Name: Melissa Birkett
Class: Honors Biology, ARHS
Date: Nov 3, 2003
Topic: Classification of living organisms. This lesson will present phylogenetic trees as
a classification tool and discuss cladistic and phenetic approaches to classification.
Reference to MA Science Framework and/or NSES:
Meets MA Frameworks 5.3: Describe how the taxonomic system classifies living things
into domains (eubacteria, archaebacteria, and eukaryotes) and kingdoms (animals, plants,
fungi, etc.).*
Reflective Introduction:
I chose this lesson topic after discussing teaching options with my pre-practicum
supporting teacher. After observing in the pre-practicum class and experiencing the first
peer-teaching session, I realize the importance of clear and concise instructions to the
success of the lesson. In this lesson, the introduction is intended to be clear and unambiguous. I would also like to include an activity such as the KWL sheets or a short
journal response to the lesson to help direct and focus student thoughts on the lesson.
Using and discussing the KWL sheets in class with reference to models helped to
organize some of my thoughts on the lesson. I also observed the use of journal-like
responses in my supporting teacher’s classroom and noticed how well they helped to
shape the subsequent lesson.
I would like to include small groups in this lesson plan. Working in small groups
in class has been very useful in class when brainstorming and listing were required. This
technique was particularly helpful in the Moon Mission activity in class, which I would
have had a great deal of difficulty completing on my own, but was reasonably successful
as a member of a group. Particularly with a brain-storming activity, I have found it
helpful to have as many different points of view as possible.
Two possible concerns about this lesson are its compatability with the assigned
text and the appropriateness of the activity. Before using this lesson with a class, I would
like to reference its contents with the text and assign any relevant reading prior to the
lesson. I would also like to present the activity as part of the peer teaching assignment
and assess its usefulness to the lesson.
Global and Curricular objectives for students:
The global objective of this lesson is for students to recognize and understand the
relationships between living organisms. Students should understand that related
organisms have a common ancestor and/or common traits.
Brief description of lesson (include start, middle, and end)
Start: Students begin the lesson by filling in a KWL form indicating what they know and
what they want to know about the classification of living things. Students with then
briefly pair with a partner to discuss what they have recorded, changing any information
on the sheets to include ideas they may have overlooked or by adding to the “learned”
column (think-pair-share).
Middle: Following the short pair-discussion, students will be called on to describe one
idea from their list (utilizing wait-time technique) as it pertains to the lesson.
New vocabulary will be introduced and defined: Classification (KPCOFGS),
phylogenetic tree, cladistics, phenetics, homology. Vocabulary will be written on the
board and recorded in student notes. Introduction of Carolus Linnaeus as creator of
modern classification (1758, Systema Naturae). Linnaeus developed binomial
nomenclature to identify organisms by a generic (genus) and specific (species) title.
Teacher will facilitate class discussion on the importance and relevance of classification
and determination of the relationships of living organisms (this may also be covered in
lessons focusing on evolution). Teacher will also introduce phylogenetic tree diagram
and/or cladogram (see figure “How to read a cladogram”
http://ology.amnh.org/biodiversity/treeoflife/pages/howtoreadclado.html, and background reading
from http://jrscience.wcp.muohio.edu/lab/TaxonomyLab.html). Student handout describing how
to construct a cladogram will be distributed and included in notebooks. It is important to
describe each step in the diagram and not assume that the figure will be self-explanatory!
End: Students will complete a modified version of “The Nuts and Bolts of Taxonomy
and Classification” activity from the website
http://jrscience.wcp.muohio.edu/lab/TaxonomyLab.html. to create a classification scheme which
meets the guidelines of modern classification. Students will be presented with an
assortment of objects (nuts, bolts, screws, fasteners etc.). Students will work in small
groups (previously assigned lab groups) and may use concepts from either the cladisitic
or phenetic schools of classification to create phylogenetic relationships between the
objects. Students will also be provided a ruler and encouraged to think about ways in
which objects are similar or different (size, shape, function, appearance etc.).
While in groups, students will discuss the questions included at the end of the activity.
Each group will be responsible for creating a phylogenetic tree, describing the rules they
followed to create their relationships and describing why they chose the classification
scheme. Oral presentations will be made to the entire class following the activity.
This activity is intended to demonstrate the common characteristics that related
organisms do or do not share and the way in which subgroups are created. Cladistic
theory states that each subgroup has branched from a common ancestor and evolved into
a new group. Students should understand that “the basic assumption behind cladistics is
that members of a group share a common evolutionary history, and are thus more
“closely related” to one another than they are to other groups of organisms”
(http://www.mhhe.com/biosci/pae/zoology/cladogram/index.mhtml ).
