Hands On With Cells - Using Slide Viewers and Microscopes
Grade level(s):Elementary School (K-5), Middle School (6-8), Grade 5, Grade 6, Grade 7
Topic:Cell Biology/Living Systems
What is a cell?
There are a variety of cell types (both plant and animal) that have a variety of functions in an organism.
Cells are microscopic (too small to see with the naked eye), so scientists use tools like microscopes to view them.
What does it mean to be a "Cell Biologist"?
What you need:
SEP Resource center - Microscopes (compound microscopes will be needed to see Elodea cells structures and Onion cell structures)
SEP Resource center - specimen slides of blood cells and any other body cells
SEP Resource center - slide viewers and slide sets of different cell types "cells of the body" and "comparing plant and animal cells".
Samples to look at under the microscope - Elodea Leaves, Onion Skin Peels, hair strands, etc....
Movies from http://cellimages.ascb.org to augment lesson (for example beating heart cells, blood vessel formation, or watching cellular embryo development, also if you are not able to get Elodea plants, it is interesting to at least watch video of cytoplasmic streaming in Elodea cells)
Students will be split into 4 or 5 groups
Allow students as much time as possible (7-10 minutes) at each station to draw results
Lead a discussion about what was seen at each station afterwards
In this activity students use microscopes and slide viewers to visualize cells and record what they see. Emphasis is on *recording observations*. Students are introduced to new technologies and to the diversity of cells that make up our body and that exist in plants.
Students should have started to discuss the human body and/or plants and the fact that they are made up of cells.
Understand that our body is made up of many cell types, and that a diverse range of cells exist in plants and animals. They should understand that even though we can not see them, cells are the building blocks of living organisms. They should learn the importance of observation and making recordings, and become familiar with some of the tools cell biologists use.
The cell is one of the most basic units of life. There are many different types of cells. There are cells that are organisms themselves, such as amoebas and bacteria (unicellular organisms), and there are cells that function as part of a larger (multi-cellular) organism, such as the cells that make up the human body. The cell is the building block of life in the body, there are skin cells, brain cells, liver cells, stomach cells, etc. each with unique functions and designs. While both plant and animal cells contain many similar structures, plant cells have some specialized features, such as the cell wall (which give plants their structure) and chloroplasts which allow plants to photosynthesize.
The aquatic plant Elodea is a great plant to show cells from as when using a high power microscope 200-400x (and peeling a thin section from one leaf) one can see the cell walls and chloroplasts (two unique plant cell structures). The chloroplast can also be seen moving through the cell because of a process call cytoplasmic streaming (where the cytoplasm flows around the nucleus).
Set up four stations in the classroom, each with a different piece of equipment or sample(s) to look at.
Station 1 - 5 slide viewers, and 5 slides of "Cells of the Body"
Station 2 - Up to 5 microscopes, and specimen slides of blood cells
Station 3 - 5 slide viewers and 5 slides of "Comparing Plant and Animal Cells"
Station 4 - Up to 5 microscopes, and microscope slides containing fresh samples from onion skin or Elodea*
Another potential station would be to have models of animal or plant cells available for observation
Have students either use their science notebook or prepare and xerox copies of worksheets to be handed out to the class. Have the students draw what they see at each station, and write at least one question down about what they are looking at.
* You will need to set up microscopes ahead of time, focusing the microscopes on the slides (as often students struggle with this, given the short amount of time at each station, doing this ahead of time will save the students time), instruct students not to disrupt the microscope's focus.
To prepare the Elodea: Peel a thin section from the surface of a single leaf, mount it in a drop of water on a microscope slide, and cover with a cover slip.
If you can't get Elodea at your local aquarium store, one can still see cell wall structures of an onion skin cell, as well as often times the nucleus.
