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Physiology is the study of living things – their structure, organization, and biochemistry. This unit gives students an opportunity to discover the fundamental characteristics of living things and explore some basic cell biology. Students begin with several activities culminating in the creation of a list of characteristics that all living things have in common – the characteristics of life list. From here, students learn to test for signs of life by growing microbes on agar plates, conducting biochemical tests, visualizing cells, and experimenting with photosynthesis and respiration. Finally, students learn about the organization plants and animals through dissection and the raising of plants and fish in the classroom. Throughout the unit, students return to the characteristics of life list, refining and revising their list as they learn new concepts. A planning guide for a voyage with the Marine Science Institute is included as a way for students to learn about the many forms of life in the San Francisco Bay.
Summary
What does it mean to be alive? Is a cactus alive? Is a seed alive? Is the air we breathe alive? What are the necessary characteristics? To hook students into the question, they are introduced to “glue monsters” (sometimes known as “scooting glue”) and the class discusses whether the “monsters” are alive or not. Next, students are given cards with the names of various objects and asked to sort them into categories: alive, once was alive, never alive, and not sure. Finally, students create a list defining the characteristics of life – a set of characteristics that all living things share. The list is initially developed in pairs, then in larger groups of 4, and ultimately as a whole class. The final list is turned into a poster that can be referenced and modified throughout the remainder of the unit as students learn more about what it takes to be alive.
Objectives
Can begin to discuss the necessary characteristics of life.
Can begin to categorize objects as alive or not alive.
Can recognize that movement does not necessarily mean something is alive.
Vocabulary
Alive
Characteristic
Cell
Metabolism
Evolve
Adapt
Homeostasis
Organic molecule
Organism
Attachment | Size |
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alive_sorting_cards.doc | 71.5 KB |
1is_it_alive.doc | 67.5 KB |
Time
10-15 min glue monsters demo
30-40 min alive or not alive card sorting and discussion
30-45 min create characteristics of life lists
Grouping
The card sorting activity and initial creation of a list of the characteristics of life is done in pairs. These pairs will eventually merge in groups of 4 to compare, discuss, and revise their lists. The remainder of the discussion takes place as an entire class.
Materials
For the “glue monsters” demo, the teacher needs:
For the card sorting activity, each pair of students needs:
For developing a characteristics of life list, each class needs:
Setting
Classroom
Teacher Background
Many middle school students believe that the defining characteristic of living things is that they move. When they see the “glue monsters” wiggle in the Petri dish, most will immediately assume they are alive. What is going on? Duco® cement is polymer mixed in a water soluble solvent. When the cement is exposed to air as it drops into the dish, a thin, solid polymer skin quickly forms around the liquid, solvent-polymer mixture. When the bead of cement is immersed in water, the solvent diffuses through the skin, causing the bead to shrink and the skin to rupture on one side of the bead. The solvent squirts out of the hole and the surface tension of the water on that side of the bead suddenly falls. Since the surface tension is now uneven, the bead will move away from the hole, towards the area with greater surface tension. The hole quickly repairs itself but the skin then bursts in another location. Thus, the bead appears to wiggle and twist as the surface tension changes depending on where the skin bursts.
Another way to demonstrate surface tension propulsion is to place a paper boat in a tub of water. Take a toothpick dipped in concentrated dish soap (which will lower the surface tension of water) and touch it to the water near the back of the boat. The boat with rush away from the toothpick.
As to the card sorting activity, students will struggle over many of the items. Do not expect students to correctly categorize items, even after a group discussion. The goal is to get students thinking and debating about the characteristics all living things share, not to get the “right” answer. Their classifications will also give you a good sense of their current state of understanding and sophistication. Keep a list of the items students disagree on or misclassified. Revisit these items at the end of the unit when students have mastered the major concepts. Keep in mind that there are some items that even scientists disagree on, such as viruses and prions. Some of the items (dirt and air) are mixtures in which some parts are alive and some are not. In addition, how you classify a part of a multicellular organism (like a single leaf, blood, or pollen) depends on your point of view. These ambiguous items provide opportunities to discuss the characteristics of life with your students.
Defining the characteristics of life is difficult and not completely clear cut. Although you will find different lists at different sources, most scientists agree that the following characteristics are shared by all living things:
In addition to these 6, some lists included 2 additional characterisitics:
The goal of these activities is not to force students to memorize the list above. Many are new, difficult concepts (like cells, metabolism, and organic molecules) that will develop over the course of the unit. Students should experience the process of creating the list themselves and revising it periodically as they learn new things. For instance, in the preliminary list, the items: “need nutrients”, “make wastes” and “need energy” may appear separately. After students learn about photosynthesis and respiration as metabolic processes, these 3 items can be combined under the umbrella of “living things metabolize”.
Student Prerequisites
none
Getting Ready
Glue monsters demo:
Alive or not alive card sorting:
Characteristics of life list:
Lesson Plan
Glue monsters demo:
Alive or not alive card sorting:
Characteristics of life list:
Assessment
Play the game “5 Alive”. On a piece of paper, the person who is “it” should write the name of any item that they know for sure is alive or not. The rest of the group gets to ask 5 yes or no questions to figure out if the mystery item is alive.
Going Further
Sources
I discovered the “glue monster” or “scooting glue” demo from Flinn Scientific (click on “Glue Monsters” to download the pdf file). Kitchen chemistry also provides a write up for the same activity with a better description of the chemistry behind the demo. For a quicktime movie of a paper boat “fleeing” from a dish soap coated toothpick, see the University of Iowa Physics and Astronomy Lecture Demonstrations.
To learn more about the characteristics of life, see the following sites:
Standards
Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope.
Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
Summary
Life trapsAs part of recognizing the characteristics of life that all organisms share, students grow microbes on nutrient agar plates. Students swipe surfaces with a sterile Q tip swab and seed plates resulting in a wide range of colorful and prolific bacteria and fungi colonies. Other plates may be simply opened to the air to catch life floating in the air. Through these experiences, students learn that all living things, even those so small and invisible as to be floating in the air, grow and reproduce when provided with the proper nutrients and water. Teachable moments abound since the “dirtiest places”, like the toilet rim, often result in the least bacterial growth while presumably “clean” places, like the surface of your skin, have the most. A fun extension of this activity (see the Going Further section) is to start a sourdough culture from wild yeast in the air and make sourdough bread.
Objectives
Can grow microbes on nutrient agar plates.
Can make observations and keep track of data over several days.
Can identify the typical growth patterns of bacteria versus fungi.
Can begin to recognize the diversity of microbrial life in the local environment.
Can explain that all living things will grow and reproduce when provided with the proper nutrients and environmental conditions.
Vocabulary
Agar
Nutrients
Microbe
Bacteria
Fungi
Yeast
Colony
Attachment | Size |
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2life_trap.doc | 62 KB |
Time
30 min to introduce the activity and seed the plates
5-10 min to make observations every other day over the next 2 weeks
Grouping
Individual or in pairs.
