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Chapter 1 Answers
The Science of Biology
Visual Understanding
Fig. 1.4
At which level(s) will cancer be a problem? Why? At which levels are air and water
pollution a problem? Why?
Cancer is a problem that begins at the atomic / molecular level, changing the
macromolecule DNA. This causes the cell to behave abnormally, with rapid cell division
and a displacement of local tissues. This will eventually cause the organ to malfunction,
the organ system to not work properly, and quite possibly the death of the organism.
Since cancer is not considered to be an infectious disease, that is the extent of the levels it
would generally affect.
Air and water pollution could well affect all of the same levels as cancer, and possibly
even cause cancer. In addition, they will affect many or all of a population. While they
will not affect an entire species, they may affect a community, and even a complete
ecosystem.
Fig. 1.5
You notice that on cloudy days people often carry umbrellas folded, or in a case. You
also notice that when umbrellas are open there are many car accidents. You conclude
that open umbrellas cause car accidents. Explain the type of reasoning used to reach this
conclusion, and why it can sometimes be a problem.
This is an example of inductive reasoning. The problem is that people sometimes assume
that because two items both occur at the same time, that one of the events causes the
other. In this case both events are caused by a third event that was not mentioned, the
fact that it is raining. There is nothing wrong with the process of inductive reasoning,
but do not assume that correlation (occurring together) implies causation.
Challenge Questions
Biology and the Living World
You are the biologist in a group of scientists who have traveled to a distant star system
and landed on a planet. You see an astounding array of shapes and forms. You have
three days to take samples of living things before returning to earth. How do you decide
what is alive?
You would look for cellular organization, evidence of metabolism (nutrients in, wastes
out), and possibly evidence of homeostasis. Obviously, in three days, you may not have
an opportunity to witness growth, reproduction, or evidence of heredity.
The Scientific Process
St. John’s wort is an herb that has been used for hundreds of years as a remedy for mild
depression. How might a modern day scientist research its effectiveness?
Use the scientific process to set up a series of experiments using people who are not
depressed and people who are mildly depressed, and giving them fixed amounts of a
placebo, or of St. John’s wort, over some period of time. Test them for mild depression
before and after the experiment, and do not tell them who is receiving the drug and who
is receiving the placebo. You may have to vary the amount of the herb used, and perhaps
the amount of time needed to establish consistent levels of the herb in the body.
Core Ideas of Biology
Explain how the four unifying themes of biology encompass all of the levels of
complexity, from atomic / molecular to community / ecosystem.
The first theme, cell theory, covers the levels through atoms, molecules, organelles and
cells. The second theme, gene theory, begins with the macromolecule DNA and covers
organelles, cells, tissues, organs, organ systems and organisms. The third theme, the
theory of heredity, moves from organisms through populations and species. The fourth
theme, the theory of evolution, affects species, and how they fit in their community of
other living organisms, and how they are adapted to live in a particular ecosystem.