The Arizona STEM Acceleration Project
Learning Through Leaf Packs!
Lesson 3 of 8: How to Use a Dichotomous Key
Learning Through Leaf Packs
How to Use a Dichotomous Key
(Lesson 3 of 8)
A Middle School (6th -8th) STEM Lesson
Susan Brown & Carrie Jenkins
12/19/22
Learning Through Leaf Packs
Note for teachers: This is an 8 lesson unit that is designed to be used together to learn about the health and diversity of your local watershed by placing leaf packs into a water source (natural or man-made ponds, lakes, streams, and rivers) and attracting macroinvertebrates. Links to all lessons are on the next slide.
Why do this?!
Carrie Jenkins, 6th math & science
You don’t need a water source. This unit has a virtual option to collect data!
Lesson Sequence
Lesson 1: What is a leaf pack?
Lesson 3: Dichotomous Keys
Lesson 4: Leaf Pack Dissection
Lesson 5: Data Analysis and the Leaf Pack Network
Susan Brown, 7th science
Notes for Teachers
You can teach using a dichotomous key using something like candy but we like using the macroinvertebrates since this is what the students will be identifying when dissecting the leaf packs.
If this is your first time using leaf packs, try to preserve specimens found so you have specimens for the following year.
List of Materials
Arizona Science Standards
6.L2U1.13 Develop and use models to demonstrate the interdependence of organisms and their environment including biotic and abiotic factors.
6.L2U1.14 Construct a model that shows the cycling of matter and flow of energy in ecosystems.
Science & Engineering Practices
Arizona Science Standards
Life Science Standards
Students develop an understanding of the flow of energy in a system beginning with the Sun to and among organisms They also understand that plants and animals (including humans) have specialized internal and external structures and can respond to stimuli to increase survival.
6.L2U3.11 Use evidence to construct an argument regarding the impact of human activities on the environment and how they positively and negatively affect the competition for energy and resources in ecosystems.
6.L2U1.14 Construct a model that shows the cycling of matter and flow of energy in ecosystems.
Core Ideas
6.L2U3.12 Engage in argument from evidence to support a claim about the factors that cause species to change and how humans can impact those factors.
● Ecosystems are dynamic in nature, their characteristics can vary over time. Disruptions to any physical or biological component of an ecosystem can lead to shifts in all its populations.
● Human activities have significantly altered the biosphere, sometimes damaging or destroying natural habitats and causing the extinction of many other species.
Arizona ELA Standards
7.RI.4 Determine the meaning of words and phrases as they are used in a text, including figurative, connotative, and technical meanings; analyze the impact of specific word choices on meaning and tone.
6.RI.10 By the end of the year, proficiently and independently read and comprehend informational texts and nonfiction in a text complexity range determined by qualitative and quantitative measures appropriate to grade 6,7,& 8.
Objective(s):
Agenda (50-60 Minutes)
Intro/Driving Question/Opening
What is a dichotomous key and how is it used to identify organisms?
What am I?
Dichotomous Key Entomology
Let’s break down the word!
From the Late Latin dichotomos, from Ancient Greek διχότομος (dikhótomos, “cut in half”), from δίχα (díkha, “apart”) + τέμνω (témnō, “I cut”).
c. 1600, "a cutting in two, division into two classes;" 1630s, "state of having a dual arrangement or order," from Latinized form of Greek dikhotomia "a cutting in half," from dikho-, combining form of dikha "in two, asunder" (from or related to dis "twice," from PIE root *dwo- "two") + temnein "to cut" (from PIE root *tem- "to cut"). Related: Dichotomous; dichotomously.
Hands-on Activity Instructions
Which of the paired statements fits best with the photos?
“KimGuthrie-The Nature Tour (Mountainmystery) on Pinterest.” Pinterest, www.pinterest.com/mountainmystery/.
“Damselfly Nymph.” Welcome to BugGuide.Net! - BugGuide.Net, bugguide.net/node/view/811754.
“Damselfly.” Wikipedia, Wikimedia Foundation, 20 June 2020, en.wikipedia.org/wiki/Damselfly.
Damselfly!
“Damselfly.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., www.britannica.com/animal/damselfly
“Damselfly.” Wikipedia, Wikimedia Foundation, 20 June 2020, en.wikipedia.org/wiki/Damselfly
Damselfly. (n.d.). Retrieved from https://vineyardgazette.com/news/2016/07/06/dear-damselfly-violet-dancer
Competition Time!
Whisper with your group to identify the macroinvertebrates in the upcoming pictures!
Ready...Set...Go!
What is it?
“Dragonfly Nymph.” Warren Photographic, www.warrenphotographic.co.uk/23655-dragonfly-nymph .
What is it?
“Pond and Water Insects and Bugs Etc.” Insects, Bugs and Other Critters, Page 3, www.jasonsteelwildlifephotography.yolasite.com/pond-life.php .
What is it?
Waldvogel, Michael, et al. “Biology and Control of Non-Biting Aquatic Midges: NC State Extension Publications.” Biology and Control of Non-Biting Aquatic Midges | NC State Extension Publications, content.ces.ncsu.edu/biology-and-control-of-non-biting-aquatic-midges .
“Midge Larva.” Welcome to BugGuide.Net! - BugGuide.Net, bugguide.net/node/view/254470 .
What is it?
“Caddisfly Larva in Case with Mica.” Welcome to BugGuide.Net! - BugGuide.Net, bugguide.net/node/view/1055316/bgimage .
Dr. Rob Cannings Contributor. “Caddisfly Architecture.” Curious, 7 Nov. 2013, curious.royalbcmuseum.bc.ca/caddisfly-architecture/ .
“Caddisflies.” DePauw University, www.depauw.edu/about/campus/naturepark/research-project-list/caddisflies /.
Assessment
Formative Assessment:
Competition checks students’ ability to identify macroinvertebrate correctly.
Exit ticket, project one macro that students have to identify on their own.
Summative Assessment:
Homework: Complete this worksheet to show proficiency in using a dichotomous key.
Students design own dichotomous key using a set of small items provided. (candy, toys)
Differentiation
Remediation
Extension/Enrichment &
Incorporating Technology