Materials
For approximately 50 plates you need:
Setting
Classroom
Teacher Background
When living things are provided with the proper nutrients, water, and environmental factors (temperature, humidity, etc.) they will grow and reproduce, often explosively and in surprising ways. To kids, microbes are abstract, invisible germs that mysteriously spread disease, but otherwise have little relevance to their daily lives. However, microbes in the form of bacteria, fungi and viruses are prolific and exist all around us and even inside us. Of the 100 trillion cells found within your skin, only 10 trillion of these (a measly 10%) are human cells! The rest are primarily bacteria living on the surface of your skin, around your eyes, mouth, reproductive organs, and digestive tract, comprising between 500-1,000 different species. Since bacterial cells are generally much smaller than human cells, a great many more bacteria fit into the borders of the human body than human cells.
Nutrient agar plates are a classic tool for culturing microbes in the laboratory. The agar plate provides all the basic organic molecules - water, carbohydrates, fats, and proteins - and will support the growth of many bacteria and fungi species, though by no means will all microbes find the appropriate nutrient and environmental conditions to grow on an agar plate. It is important for students to recognize that many organisms that arrive on the plate will not have the right conditions to grow, thus, an empty plate does not necessarily mean no life exists there – only that this method could not detect life.
Luckily, pathogenic bacteria find it difficult to grow on nutrient agar so it is reasonably safe to use in schools. However, do NOT open the dishes once they have been seeded. High levels of mold and bacterial spores can be released. When you are finished with the experiment, disinfect the plates before disposal.
It is difficult to positively identify specific species from so rough a measure, however, it is possible to determine certain things about the colonies that grow. Bacteria tend to form low-growing buttons or streaks that are glistening and smooth. On the other hand, fungi tend to form fuzzy, irregular patches or fern-like, thread-like patterns. Different varieties can be distinguished by their color and texture. Colonies that were collected on a Q-tip swab from a hard surface will begin their growth where the Q-tip touched the agar. Colonies from the air that landed on the agar while the lid was open will begin as a dot located on part of the plate not touched by the Q tip swab. Each dot represents a single spore that landed on the plate.
Student Prerequisites
None
Getting Ready
To prepare agar plates:
To sterilize Q-tips:
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Lesson Plan
Introducing the activity and seeding plates:
Further observations and discussions:
Assessment
Going Further
Sources
The inspiration for this lesson was Mission 11 from the Life in the Universe curriculum, published by the SETI Institute. The recipe for the nutrient agar came from Biology F.A.Q. at Flinn Scientific. Sterilization tips were found at Science-Projects.com and Wikipedia. Finally, many teaching tips were discovered from Leslie Hathaway’s Bacteria Gathering lesson plan.
Statistics on bacteria in the human body were taken from Wikipedia.
Standards
Grade 6
5. Organisms in ecosystems exchange energy and nutrients among themselves and with the environment. As a basis for understanding this concept:
e. Students know the number and types of organisms an ecosystem can support depends on the resources available and on abiotic factors, such as quantities of light and water, a range of temperatures, and soil composition.
Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope.
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
a. Select and use appropriate tools and technology (including calculators, computers, balances, spring scales, microscopes, and binoculars) to perform tests, collect data, and display data.
e. Communicate the steps and results from an investigation in written reports and oral presentations.
Summary
All known life is made out of a small group of chemical compounds called organic molecules. Common organic molecules include proteins, glucose, starch, lipids, and nucleic acids. This lesson plan asks students to conduct tests for proteins, glucose, and starch. At the beginning of the activity, they choose 3 items to test: one known to be “never alive”, one known to be “once was alive”, and one mystery item. In addition, each station includes a positive control. By the end of the experiment, students should be familiar with some of the major organic molecules and should recognize that living things, and substances derived from them, are made of organic molecules. In addition, this is a chance to bring in topic surrounding nutrition, health, and digestion. Since our bodies are made up of organic molecules, we need each of these molecules as nutrients in our food.
Objectives
Can define and give examples of organic molecules.
Can recognize that living things are mode of organic molecules.
Can test for the presence of protein, glucose and starch.
Can interpret the results of an experiment.
Vocabulary
Organic molecule
Protein
Biuret solution
Carbohydrates
Glucose
Simple sugar
Benedict’s solution
Starch
Iodine
Lipids
Attachment | Size |
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3testing_life.doc | 63 KB |
life_test_directions.doc | 34 KB |
life_test_handout.doc | 40 KB |
Time
10-20 min introduction (depending on how deeply you want to talk about the biochemistry)
35-50 min to conduct tests (10-15 min per station)
20-30 min to discuss results
Grouping
Teams of 3 students
Materials
General materials for students and test stations:
A variety of solutions to test:
Setting
Classroom
Teacher Background
All living things (at least on Earth) are composed of organic molecules. All organic molecules include carbon-hydrogen bonds. The major classes of organic molecules are:
GlucoseCarbohydrates are particularly important for energy storage in living things. Sugars and starches are common examples of carbohydrates. Carbohydrates are can be found as simple sugars or monosaccharides such as glucose, a ring of 6 carbons with attached hydrogens and oxygens (C6H12O6). Other simple sugars include fructose (a common sugar found in fruit) and galactose. These simple sugars may be joined together in pairs. For instance, sucrose (table sugar) is a combination of glucose and fructose. Similarly lactose (the sugar found in milk) is a combination of glucose and galactose. Finally, simple sugars may be assembled into long chains called polysaccharides. Starch is a familiar example of a polysaccharide that is found in many foods including potatoes, flour, and corn. It is made from a long chain of glucose molecules.
Starch: chemical name amyloseTwo tests for carbohydrates are provided: a simple iodine test for starch and a Benedict’s test for glucose. Iodine is a yellow-brown solution that will react with starch to make a blue-black color. Benedict’s solution is a clear blue solution that will react with glucose to make a green, yellow, or red color depending on how much sugar is present. Test tubes must be kept in a 40-50 degrees Celsius water bath for 5 minutes in order for the color to change. An alternative test for glucose is described in the Sources section. Expect to spend some time explaining why starch does not test positive for glucose even though it is made of a long chain of glucose molecules and vice versa.
Protein: structure of hemoglobinProteins are important for many processes within living things. They contribute to the overall structure of a cell such as muscle cells, to binding to specific molecules such as the protein hemoglobin that binds to oxygen, and to catalyzing chemical reactions in the cell through proteins known as enzymes. Proteins are composed of building blocks known as amino acids. There are 20 total amino acids. Proteins are long chains of amino acids. The length of the chain and the precise sequence of the amino acids in the chain determines what the protein can do.
Amino acid assembly into proteinsThe Biuret test is a simple test for the presence of proteins. Biuret solution is a blue solution that will react with proteins to make a pink-purple color.
Lipids are a very diverse group of organic molecules. Their defining feature is that a large part of the molecule is hydrophobic, literally “water-fearing”. Most also have a water-loving or hydrophilic end as well. This property allows lipids in water to assemble into membranes or spheres with the hydrophilic ends facing outward and the hydrophobic ends facing in. Most of the membranes in cells are comprised of lipids. The lipids found in membranes are called phospholipids since their small hydrophilic head is linked to a long hydrophobic tail by a phosphate group.
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Finally, nucleic acids are the building blocks of DNA. For more on DNA structure, see the background section of DNA models.
A common organizing principle for all organic molecules is that they are composed of building blocks assembled into a long chains. For instance, proteins are long chains of amino acids. Polysaccharides like starch that are long chains of simple sugars. DNA is a long chain of nucleic acids. Many lipids have a tail that is a long chain of carbon and hydrogen atoms.
