|Title: What is it? Using a
Dichotomous Key |
|Subject: Science |
Level: 7 |
|TLW be pre and post assessed on knowledge of how to use and how
to create a dichotomous key. TLW gain field experience that requires
using a dichotomous key before designing their own key. Students
will used info gathered in Webquest to design a Kingdoms of Life
Brochure. A Webquest and field trip extension are offered but not
required. Extensions use Excel to graph student gathered data.
Rubrics for assessment are included as well as practice test items.
Duration: 4 - 6 : 45 minute class periods;
Webquest one day |
- Science as Inquiry
students will do science by engaging in partial and full inquiries
that are within their developmental capabilities.
- Life Science
students will become aware of the characteristics and life cycles
of organisms and understand their relationships to each other and
to their environment.
- Science and the
environmental science, students will develop an appreciation of
the natural environment, learn the importance of environmental
quality, and acquire a sense of stewardship. As consumers and
citizens, they will be able to recognize how our personal,
professional, and political actions affect the natural world.
models and predictions using the relationships between data and
scientific procedures, information, and explanations;
safety procedures during scientific investigations.
that scientific investigations can result in new ideas, new
methods or procedures, and new technologies;
and using classification systems based on the structure of
interpreting food chains and food webs;
major ecosystems and recognizing physical properties and organisms
interaction and interdependence of nonliving and living components
concept of pollutant and describing the effects of various
pollutants on ecosystems;
that human actions can create risks and consequences in the
flow of energy through an ecosystem and demonstrating a knowledge
of the roles of producers, consumers, and decomposers in the
|Grade-Level Expectations (GLEs):
- Science and the Environment
39. Analyze the consequences of human
activities on ecosystems (SE-M-A4)
40. Construct or draw food webs for various
- Populations and Ecosystems
23. Classify organisms based on structural
characteristics, using a dichotomous key (LS-M-C1)
27. Identify the various relationships among
plants and animals (e.g., mutualistic, parasitic,
- English/Language Arts : Standard
Students read, comprehend,
and respond to a range of materials, using a variety of strategies
for different purposes.
- English/Language Arts : Standard
Students write competently
for a variety of purposes and audiences.
- English/Language Arts : Standard
Students communicate using
standard English grammar, usage, sentence structure, punctuation,
capitalization, spelling, and handwriting.
- English/Language Arts : Standard
competence in speaking and listening as tools for learning and
- Social Studies : Geography: Physical and Cultural
Students develop a
spatial understanding of Earth's surface and the processes that
shape it, the connections between people and places, and the
relationship between man and his environment.
- Demonstrate the operations of a computer (e.g.,
touch-keyboarding skills, save, organize and back-up files) and
other peripheral devices (scanner, digital and video cameras, VCR,
laser disc player) at an intermediate level.
- Use information, media, and technology in a responsible manner
which includes following the school's acceptable use policy,
adhering to copyright laws, respecting the rights of others, and
employing proper etiquette in all forms of communication.
- Use technology tools (e.g., multimedia authoring, writing
tools, digital cameras, drawing tools, web tools) to gather
information for problem solving, communication, collaborative
writing and publishing to create products for various audiences.
- Understand Internet concepts (e.g., website, hypertext link,
bookmarks, URL addresses) and apply intermediate on-line searching
techniques (e.g., employ keyword, phrases, and Boolean Operators).
- Use telecommunications and online resources efficiently and
effectively to collaborate with peers, experts, and others to
investigate curriculum-related problems, issues, and information
and to develop solutions or products for various audiences.
Students will practice using
a dichotomous key in the classroom prior to their field
Students will collect and identify 8 different tree
samples using a dichotomous key and leaf characteristics.
Students may participate in a field trip extension that will
tie in food web, predator/prey and habitat/niche benchmarks. A
scavenger hunt, field tree id and pollution scavenger hunt are
included in this lesson plan. Data gathered on field trip can be
organized into a graph using Microsoft Excel.
synthesize knowledge they have gained to practice classifying
different types of beans and write a 5 sentence
paragraph/constructed response to explain how they classified the
Students will create a dichotomous key to classify 2
assigned objects (beans can be used).
