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CLASSIFICATION
CHAPTER 3
WHY THINGS ARE GROUPED
• TO CLASSIFY MEANS TO GROUP THINGS BASED ON SIMILARITIES
• CLASSIFYING THINGS IS DONE FOR SEVERAL REASONS
• IT MAKES THINGS EASIER TO FIND
• IT HELPS WITH COMMUNICATION
• IT KEEPS THINGS ORGANIZED
BIOLOGICAL CLASSIFICATION
• BIOLOGISTS CLASSIFY THINGS TO SHOW THAT THEY SHARE CERTAIN TRAITS
• WHAT’S A TRAIT?
• A TRAIT IS A FEATURE OR CHARATERISTIC THAT A THING HAS
• GROUPING ORGANISMS LIKE THIS HELPS TO ORGANIZE THE 10 MILLION KNOWN SPECIES AND HELPS TO
PAINT A FULL PICTURE OF THE INTERCONNECTEDNESS OF ALL LIVING THYNGS ON EARTH
METHODS OF CLASSIFICATION
• Classifying living things is not necessarily easy
• Scientists don’t always agree on how to group things
• Aristotle, a famous Greek scientist, was one of the first known scientists to classify living
things
• He fit living things into two main groups: Plants and Animals
• He then divided these groups into 3 smaller groups
MODERN CLASSIFICATION
• As more and more species were discovered, Aristotle’s system became less useful
• Some organisms didn’t fit into his system at all
• Enter Carl von Linné in 1735, he later changed his name to Carolus Linnaeus
• He developed a new system of classifying things, part of which is still used today
LINNAEUS
• Linnaeus gave the groups names and classified things according to their traits
• He called the largest grouping of living things a kingdom
• Linnaeus had two kingdoms: plants and animals
• Within each kingdom he placed things with similar traits into a smaller group called a genus
• Each genus contained even smaller groups called species
LINNAEUS
• Linnaeus made a number of important changes to Aristotle’s system
• 1. He classified plants and animals into more groups
• 2. He based his system on specific traits
• 3. He gave organisms names that described their traits. The names had two parts. All living
things still have two-part names.
MODERN CLASSIFICATION
• Today there are 2 domains, 6 kingdoms and 7 smaller groups for classifying in each kingdom
• Classification is done in this order, where kingdom is the largest, least specific grouping and
species is the smallest, most specific grouping
• Kingdom, phylum, class, order, family, genus, species
KINGDOM
• The kingdom is the largest, least specific group
• There are currently 6 kingdoms (your book only lists 5). The kingdom Monera
has recently been divided into two distinct kingdoms
• The kingdoms are: Archarbacteria, Eubacteria, Protista, Fungus, Plant and
Animal
• Kingdoms are divided into phyla
PHYLUM
• A Phylum is the largest group in a kingdom
• Phyla are divided into classes
CLASS
• Classes are the largest groups in each phylum
• Classes are divided into orders
ORDER
• Orders are the largest groups in each phylum
• Orders are divided into families
FAMILY
• A family is the largest group in an order
• Families are divided into groups called genera (genus)
GENUS
• A genus is the largest group in each family
• Each genus is divided into smaller groups called species
SPECIES
• Species is the smallest but most specific grouping in biological classification
HOW ORGANISMS ARE CLASSIFIED
• Organisms get classified by how closely related they are
• Lots of evidence is used to support this
• The evidence used comes from the following areas:
• biochemistry, genetics, embryology, comparative anatomy
COMPARATIVE ANATOMY
BIOCHEMISTRY AND GENETICS
• ALL organisms use DNA as their genetic code
• ALL organisms use chains of amino acids to build their proteins
• ALL organisms use ATP as their energy carrying molecule
• But each specific type of organism makes their own specific types of proteins
• Each type of organism has a specific sequence of nucleotides to make their
DNA
• This helps to classify living things too
SCIENTIFIC NAMES
• The genus and species names together make the scientific names for all
organisms
• A house cat’s scientific name is Felis catus. Felis is the genus name and catus
is the species name.
• The genus part of the name is always capitalized and the whole thing is always
in italics
WHY DO WE USE SCIENTIFIC NAMES?
• 1. No mistakes can be made about which living is being described. No two living things ever have the
same scientific names but sometimes living things have the same or similar common names.
Sometimes common names are misleading
• 2. Scientific names seldom change
• 3. Scientific names are written in the same language all over the world. Scientific names are written in
Latin. Latin is used because the language doesn’t change.
• What do you think of when I say “Irish Moss”?
• Maybe this?
• Wrong! It’s this.
• Okay, how about if say “dolphin”?
• This?
• Okay, but so is this.
• This is why we use scientific names.
THE KINGDOMS
• There are 6 kingdoms
• (read Technology: six kingdoms instead of five on page 61)
• Your book only lists five, starting with the kingdom monera
MONERA
• This is the bacteria kingdom
• Organisms in this kingdom are ALL single-celled
• Their cells DO NOT have a nucleus or the other membrane-bound organelles that we discussed earlier
• This kingdom has recently been divided into two separate kingdoms: Archaebacteria and Eubacteria
• They reproduce asexually but can reproduce sexually
FUNGI
• This is the fungus kingdom
• This kingdom includes mushrooms, mold and yeast
• Some are single-celled and some are multi-celled
• Fungi have cell walls and most of the organelles we discussed
• They are decomposers
• They reproduce sexually or asexually
PLANTS
• Plants are ALL multi-celled
• Most of them contain chlorophyll and photosynthesize
• They have most of the organelles we discussed earlier
• They reproduce sexually
ANIMALS
• ALL animals are multi-celled
• They have most of the cell organelles we discussed
• They have the ability to move at some point in their live cycle
• They reproduce sexually
• They cannot photosynthesize
PROTISTA
• This kingdom contains everything that is alive but doesn’t fit in any other kingdom
• They have most of the organelles
• They can reproduce sexually or asexually
• They can be single or multi-celled