In my classroom, I set up this activity so that students rotate among several testing stations. They carry 3 cups with test solutions and a rack of test tubes with them. Students will empty and rinse their test tubes after each station. The reagents, eyedroppers, and positive controls, are found at each station.
Student Prerequisites
Some exposure to chemistry is useful, particularly if students are familiar with the idea of molecules, polymers, and pH testing with color-change indicators.
Getting Ready
Lesson Plan
Protein test | Starch test | Glucose test | Alive? | |
Chicken broth | ||||
Wheat flour | ||||
Orange juice | ||||
Water | ||||
Rubbing alcohol | ||||
Dish soap | ||||
Vinegar | ||||
Fish tank water (pond water) | ||||
Unsweetened powdered lemonade |
Assessment
Going Further
Sources
All the materials needed for this lab may be purchased from Flinn Scientific or other science supply companies.
Unfortunately, the common tests for nucleic acids, such as the Dische test, are highly toxic (the Dische test solution is dissolved in 2M sulfuric acid) and is not ideal for use in a middle school classroom.
Testing for organic molecules is a common activity in biochemistry classes. The following are some of the resources available:
Standards
Grade 8
Chemistry of Living Systems (Life Sciences)
6. Principles of chemistry underlie the functioning of biological systems. As a basis for understanding this concept:
a. Students know that carbon, because of its ability to combine in many ways with itself and other elements, has a central role in the chemistry of living organisms.
b. Students know that living organisms are made of molecules consisting largely of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
c. Students know that living organisms have many different kinds of molecules, including small ones, such as water and salt, and very large ones, such as carbohydrates, fats, proteins, and DNA.
Grades 9-12 Biology
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:
a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.
b. Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings.
h. Students know most macromolecules (polysaccharides, nucleic acids, proteins, lipids) in cells and organisms are synthesized from a small collection of simple precursors.
Grades 9-12 Chemistry
Organic Chemistry and Biochemistry
10. The bonding characteristics of carbon allow the formation of many different organic molecules of varied sizes, shapes, and chemical properties and provide the biochemical basis of life. As a basis for understanding this concept:
a. Students know large molecules (polymers), such as proteins, nucleic acids, and starch, are formed by repetitive combinations of simple subunits.
b. Students know the bonding characteristics of carbon that result in the formation of a large variety of structures ranging from simple hydrocarbons to complex polymers and biological molecules.
c. Students know amino acids are the building blocks of proteins.
Summary
The invisibly small world of the cell comes to life as students look at plant and animal cells through a microscope. Students create wet-mount slides of onion skin, elodea leaf, and human cheek cells. They learn some of the gross differences between plant and animal cells (cell walls are present in plant but not in animal cells), and even some of the differences between different plant cells (chloroplasts are found in the leaves but not in the roots). It is suggested that this lesson take place after students learn the parts of a cell and their functions. Resources for good cell diagrams are provided in the Sources section. This lesson may be used in conjunction with the Pond Water activity for students to get a sense of the diversity of microscopic life, both single celled and multi-celled.
Objectives
Can name and describe the function of certain plant and animal cell organelles.
Can identify whether a cell viewed through a microscope if plant or animal.
Can draw and label a picture of plant and animal cells.
Can recognize that all living things are made of cells.
Can begin to recognize the huge variations in cell size, shape, structure, and function.
Can operate a compound light microscope.
Can make simple wet-mount slides.
Vocabulary
Cell
Organelle
Cell membrane
Cell wall
Cytoplasm or cytosol
Nucleus
Chloroplast
Microscope
Objective lens
Eyepiece
Focus
Stage
Elodea
Methylene blue
Attachment | Size |
---|---|
4seeing_cells.doc | 57.5 KB |
cell_images.doc | 1.64 MB |
cells_lab_handout.doc | 41.5 KB |
cell_quiz.doc | 316.5 KB |
Time
45-75 min introduce the parts of a cell and their functions
Optional: 10-15 min discuss microscope parts and usage
5-10 min demonstrate proper procedures for making slides
45-90 min make slides, look at cells, create diagrams, and answer questions
10-15 min discussion and review
Grouping
Teams of 2.
Materials
Setting
Classroom
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Teacher Background
Students often have difficulty conceptualizing that cells are the basic building block of all living things. Thus, it is essential for them to have experience making slides of familiar living things – onions, plants and their own cheek cells – and viewing them under a microscope to see that cells really do make up all living things.
Multicellular creatures such as plants and animals have different levels of organization, from organic molecules to organelles to cells to tissues to organs to organ systems to a whole organism. Cells are the smallest unit that can fulfill all the necessary characteristics of life – it can metabolize, grow, reproduce, maintain homeostasis, evolve, respond to its environment and so on. Its organelles (parts of a cell, each has a specific job similar to the organs in the human body) participate in fulfilling these various functions.
Important organelles in eukaryotes such as plants and animals (prokaryotes such as bacteria have much simpler cells):
Using a light microscope only the largest features of a cell can be observed (the first 5 organelles on the list above). Greater magnification is required to visualize other cell parts. Still students can discover how all living things are similar in that they are made of cells but also discover the great diversity in cells themselves.
Student Prerequisites
Experience with light microscopes is helpful. A basic understanding of the parts of a cell is essential to the completion of this activity.
Getting Ready
Lesson Plan
Assessment
Going Further
Sources
Blank cell coloring diagrams can be found at:
The best resource for this lesson is the fabulous Biology Corner website of Shannan Muskopf. In Biology 1 and 1A, Chapter 3, she provides:
Thank you thank you thank you! Check out all the other fantastic labs, projects, field trips and assessments at Biology Corner.
Standards
Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope. As a basis for understanding this concept:
a. Students know cells function similarly in all living organisms.
b. Students know the characteristics that distinguish plant cells from animal cells, including chloroplasts and cell walls.
c. Students know the nucleus is the repository for genetic information in plant and animal cells.
d. Students know that mitochondria liberate energy for the work that cells do and that chloroplasts capture sunlight energy for photosynthesis.
e. Students know cells divide to increase their numbers through a process of mitosis, which results in two daughter cells with identical sets of chromosomes.
f. Students know that as multicellular organisms develop, their cells differentiate.
Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
b. Students know organ systems function because of the contributions of individual organs, tissues, and cells. The failure of any part can affect the entire system.
Grades 9-12 Biology
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:
a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.
c. Students know how prokaryotic cells, eukaryotic cells (including those from plants and animals), and viruses differ in complexity and general structure.
e. Students know the role of the endoplasmic reticulum and Golgi apparatus in the secretion of proteins.
f. Students know usable energy is captured from sunlight by chloroplasts and is stored through the synthesis of sugar from carbon dioxide.
g. Students know the role of the mitochondria in making stored chemical-bond energy available to cells by completing the breakdown of glucose to carbon dioxide.
j. * Students know how eukaryotic cells are given shape and internal organization by a cytoskeleton or cell wall or both.
Summary
To solidify students’ conceptualization of cells, students build a model of a cell in a ziplock bag using polyvinyl alcohol slime as cytoplasm. So far, students’ experience with cells has been 2 dimensional – diagrams and microscopic slides. The 3 dimensional nature of cells comes to life as students use everyday objects to represent the many parts of a cell. In addition, students can use this activity to develop a sense of scale, calculating how big a human would be if the ziplock bag cell model were really the size of a cheek cell.
Objectives
Can build a three dimensional scale model of a cell.