Students will engage in
web based learning using a webquest to explore
Student text for Calcasieu Parish
Glencoe/McGraw Hill Life Science Copyright 2002
1 pages 22-29
Computer with printer and internet
MS Word, MS Excel
Make sure that students understand that
dichotomous keys can be used to identify organisms from all kingdoms
Here is an article that has great examples of
characteristics that might be used to distinguish different species
Different groups of plants
believe that there are more than 300,000 species of plants. The
variety of plants on our planet is amazing. Giant sequoia trees are
plants just as much as strawberries or tiny mosses. Plantae is the
scientific name for the plant kingdom. It consists of many different
divisions and groups of plants. Scientists group plants according to
their common characteristics.
2 Scientists group plants by
their similar parts, for example, plants' roots. Just think of the
huge roots of some trees. Sometimes they can grow through the
pavement on walkways. Compare that to the roots of beets or yard
grass. They do look very different, don't they?
3 There are
two major kinds of root systems. The root system that looks like one
major root--like the one the beet plant has--is called a taproot. A
taproot grows down and forms many small secondary roots. Plants with
taproot systems use their roots to store food. You can see these
plants and roots in many gardens and grocery stores--carrots, beets,
radishes, and turnips. Some trees also have taproot systems. Pine
trees can grow their taproots as far down as 6 meters (about 20
4 The second major kind of root system is called
fibrous roots. They are made up of large numbers of roots that are
more or less equal in size. Instead of growing deep down, they
usually spread over large areas. Most grasses and some trees, like
maple and beech trees, have fibrous root systems.
though the roots are different, their functions are the same--to
anchor and support the plant, and to absorb, transport, and store
water and nutrients. The tissues that roots are made of are the
same, too. The outside covering of a root is called epidermis
(ep-i-dur-mis).This term is also used for the outer covering of
human skin! Epidermis directly contacts the soil and absorbs water
6 The tissues inside the roots are called
xylem (zi-lem) and phloem (flo-em). They are tube-like tissues
through which water and nutrients move. Xylem helps to move water
and nutrients from the roots to the stems and leaves. Phloem
conducts food made in the leaves to all other parts of a plant that
need them. Xylem and phloem are separate inside the plant, and they
are continuous from the root, stem and leaves.
7 For our
purposes today, we will use the leaves of trees to differentiate the
Pretest knowledge of dichotomous
Practice using dichotomous
1.Pretest Knowledge. (see
2. Arrange chairs in a circle.
Instructor takes off
one shoe and places it on the floor in the middle of the
3."There's one of my shoes, so let's
have a shoe from some of you". Ask five-ten reliable students to put
one of their shoes in the middle of the circle.
students that they are to divide the shoes into two piles. Tell them
the piles don't have to have equal numbers of shoes but, that they
all have to agree on some obvious characteristic that will
distinguish the shoes in one pile from the shoes in the other
pile. After agreement is reached, tell the students a record of the
agreement will be kept on the board.
5.Draw two horizontal lines
some distance apart on the chalkboard. Label the lines with the
agreed upon characteristics.
6.Return to the pile of shoes. Tell
the students one pile will be pushed aside for the moment but, now
they must again divide the pile of shoes into
piles. After agreement is reached add this information to the
ovehead or classroom board sketch.
7. Continue the procedure
of dividing the shoes into two distinct piles and adding the
information to the sketch until there is only one shoe with the
identifying characteristic, at which point the shoe is
identified and the owners name is added to the sketch
the second pile of shoes in the same manner as the first pile
until all the shoes have been identified.
