Scientists Develop Systems For
Classifying Living Things
• Scientists Classify Millions of Species:
– CLASSIFICATION & TAXONOMY
• Classification = process of arranging organisms
into groups based on similarities.
• Taxonomy = science of naming and classifying
organisms
– USING CLASSIFICATION
• Taxonomists study biological relationships
– PHYSICAL EVIDENCE
– GENETIC EVIDENCE
Classification & Taxonomy
• A good system of classifying lets you organize a large
amount of information so its easy to find & understand.
• A good system of taxonomy lets people communicate about
organisms.
• Common names (like daddy longlegs) can mean a relative of
the spider (in U.S.) or the mosquito (in England).
• Biologists need both a system for organizing and a system for
naming. Each name should refer to one specific type of
organism. (use species name so everyone knows which
organism they are talking about)
Using Classification
• Classification system can help identify unfamiliar organisms.
A caracal may be unfamiliar, but if its was a cat, you know it
has: fur, fangs, claws, meat eater… all characteristics of cat
family.
• The more characteristics 2 organisms share, the more similar
their names should be in the classification system. The cats
below, all belong to the cat family, Felidae.
Taxonomists study Biological
Relationships
• Scientists need a simple, standard way of
arranging all of the different species. The science
of taxonomy is related to the Greek word taxis
(arrangement).
– Taxonomists are scientists who classify & name
organisms based on their similarities and differences.
– Taxon = group of organisms that share certain traits.
– Species that share ancestors are grouped together.
• To determine how to classify, scientists compare
many traits (a characteristic or behavior that can
be used to tell 2 species apart, like size or bone
structure. If 2 organisms share a trait,
taxonomists will try to discover if they shared a
common ancestor.
•
Taxonomists
The leafy sea dragon shares traits with all the organisms
pictured. (but sea dragon is animal that moves, gets food
from other organisms & breathes air, while sargassum
seaweed is an algae). Sargassum fish shares traits with sea
dragon, but looks very different. Sea dragon is actually
closely related to sea horse.
• Taxonomists use physical evidence (fur, bone, teeth) and
genetic evidence (DNA) to place organisms in the
classification system.
Physical Evidence
• The early tools taxonomists used to
classify were eyes & measuring
devises. Collected examples of
organisms and noted characteristics
(color, size, weight, internal structure,
etc.)
• 2 jay birds have common ancestor but
also some difference. Blue jay is
Cyanocitta cristata and the Steller’s Jay
is Cyanocitta stelleri.
• Scientists can study bones & fossils to
compare organisms too.
• Physical evidence gives clues how an
organism may have lived,moved and
what type of food it ate.
Genetic Evidence
• Today, scientists can use lab machines to catalog each
component of an organism’s DNA. They can compare a gene
from one organism with the gene of another organism.
Usually genetic evidence supports physical evidence, but not
always.
• For years scientists classified the “Red Panda” as a close
relative of the Giant Panda (both from China); they both had
similar appearances and ate bamboo. Molecular evidence
showed that the red panda is closer to a Raccoon, while a
Giant Panda is closer to a Spectacled Bear.