Can name and describe the function of certain plant and animal cell organelles.
Can draw and label a picture of plant and animal cells.
Can recognize that all living things are made of cells.
Can use proportions and ratios to calculate the size of a person made of ziplock bag sized cells.
Can begin to use the metric system of measurement.
Vocabulary
Polyvinyl alcohol (PVA)
Borax
Polymer
Cell
Organelle
Cell membrane
Cell wall
Cytoplasm or cytosol
Nucleus
DNA
Chloroplast
Mitochondria
Ribosome
Golgi apparatus
Endoplasmic reticulum
Vacuole
Lysosome
Scientific notation
Metric system
Attachment | Size |
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5slimy_cells.doc | 67 KB |
cell_model-handout.doc | 44 KB |
Time
20-25 min introduction and make PVA slime
30-45 min assemble cell models
10-15 min create cell model keys
20 min discuss the metric system of measurement and use ratios to calculate the relative size of a person made of ziplock bag sized cells
Grouping
Individual
Materials
Each student needs a copy of the Slimy Cell Models handout.
For enough PVA slime for a class of 30 students:
For cell walls, gather as many pint-sized strawberry baskets as you can – two baskets, one inverted over the other, readily enclose a filled ziplock bag, demonstrate the structural support provided by the cell wall, and illustrate the permeability of the cell wall.
For organelles, assemble a wide assortment of small, inexpensive items that students can select from. It is best to avoid food items like beans and candy since they will decompose and grow mold inside slime, creating a disgusting mess. An alternative is for students to bring objects from home for their models. Some items you may want to consider include:
Setting
Classroom
Teacher Background
Making models of cells is a fun, meaningful activity for students to help them visualize the 3 dimensional nature of cells. See the background section of the Seeing Cells activity for a description of cell parts and their functions. This puts a slightly different twist on the standard shoebox cell model by using PVA slime to suspend the various organelles much like a real cell's cytoplasm does. It is also much less messy than the often-used jello cell models since everything stays contained within a ziplock bag (and is not sticky if spilled on the floor - though avoid getting slime on carpet).
The PVA slime recipe used in this activity is:
This makes a wonderful, viscous, oozing slime that is wet to the touch but holds together well even if removed from the ziplock bag. Polyvinyl alcohol exists in water as a long polymer of (C2H4O)n units. Each chain is up to 2,000 units long. When Borax is combined with the PVA solution, the PVA chains crosslink, forming a highly viscous gel. Since the crosslinks are weak, they continually break and reform as the slime is handled.
PVA slime is quite safe to touch and handle, although you don't want to eat any since the Borax is toxic in large doses. It is easy to clean up with soap and water. Unadulterated slime can be stored for several weeks in a ziplock bag.
I also use this activity to introduce students to the metric system of measurement and the use of ratios to see the relative size of things. Although students realize that cells are tiny, especially after looking through the microscope at them, it is often hard for them to imagine just how tiny cells really are. By going through all the steps of calculating how big a human would be if one of their ziplock bag cell models was really a cell, they are better able to recognize just how tiny a cell is.
For your reference, below is a table showing standard versus scientific notation as well as the common metric prefixes for each.
Standard notation | Scientific notation | Common prefix | Common symbol | Example |
1000 | 1 x 103 | kilo- | k | kilometer (km) |
100 | 1 x 102 | |||
10 | 1 x 101 | |||
1 | 1 x 100 | none | none | meter (m) |
0.1 | 1 x 10-1 | deci- | d | decimeter (dm) |
0.01 | 1 x 10-2 | centi- | c | centimeter (cm) |
0.001 | 1 x 10-3 | milli- | m | millimeter (mm) |
0.0001 | 1 x 10-4 | |||
0.00001 | 1 x 10-5 | |||
0.000001 | 1 x 10-6 | micro- | u | micrometer (um) |
0.0000001 | 1 x 10-7 | |||
0.00000001 | 1 x 10-8 | |||
0.000000001 | 1 x 10-9 | nano- | n | nanometer (nm) |
0.0000000001 | 1 x 10-10 |
A human cheek cell is approximately 58 micrometers (um) or 0.000058 meters (m) wide. A typical seventh grader is approximately 1.6 meters (m) tall. A standard ziplock sandwich bag is approximately 16 centimeters (cm) or 0.16 meters (m) wide. Thus you can set up a proportion to figure out how big a human being would be (x) if the ziplock bag represented a cheek cell:
__x__ = __0.16 m__
1.6 m 0.000058 m
Solving for x you get 4414 meters or 4.4 kilometers. Thus, a human made of cells as big as a ziplock bag would be 4.4 kilometers tall (over 2.7 miles)! Just imagine how many slimy cell models it would take to fill a statue over 4 kilometers tall (around 10 trillion, that's 1 x 1013). A blood cell takes around 30 seconds to circulate around the human body - in our enlarged model, that's comparable to a ziplock bag blood cell completing a 3 mile round-trip journey in 30 seconds, at 360 miles an hour!
Student Prerequisites
Students need a good background in cell structure, parts of a cell, and their functions before undertaking this activity. It is helpful if students have experience with ratios and proportions in math class and if they have had some exposure to the metric system of measurement though not required.
Getting Ready
To make PVA solution:
To make Borax solution:
Lesson Plan
Assessment
Standards
Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope. As a basis for understanding this concept:
a. Students know cells function similarly in all living organisms.
b. Students know the characteristics that distinguish plant cells from animal cells, including chloroplasts and cell walls.
c. Students know the nucleus is the repository for genetic information in plant and animal cells.
d. Students know that mitochondria liberate energy for the work that cells do and that chloroplasts capture sunlight energy for photosynthesis.
e. Students know cells divide to increase their numbers through a process of mitosis, which results in two daughter cells with identical sets of chromosomes.
f. Students know that as multicellular organisms develop, their cells differentiate.
Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
b. Students know organ systems function because of the contributions of individual organs, tissues, and cells. The failure of any part can affect the entire system.
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
d. Construct scale models, maps, and appropriately labeled diagrams to communicate scientific knowledge (e.g., motion of Earth's plates and cell structure).
Grades 9-12 Biology
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:
a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.
c. Students know how prokaryotic cells, eukaryotic cells (including those from plants and animals), and viruses differ in complexity and general structure.
e. Students know the role of the endoplasmic reticulum and Golgi apparatus in the secretion of proteins.
f. Students know usable energy is captured from sunlight by chloroplasts and is stored through the synthesis of sugar from carbon dioxide.
g. Students know the role of the mitochondria in making stored chemical-bond energy available to cells by completing the breakdown of glucose to carbon dioxide.
j. * Students know how eukaryotic cells are given shape and internal organization by a cytoskeleton or cell wall or both.
Summary
Here you will find a toolbox full of inquiry investigations on photosynthesis and respiration. Rather than the detailed lesson plans provided elsewhere at My Science Box, each experiment only contains a short background, materials, procedure, and going further section. It is up to you to decide which of the many experiments you wish to try with your students and how to sequence them. You will find everything from descriptions for how to extract chlorophyll, discover that plants “breathe”, recreate the experiments of Priestly and Ingenhousz, detect carbon dioxide production, and measure the rate of yeast respiration. None of these experiments require expensive equipment such as metabolism chambers or oxygen meters although those are great tools if you can afford them.