Lesson Implementation / Outline
10 minute attention grabbing introduction – going from cells to organs
•Cells are the most basic unit of life in the body
•Cells are very diverse – they can take many forms and become very specialized depending on the job they have to do in the cell •Single cells divide and grow, and millions of cells work together to form multi-cellular tissues and organs which can do incredible things
Definition of a cell biologist. A cell biologist is someone who studies the activities, functions, properties, and structures of cells. They must observe, record what they see and ask questions about what they find.
Show movies from http://cellimages.ascb.org to get students excited about cells - beating heart cells, blood vessel formation, or watching cellular embryo development. We recommend turning off the sound, as the narration is too complext for 5th grade level. See the pages below for links and click on "Access this item" to actually watch the video.
Embryonic fish cells: http://cellimages.ascb.org/cdm4/item_viewer.php?CISOROOT=/p4041coll12&CISOPTR=245&CISOBOX=1&REC=16
Brain Cells: http://cellimages.ascb.org/cdm4/item_viewer.php?CISOROOT=/p4041coll12&CISOPTR=238&CISOBOX=1&REC=16
Cell division in Drosophila embryo: http://cellimages.ascb.org/cdm4/item_viewer.php?CISOROOT=/p4041coll12&CISOPTR=254&CISOBOX=1&REC=12
Blood Vessel Formation in fish: http://cellimages.ascb.org/cdm4/item_viewer.php?CISOROOT=/p4041coll12&CISOPTR=241&CISOBOX=1&REC=2 Fern sperm cells: http://cellimages.ascb.org/cdm4/item_viewer.php?CISOROOT=/p4041coll12&CISOPTR=246&CISOBOX=1&REC=7
Elodea Cytoplasic Streaming (can see cholorplasts moving): http://cellimages.ascb.org/cdm4/item_viewer.php?CISOROOT=/p4041coll12&CISOPTR=247&CISOBOX=1&REC=8
After the movie clips, spend 5 minutes on an equipment introduction – slide viewers/microscopes/magnification. Emphasize how scientists make OBSERVATIONS with these tools, and use them to see things too small for the naked eye to see.
Have the class rotate between the four stations for approximately 8 minutes at each station. Have students record observations at each, and circulate around the room to make sure everything is working smoothly. Teachers/assistants should focus most on the stations with the microscopes, because they will need to prepare slides/use the scopes, or pre-focus them and tape over the focus so students can just look through the scope.
Critically - do not emphasize or point out what the student should be seeing in the microscope. Let them view for themselves what is there, and draw any observations or questions they have. By highlighting something on the slide, you discourage the student from making his own naive judgements about what he/she is looking at.
Teacher should rotate through the differnt stations to check in on students' understanding.
Ask students to describe the most interesting or surprising thing they saw, write down the observations on the whiteboard.
Ask students to share questions that they might have about what they saw.
Share questions that you have for the students, and answer one or two (if you know any answers). For example, "Why do red blood cells look smooth?" Perhaps the answer may come up that it helps the blood cells travel through the bloodstream without getting stuck in blood vessels. Maybe no one will have any idea, and that's ok! Emphasize that it is the job of a cell biologist/scientist to look at cells, make observations and ask questions, and then try to figure out how they work.
Extensions and Reflections
Keep it simple - the problem we got into was that we tried to set up too many stations, or had too many samples at each station. It doesn't have to be any more complicated than just one or two slides and slide viewers to look at.
It may seem like a simplistic lesson, and a lot of extra work, to have students look at pictures in a slide viewer instead of on a poster or in a textbook. But there was great excitement from the students getting to be hands on with "tools" that scientists use, and not being told explicitly what they were looking at in a labeled diagram. They seemed to get a lot of excitement and a deeper understanding of what it meant to be a "cell" after this lesson
This serves as a bridging lesson to add more focus to the idea of what a "single cell" is. The FOSS curriculum, Living Systems, does not focus much on a single cell, and simply shows a couple of pictures in the book. By exposing students to the diversity of cells that make up our body, it helps them to understand the features of multicellularity which come up throughout the unit.