CAS Biology
1020
Mark Stacey
Evaluation
Tests – 30%
Midterm – 15%
Lab + Assignments – 15%
Final Exam – 40%
Unit 1 – Intro to Biology
• Chapter 1 in text.
• In this chapter, we will overview the biology from
both a historical and scientific viewpoint.
Science
• What is science?
• The word “science” derives from a Latin word meaning
“knowledge”.
• Science is a way to understand the world and how it
works by using the Scientific Method.
• The scientific method works by observing and recording
results and then drawing conclusions that fit the data. By
repeating this process, ideas are tested and
modified/discarded as new evidence comes up.
Biology
• What is biology?
• Biology is the scientific study of life.
• There are many, many different ways to observe,
understand and work with living things.
Life
• What is life? What distinguishes it from non-living
things?
• 1 – Homeostasis – the ability to maintain a steady
internal state while the external environment
changes.
• 2 – Metabolism – the ability to perform chemical
reactions to gain energy and to build new
biological molecules
Life
• 3 – Energy Transformation – the ability to convert
one form of energy to another
• 4 – Growth/Development – the ability to increase
the amount of biological material and thus increase
in size and/or complexity.
• 5 – Reproduction – the ability to produce offspring.
All life as we know it is created from other life.
Life
• 6 – Evolutionary Adaptation – the ability to change
the characteristics of oneself to respond to new
environmental challenges.
• 7 – Environmental Response – the ability to respond
to stimuli in the environment.
Viruses – Alive or Not?
• Although both bacteria and viruses can make us
sick in very similar ways, the two are VERY different.
• Bacteria are simple living creatures. Each little cell
can perform all of the life processes on it’s own.
• Viruses, however cannot. A virus does not fulfill most
of the properties of living things and so they are NOT
considered to be living things.
Viruses – Alive or Not?
• Homeostasis – viruses have no mechanism to
control their integral environment. When not
infecting a host, they simply float around inert.
• Metabolism – viruses only have the biological
machinery to infect a host and replicate.
• Energy Transformation – viruses do not take in
“food” to obtain energy from.
Viruses – Alive or Not?
• Growth/Development – A virus does not grow. It
simply makes copies of itself.
• Reproduction – a virus requires a host cell to infect
to reproduce. Without hijacking the machinery of a
host cell, a virus cannot reproduce.
• Response to environment – a virus does not change
itself in any way outside of its infection cycle.
Levels of Biology
• Life can be studied at many levels:
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Biosphere
Ecosystem
Community
Population
Organism
Organ System
Organ
Tissue
Cell
Sub-Cellular Structures
Fields of Biology
• Biologists can specialize into many different fields
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Cytology - cells
Anatomy - structures
Physiology – functions
Ecology – interactions between species
Zoology – animals
Botany - plants
Mycology - fungi
Entomology - insects
Taxonomy – lineages
etc
Researching Biology
• There are two main methods used to gather knowledge
in biology:
• Discovery Science
• The simplest and oldest form of biology; information if
gathered by careful observation and comparing of
data.
• Hypothesis-Driven Science
• More complex method where ideas (hypothesises) are
tested in experiments by the scientific method.
• Discovery Science will often tell you the basic answers
while Hypothesis-Driven Science can tell you why and
how things happen.
Discovery or Hypothesis?
• Galileo using a telescope to first see the moons of
Jupiter.
• The detection of the long-proposed Higgs Boson
particle.
• A group study to determine if a new drug will lower
cholesterol levels.
The Scientific Method
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A Basic Framework of the Method:
1 - Determining a Question
2 - Forming a Hypothesis
3 – Conducting an Experiment
4 – Collecting Data
5 – Interpreting Data
6 – Drawing a Conclusion
• 7 – Review/Repeat/Alternate Hypothesises
Hypothesis vs. Theory vs. Law
• While often used differently in everyday language,
theory has a specific meaning within science.
• A hypothesis is a proposed idea that scientists want
to prove. Scientists carefully perform experiments
and read the results to either prove/refine/disprove
their hypothesis.
Hypothesis vs. Theory vs. Law
• A theory is a hypothesis that has been tested time
and again and is supported by the observations of
multiple experiments.
• Thus, a theory is a model that can be used to
explain current observations and also predict new
ones.