Briefly, photosynthesis occurs in the chloroplasts of plants as a means of turning solar energy into chemical energy in the form of glucose, the primary food/energy source of cells. Through a series of biochemical reactions, sunlight energy transforms carbon dioxide and water into glucose and oxygen.
6CO2 + 6H2O + light → C6H12O6 + 6O2
Respiration releases the chemical energy stored in glucose and turns it into energy that can be used by the cell in the form of ATP (adenosine 5’triphosphate). ATP may be considered the standard currency of the cell, much as the dollar is the standard currency in American society. Nearly all cellular processes depend on ATP as their energy source. The chemical equation for respiration using glucose is the mirror image of the chemical equation for photosynthesis.
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
Objectives
Can recognize that all living things metabolize and thus require nutrients, take advantage of chemical reactions to release energy, and produce wastes.
Can describe the general process of photosynthesis and respiration.
Can recognize the reciprocal relationship between photosynthesis and respiration.
Can explain the jobs of chloroplasts and mitochondria and their importance to cells.
Can design, conduct, and interpret experiments on plants and animals related to photosynthesis and respiration.
Vocabulary
Metabolism
Chemical reaction
Energy
Photosynthesis
Respiration
Chloroplast
Chlorophyll
Mitochondria
Carbon dioxide
Oxygen
Glucose
Bromthymol blue
Carbonic acid
Elodea
Yeast
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6cell_energy.doc | 41.5 KB |
Chlorophyll extractionSummary
Chlorophyll is the pigment in plants that captures sunlight energy and uses it to drive photosynthesis. While chlorophyll does give plants their characteristic green color, chlorophyll actually comes in many colors and subtypes ranging from green to yellow to orange to red. In this experiment, students use paper chromatography to separate the many pigments from one another. First the pigments are extracted from the plants by simply crushing the plant cells open on the filter paper with the edge of a penny. When the filter paper is then immersed in rubbing alcohol, the pigments are carried upwards through capillary action. The smallest pigments travel more quickly and thus separate from the larger pigments that remain closer to the origin line.
Chlorophyll is an amazing chemical that is the essential ingredient in photosynthesis, the process through which plants capture light from the sun to create glucose. When photons of light hit chlorophyll, the electrons in the central magnesium atom donate an electron to a series of chemical reactions – the electron transport chain – that produce ATP, the cells primary unit of energy currency. The chlorophyll gets this electron back by taking one from water, resulting in the release of oxygen gas as a byproduct.
Chlorophyll comes in two main forms: chlorophyll a and chlorophyll b. Each has a slightly different chemical structure and therefore absorbs light of different wavelengths. In this paper chromatography experiment, chlorophyll a will appear as a bright yellow-green band while chlorophyll b will appear as a dull green band. In addition, there are many other accessory pigments in plants that absorb light and help transfer photons to the chlorophyll. These include carotene (an orange band) and xanthophyll (a yellow band). A final pigment that may be detected is anthocyanin (a red-brown band) that acts as a type of sunscreen for plants, protecting the plant from UV damage.
For more information on paper chromatography and its use in chlorophyll extraction, a fabulous scientific description may be found on the Science Buddies website. Also see this photosynthesis lesson plan by Sara Swisher, Barb Wilson, and Jean Wilson. Finally, Cheryl Massengale has a great write up for chlorophyll extraction including a table illustrating how to calculate the Rf value for each band and use that as a quantitative means of identifying the various pigments.
Materials
Procedure
Going Further
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plant_pigments.doc | 38 KB |
Elodea nuttallii: Image courtesy of Christopher Fischer.Summary
Students often believe that only animals “breathe”, but all things exchange gases with their environment. It’s just that the process is not so obvious in plants. Elodea is a very common water plant that can be found in aquarium stores. As photosynthesis occurs, oxygen is produced as a by-product. Elodea releases bubbles of oxygen as it photosynthesizes. In fact, the number or volume of bubbles in a certain amount of time can be used as a rough measure of photosynthetic rate.
The measure is rough because oxygen dissolves in water so may not always appear as a gas. Moreover, most light sources produce heat, which causes the water temperature to increase, which in turn causes lower gas solubility, and thus may produce bubbles just by turning the light on. Finally, the size of a bubble is not constant thus counting the number of bubbles per unit time is only a very rough measure. The total volume of gas produced is a better measure but again falls victim to the other caveats. The best measure is to use a dissolved oxygen meter which unfortunately costs a fair bit of money (between $400 to over $1000). You can also try disposable dissolved oxygen tests (see the Sources section of the Water Analysis activity).
An important note is that freshly cut Elodea stems produce more bubbles than the leaves. That is because Elodea stems contain large intracellular air passageways. As oxygen is produced, the plant transports the oxygen away from the leaves towards the roots. Thus, a freshly cut stem will produce oxygen bubbles at an observable rate. The cells in the leaves are much more tightly packed together and provide greater resistance to the emerging oxygen gas than the stems. Thus, to maximize oxygen gas production in this experiment, cut the stem of the Elodea then place the plant upside-down in the test tube. For more information about why the bubbles emerge from the stems, not the leaves, see this article by David Hershey of the Mad Scientist Network.
An excellent resource with more information about the use of Elodea in this experiment can be found at the Clifton College Science School website. There you will find detailed information about Elodea, how oxygen is produced, experiments by Frost Blackman, practical advice and more.
Materials
Procedure
Going Further
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bubbling_plants.doc | 43.5 KB |
Summary
These experiments use a bell jar (or any other very large, clear, glass jar) to determine the identity of the gas produced by plants. It mirrors the famous experiments of Joseph Priestley and Jan Ingenhousz from the 1700’s that first demonstrated the existence of oxygen and its importance to plants and animals.
In 1771 and 1772, Priestly conducted a series of experiments using a bell jar. It was known that a candle placed in a sealed bell jar would eventually burn out and could not be relighted while still in the jar. Priestly discovered that a plant can survive indefinitely within a jar. Thus, he tried placing a plant into the jar with the burning candle. The candle went out as before and could not be relit right away. Priestly waited several days and tried again. The candle could be relit! The plant had restored the air inside the jar! (Do not try the next series of experiments since it harms animals!) Next priestly investigated what would happen to animals. He found that a mouse placed inside a sealed jar will eventually collapse. However, a mouse can survive in a sealed jar with a plant since the plant restores the air. Priestly was the first to demonstrate that oxygen is necessary for fire and animals but that given time, plants can create oxygen, allowing fires to burn and animals to breathe.
A few years later, Jan Ingenhousz investigated the effect of light on a plant’s ability to restore air. He found that a plant left in darkness cannot restore the air for a candle. To demonstrate this, he burned up all the oxygen in a jar with a plant then left the plant in sunlight for a few days to restore the air. Then without relighting the candle, he put the plant into darkness for several more days. At the end of the dark period, he was unable to relight the candle. He concluded that a plant in darkness acts like animals, using up the oxygen that it had created. Ingenhousz had discovered that plants can photosynthesize and create oxygen but only in the light. If left in the dark, plants do not photosynthesize and thus no oxygen is produced. Moreover plants are always performing respiration, just like animals. In sunlight, the rate of photosynthesis outstrips respiration so there is an excess of oxygen being produced. But in darkness, no photosynthesis takes place but respiration continues to occur. Thus, by keeping a plant in darkness you can demonstrate that plants need oxygen and use it up, just like animals.
