Introduction: Tear It Up and Tape It - Middle School Flower Dissection Lab
Seventh grade science stretches the gamut of teaching, ranging from symbiotic relationships of the pistol shrimp and goby fish to electromagnetic force. Somewhere in the middle I am supposed to teach them about reproductive methods of organisms and the resultant genetic diversification of life (yes, with 13 year old kids). One of the best, and least awkward, ways to teach reproductive methods is through the investigation of plants. Looking at plants that can reproduce asexually (maternity plant, cacti, garlic, strawberry, etc...) and plants that reproduce sexually (all angiosperms - flowers) gives the students a much clearer picture and totally (well almost) removes the awkward nature of the curriculum.
Many kids love the idea of dissecting something, but there are a good number that definitely rather not put a scalpel into a formaldehyde preserved animal. Dissecting a flower doesn't quite have the cringe factor and it allows the students to see all of the inner workings of a sexually reproducing organism. No matter which way you slice it (sorry for the pun) there is still sperm and egg involved with angiosperm reproduction.
What follows is a step by step process for completing this lab in the classroom with a wide range of ages. I teach it to seventh grade students but you could easily modify it for upper elementary up through eighth grade. I have included all of the activity sheets with this Instructable along with details and explanations on how to run the activity. We used alstroemeria flowers with the lab since they are readily available at our local grocery store and are pretty easy to work with and to identify all of the parts. We used simple equipment to conduct the dissection; magnifying lenses, tweezers, sharp scissors, and transparent tape.
Step 1: Getting Prepped - How Do Flowers Turn Into a Fruit With Seeds on the Inside?
Ultimately the goal is for students to identify how flowers act as a sexually reproductive structure allowing flowering plants (angiosperms) to reproduce and continue that plant's specific genetic qualities. With the lab the students will be exploring each component of the flower and identifying the reproductive structures within it. It is wise to do some preliminary work with the students identifying various forms of reproduction and discussing the various structures involved in flower reproduction.
I have included for your use my lesson plan that I wrote specifically for dissecting alstroemeria flowers. You should access each of the following documents (they are Google Drive based and are open for anyone to view):
Flower Dissection Lab Packet (includes introduction, flower dissection instructions and taping areas, and focus questions for the end of the lab)
Dissecting Alstroemeria Hints Presentation (gives some helpful hints on how to identify the specific parts of these flowers)
Step 2: Conducting the Lab
I make containers (old salad containers or Trader Joe's animal cracker bins) available for each table with the following materials in it (typically there are enough for one per student):
- Scissors and/or dissecting knife (depends on the class)
- Magnifying lenses
- Transparent tape (one per table is fine)
I don't hand these materials out until we have reviewed the lab directions and the students have gone through the entire lab to identify their jobs. I then hand out the lab packet and read through the entire front page with the class going through all of the details on how these flowers specifically can reproduce. You can have the students highlight key points, especially those that connect to identifying the correct components and will help with the final focus questions.
Next I hand out one Alstroemeria flower to each student and tell them to hold off on the dissection. Using the Google Slides presentation I provided, I go through each part of the flower so that the students can more easily identify the components of alstroemeria during the actual dissection. Things such as the sepal being fused to the back of the petal can cause confusion due to the previous activities involving flowers with non-fused sepals.
Once you feel confident that the students are ready to begin the dissection, hand out the bucket of materials to each table and have the students begin working on the lab. I usually go around the room to make sure that each student is placing the correct part in the boxes provided. They should use tape to cover the entire part if they want to preserve it. Also, when it comes to dissecting the ovary, it is best to use a dissecting knife, pallet knife, or other sharp-edged tool. Scissors do work but make sure they are decent enough to cut up the center of the stem and through the ovary.
Once the student is finished with the dissection portion of the lab they should begin working on the conclusion questions. There are a couple that I wrote that really do take some time to think through. so encourage the kids to try their best on them and apply all of what they have learned about flower pollination and to use the front of the lab packet for assistance.
As for grading, I use a standards-based grading system that I developed for my class and use for all assignments and assessments. You will see it on the very last page. I believe that this grading system creates goals that are clear and easily accessed by the students. It also makes grading assignments less subjective for the teacher and provides clearer feedback for the students to see where they need to improve. Coupled with this grading system I use a token system allowing the students to cash in up to three tokens per quarter to improve their work on assignments and assessments... maybe I will have to write another instructable on my grading system?
Step 3: Taking It to Another Level - Teaching Is the Key to Learning
"While we teach, we learn" - Seneca (Roman philosopher 4 BC to 65 AD)
We are lucky to have our elementary school within a quick walk to our middle school. The opportunities to collaborate between the two schools are endless and we have taken advantage of a number of instances to help further our own student's understandings through teaching the younger students. Both party's benefit immensely from the interaction and it is fantastic to see our student's take full ownership of the work they do.
Once my students are proficient with flower reproduction I tell them that they are not going to be tested on their understanding in the normal, summative manner but instead will be tested through their ability to teach. I have the students get into groups of between two and three students and then hand out this sheet to each of them. We discuss the components of a good lesson plan (i.e. pre-assessment, models, etc...) listed on the first page and then talk about the standards for second grade students in the state of Massachusetts, listed on the back. Groups are then given the challenge to design a full lesson plan used to teach a small group of second grade students about the purpose and function of flowers.
I tell the students that I will provide a pre and post assessment to their second grade students so that they will have some sort of gauge on how effective their lesson plan was. I also give the disclaimer that they cannot rely only on this summative assessment to determine what their students do and don't know about the topic. I try to connect this to the current drive in public schools for standardized tests, and how they determine so much for both students and educators. I typically deliver the pre-assessments to the second grade teachers a week or two before they are set to come down for the lessons.
Students are then given approximately three class periods (50 minutes each) to create and develop their lesson plans. As you can see from the pictures, the students are extremely creative and come up with some fantastic ideas to teach their students the purpose and function of flowers on angiosperms. These lessons will typically take 40 minutes to complete and do require some decent coordination between the two schools, but they are worth their weight in gold. I have seen students who were somewhat unenthusiastic throughout the entire school year come to life through the process of making the lesson plans and especially when initiating them. You see those kids who have a future in teaching right off the bat and it's refreshing to see your students in a different light.
As a summarization of the entire process and as a reflection of what was learned I have students complete a student reflection page. While the kids are teaching I go around the room and take pictures of them working with their students. I then print those photos off so that they can paste them onto their student reflection sheet. The post-assessments are completed a day or two after the second grade students complete the lessons and I pick them up when they are ready. My students will then compare the pre and post assessments and look for where they can find summative growth while keeping in mind that it is only on portion of the entire puzzle.
This is one of my favorite lessons of the year and I hope that you will find a way to incorporate it into your curriculum.
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