While remaining in groups, students will complete the last column of the KWL sheets
(what they have learned) and discuss their answers with the group. The teacher will be
circulating throughout the groups during the group activity to answer questions and make
suggestions.
Timing:
Time
6 minutes
20 minutes
29 minutes
Teacher activity
Passing out KWL sheets/writing
instructions on the board
Vocab introduction, writing
definitions on board, facilitating
class discussion
Facilitating classification activity
Homework
Student activity
Filling in KWL sheets/think-pairshare responses
Taking notes, participating in class
discussion
Completing group activity,
completing KWL, presenting final
results of the activity
Research Carolus Linnaeus. Who was he? What did he
do? Why was his work important? Write a 1-2 paragraph
response on what you found.
*May want to include brief
journal entry as an alternative
to KWL, detailing what was OR
learned about classification or
what questions remain about Create your own cladogram for 7 species of your choice
the topic.
and indicate the characteristics used to differentiate them
from one or more common ancestors.
Lesson evaluation (Identify
successful management,
learning, enjoyment and the
evidence of it. Refer to
objectives. Areas for
development.)
Student assessment
(Knowledge, skills, and
understanding)
Lesson eval judged by student interest and engagement in
the discussion and activity.
Students will be evaluated based on quality of group work
and explanation of their use of classification scheme.
Additional assessment may be based answering homework
for understanding of main concepts.
KWL or journal entries can be used to evaluate effectivness
of lesson (to enhance understanding, answer initial
questions, demonstrate progressive understanding).
New targets
Adjustments for special needs students: Prepare notes ahead of class, be aware of wait
time when asking class questions, provide alternative homework assignment.
Materials, equipment and supplies: Assorted hardware/fasteners. Markers and paper
or posters for presenting phylogenetic trees.
Safety concerns: none.
Based on Turner, T. and DiMarco, W. (1998). Learning to Teach Science in the
Secondary School. NY: Routledge.
Student Handout (to be given prior to class period)
(http://jrscience.wcp.muohio.edu/lab/TaxonomyLab.html)
Background
It has become apparent to scientists that the biosphere consists of, at a minimum, 1.5 million described
species. Some researchers estimate that there may be upwards of 40 million species (Go here for an Index
of Animal Phyla) alive today! The species alive today are only a very small percentage of the perhaps
billions of species which have lived on this earth since life first evolved over 3.5 x 109 years ago. Over
75% of the described extant species belong to the Phylum Arthropoda, which includes such diverse
organisms as lobsters, barnacles, hermit crabs, crabs, scorpions, shrimp, horseshoe crabs, spiders, mites,
millipedes, and insects. The insects are by far the most abundant arthropods. How are the many species of
insects (for that matter, all animals and plants) arranged, categorized, and classified? How does the
classification scheme reflect phylogenetic relationships? It can be a bewildering yet extremely interesting
problem. Taxonomy (Gr. taxis, "arrangement, order", nomos, "law") is the science, laws, or principles of
classification (Latin, classis, "a class", facere, "to make").
The Role of Taxonomy
1. Taxonomy works out for us a vivid picture of the existing organic diversity of the earth.
2. Taxonomy provides much of the information permitting a reconstruction of the phylogeny of life.
3. Taxonomy reveals numerous interesting evolutionary phenomena.
4. Taxonomy supplies classifications which are of great explanatory value in most branches of biology and
paleontology.
Rules of the Game
Without a set of international rules to follow, the results of taxonomy would be confusing at best. The rules
of zoological nomenclature are contained in a document known as the International Code of Zoological
Nomenclature (ICZN). The object of the code is to promote stability and universality in the scientific
names of animals. All names must be unique, universal, and show stability.
Uniqueness Every name has to be unique. If several names have been given to the same taxon, priority
decides which name will be the valid name.
Universality Zoologists have adopted, by international agreement, a single language to be used on a
worldwide basis. All animals are given a generic and specific name in Latin. These names are in italics or
are underlined (i.e. Homo sapiens).
Stability The ICZN attempts to prevent the frequent changing of names to provide stability.
Classifications - The Linnaean Hierarchy
Although rudimentary biologic classification may predate civilization, the questions of how classifications
are to be constructed and even to what use they should be put are by no means settled. Carl Linnaeus, in
1758, published Systema Naturae. This marks the beginning of the modern classification of plants and
animals. He devised practical techniques for the naming of groups of organisms and their ranking and
ordering. He developed a system of binomial nomenclature - the scientific name of an organism consists of
a collective generic name and a specific or species name. His techniques are basically intact today. Of
course, there are numerous philosophies and methods of classification which are in use today which help
add to the overall confusion in the world of taxonomy. Linnaeus' great contribution was to provide order in
the method used in the classification of living organisms.