For more information, see the wonderful website of Julian Rubin which describes many of these experiments and offers links and resources on how to recreate them in the classroom. Also, NSTA has produced a great set of photosynthesis related inquiry activities including the bell jar experiments.
Materials
Procedure
A candle uses up the oxygen in the jar:
A plant restores the oxygen in the jar:
A plant in darkness does not restore oxygen:
A plant in darkness uses oxygen:
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photosynthesis_in_a_jar.doc | 44 KB |
Summary
Blow through a straw into bluish liquid and watch it turn green then yellow before your eyes. Put some plants into the yellow liquid, leave it in a sunny window, come back the next day and the liquid is green. What if you leave the plants in the dark? What if you put some pond snails in? What if you put both pond snails and plants? What’s going on?
The liquid is bromthymol blue (BTB) a non-toxic acid-base indicator that can be used to indirectly measure levels of dissolved carbon dioxide (CO2). The amount of CO2 in a solution changes the pH. An increase in CO2 makes a solution more acidic (the pH gets lower). A decrease in CO2 makes a solution more basic (the pH gets higher). The reason for this is that carbon dioxide that is dissolved in water is in equilibrium with carbonic acid (H2CO3).
CO2 + H2O ↔ H2CO3
In any solution, while the majority of CO2 stays as CO2, some of it is converted to H2CO3, turning the solution slightly acidic. If CO2 is added to the water, the level of H2CO3 will rise and the solution will become more acidic. If CO2 is removed from the water, the amount of H2CO3 falls and the solution becomes more basic. Thus, acid-base indicators such as BTB can indirectly measure the amount of CO2 in a solution.
For more than you ever wanted to know about carbonic acid, see the Wikipedia article on carbonic acid. For the example lesson plans developed by Bob Culler through Access Excellence at the National Health Museum. For a great time lapse video showing BTB color changes using elodea and snails, see Activity C13 from Addison-Wesley’s Science 10 curriculum.
Materials
Procedure
BTB solution | Living things |
Light conditions |
bubbled BTB (yellow) | spring of Elodea | Sunny window/bright light |
unbubbled BTB (blue) | 5 pond snails | Dark closet/drak heavy cloth |
both Elodea and 5 pond snails |
Going Further
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bromthymol_blue.doc | 20.5 KB |
colorful_respiration.doc | 38.5 KB |
Summary
Bubbling Yeast: Thanks to Ellen Loehman for creating this image.Yeast are a single celled fungi that are a great model organism for studying respiration in the classroom. The species Saccharomyces cerevisiae is commonly used for leavening bread and fermenting beer but other species such as Candida albicans are known to cause infections in humans (vaginal yeast infections and diaper rash being the most common). In this investigation, students fill the bulb of a disposable pipet (eyedropper) with yeast, then submerge the pipet in a test tube of water. They can then measure the rate of respiration by counting the number of bubbles of carbon dioxide gas that emerge from the tip of the pipet in a certain length of time. By varying the temperature and the nutrient source, students can discover what variables affect the rate of respiration in yeast. By submerging the pipet in bromthymol blue (see Colorful Respiration activity), students can identify the gas being produced as carbon dioxide.
For more information about yeast in classroom experiments, see this experiment from the Exploratorium or this one from PBS Kids that has snippets of what different kids saw with different manipulations. The idea of using inverted disposable pipets to contain the yeast and measure their respiration rate came from a workshop led by Steve Ribisi of the University of Massachusetts – thanks Steve!
Materials
Procedure
Going Further
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bubbling_yeast.doc | 38.5 KB |
Standards
Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope. As a basis for understanding this concept:
a. Students know cells function similarly in all living organisms.
b. Students know the characteristics that distinguish plant cells from animal cells, including chloroplasts and cell walls.
d. Students know that mitochondria liberate energy for the work that cells do and that chloroplasts capture sunlight energy for photosynthesis.
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
a. Select and use appropriate tools and technology (including calculators, computers, balances, spring scales, microscopes, and binoculars) to perform tests, collect data, and display data.
c. Communicate the logical connection among hypotheses, science concepts, tests conducted, data collected, and conclusions drawn from the scientific evidence.
e. Communicate the steps and results from an investigation in written reports and oral presentations.
Grade 8 Life Science
5. Chemical reactions are processes in which atoms are rearranged into different combinations of molecules. As a basis for understanding this concept:
a. Students know reactant atoms and molecules interact to form products with different chemical properties.
b. Students know the idea of atoms explains the conservation of matter: In chemical reactions the number of atoms stays the same no matter how they are arranged, so their total mass stays the same.
c. Students know chemical reactions usually liberate heat or absorb heat.
Grades 9-12 Biology
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:
f. Students know usable energy is captured from sunlight by chloroplasts and is stored through the synthesis of sugar from carbon dioxide.
g. Students know the role of the mitochondria in making stored chemical-bond energy available to cells by completing the breakdown of glucose to carbon dioxide.
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Summary
To learn about the structure and function of living things, it is essential to explore the anatomy of real organisms up close and personal. While much can be accomplished by studying living things and their life cycles (see Raising Plants and Raising Trout projects), dissections offer a view of the internal structures and how they contribute to the whole. What follows are resources and information for teachers interested in conducting a flower and/or frog dissection. There are many excellent lesson plans and dissection guides on the web already. Rather than recreate these resources here, My Science Box provides nitty-gritty logistics and resources such as a selected list of great web resources, how to order frogs, what equipment you need, student handouts, and teaching strategies.
Objectives
Can identify the major parts of a plant and flower and describe the function of each part.
Can identify the major organs in a frog and describe the function of each organ.
Can thoughtfully, safely and respectfully complete an anatomical dissection.
Attachment | Size |
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7dissections.doc | 50.5 KB |
Materials
Teaching Tips
The best resource that I have found for flower dissections is Gertrude Battaly’s website. There you will find comprehensive background information, step-by-step dissection directions, discussion questions and more. I recommend using her handout for the clarity of the directions. The handout I have provided includes only a summary table and conclusion questions.
Sources
To learn more about flower anatomy, see the following websites:
In addition to Gertrude Battaly’s site, other good lesson plans include:
Standards
Grade 7
Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
b. Students know organ systems function because of the contributions of individual organs, tissues, and cells. The failure of any part can affect the entire system.
f. Students know the structures and processes by which flowering plants generate pollen, ovules, seeds, and fruit.
Attachment | Size |
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flower_handout.doc | 31 KB |
Materials
Teaching Tips
The best resource that I have found for frog dissections is Net Frog by Mabel Kinzie has a fabulous interactive virtual frog dissection including many multimedia resources such as videos and narration for every step of the dissection. It is an excellent resource for teachers, for students to preview or review the material, and as an alternative to an actual frog dissection.
Sources
To learn more about frogs, visit the following websites:
In addition to Net Frog, other good lesson plans include:
Standards
Grade 7
Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
b. Students know organ systems function because of the contributions of individual organs, tissues, and cells. The failure of any part can affect the entire system.
c. Students know how bones and muscles work together to provide a structural framework for movement.
d. Students know how the reproductive organs of the human female and male generate eggs and sperm and how sexual activity may lead to fertilization and pregnancy.
Physical Principles in Living Systems (Physical Sciences)
6. Physical principles underlie biological structures and functions. As a basis for understanding this concept:
j. Students know that contractions of the heart generate blood pressure and that heart valves prevent backflow of blood in the circulatory system.
