Download Investigating Cell Theory through Observation, Testing

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Resource ID#: 157232
Investigating Cell Theory through Observation, Testing,
and Modeling
Students will address the three main tenets of cell theory by investigating: (1) "How big is a cell?" (using virtual scaling and compound microscope
skills); (2) "What do cells do?" (students will build a model of a cell using craft materials); and (3) "Where do new cells come from?" (interpreting
evidence from graphs and making new predictions). This lesson would work well paired with a review on what constitutes a scientific theory and
student practice of using compound microscopes.
Subject(s): Science
Grade Level(s): 8, 9, 10, 11, 12
Intended Audience: Educators
Instructional Time: 1 Hour(s) 30 Minute(s)
Keywords: cell theory, microscopes
Resource Collection: FCR-STEMLearn Cell Biology 2016
ATTACHMENTS
Teacher Guide.docx
Student Handout.docx
Station 3 Handout _1.docx
Station 3 Handout _2.docx
Cell_Theory_PowerPoint.pptx
LESSON CONTENT
Lesson Plan Template: General Lesson Plan
Learning Objectives: What should students know and be able to do as a result of this lesson?
Students will be able to:
Identify the parts and functions of a microscope to successfully focus the microscope and view cells
Articulate and apply the 3 principles of cell theory
Describe the scientific advances that led to the development of cell theory and relate these advances to the scientific process
Prior Knowledge: What prior knowledge should students have for this lesson?
Students should know that:
Some objects are living organisms and some are non-living.
Scientists uses tools and techniques to understand living materials.
Potential misconceptions:
Cells are all the same size and shape (there is a "generic" cell).
page 1 of 4 There are no single celled organisms.
Cells do not carry out essential life functions for themselves.
Guiding Questions: What are the guiding questions for this lesson?
Guiding questions are mainly used with small groups as they work at each station. They are detailed within the "Guided Practice" section, but include:
What sorts of objects have cells? What are some examples of cell types?
How do the organelles contribute to the function of the cell?
What are some essential life functions that a cell can perform for itself?
Would the cell be able to perform its function if it was not complete? Could cellular respiration or reproduction take place? Do you think that the organelles could
function outside of the cell?
How does a model help us to better understand how a cell operates?
Teaching Phase: How will the teacher present the concept or skill to students?
An attached PowerPoint is provided to introduce the tools of observation, experimentation, and modelling for scientific inquiry. The instructor may use this to present
the how all of these were used in the making of cell theory.
Key points for instructors:
Many scientists contributed to the development of modern cell theory, which occurred over many years of study. Cell theory states that:
1. All known living things are made up of cells.
2. The cell is the structural and functional unit of all living things.
3. All cells come from pre-existing cells by division.
Basic timeline:
1595 – Jansen credited with 1st compound microscope
1655 – Hooke described "cells" in cork.
1674 – Leeuwenhoek discovered protozoa and was the first to view live cells.
1833 – Brown described the cell nucleus in cells of the orchid.
1838 – Schleiden and Schwann proposed cell theory.
1840 – Albrecht von Roelliker realized that sperm cells and egg cells are also cells.
1856 – N. Pringsheim observed how a sperm cell penetrated an egg cell.
1858 – Rudolf Virchow (physician, pathologist and anthropologist) expounds his famous conclusion: omnis cellula e cellula, that is cells develop only from existing
cells [cells come from preexisting cells]
The original theory of Schleiden and Schwann proposed that new cells arose via "free cell formation," an intracellular variant of spontaneous generation.
Reference:
History of Biology: Cell Theory and Cell Structure
A Unifying Concept: The History of Cell Theory
History of Cell Biology
Central vocabulary:
Compound microscope – a microscope that consists of 2 lenses in series: an ocular lens (close to the eye) and objective lens (close to the object to be viewed)
Model – a representation of something in order to make it easier to understand
Experiment – a procedure done in controlled conditions for the purpose of collecting data and testing hypotheses
cell – the basic structural and functional unit of life
Organism – a contiguous living system, such as a plant, animal, or bacterium
Organelle – structures inside of a cell that do a job for a cell
Guided Practice: What activities or exercises will the students complete with teacher guidance?
See attached Teacher Guide.
Station 1: How big is a cell? Using a compound microscope.
At this station, students learn how to use a compound microscope to view cells, use a computer simulation to compare the sizes of biological structures, and view
plant and animals cells.
1. First, the instructor uses the computer program "Cell Size and Scale" from Learn.Genetics to demonstrate the relative sizes of several biological structures,
emphasizing the importance of the invention of the compound microscope to the study of cells.
2. Briefly review some of the microscope parts with the students, particularly the difference between the coarse and fine adjustments and the objectives (see diagram
and instructions for focusing the microscope below). At this station every single student will be focusing the microscope to clearly view examples of plant cells,
animal cells, and microorganisms. If one partner focuses the image, the second partner should also have a chance to focus the image. The students will identify
which part of the image in their view is a cell by sketching a cell on the back of their handout.
3. After the group has collectively viewed the cell types from various sources, the instructor may ask guiding questions such as: "If we went outside and collected
other types of living things, do you think they would also have cells? Why? How would you be able to tell?"
4. Explain to students that by viewing cells under the microscope and identifying the common features of plant and animal cells, scientists proposed that all known
living things are made up of cells. This is the first part of cell theory.
