TAXONOMY: Kingdoms, Domains & Dichotomous Keys
by Bryanna Wagner
Curriculum Expectations
B2.4: Create and apply a dichotomous key to identify and classify organisms from each of the kingdoms.
B3.1: Explain the fundamental principles of taxonomy and phylogeny by defining concepts of taxonomic rank and relationship, such as genus, species and taxon.
B3.3: Describe unifying and distinguishing anatomical and physiological characteristics (e.g., types of reproduction, habitat, general physical structure) of representative organisms from each of the kingdoms.
B3.1: Explain the fundamental principles of taxonomy and phylogeny by defining concepts of taxonomic rank and relationship, such as genus, species and taxon.
B3.3: Describe unifying and distinguishing anatomical and physiological characteristics (e.g., types of reproduction, habitat, general physical structure) of representative organisms from each of the kingdoms.
Learning Goals
Students will be able to:
1. Identify the distinguishing characteristics of the three domains and the five kingdoms.
2. Explain the purpose of classifying organisms and the fundamental principles of taxonomy.
3. Use different dichotomous keys to identify a variety of organisms.
4. Construct a dichotomous key and use it to identify a group of organisms.
5. Explain how dichotomous keys are used to identify organisms.
1. Identify the distinguishing characteristics of the three domains and the five kingdoms.
2. Explain the purpose of classifying organisms and the fundamental principles of taxonomy.
3. Use different dichotomous keys to identify a variety of organisms.
4. Construct a dichotomous key and use it to identify a group of organisms.
5. Explain how dichotomous keys are used to identify organisms.
Taxonomic Systems
Our present biological system of classification was developed from the system created by Swedish botanist Carl Linnaeus (1701-1778). His system was based on an organism's physical and structural features, and operated on the idea that the more features organisms have in common, the closer their relationship.
Linnaeus created rules for assigning names to plants and animals. He was the first to use binomial nomenclature, which assigns each organism a two-part scientific name using Latin words. Latin (and sometimes Greek) is still used today for naming organisms, and provides a common language for all scientists, regardless of their national origin. A scientific name is often based on some characteristic such as colour or habitat; an example is Castor canadensis (Castor meaning "beaver", and canadensis meaning "from Canada"). The first part of any scientific name is called the genus (plural: genera). Its first letter is always capitalized and can be written alone; for example, the Acer genus refers to maple trees. The second part is called the species and is never used alone; for example, Acer rubrum refers to the red maple. Living organisms within a species can only breed with members of their own species.
The two-name system provides an added advantage by indicating similarities in anatomy, embryology, and evolutionary ancestry. For example, binomial nomenclature suggests that the North American black bear (Ursus americanus) and the grizzly bear (Ursus horribilis) are closely related. Similar organisms are grouped into the same genus. The giant Alaskan bear brown bear (Ursus arctos) and polar bear (Ursus maritimus) are other relatives belonging to the same genus. By contrast, the koala bear and panda do not belong to the genus Ursus and are not considered true bears.
Linnaeus created rules for assigning names to plants and animals. He was the first to use binomial nomenclature, which assigns each organism a two-part scientific name using Latin words. Latin (and sometimes Greek) is still used today for naming organisms, and provides a common language for all scientists, regardless of their national origin. A scientific name is often based on some characteristic such as colour or habitat; an example is Castor canadensis (Castor meaning "beaver", and canadensis meaning "from Canada"). The first part of any scientific name is called the genus (plural: genera). Its first letter is always capitalized and can be written alone; for example, the Acer genus refers to maple trees. The second part is called the species and is never used alone; for example, Acer rubrum refers to the red maple. Living organisms within a species can only breed with members of their own species.
The two-name system provides an added advantage by indicating similarities in anatomy, embryology, and evolutionary ancestry. For example, binomial nomenclature suggests that the North American black bear (Ursus americanus) and the grizzly bear (Ursus horribilis) are closely related. Similar organisms are grouped into the same genus. The giant Alaskan bear brown bear (Ursus arctos) and polar bear (Ursus maritimus) are other relatives belonging to the same genus. By contrast, the koala bear and panda do not belong to the genus Ursus and are not considered true bears.
Levels of Classification
In our present classification system, there are seven main levels or taxa (singluar: taxons), as shown in Table 1. Originally, the first level consisted of only two kingdoms: plants and animals. Later, single-celled organisms that displayed both plant and animal traits were discovered. To recognize this unique group, scientists created a third kingdom: Protista. However, shortly after the introduction of the protist kingdom, it was noted that certain microorganisms within this group shared an additional distinct feature. Bacteria and cyanobacteria, unlike protists, lack a true nucleus. This distinction resulted in the establishment of a fourth kingdom: Monera. The monerans are referred to as prokaryotes since they lack a true nucleus. All other groups of living organisms are known as eukaryotes. Later, taxonomists acknowledged that mushrooms and moulds are sufficiently different from plants and thus were placed in a separate kingdom called Fungi. This five kingdom classification system, which included animalia, plantae, fungi, protista, and monera, was originally proposed by Robert Whittaker in 1969. It enjoyed wide acceptance until recently. In the 1970s, microbiologist Carl Woese and other researchers at the University of Illinois conducted studies indicating that a group of prokaryotic microorganisms called archaebacteria are sufficiently distinct from bacteria and other monerans that they, in fact, constitute their own kingdom.
