Introduction: The Themes in the Study of Life Chapter 1

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					           Exploring Life
               Chapter 1




General Biology – Science Majors I – 1406
                 What is Biology?


• Biology is the science of life and of living organisms,
  including their structure, function, growth, origin,
  evolution, and distribution.
                  Unifying Themes


Three Major Groups:

          1. Exploring Life on Its Many Levels

          2. Evolution, Unity, and Diversity

          3. The Process of Science
1. Exploring Life on Its Many Levels
    Hierarchy of Biological Organization
2. Emergent Properties of Life

                       Reproduction

                •  All organisms are capable
                  of reproducing and passing
                  their genetic material to
                  their offspring.
                • Organisms reproduce only
                  their own kind.
                • Life comes only from life.
           Emergent Properties of Life


   Growth and Development

• All organisms are capable of
  growing.

• DNA directs the pattern of growth
  and development of an organism.
Emergent Properties of Life

                  Utilization of Energy

             • All organisms use energy
               and transform it in order to
               do work.
                – Ex: Plants take in energy from
                  the sun and transform it into
                  chemical energy.
                – Ex: Bat gets its energy from
                  the nectar from the saguaro
                  cactus, and use it to fly and
                  carry out its nocturnal
                  activities.
Emergent Properties of Life

                      Homeostasis

              • Organisms maintain
                relatively constant internal
                conditions different to their
                environment through
                regulatory mechanisms
              • The blood vessels of the
                jackrabbit regulate the loss
                of heat to its environment.
           Emergent Properties of Life


 Evolutionary Adaptation

• Organisms adapt to their
  environment.
• This white-tailed ptarmigan
  has evolved white plumage
  and it is almost invisible
  against the snow. This
  adaptation protects it from
  predators.
              Cells the Basic Units of
               Structure & Function

                          The Cell Theory

Three Basic Principles:

   1. All organisms are made up of one or more cells
   2. Cells are the smallest unit of life
   3. Cells come from preexisting cells
Two Types of Cells

             • Prokaryotic Cells
                – Bacteria
                – Archaea bacteria
             • Eukaryotic Cells
                – All other organisms are
                  composed of eukaryotic
                  cells:
                    • protists
                    • fungi
                    • plants
                    • animals
                Continuity of Life – DNA

                 DNA

• DNA (Deoxyribunucleic Acid) is the
  hereditary blueprint in each cell of all
  living organisms.
• Double helix
• The two strands are held together by
  a base pairing.
• Biological instructions are encoded
  in the DNA
• DNA carries the units of inheritance
  that transmit information from
  parents to offspring.
Structure and Function



            • Structure and function are
              correlated at all levels of
              biological organization.

            • Birds have hollow bones
              which provide a strong
              lightweight skeleton.
Organisms Interact with their Environment




• Organisms are open systems that exchange materials and
  energy with its surroundings.
Regulatory Mechanisms

            •   Many biological processes are
                self regulating. They operate by
                a mechanism called feedback.

            •   The product of the process
                regulates the process.


            Two kinds of feedback:
               1. Positive feedback speeds up
                   the process
               2. Negative feedback slows
                   down or stops the process
              The Kingdoms of Life
              (Carl Woese, University of Illinois)

                   Common Ancestor


  Bacteria Archaea                          Eukarya (3 Domains)



Eubacteria Archaebacteria      Protista Plantae Fungi Animalia



                            (Six kingdoms)


           (Ref: Life the Science of Biology, 5th Edition, 1998)
             3. How do we do Science?

                    Scientific Methodology
1. observations and make generalizations
2. generate a question (s)
3. generate a hypothesis (tentative statement about the natural
   world)
   •   formulate a testable prediction
4. design an experiment to test the prediction
   •   if statistical analysis shows significant difference between the
       control group and the experimental group, your hypothesis is
       accepted, otherwise it is rejected
5. if rejected, then modify the hypothesis and repeat steps 3
   and 4
               What is a Hypothesis?


Commonly
  – A hypothesis is an idea of “how things work”.



Formally
   – A hypothesis is a tentative answer to some question.
          How do we test a hypothesis?


• Hypothesis testing is based on deductive reasoning.

• Deductive reasoning involves making a specific prediction
  about the outcome of an action and is based on observable
  facts.

• Thus, deductive reasoning takes the “if/then” statements.
How Do We Test a Hypothesis?



• We test the hypothesis by
  performing the experiment to
  see whether or not the results
  are as predicted.
                 Experimental Method

Experiments are designed to test hypotheses.

   – Controlled Experiments
       • Control Group – data from a control group are used as baseline
         values for comparison to the measurements of the experimental
         group.
       • Experimental Group – data from the experimental group are
         compared against the control group and determine whether the
         hypothesis being tested is accepted or rejected.

   Example of an unbiased experimental design:
      • Double-blind experiments
              Double-Blind Experiments




• Results from double-blind experiments produce more objective data.
                    Analysis of the Data

• The data that is collected from an experiment must be
  statistically analyzed.
• Statistically significant results indicate that there is a 5%
  probability or less that the results may be due to chance alone.
• Types of statistical analysis include:
   –   Correlation between two variables
   –   Analysis of Variance
   –   t-test
   –   Multivariate tests
• If the results of the statistical analysis do not support the
  hypothesis, then the hypothesis is rejected.
        Evaluating Scientific Information
                           Primary Sources
• New findings are published in scientific journals for peer
  review.
   – A group of scientists (peers) scrutinize the article before they approve it
     for publication
• Scientific journals contain the most recent and accurate
  scientific information.
• After a hypothesis has been tested extensively and the results
  support the hypothesis then the hypothesis becomes a theory.
• A theory is the highest degree that a hypothesis can ever
  achieve.
   – Ex. Theory of Evolution by Charles Darwin provides a good example
     of how scientific theory grows and wins acceptance.
                      Critical Thinking


• Skepticism – questionable attitude
   – what are the credentials of the individual making the statement?
   – is there verifiable evidence to support the statement?
   – is there a political or monetary incentive behind the statement?

• Most scientists are skeptical about radical findings
   – Ex. Stomach ulcers
      • The scientist who discovered that most stomach ulcers are caused
        by Heliobacter pylori bacteria encountered much ridicule from the
        scientific world because stomach ulcers were believed to be caused
        by stress.
                    Critical Thinking


• The validity of a statement is supported by sound statistical
  analysis.
• Beware of the claims made by nonscientists and even by some
  scientists.
• If the claim states something like “scientific research proved
  that …” be very careful because
   – Scientific studies NEVER EVER prove anything.
   – Scientists conduct research to test a hypothesis, to disprove
      a hypothesis.
   Are there any limitations to science?


Is science limited? YES !!!


• Science is based on testable facts.

• Science cannot be applied to:
   – religious beliefs because they are based on faith
       • faith cannot be tested
   – morals, value judgments, social issues, attitudes, love, or
     supernatural forces
              Science is Self-Correcting


• Science is limited by the ability of the scientists to collect data
  and interpret data.

• New advances in technology have made it possible for science
  to correct misinterpreted data. New interpretation replaces the
  old incorrect information.

   Example:
      • belief that the earth was merely 6000 years old.
      • belief that the sun revolved around the earth.

				
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