Grades 9-12 Biology
Physiology
9. As a result of the coordinated structures and functions of organ systems, the internal environment of the human body remains relatively stable (homeostatic) despite changes in the outside environment. As a basis for understanding this concept:
a. Students know how the complementary activity of major body systems provides cells with oxygen and nutrients and removes toxic waste products such as carbon dioxide.
b. Students know how the nervous system mediates communication between different parts of the body and the body's interactions with the environment.
f. * Students know the individual functions and sites of secretion of digestive enzymes (amylases, proteases, nucleases, lipases), stomach acid, and bile salts.
g. * Students know the homeostatic role of the kidneys in the removal of nitrogenous wastes and the role of the liver in blood detoxification and glucose balance.
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frog_handout.doc | 3.85 MB |
Summary
Sail aboard a research vessel and explore the living treasures of the San Francisco Bay. The Marine Science Institute (MSI) provides some of the best hands-on science and environmental education in the Bay Area. On the Discovery Voyage, students spend 4 hours learning about the San Francisco Bay ecosystem by examining water quality and collecting organisms at every level of the food web from microscopic plankton to mud dwellers to bat rays and fish. The diversity of life in the Bay is astounding and surprising to students who have spent their whole lives living by its water but never “diving in”. If a half-day voyage isn’t for you, many other fantastic programs are available including Inland Voyages (where live marine organisms come to you), Ocean Lab (where students explore animals of the rocky coastal ecosystem in MSI’s Discovery Lab classrooms), and Tidepool Expeditions (where MSI naturalists provide a guided tour of the tidepool creatures at Pillar Point).
Objectives
Can apply knowledge about the characteristics of life to the organisms living in the San Francisco Bay.
Can conduct a scientific investigation.
Can use a dichotomous key to identify animals.
Can recognize the extraordinary diversity of life in an ecosystem from single cells to sharks.
HAVE FUN!
Time
The Discovery Voyage lasts 4 hours.
Other programs range in length from 1-4 hours or programs may be combined for a full day adventure.
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trip_msi.doc | 37.5 KB |
Planning Guide
MSI has an extraordinary team of instructors that quickly engage students’ curiosity about the Bay. All of their adventures have students collecting, measuring, and studying marine organisms up close and personal. They offer a wide range of programs for every grade K-12, suitable for any budget and timeframe. See their School Programs page for details.
While the land-based programs are excellent, my recommendation is to go on the Discovery Voyage. Their 90 foot research vessel, the Robert G. Brownlee, sails out on 2 voyages virtually every day of the school year. It is one of the most fun-filled learning experiences I have ever had. They also provide an extensive Educator’s Guide that include a complete overview of the voyage as well as pre- and post-trip activities for the classroom (download it from the MSI website).
The trip begins with an overview of the geography of the San Francisco Bay and a rough sketch of the many organisms within its boundaries. From there students divide into groups to rotate through 4 stations.
The ship accommodates 42 students (up to 60 students may be accommodated with $200 extra fee) and costs between $1,000 – 1,600 depending on the level of sponsorship and the number of students (a very reasonable $25 - 40 per student for what you get). In addition to their home port in Redwood City, they sail from many other ports of call around the Bay including San Francisco, Richmond, and the Sacramento/San Joaquin River Delta.
To schedule a program, contact Gail Broderick at: 650-364-2760 ext. 10 or [email protected]
Summary
To study the life cycle and structure of plants, students grow plants from seed, fertilize them, and collect seed, starting the process over again. With the right growing conditions, almost any plant can be grown successfully in the classroom – native plants for a restoration project, vegetables, cut flowers, etc. The instructions provided here are for growing Wisconsin Fast Plants since they are the most widely used species in classrooms across America. These plants have been artificially selected to grow well in small spaces, with indoor lighting, with little soil, and with an exceedingly short life cycle (14-20 days to flower and 21-40 days to set seed). Therefore, they are incredibly well adapted to survive in classroom conditions as well as participate in multi-generational studies such as plant life cycle studies, Mendelian crosses and artificial trait selection. However, the light boxes and terraqua columns lend themselves to growing virtually any
Objectives
Can observe and document the stages of a flowering plant’s life cycle from seed to flower to seed.
Vocabulary
Brassia rapa (Wisconsin Fast Plants)
Seed
Embryo
Seed coat
Germinate
Radicle (embryonic root)
Hypocotyl (early stem)
Cotyledons (early leaves)
Leaf
Stem
Root
Flower
Fruit/seed pod
Attachment | Size |
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proj_plants.doc | 69.5 KB |
Time
40-50 min to build a light box
20 min to build terraqua columns (See Terraqua Columns activity for details)
20 min to plant seeds
5-10 min to build bee sticks
5-10 min to fertilize on day 14-20
5-10 min to harvest seeds on days 21-40
Time to conduct experiments and make observations varies.
Grouping
Each light box fits up to 9 terraqua columns constructed from 500 ml water bottles. Each water bottle terraqua column can accommodate 4 mature Fast Plants. Determine the grouping size based on the experiment you plan to try. Calculate the number of terraqua columns and light boxes required.
Materials
Light box
For one light box you need:
Don’t want to build light boxes? Have money to spare? Order one ready-made! Carolina Biological has several options:
Terraqua columns
For 30 terraqua columns you need:
Don’t want to build terraqua columns? Have money to spare? Order growing systems ready-made! Carolina Biological has several options:
Bee sticks (for pollinating your plants)
For 30 bee sticks you need:
Setting
Classroom
Teacher Background
Wisconsin Fast Plants (Brassica rapa) are an extraordinary resource for teachers since they have been selected for over 30 years for traits that make them ideal model organisms for the classroom. They thrive under fluorescent lighting, need very little soil, complete their life cycle in about a month, and take up very little space. Moreover, for under $50, a teacher can set up a classroom greenhouse and growing system for 32 students (2 light boxes and 18 terraqua columns growing 4 plants each).
There are 4 growing requirements for Fast Plants:
Student Prerequisites
None
Getting Ready
Procedures
To build a light box:
See the light box assembly directions on the Wisconsin Fast Plant website for detailed information.
To build a terraqua column:
See the lesson plan of the Terraqua Column activity for a description of how to build terraqua columns with students.
Day 0 - Plant Wisconsin Fast Plant seeds:
See the planting and fertilizing tips on the Wisconsin Fast Plant website for detailed information.
Day 4-5 – Thin seedlings
By now, seedlings should have pushed through the surface of the soil. Thin your seedlings so that there are no more than 4 seedlings per terraqua column or 1 seedling per cell in a quad. Try to leave seedlings that are spaced reasonably far apart.
Days 5-14 – Maintain your plants and make observations
By now, your plants should be growing well. Make sure the water reservoirs are full of nutrient rich water (especially before the weekend). Make sure the lights are 5-10 cm away from the plants (use books to prop them up). Make observations of your plants as they grow. Some traits that are easily measured:
Before day 14 – Make bee sticks
Day 14-20 – Fertilize flowers
By now, the flowers should have bloomed. Take the bee stick and rub it against the anthers of a blossomed flower. Move to the flowers of a different plant and rub against the pistil. Continue fertilizing until all the flowers in the classroom have been cross-fertilized. See the pollination directions on the Wisconsin Fast Plant website for detailed information.