Archaebacteria have been known for a long time. They thrive in harsh habitats such as salt lakes, hot springs, and the stomach chambers of cattle and other ruminants. Archaebacteria possess cell walls and ribosome components that are very different from those in eubacteria. Eubacteria possess a rigid cell wall composed of peptidoglycan, a three-dimensional polymer containing carbohydrate and protein subunits. Thus Woese and his colleagues proposed that the kingdom Monera be divided into two kingdoms, Archaebacteria and Eubacteria (true bacteria). The resulting six-kingdom system includes animalia, plantae, fungi, protista, eubacteria, and archaebacteria. Table 2 summarizes a six-kingdom system of classification.
Today, most scientists believe that organisms have changed over time. The history of the evolution of organisms is called phylogeny. Relationships are often shown in a type of diagram called a phylogenetic tree, where the tree starts from the most ancestral form and includes branchings that lead to all of its descendants.
DNA sequencing studies conducted by Carol Bult and Carl Woese in 1996 revealed that some of the genes in archaebacteria are more closely related to the genes of humans and other eukaryotes than to those of eubacteria. Woese proposed that archaebacteria are so different from other prokaryotes that their name should not contain the term bacteria. He suggested the name Archaea for this group. While the six-kingdom system grows in popularity among biologists in general, many microbiologists feel that all traditional kingdom systems should be replaced with a system that better reflects the evolutionary history of life. This has led to a three-domain classification system. Scientists continue to update evolutionary history and classification schemes as more DNA evidence is collected and analyzed.
Many scientists regularly use classification manuals to conduct their identification work. Usually it involves the use of a dichotomous key. The key is constructed so that a series of choices must be made, and each choice leads to a new branch of the key. If choices are made accurately, the end result is the name of the organism being identified.
DNA sequencing studies conducted by Carol Bult and Carl Woese in 1996 revealed that some of the genes in archaebacteria are more closely related to the genes of humans and other eukaryotes than to those of eubacteria. Woese proposed that archaebacteria are so different from other prokaryotes that their name should not contain the term bacteria. He suggested the name Archaea for this group. While the six-kingdom system grows in popularity among biologists in general, many microbiologists feel that all traditional kingdom systems should be replaced with a system that better reflects the evolutionary history of life. This has led to a three-domain classification system. Scientists continue to update evolutionary history and classification schemes as more DNA evidence is collected and analyzed.
Many scientists regularly use classification manuals to conduct their identification work. Usually it involves the use of a dichotomous key. The key is constructed so that a series of choices must be made, and each choice leads to a new branch of the key. If choices are made accurately, the end result is the name of the organism being identified.
Sample Dichotomous Keys
Taxonomy Activities
Activity #1:
Students can complete the attached worksheet as a fun way to practice their dichotomous key skills.
Students can complete the attached worksheet as a fun way to practice their dichotomous key skills.
taxonomy_classification_and_dichotomous_keys.docx | |
File Size: | 64 kb |
File Type: | docx |
Activity #2:
Students can also practice making their own dichotomous keys using given groups of organisms. After they have created their own dichotomous keys, they should switch with another group to see if they are able to identify the organisms using their key.
Activity #3:
The website www.explorelearning.com has a wide variety of activities, or "gizmos" available for engaging and educational lessons. One of these gizmos is focused on the topic of taxonomy and comes with both teacher and student guides, as well as a handy vocabulary list. These three resources are attached.
Students can also practice making their own dichotomous keys using given groups of organisms. After they have created their own dichotomous keys, they should switch with another group to see if they are able to identify the organisms using their key.
Activity #3:
The website www.explorelearning.com has a wide variety of activities, or "gizmos" available for engaging and educational lessons. One of these gizmos is focused on the topic of taxonomy and comes with both teacher and student guides, as well as a handy vocabulary list. These three resources are attached.
dichotomouskeystg_-_teacher_guide.pdf | |
File Size: | 116 kb |
File Type: |
dichotomouskeysse_-_student_worksheet.pdf | |
File Size: | 187 kb |
File Type: |
dichotomouskeysvocab_-_vocabulary_sheet.pdf | |
File Size: | 60 kb |
File Type: |
Activity #4:
The Toronto Zoo has some excellent resources for learning about the classification of animals as well as identifying the distinguishing characteristics of organisms from each of the kingdoms and domains. In the attached document, there are a variety of biodiversity activities for grade 11 university students.
