Biology Week 9: Classification

Day 1 | Day 2 | Day 3 | Lab | Review | Weekly Quiz | Quizstar

  • Classification
  • Taxonomy
  • Aristotle
  • Linnaeus
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
  • Scientific name
  • Common name
  • Binomial nomenclature
  • Authority
  • Phylogeny
  • Systematics
  • Hypothesis
  • Cladistics
  • Derived character
  • Cladogram
  • Dichotomous Key

link to an Internet Website Classification: grouping based on characteristics.

click to find the answer to today's question What is the scientific name for humans?

living things Taxonomy is the branch of biology that names and groups organisms according to their characteristics and evolutionary history.

The Greek philosopher Aristotle is known to have grouped living things as either plants or animals over 2,000 years ago. He divided animals into three groups based on where they lived; land, water, or air and he divided plants into three groups based on differences in their stems.

the key points to useful information on this page
As philosophy became science, more and more was learned about living things. It became obvious that Aristotle's system of classification was not adequate. In the mid 1700's Carolus Linnaeus link to an Internet Website a Swedish naturalist devised a system of grouping organisms into hierarchical categories based on characteristics, such as form or structure. He did not use characteristics that seemed to vary from one individual to another, such as size or color. Our classification of living things is always changing as more information becomes available, but Linnaeus' system formed the framework that is still in use today. For this reason, Carolus Linnaeus is known as the father of our modern system of classification.

The major classification levels,
from largest group to smallest

(several of these have subdivisions)


Scientific names vs common names:

Binomial nomenclature: a two name system for writing scientific names.

The genus name is written first (always Capitalized).
The species name is written second (never capitalized).
Both words are italicized or underlined.

"Formal" scientific names should have a third part, the authority.

The authority is written as an abbreviation of the last name of the person responsible for naming the organism. Since Carolus Linnaeus was the first person to name many plants, the L. for Linnaeus is very common in plant scientific names. An example is Quercus alba L.

Some examples of scientific names:link to an Internet Website

Day 1 Assignment - Classification
This assignment must be turned in by the beginning of class tomorrow to receive credit.
Scoring criterialink to a local webpage

  1. Who is considered the father of modern classification systems? Why?
  2. What is the Systema Naturae?
  3. What are some of the reasons scientist need to use classifications systems?
  4. Name the seven classification levels.
  5. Name the seven taxanomic levels to which humans belong.
  6. Name the seven taxanomic levels to which a great white shark belongs.
  7. What is binomial nomenclature? What is the criterea for writing a scientific name?
  8. The species name is sometimes called a "species identifier" because it describes some trait of the organism. In addition to traits, give at least two other commonly used sources for species names.
  9. There is a fish found in waters around Red Rock, Oklahoma called the white to a local picture In Lousiana, this same fish is known as the white perch. What name does a zoologist give to this fish?
  10. What is the scientific name for a Rainbow trout?
  11. What is the scientific name for the Caribean spiny lobster and the Blue spiny lobster? Why do they have different species names?
  12. Many biologists think that there are probably millions of undescribed and unclassified species on Earth. Write a paragraph explaining why so many species might still be undescribed or unclassified today?

Week 9 - Classification: Day 2

click to find the answer to today's question What is a hypothesis?

Phylogenylink to a local webpage the evolutionary history of an organism, is the cornerstone of a branch of biology called systematic taxonomy. Systematics, as systematic taxonomy is commonly called, organizes the diversity of living things into the context of evolution. A phylogenetic tree is a family tree that shows a hypothesis about the evolutionary relationships thought to exist among groups of organisms.

Phylogenetic trees are usually based on a combination of these lines of evidence:

A phylogenetic tree or cladogram Cladisticslink to an Internet Website is a relative new system of phylogenetic classification that uses shared derived characters to establish evolutionary relationships. A derived character is a feature that apparently evolved only within the group under consideration. Cladistics is based on the hypothesis that organisms that share a derived character probably share it because they inherited it from a common ancestor. A phylogenetic tree based on a cladistic analysis is called a cladogram.

What derived character is shared by all the animals on the cladogram at right?
Aristotle placed all living things into two large groups, plants and animals. Linnaeus was the first to call these groups kingdoms. This 2-kingdom system was used until the microscope made scientists aware of a world too small to be seen with the unaided eye. Disagreements occured as microorganisms began to be placed into either the plant or animal kingdoms. This eventually lead to a 3-kingdom system, with the new kingdom Protista being formed into which these organisms were placed.

As more was learned about cell structure in organisms, bacteria were taken out of the protist kingdom and fungi were taken out of the plant kingdom. This lead to the five kingdom systemlink to a local webpage that served taxonomists well for over 30 years. The bacteria have recently been divided into two kingdoms, making six kingdoms of living things.

Day 2 Assignment - Classification
This assignment must be turned in by the end of class tomorrow to receive credit.
Scoring criterialink to a local webpage

  1. Today, a six kingdom system is beginning to be used.
    1. What are the six kingdoms in this system?
    2. Which Kingdom are humans placed?
    3. which kingdom are mushrooms placed?
    4. Which kingdom is anthrax placed?
    5. Write a paragraph that explains what has caused the change from five to six to a local webpage
  2. What is synapomorphies? (use the globe link above)
  3. Currently, what is considered the best method of hypothesizing relationships amoung organisms (making phylogenetic trees).
  4. Briefly summarize in your words how cladistics works?
  5. Copy any phylogenetic tree with 5 or more organisms on it. Interpet what the tree is hypothesizing about the relationship among the organisms (more closely related, less related).
  6. How can the length and branches of the lines of your tree be interpreted?
  7. Examine these dog breed pictures. link to a local picture
    1. Based on Cladistics, is the Chinese Shar-Pei more closely related to the Bulldog or the Doberman Pincher?
    2. Write a paragraph explaining how you arrived at this answer?

Week 9 - Classification: Day 3

click to find the answer to today's question What does the prefix "di" mean?

click for a career
Forestry Technician
A dichotomous keylink to a local webpage is used to identify plants and animals that you do not already know.

Day 3 Assignment - Classification
This assignment must be turned in by the end of class today to receive credit.
Scoring criterialink to a local webpage

  1. List the characteristics that define each of the five kingdoms (In other words, what criteria must an organism meet in order to be place in one of the 5 kingdoms).
  2. Seach the internet for a dichotomous key (other then one linked to this web page). What is the key designed to identify? How is the key organized (what is the format)? Name three organisms that are identified by the key (scientific and common name).
  3. Construct a dichotomous key to identify these nine breeds of dogs. link to a local picture
    1. Dichotomous key must be neat and easy to read. Use specific characteristics.
    2. Dichotomous key must include common names for each dog.
    3. Get signatures of two people that can successfully use your key to identify two dogs of their choosing.
    4. Show your instuctor that you can successfully use your key to identify one dog.

Research Links:

Biology Class










The scientific name for humans is Homo sapiens.










A hypothesis is a "possible" answer to a question or solution to a problem.
A good hypothesis is based on research. A wild guess is not really a hypothesis.










The prefix "di" means "two".