• Science keeps trying to prove theories wrong to
make sure they are as accurate as possible.
Hypothesis vs. Theory vs. Law
• Laws are rules that describe how one thing in nature
affects another. Many of these are mathematical
formulas. Laws, like theories, are tested again and
again to make them as accurate as possible.
• Theory: gravity pulls people down towards the Earth
• Law: F = m*g (the force exerted by gravity is
proportional to the mass of the object)
Experimentation
• What makes up an experiment? What makes the
results reliable?
• Experiments search for cause and effect
relationships.
• To see if a certain factor causes another, very similar
scenarios are created, with a slight difference
between each to see what different inputs cause
different outputs.
Experimentation
• These changing factors are called variables.
• The independent variable is one that the scientist
changes in each scenario.
• The dependent variable is the changing results that
arise from changing the independent variable.
• By trying different situations, an experiment can
create data to support or refute that the hypothesis
that the independent variable causes the
dependent variable to change.
Experimentation
• An experiment wants to see if different brands of
soda harm teeth. Three teeth are placed in
separate jars and a different soda added to each.
These are left for 48 hours and then the teeth are
inspected for decay.
• The independent variable is the different types of
soda.
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The dependent variable is the level of tooth decay
on the teeth.
Experimentation
• In an experiment, it is very important that we are
sure that the independent variable is the only thing
changing, so we are certain it is what is causing
changes in the dependent variable.
• As such, any other factor must be carefully kept
consistent. These are controlled variables.
• Similar to this is a control. This is one of the
experiments done without the independent
variable at all, to make sure the results do not
happen on their own, or by some other factor.
Experimentation
• In the tooth decay experiment, controlled variables
include: starting with teeth of similar quality, using
the same amount of soda in each jar, using fresh
soda for each brand, etc. This is done to prove the
soda type caused the differences, and not other
factors.
• A control for this experiment would be another
tooth placed in a jar without any soda added. This
would serve to prove that teeth do not decay on
their own, and any decay is caused by the soda
only.
Experimentation
• What are the independent and dependent variables in
each case?
• How much water flows through a faucet when the tap is
turned to different angles?
• Does heating a cup of water allow it to dissolve more
sugar?
• Does fertilizer make a plant grow bigger?
• Does an electric motor turn faster if you increase the
voltage?
Experimentation
• When a factor other than the independent variable
effects the dependent variable, it is called an
extraneous variable.
• Doing a control will often help you figure out how much
these contribute to the result.
• However, sometimes extraneous variables make results
unreliable. Extra care must be taking in designing the
experiment to avoid these factors.
• Extraneous variables are very present in psychological
experiments and in very complex systems.
Experimentation
• Extraneous variables are often time-related. Test
one fertilizer in summer and another in winter isn’t a
fair comparison as the weather conditions are very
different.
• In tests on people, mood/emotions are often
extraneous. Doing a survey early in the morning
may get different results from the same people than
if the same people were asked in the afternoon.
Experimentation
• Discuss the potential extraneous variables:
• EXAMPLE 1
• A researcher wanted to assess whether mood
influenced people's memory. The researcher
hypothesized that positive moods would lead to greater
memory performance than would a negative mood
state. On Monday the researcher had 50 subjects learn
a list of nonsense syllables and then watch a very
humorous comedy film. Their recall of the list of syllables
was then assessed. On Tuesday the researcher had a
second group of 50 subjects learn the same list of
nonsense syllables and then watch an upsetting
documentary on World War II. Their recall of the list was
then assessed after having watched the film
Experimentation
• Discuss the potential extraneous variables:
• EXAMPLE 2
• A researcher wanted to see whether a new way of
teaching English was superior to a more traditional
approach. The researcher selected two Thursday
night classes at a local community college. In one
class the instructor used a traditional method, the
second instructor used the newer approach. The
researcher then assessed students language ability
after they had completed the program.
Error
• Nothing is perfectly accurate. Even very high-tech
tools are not absolutely perfect. Therefore, all
experiments have a certain amount of error. For
example, the exact weight of a sample might not
be known; it might only be measured to the nearest
gram.
• Human error is when a person makes a mistake
during an experiment. This is avoidable and not
counted in with the regular errors from other
sources. Repeating experiments is a way to try to
remove human error.