The Toronto Zoo has some excellent resources for learning about the classification of animals as well as identifying the distinguishing characteristics of organisms from each of the kingdoms and domains. In the attached document, there are a variety of biodiversity activities for grade 11 university students.
grade_11_-_biodiverstiy_activities_-_toronto_zoo.doc | |
File Size: | 418 kb |
File Type: | doc |
Assessment Examples
1. Taxonomy Quiz
An assessment tool that I created to assess students understanding of this material is attached below.
An assessment tool that I created to assess students understanding of this material is attached below.
grade_11_university_biology_taxonomy_quiz.docx | |
File Size: | 20 kb |
File Type: | docx |
2. Taxonomic Mini-Book Project
For this assessment, students are required to make a mini-book about organisms, one that is a plant and one that is an animal. They will learn about these organisms and about each of the levels that the organisms occupy. The information for this assessment can be found at the following link:
http://www.sharemylesson.com/teaching-resource/Taxonomic-Mini-Book-Project-50008308/
For this assessment, students are required to make a mini-book about organisms, one that is a plant and one that is an animal. They will learn about these organisms and about each of the levels that the organisms occupy. The information for this assessment can be found at the following link:
http://www.sharemylesson.com/teaching-resource/Taxonomic-Mini-Book-Project-50008308/
On-line Resources
Khan Academy - Taxonomy and the Tree of Life
Crash Course Biology - Taxonomy: Life's Filing System
Glossary
classification - the systematic grouping of living things based on characteristics, hierarchical or phylogenetic relationships.
dichotomous key - a key used to identify a plant or animal in which each stage presents descriptions of two distinguishing characters, with a direction to another stage in the key, until the species is identified.
domain - the highest taxonomic rank of organisms in which there are three groupings: Archaea, Bacteria and Eukarya.
genus - a taxonomic category ranking used in biological classification that is below a family and above a species level, and includes group(s) of species that are structurally similar or phylogenetically related.
hierarchy - any system of persons or things ranked one above the other.
kingdom - a taxonomic rank that is composed of smaller groups called phyla (or divisions, in plants).
organism - an individual living thing that can react to stimuli, reproduce, grow, and maintain homeostasis. It can be a virus, bacterium, protist, fungus, plant, or an animal.
phylum - (1) a taxonomic rank at the level below kingdom and above class in biological classification. (2) A group of classes with similar distinctive characteristics.
scientific name - the recognized Latin name given to an organism, consisting of a genus and species, according to a taxonomy.
species - (1) The lowest taxonomic rank, and the most basic unit or category of biological classification. (2) An individual belonging to a group of organisms having common characteristics and are capable of mating with one another to produce fertile offspring.
taxonomy - the classification of organisms in a hierarchical system or in taxonomic ranks (e.g. domain, kingdom, phylum or division, class, genus, species) based on shared characteristics or on phylogenetic relationships inferred from the fossil record or established by genetic analysis.
trait - characteristics or attributes of an organism that are expressed by genes and/or influenced by the environment.
dichotomous key - a key used to identify a plant or animal in which each stage presents descriptions of two distinguishing characters, with a direction to another stage in the key, until the species is identified.
domain - the highest taxonomic rank of organisms in which there are three groupings: Archaea, Bacteria and Eukarya.
genus - a taxonomic category ranking used in biological classification that is below a family and above a species level, and includes group(s) of species that are structurally similar or phylogenetically related.
hierarchy - any system of persons or things ranked one above the other.
kingdom - a taxonomic rank that is composed of smaller groups called phyla (or divisions, in plants).
organism - an individual living thing that can react to stimuli, reproduce, grow, and maintain homeostasis. It can be a virus, bacterium, protist, fungus, plant, or an animal.
phylum - (1) a taxonomic rank at the level below kingdom and above class in biological classification. (2) A group of classes with similar distinctive characteristics.
scientific name - the recognized Latin name given to an organism, consisting of a genus and species, according to a taxonomy.
species - (1) The lowest taxonomic rank, and the most basic unit or category of biological classification. (2) An individual belonging to a group of organisms having common characteristics and are capable of mating with one another to produce fertile offspring.
taxonomy - the classification of organisms in a hierarchical system or in taxonomic ranks (e.g. domain, kingdom, phylum or division, class, genus, species) based on shared characteristics or on phylogenetic relationships inferred from the fossil record or established by genetic analysis.
trait - characteristics or attributes of an organism that are expressed by genes and/or influenced by the environment.
References
Nelson Biology 11. 2008
www.biologycorner.com/worksheets/pamishan.html
www.explorelearning.com
www.shutterstock.com
www.torontozoo.com
www.biologycorner.com/worksheets/pamishan.html
www.explorelearning.com
www.shutterstock.com
www.torontozoo.com