. He had boiled a mutton broth to kill all organisms and then let them sit, loosely stoppered, to allow air to enter. After a period of time, he examined the jars and found microorganisms had indeed grown in the jars.

    Lazzaro Spallanzani challenged Needham's results, saying his experiment was flawed because:

     So Spallanzani repeated Needham's experiment, boiling longer and sealing better. His jars grew no organisms. Critics of Spallanzani said he boiled so long that he killed the food value of the broth. However, Spallanzani opened the jars and exposed them to microorganisms and showed that microorganism grew well in the jars that were boiled longer.
     
     

    Pasteur Settles the Question (The Swan-necked Flask Experiment)
    Louis Pasteur (of Pasteurization fame) boiled a broth in open flasks whose necks had been bent into an S-shaped curve. This allowed air to enter the flask but trapped dust particles in the lower part of the curve. No microorganisms developed until he tipped the flask and allowed dust into the broth. This final experiment from Pasteur, who would later be known as the Father of Bacteriology, put an end to the belief in spontaneous generation.

    The prevailing theory on where living things come from is called Biogenesis. This means that life comes from other living things by reproduction.
     
     

    A case study in Science

    Read the section in your textbook about the discovery of the cause of malaria. It begins on page 11 in your textbook.
     

    Not all discoveries are made by scientists who have looked for the answer to a problem. Sometimes discoveries are almost accidental. Do some research on Alexander Fleming and his famous accidental discovery.
     
     

     Go to the multiple choice practice quiz 5.  

    Read the investigation in your textbook on page 22-23. Do the procedure on yourself, and then compare results with your classmates. Record your data on the blackboard and record other's data as they add theirs to the board.


    The Biologist's Most Important Tool


     


    The most important tool ever invented for biologist has to be the microscope. The first simple microscopes, magnifying glasses, were used to look at all sorts of things. One biologist, Anton van Leeuwenhoek, made over 250 different kinds of simple microscopes to look at different things. But it was the invention of the compound microscope that really made the difference. A compound microscope uses two lenses to magnify the image. The eyepiece, or ocular lens, usually magnifies about 10 times (10x). The other lens, the one closest to the object being viewed is called the objective. The first compound microscope was invented by two Dutch lensmakers, the Janssen brothers. Modern compound microscopes usually have more than one objective mounted on a revolving nosepiece that that the objectives can be changed. A typical arrangement uses a low-power objective that magnifies 4X, a medium-power objective that magnifies 10X, and a high-power objective that magnifies about 40X. The total magnification is found by multiplying the ocular lens times the objective lens being used at the time. So a person using the medium-power lens would see an image magnified approximately 100 times. Magnification, the apparent increase in an object's size when view through the lens, is limited. The maximum that most modern compound microscopes can magnify is somewhere between 1000X and 1500X. As the light rays are spread apart by the lens during magnification the image becomes dimmer and less clear. Thus, the larger the magnification, the less resolution (clear, detailed image) is obtained.

    See the diagram of the compound microscope for a complete list of parts.
     
     

    In modern times, the electron microscope has broken the magnification barrier. Using electrons and electromagnets instead of light and lenses, the electron microscope is able to magnify hundreds of thousands of times. There are two major types of compound microscopes, the scanning electron microscope, and the transmission electron microscope. The scanning electron microscope magnifies less but gives a 3-dimensional image of the object viewed. The transmission electron microscope gives greater magnification, but sees only a 2-dimensional image of very thin slices of tissue.
     

    See your teacher for a lab exercise on using the microscope.

    Go to the multiple choice practice quiz 6.

    Go to the microscope quiz 7.

    Go to the completion question quiz 8.

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