Animals are classified according to the Linnaean system. This consists of the following scheme, for
example, in the classification of several edible invertebrates. Each organism is uniquely identified using a
combination of its genus and species names. Species are grouped into genera, families, orders, classes, and
phyla, depending upon similarities and inferred evolutionary relationships.
American
Lobster
Arthropoda
Phylum
Malacostraca
Class
Decapoda
Order
Nephropidae
Family
Homarus
Genus
americanus
Species
Market
Blue
Virginia
European
Squid
Mussel
Oyster
Oyster
Mollusca
Mollusca
Mollusca
Mollusca
Cephalopoda Bivalvia
Bivalvia
Bivalvia
Decapoda
Mytiloida
Pterioida
Pterioida
Loliginidae Mytilidae
Ostreidae
Ostreidae
Loligo
Mytilus
Crassostrea
Ostrea
opalescens
edulis
virginica
edulis
The names of genera are required by the rules of nomenclature to be unique. But such rules do not apply to
other taxons, even though duplicate names should be avoided. For example, in the table above, the order
name Decapoda occurs in both arthropods and molluscs, and the species name edulis occursin bivalves of
different genera. Wouldn't it be nice if duplicate names did not exist?
A category designates a given rank or level in a hierarchic classification. Such terms as species, genus,
family, and order designate categories. A category is an abstract term. The organisms placed in these
categories are concrete zoological objects.
Organisms, in turn, are not classified as individuals, but as groups of organisms. Words like "bluebirds" or
"thrushes" refer to such groups. These are the concrete objects of classification. Any such group of
populations is called a taxon if it is considered distinct to be worthy of being formally assigned to a definite
category in the hierarchic classification.
Categories, which designate rank in a hierarchy, and taxa (plural for taxon), which designates named
groupings of organisms, are thus two very different kinds of phenomena. Controversy usually reigns
supreme over whether or not a particular group is truly distinct enough to be a new taxon. If it is a new
taxon, taxonomists then determine which category the taxon will be placed in.
Much of the task of the taxonomist consists of assigning taxa to the appropriate categorical rank. The
hierarchy of categories that the classifying taxonomist recognizes is an attempt to express similarity
("characters in common") and recency of common descent. The most closely related species (occasionally
subject to intense debate) are combined into genera, groups of related genera into subfamilies and families,
these into orders, classes, and phyla. In this procedure there is a drastic difference between the species
taxon and the higher taxa (genus on up to phylum). Higher taxa are defined by intrinsic characters. For
instance, the Class Aves (birds) is the class of "feathered vertebrates". Any and all species that satisfy the
definition of "feathered vertebrates" belong to the Class Aves.
Species Groups of actually or potentially interbreeding natural populations which are reproductively
isolated from other such groups. May or may not be morphologically distinct.
Genus The lowest higher category. A taxonomic category containing a single species, or a monophyletic
group of species, which is separated from other taxa of the same rank by a decided gap (behavior,
morphology, or some other characteristics).
If these three species belong to the same genus, they are descended from a common ancestor.
Family A taxonomic category including 1 genus or a group of genera of common
phylogenetic origin, which is separated from other families by a decided gap.
Currently, there are about 26 known phyla, 80 classes, and 350 orders of extant animals.
As one goes up the hierarchic scale from the species rank up to phylum, each
category becomes more inclusive.
When a species is collected and it is new to science, the most important rules of ICZN cover:
1. Choice of a name - must be Latin, must not be already used, and it must be in binomial form.
2. The name must be published in a well respected, preferably international, scientific journal.
3. The publication must include a description of the new species.
4. Described species must be accompanied by a type or preferably a set of type specimens which must be
accessible to scientists from the world over (i.e. the type specimens are placed into a museum which allows
access to all).
The following information is from:
http://www.utm.edu/~rirwin/b120lab.htm.
Phylogeny:
Remember that phylogeny refers to the evolutionary relationships among species. The
process of evolution of more than one (usually two) new species from a pre-existing
species is called speciation and can be represented as follows:
Reading tree diagrams of phylogeny:
Phylogenies are typically diagrammed as trees; the shape of these trees can vary, but all
can be interpreted as follows. Lines with names associated with them refer to species or
groups of species all more closely related to each other than to other groups on the tree.
