Notes

The more characteristics two organisms share, the more similar
their names should be in the classification system. The caracal, a pet
cat, and all the cats below are different in size, habitat, and other
characteristics. But they also have many similarities, and all
belong to the cat family, Felidae.
Two scientific processes deal with classifying and naming living things.
is the process of arranging organisms into groups based
on similarities. is the science of naming and classifying
organisms. Classification and taxonomy are related studies. A good
system of classification allows you to organize a large amount of
information so that it is easy to find and to understand. The system
should provide a tool for comparing very large groups of organisms as
well as smaller groups. Large groups might include all animals.
Smaller groups might include birds, reptiles, or mammals
A good system of taxonomy allows people to communicate about
organisms. Before the 1700s, scientists had not agreed on a system of
naming and grouping organisms. Take, for example, the common wild
briar rose. Some scientists called it Rosa sylvestris inodora seu canina.
Others used the name Rosa sylvestris alba cum rubore, folio glabro. And
any scientist studying a species could change the name.
About 400 years ago, scientists who studied insects classified them
based upon their appearance and behavior. If animals looked alike,
researchers concluded that they were related. In the last few centuries
scientists have realized that appearances can suggest false connections.
Although caterpillars look like worms, they are more like butterflies.
In fact, the caterpillar is a stage of a butterfly’s life.
For some people, the world seemed to grow larger during the
1600s. Travelers sailed to distant lands and oceans. Scientists went on
many of these trips, observing and collecting samples of living things
they had never seen before. In addition, the microscope allowed
scientists to see tiny organisms that had been invisible before. But
how could scientists organize and talk about this wonderful new
knowledge?
Taxonomists take evidence and try to reconstruct the evolution of
a species. Then they place the species in the classification system.
Scientists use physical evidence, such as fur, bones, and teeth. They
also use genetic evidence, which is found within an organism’s DNA.
The primary tools early scientists used for taxonomy were their eyes
and measuring devices. They collected examples of organisms and
noted characteristics, such as color, size, weight, and how groups of
organisms obtain energy. Scientists who studied animals observed
the internal structure, as well as outward appearances. These physical
features are still important today.
Individuals of two species, such as the two jays shown to the left,
can have many similarities as well as some differences. One obvious
difference is the color pattern. Another is the area of the world in
which they live. Blue jays live east of the Rocky Mountains, and
steller’s jays live west of the Rockies. The common names and the
scientific names reflect the differences and the common ancestor:
blue jay, Cyanocitta cristata and steller’s jay, Cyanocitta stelleri.
Skeletons, shells, and other hard parts of organisms become fossilized
more easily than soft parts do. Scientists can observe and
measure fossilized bones or pieces of bones and compare them with
each other. They can also compare bones of species that are extinct
with bones of modern species. From such studies, scientists can
determine many things about how the organism. Physical evidence
provides clues about how an organism may have lived, how it
moved, or what type of food it ate.
All of this physical evidence helps scientists see that all living
organisms are related by evolution. Some are more closely related
than others. This means they share a more recent ancestor.