5. By the end of this station, students should have cell theory #1 completed on their handout.
Microscope Diagram:
page 2 of 4 Image: Thebiologyprimer, Wikimedia (CC0)
Microscope Parts and Functions:
Arm: Use this to carry the microscope
Base: Use this to carry the microscope
Eye Piece: Use this to look through the microscope (magnifies image 10x)
Objectives: Switch these to change the magnification so that you can "zoom in" and "zoom out" by changing the magnification
Stage: Place where you put your slide
Stage Clips: Use these to secure your slide
Light Source: Use this to illuminate your slide
Coarse Adjustment: Use only on lowest objective, brings image into focus
Fine Adjustment: Use to sharpen the image (after coarse adjustment)
Focusing the Microscope:
1. Lowest objective (shortest one)
2. Add your slide
3. Turn on the light source
4. Lower the stage
5. Raise the stage
6. Make fine adjustments
Station 2: What do cells do? Cells as the basic unit of life.
At this station, students will build a model of an animal cell. The instructor hands out index cards with descriptions of an organelle's structure and function to each
student. They contribute to the model by choosing how to best represent it in the model and explaining its function to the group. By the end of this station, students
should have cell theory #2 completed on their handout.
Organelles:
Cell membrane – protects the cell and allows substances to enter and exit the cell through tiny holes called pores (made of cardboard with small hole poked into the
sides)
Nucleus – the control center of the cell where DNA is stored
Cytoplasm – a jelly­like substance that supports the organelles
Mitochondrion – the powerhouse of the cell – it breaks down nutrients into energy the cell can use
Vacuole – a bubble shape organelle that can store food, water, and waste.
Guiding questions:
How do the organelles contribute to the function of the cell?
What are some essential life functions that a cell can perform for itself?
Would the cell be able to perform its function if it was not complete? Could cellular respiration or reproduction take place? Do you think that the organelles could
function outside of the cell?
How does a model help us to better understand how a cell operates?
By recognizing cells as the fundamental element of living tissue, scientists proposed that cells are the structural and functional unit of living things. This is the
second part of cell theory.
Station 3: Where do new cells come from? Making predictions and gathering evidence.
1. First, the instructor will present two graphs (shown below and attached) as results from previous experiments and ask the students to propose several mechanisms
that would explain the pattern. Then, in their pairs, students will brainstorm a way to gather evidence in order to identify the probable mechanism (observations
under certain conditions, an experiment, etc). Students draw what they would expect to observe as evidence for each of the proposed mechanisms.
2. Then, the instructor will present additional data – images of cells growing and dividing. The group discusses which proposed mechanism is the most likely and
compares their conclusion to that of Schwann and Schleiden, then Virchow.
3. After observing the behavior of many different types of cells, repeatedly, and in many environments, scientists updated the original proposition that cells are created
via "free cell formation" and instead proposed that all cells are formed from pre-existing cells via division. This has held up to continued scrutiny and is the third part
of cell theory.
4. By the end of this station, students should have cell theory #3 completed on their handout.
Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the
lesson?
Students will practice independently within each station; however, all activities are included under "Guided Practice" for clarity.
Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
Students will carry and put away the microscopes; teacher will assist by reviewing proper handling (lowest objective engaged, stage set furthest away from objective,
carry by the neck by grasping securely).
Summative Assessment
Exit Ticket:
1. What are the 3 main components of cell theory?
2. Name 1 type of tool or scientific technique that contributed to the development of cell theory.
page 3 of 4 3. Give 2 reasons why cell theory is considered a scientific theory.
Exemplary response:
1. All known living things are made up of cells; The cell is the structural and functional unit of all living things; All cells come from pre-existing cells by division.
2. Possible responses include: the microscope, observations of plant and animal cells, the discovery of the nucleus.
3. Possible responses include: it describes how new cells are formed, it is based on lots of scientific evidence from many sources.
Formative Assessment
Instructor will visit each station and ask students guiding questions throughout.
Feedback to Students
The instructor will circulate the room and prompt students with guiding questions. Clear up any misconceptions as needed.
ACCOMMODATIONS & RECOMMENDATIONS
Special Materials Needed:
Compound microscopes (at least 1 for every two students)
Slides of plant cells, animal cells, and microorganisms (at least 1 type per microscope; can be shared between groups)
Box of craft or modeling supplies, such as bubble wrap, newspaper, construction paper, toilet paper rolls, cotton balls, empty plastic containers, ziplock bags, pipe
cleaners
Copies of "experimental results" graphs for station 3
Copies of microscope images ("additional evidence") for station 3
Copies of student handout (1 per student)
Organelle index cards for station 2
SOURCE AND ACCESS INFORMATION
Contributed by: Jessie Mutz
Name of Author/Source: Jessie Mutz
District/Organization of Contributor(s): Florida State University
Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Related Standards
Name
SC.912.L.14.1:
SC.912.L.14.4:
Description
Describe the scientific theory of cells (cell theory) and relate the history of its discovery to the process of science.
Remarks/Examples:
Describe how continuous investigations and/or new scientific information influenced the development of the cell
theory. Recognize the contributions of scientists in the development of the cell theory.
Compare and contrast structure and function of various types of microscopes.
page 4 of 4