Following these lines back to the points where they join other lines leads to ancestral
species to the named groups. Lines that lead back to the same line represent species that
share a common ancestor.
Here are three phylogenetic trees; all represent the same pattern of phylogenetic relationship among the
species shown. Be sure to study these until you can see that all are the same. In this exercise you will need
to be able to interpret phylogenetic tree diagrams drawn by different people in different ways.
Taxonomy:
Taxonomy is the name given to the study of classification of organisms based on their
phylogenetic relationships. In making a phylogenetic classification, taxonomists name
groups of organisms that are all close relatives of one another. There is some variation in
the criteria taxonomists use for making classifications; here, we will only consider
phylogenetic classifications , that is, classifications based purely on phylogenetic
relationships among species.
Classification schemes are hierarchical in nature. Large groups containing many different species are
divided into smaller more specific groups, each with fewer species. Each of these is divided into still
smaller groups with still fewer species. These groupings reflect phylogenetic relationships. For example, all
animals -- all the descendents of the species that was the ancestor to all mammals -- are placed together into
one large group; within that group, more closely related animals are placed together into smaller groups,
and so on.
There are seven traditional major levels in a classification scheme. Arranged from most general (the largest
groups, containing many different species) to most specific (the smallest groups, containing, at the lowest
level, only the members of a single species), these are:
Kingdom
Phylum (in animals) or Division (in plants)
Class
Order
Family
Genus
Species
Every organism is placed into one of five kingdoms. These are the:
Kingdom Monera
Bacteria and cyanobacteria. Unicellular organisms that are prokaryotic , that is,
do not have a nucleus surrounded by a nuclear membrane. The bacteria are mostly
heterotrophic, that is, they cannot obtain energy from non-living forms and must
eat other organisms, or their products, to obtain energy. The cyanobacteria are
autotrophic, that is, they can convert energy from non-living forms into
biologically useful energy (stored in the chemical bonds of biological molecules);
cyanobacteria, like plants, accomplish this through the process of photosynthesis
Kingdom Protista
Unicellular organisms that are eukaryotic , that is, have a nucleus separated from
the cytoplasm of the cell by a nuclear membrane. Some are plant-like in that they
are autotrophic, while others are animal-like in that they are heterotrophic.
Kingdom Animalia
Animals. Multicellular organisms with cells that lack a cell wall. Many are
capable of movement, or movement of some of their body parts, at some time of
their life. Animals are heterotrophic , that is, they cannot obtain energy from
non-living forms and must eat other organisms, or their products, to obtain
energy.
Kingdom Plantae
Plants. Multicellular organisms with cells surrounded by a cell wall made of the
carbohydrate cellulose . Plants are typically non-moving. They are autotrophic ,
that is, they can convert energy from non-living forms into biologically useful
energy (stored in the chemical bonds of biological molecules); plants accomplish
this through the process of photosynthesis , synthesis of energy-containing
biological compounds by trapping light energy.
Kingdom Fungi
Mushrooms, yeasts, and other fungi. Multicellular organisms that are typically
non-moving, have a cell surrounded by a cell wall, and are heterotrophic , that is,
they cannot use energy from non-living forms and must consume other organisms,
or their products, to obtain energy. Many are decomposers , that is, they obtain
energy by breaking down molecules in dead, decaying organisms.
Classification Activity
We usually use about 15 different hardware items!
Divide into research teams. You have been handed a bag of various fasteners (nails, staples, screws, etc.)
As renowned taxonimists, you are to develop a classification scheme that meets the established rules of the
Linnaean system or follows the guidelines of the cladistic or phenetic systems. Be prepared to defend your
classification scheme orally.
Tasks:
1. Make a phylogenetic chart of your classification scheme (as shown on this handout) using the poster
paper, tape, and objects. Include all of the categories from phylum to species. What rationale (s) did you
use to for each category and what criteria did you use to differentiate among categories? Did you rely more
on "form" or "function?" Or derived and ancestral traits? Optional :Provide descriptive names for each
category from phylum, class, order, family, genus and species. Apply names that best describe each object
and their heirachical location in your classification scheme.
2. What are some of the difficulties and differences between classifying inanimate objects and living
organisms? Is it easier or more difficult to classify living or inanimate objects? Why? If you knew nothing
about each object's function, would that have made a difference in your classification scheme?
3-Does your classification scheme reflect the evolutionary relationships and phylogeny among taxa?
Who evolved from whom? Which "body type" do you consider to be the most primitive? The most
advanced? Be sure to consider evolutionary relationships.
4- What roles did form, function, derived characters, and ancestral traits play in your classification scheme?