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Scientists classify millions of
species.
 Until
the 1600s, scientists classified
organisms according to their
appearance.
 The invention of the microscope allowed
scientists to see structures and organisms
that were not visible before.
Classification and Taxonomy
 Classification:
the process of arranging
organisms into groups based on similarities
 Taxonomy:
the science of naming and
classifying organisms
 The
purpose of classification and
taxonomy is to make information easier to
find and understand.
Classification and Taxonomy
 Until
1700s scientists could not agree on a
system
 Both overly long Latin scientific names
and common names can be confusing.
Using Classification

Scientists use similarities and differences
among species, including appearance,
biology, and genetics.

The more characteristics 2 organisms share,
the more similar their scientific names should
be in the classification system.

See examples on page 45B.
Taxonomists study biological
relationships.

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

Taxonomists: the scientists who classify and
name organisms based on their similarities
and differences.
Taxon: a group of organisms that share
certain traits
Taxons can be broad (animal) or more
specific (cat).
A single species found in a fossil record can
be the ancestor of many species on Earth
today.
Taxonomists study biological
relationships (continued)
 In
order to classify organisms, scientists
compare a variety of traits.
 Trait: a characteristic or behavior
 If 2 organisms share a trait, taxonomists try
to determine if they share that trait
because they share an ancestor.
Continued
 Page
47B—the seahorse shares more traits
with a leafy sea dragon than the
sargassum seaweed or sargassum fish.
 Taxonomists take evidence and try to
reconstruct the evolution of a species.
 Then they place the species in the
classification system.
Physical Evidence
 Primary
devices used—eyes and
measuring devices
 Collect samples and note
characteristics—size, color, weight, how
obtain energy, internal structures,
outward appearance
 Individuals of a species have many
similarities and some differences.
Physical Evidence





Skeletons, shells, and other hard parts of
organisms fossilize more easily.
Scientists observe and measure this evidence.
They also compare bones.
All this physical evidence helps scientists see
that all living organisms are related by
evolution.
Those most closely related share a more
recent ancestor.
Genetic Evidence
 Scientists
can compare the components
of a gene from one organism with the
components of the same gene from
another organism.
 Genetic evidence usually supports
physical evidence.
 See p. 49B—Red pandas are more closely
related to raccoons than Giant Pandas
Review Questions 49B
1.
Classification allows
taxonomists to organize
a great deal of data so
that it is easier to find
and understand.
Number 2
Taxonomists
study
biological relationships
to discover how one
species evolved as
compared with another
species.
Number 3
Scientists
look at DNA
and compare genes
of organisms.
Number 4
Having
a universal naming
system allows people
speaking different
languages to refer to all
organisms the same way.
It’s easier to understand.
Number 5
A marbled godwit would
have marbled feathers,
wings, feet, and a beak.
Number 6
 Compare
physical traits, such as color,
size, weight and how they get energy.
Analyze bones; compare to fossils;
compare DNA.