Unit B
Chapter 2
Classification of Living Things
2.1
Scientists Develop
Systems for Classifying
Living Things
• Two scientific processes are involved
in the classification of living things
• Classification
• Taxonomy
• Classification
• Process of arranging organisms
into groups based on similarities
• Out of the 7 levels of classification, house
cats and tigers have 6 in common
• Taxonomy
• Science of naming
and classifying
organisms
• A good classification system allows
you to organize a large amount of
information so it is easy to find and
understand
• Did your leaf classification system
meet these requirements?
• To classify organisms, scientists use
similarities and differences among
species
• Some examples are easy to see
• Fur
• Feathers
• Scales
• Sometimes you have to look at the
DNA
• Classification systems help us identify
unfamiliar organisms
• The more characteristics two
organisms share, the closer they will
be in the classification system and
the more similar their names will be
• Scientists need a simple, standard
way of arranging species
• Why is it important for scientists to have
a standard system?
• Scientists who classify and name
organisms based on their similarities
and differences are called
taxonomists
• They also study the
relationships between
species in order to
discover how one
species evolved as
compared to another
species
• Species that share common
ancestors are grouped together in the
classification system
• Taxonomists compare a variety of
characteristics, or traits, in order to
determine classification
• Example – bone structure, size
• If two organisms share a trait,
taxonomists investigate to see if they
share an ancestor
• Two types of evidence used to place
species in the classification system
• Physical evidence
• Helps scientists see that all
living organisms are related
by evolution
• Genetic evidence
• Usually supports physical
evidence, but not always
Physical evidence
• color
• size
• weight
• How they obtain energy
• Internal structure
• skeleton
• shells
• Genetic evidence
• Laboratory
machines are used
to analyze and
compare DNA
• Example:
• The red panda
and the giant
panda have very
similar physical
features
• The red panda
is genetically
more like the
raccoon