9. Push all the
shoes back together in one pile, adding perhaps a shoe from the
distance past or one with characteristics unlike those used in the
Discuss the meaning of the term
dichotomous explaining that the word means "two forks".
the students that dichotomous keys usually appear in a more compact
form and that the diagram can be easily converted by adding numbers
to each characteristic used. Label the diagram in numerical sequence
following the same order the characteristics were agreed
11. Have the students redeem their shoe by taking it from
the pile and placing it on the correct branches of the key which
will lead to its'
correct identification. After all the shoes
have been redeemed the shoe added earlier should remain. Ask a
student to follow the key until the shoe is identified. Students
should discover that a key works only for identification of those
items used in its' original construction.
12. Pass out the
practice worksheet(s). Complete the " Using A Dichotomous Key" sheet
If needed repeat the procedure with the "Some Common
Beetles of North America" sheet in class.
needed, either before or after the Web quest, the teacher should
spend another class period repeating this procedure using a variety
of beans. I usually buy a bag of 15 bean soup and put 2-3 beans of
each variety into a set of Ziplocs to be uses by cooperative groups.
Card stock works well to do the grouping and for students who need
even more reinforcement to get to the written step, you can have
them glue the beans into place. Then they can work from the glued
bean page to develop a written dichotomous key. In our textbook,
there is a lab activity on page 27 that sorts and classifies beans
according to shape, size, color, texture, etc..
Day Two: Web
Objective: TLW complete the teacher designed web quest to use technology resources to garner further understanding
of classification and dichotomous keys. Information gathered will
used to create a "Kingdoms of Life " booklet that can be
assessed. Students can use technology skills of cutting and pasting
or copying and pasting from the websites into the Classification
Student journal page and classification chart task page
are to be printed out by the student and turned into the teacher for
assessment. Rubric is attached. Resources are all embedded in the
Day Three: Practice using Dichotomous
Objective: TLW practice using physical characteristics
to classify organisms.
There are three lessons included to
meet individual differences. If your students are catching on and
need to be challenged, use the High School lesson
Classification of Aliens. If students are weak, use the Buttons
Classification and if students are in the middle, use the Tree ID.
Microsoft Excel graphs can be created to show class data on two
differentiated characteristics to be determined by class. For
1. Aliens (socks and no socks; eyes on stalks and eyes
not on stalks, etc...)
2. Buttons (round and non-round)
Tree Leaves (lobed and non lobed; evergreen and deciduous,
Day Four: Design a Dichotomous Key
design a dichotomous key that maps out at least 5 different
characteristics to distinguish between the two assigned
Beans can be used and classified by characteristics
like size, shape, color, texture, etc... Students will write
characteristics used to differentiate and classify on the chart they
design. I like to use cardstock and have students glue beans or
leaves onto the chart. Students then write a five sentence
constructed response paragraph explaining how they classified their
Students use their chart from the
previous day to compose and write 5 steps with 2 choices "a" and "b"
at each step for a total of ten statements. Remember, the final two
statements serve to identify by Genus and species name, the given
Post test, Closure--class discussion and
reflection on Plus/Delta or K-W-L chart.
Field Trip Extension
Rubric for Creating a Dichotomous
Rubric for Web quest
standard 504 guidelines for your students
----- written by Elizabeth Winfrey
Field trip extension: If possible, have kids
visit a campus or nearby botanical garden or public park where they
will be asked to identify 4-8 trees using available field guides.
Field trip could include a food-web scavenger hunt and a pollution
scavenger hunt. To make the field trip data driven have students
gather data on two to six specific characteristics like leaves:
lobed and non lobed, evergreen and deciduous and have kids create an
Excel graph using this data.
Brain pop movie is great way to
reinforce what the student's have learned so far. See reproducible.
In reproducibles, find the field
1. Food/Energy Web
2. Tree id
Here is a great
classification lesson from the state website. The students will love
classifying aliens according to physical characteristics. It is
considered High School but your students should have no
There were a lot of
adjustments I had to make along the way in teaching this series of
lessons or Unit, but I think in the long run, your students will
have a comprehensive in depth understanding of classification.
Oak Park Middle School
Lesson: No |