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Biology
Biology- The science of life –
The study of living things.
Organism – A living thing
If an organism is alive, it will share
certain characteristics with all living
things:
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All living things are made of cells.
Organisms may be unicellular (one-celled)
or multicellular (thousands of differentiated
cells).
The cells of living things are organized.
Similar cells are organized into tissues.
Organisms that are composed only of
tissues are classified as colonial. Similar
tissues are organized into organs, organs
into systems, and systems into
multicellular organisms.
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Organisms have a constant energy
demand to maintain their metabolism.
Metabolism is the sum of all the
processes necessary to maintain life.
This energy demand means that the
organism needs nutrients.
Heterotrophs are organisms that must
consume nutrients such as a lion.
Autotrophs are organisms that are
able to make their own nutrients.
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Organisms maintain homeostasis or a
stable internal environment such as
birds puffing their feathers in cold
weather.
Organisms grow. This growth occurs
because of cell division, cell growth,
and development of the organism.
Simple enlargement such as a sand
dune adding on layers cannot be
considered true growth.
Organisms are irritable. That is
they can respond to their
environment.
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Organisms reproduce. While reproduction
is not a requirement of each individual, it is
necessary for the species to continue.
Organisms produce similar offspring in a
process called heredity. DNA or the code
for traits form genes which form traits. A
large number of genes forms a
chromosome which is duplicated in
reproduction. Reproduction such as cell
division that involves only one parent is
considered asexual reproduction.
Reproduction that involves the
combination of two gametes to form a
zygote as in the pollination of a flower is
considered sexual reproduction.
The world contains a diverse
range of organisms. Many
organisms have not been
discovered yet. Scientists
have agreed that this
diversity or biodiversity is
necessary for our planet to
remain stable.
Unifying Themes of Biology
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Cellular Structure and Function
Reproduction
Metabolism
Homeostasis
Heredity
Evolution
Interdependence
Biology Solves Real World
Problems
• Preserving our environment
• Improving the food supply
• Understanding the human genome
• Fighting diseases such as AIDS, cancer, and
emerging diseases
• Developing gene therapy
The rainforests are being burned at a rate of
more than one acre per second.
Genetically engineered crops can be resistant to
herbicides, poisonous to some pest, and yield
phenomenal quanities of food.
By understanding the human genome,
thousands of gene related medical
mysteries will be solved
Scientific Processes
In the summer of 1988, David Bradford was studying a
species of small frogs in some Rocky Mountain lakes. These
frogs had inhabited these lakes since records had been kept.
Bradford discovered that the frogs had disappeared from 98
percent of their habitat. Bradford reported his findings to
other biologists. John Harte who was studying salamanders
in the Rocky Mountains read about Bradford’s findings.
Statement of a Problem
Harte wanted to discover the
facts surrounding the
disappearance of the
amphibians in the Rockies and
began a scientific investigation.
Scientific investigations generally follow a set of
steps called the scientific method. The scientific
method lends itself to logic thought. It generally
contains some sequence of the following steps:
Collecting accurate observations.
Asking questions
Forming a hypothesis and making predictions
Confirming predictions with a controlled
experiment
Drawing conclusions
Collecting Accurate Observations
Accurate observations are a
necessity for the validity of the
whole study.
Harte had his college students
help him collect water samples
and make other observations of
ponds in the mountains.
Asking Questions
Harte knew by observation that acid rain
precipitation was released as the snow
melted in the spring causing a sudden
change in the ponds and lakes of the
Rockies.
Forming a Hypothesis
A hypothesis is an educated guess or, more
precisely, a testable statement. Harte developed
two related hypotheses:
Acids that were formed in the upper atmosphere
by pollutants were falling onto the mountains in
winter snows.
Melting snow was making the ponds acidic and
harming the salamander embryos.
Harte predicted that the acidity of the ponds
would increase as the winter snow melted
and that the acidity would be high enough to
harm salamander embryos.
Confirming Predictions With a
Controlled Experiment
Harte gathered years of data about the changes in the pH
of Rocky Mountain Lakes. Harte's data indicated a distinct
drop in the pH of mountain ponds during the May and June
snow melt. Then, it leveled off and began to rise again.
Minerals in the rocks probably provided a neutralizing
effect.
To test his second hypothesis, Harte would
perform a controlled experiment in which he
would expose salamander embryoes to
changes in pH. He would keep one group in
a normal pond water environment as a
control. Experimental groups would be
subjected to changes in pH.
In the experiment, the factor that Harte
would change, the pH, was the independent
varible. The factor that was measured, the
health of the embryoes, was the dependent
varible.
Harte found that the drop in pH did have a
distinct effect on the health of the
embryoes. In fact, many of the embryoes
did not hatch and some that did had
abnormalities that caused them to die.
Drawing Conclusions
Once experimentation was completed and the data
organized, Harte had to decide if his hypotheses were
supported or rejected. His data distinctly supported
both of his hypotheses and other scientists repeated his
findings with many other amphibian groups in the Rocky
Mountains.
Viewing Conclusions in
Context
Scientists have communicated their results and worked
together to attribute the decline in amphibians worldwide to
4 major factors:
• Habitats are deteriorating and being
destroyed.
• Nonnative species are outcompeting
native amphibian species.
• Chemical pollutants tend to accumulate in
amphibian habitats.
• Amphibians suffer from a high rate of
infections.
Scientific Explanations
Like the sculpting of a statue, scientific
research chips away at the useless stone of
problems such as the decline of amphibians
until the larger problem can be described and
studied. It has now been described and a
model has been constructed.
Constructing a Theory
As scientists analyze each other's
work and streamline the model, an
explanation emerges that is widely
believed because it has been
tested many times. This is a
theory.