Day 21-40 – Collect seeds
See the fertilization and seed development directions on the Wisconsin Fast Plant website for detailed information.
Experiment Ideas
See activity ideas on the Wisconsin Fast Plant website for detailed information.
Sources
For information on Wisconsin Fast Plants, see:
Standards
Grade 6
Ecology (Life Sciences)
5. Organisms in ecosystems exchange energy and nutrients among themselves and with the environment. As a basis for understanding this concept:
a. Students know energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis and then from organism to organism through food webs.
e. Students know the number and types of organisms an ecosystem can support depends on the resources available and on abiotic factors, such as quantities of light and water, a range of temperatures, and soil composition.
Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope. As a basis for understanding this concept:
f. Students know that as multicellular organisms develop, their cells differentiate.
Genetics
2. A typical cell of any organism contains genetic instructions that specify its traits. Those traits may be modified by environmental influences. As a basis for understanding this concept:
a. Students know the differences between the life cycles and reproduction methods of sexual and asexual organisms.
Evolution
3. Biological evolution accounts for the diversity of species developed through gradual processes over many generations. As a basis for understanding this concept:
a. Students know both genetic variation and environmental factors are causes of evolution and diversity of organisms.
Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
b. Students know organ systems function because of the contributions of individual organs, tissues, and cells. The failure of any part can affect the entire system.
f. Students know the structures and processes by which flowering plants generate pollen, ovules, seeds, and fruit.
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations.
Summary
Raising trout from eggs to fry in the classroom is a fabulous way for students to observe and study the life cycle of vertebrates and simultaneously learn about threatened species in local watersheds. Many states have programs where teachers and students raise trout in their classrooms in partnership with the Department of Fish and Wildlife for later release into a designated lake, creek or river. Described here is information for teachers on how to partner with state agencies, fish hatcheries, and local fly-fisher groups to raise rainbow trout in the classroom. A worksheet for the trout release field trip is provided. Best of all, many Trout in the Classroom Programs are fully supported by local fly-fisher groups and the California Department of Fish and Game (such as the California program that I participated in), and thus there is no materials cost to the teacher beyond the costs of organizing the trout release field trip at the end of the project.
FIsh Release: Atlantic salmon release in New Hampshire. Image contributed by the National Conservation Training Center.Objectives
Can observe and document the stages of a trout’s life cycle from egg to fry.
Can describe the environmental conditions needed for trout survival in the classroom and in local habitats.
Vocabulary
Anadromous salmonids
Trout
Salmon
Steelhead/rainbow trout (Oncorhynchus mykiss)
Eggs
Alevin
Yolk sac
Fry
Juvenile
Smolt
Spawn
pH
Dissolved oxygen
Nitrates
Migration barrier
Diversion
Competition
Non-native species
Channelization
Attachment | Size |
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trout_habitat_survey.doc | 52 KB |
proj_trout.doc | 51.5 KB |
Time
30 min set up tank
1 week for tank to equilibrate
1 month (approximately) between fertilization and hatching
2-3 weeks from hatching to release
Time required for the trout release field trip varies depending on the distance from your school and desired activities at the release site.
Grouping
The raising and care of the fry takes place as a whole class. During the trout release field trip, students may collect data in groups of 4 students.
Materials
Trout or salmon eggs are provided by your state’s Department of Fish and Wildlife, often through a local fish hatchery. Usually, a training workshop is required to participate, and a permit to transport and rear eggs is required from the state.
Aquarium set up (many state agencies and their partners offer the following equipment for classroom use for free):
1 10 gallon aquarium tank
1 undergravel filter
1 pump for undergravel filter (such as the Powerhead 201 pump from Hagen Aquaclear, available at most aquarium stores for $15-20)
Pea gravel, enough to cover the bottom of the aquarium to a depth of 1 inch
1 aquarium chiller or refrigeration unit that can maintain a 10 gallon tank at a stable 50°C (try the Cool Works Ice Probe Model IPWC-50W and power supply Cool Works P/N 5239, available at specialty aquarium supply companies for $100-120)
Aquarium thermometer that can monitor 1°C intervals between 40-60°C
10 gallons of non-chlorinated spring water
Aquarium net
Turkey baster (for siphoning away unhatched eggs
Aquarium insulation (make a Styrofoam box to surround your aquarium using insulating Styrofoam sheets available at most hardware stores)
Optional: if not using insulation, you will need a heavy black cloth to protect the alevins from UV radiation
For water testing
Dissolved oxygen test kit (see Water Analysis lesson for sources)
pH test strips
Setting
Trout are raised in the classroom then released on a field trip to a local lake, creek or river.
Salmon alevins: Just hatched salmon with yolk sacs. Image courtesy of U.S. Fish and Wildlife Service.Teacher Background
Raising trout provide a fabulous way to introduce students to the life cycle and physiological requirements of other species. Moreover, you can use these fish to teach students about threatened and endangered species.
Oncorhynchus mykiss (rainbow trout or steelhead trout) are the most commonly encountered species in classrooms. They are native to the West coast of North America but have been introduced to oceans, lakes and rivers world wide. They are a highly prized game fish in many North American rivers.
They belong to a class of fish known as salmonids that includes salmon and trout. Salmonids are anadromous, that is, they are born in fresh water but may spend much of their adult lives in the ocean, returning to the rivers in which they were born to spawn and lay their eggs. The freshwater form of Oncorhynchus mykiss is called rainbow trout. These fish may spend their entire lives in fresh water. The saltwater form is known as steelhead trout. These are generally larger than rainbow trout and can find their way back to the stream of their birth to spawn and lay eggs. Steelhead are then able to migrate back to the ocean and repeat the cycle several times in their life. Salmon, the other genus of salmonids, die after spawning and do not return to the ocean. For more information on the trout life cycle, see the Nevada Trout in the Classroom website.
Rainbow trout: Image courtesy of US. Fish and Wildlife ServiceIn order for young trout to survive to adulthood, several conditions must be met:
Each of these factors (besides the food supply since the alevin will have a yolk sac while in the classroom) must be carefully recreated in the classroom aquarium. Steelhead are classified as a threatened species since water diversion (dams), migration barriers (culverts, roads, and walls), habitat destruction, introduced species and creek disturbances (pollution, trash, dogs, erosion, etc.) have dramatically reduced the amount of acceptable habitat.
Different parts of the country have different programs for teachers to raise salmonids in their classrooms, each with its own set of rules and regulations. See the Procedures below to get in contact with a program near you. Information on how to set up a tank and care for your fish can be downloaded from Trout Unlimited. Curriculum resources may be downloaded from the Nevada Department of Wildlife.
Student Prerequisites
None
Procedure
To start a Trout in the Classroom program at your school, contact your state’s Department of Fish and Wildlife or find a local chapter of Trout Unlimited. These agencies sponsor training programs for teachers to show them how to set up an aquarium, get eggs, raise the fry, and release them into designated ecosystems. For specific resources, see the list of selected programs below:
On your trout release field trip, organize students into groups and assign each group an area of the creek, stream or river to survey. Groups are responsible for collecting data about the quality of the habitat and whether the newly released trout will have what they need to survive. Gather data on factors such as temperature, dissolved oxygen content, pH, shade, cover, and food availability. See the Water Analysis activity or the Habitat Survey activity or the Sediment Study project for details. A handout is provided but should be adapted to your specific release site.
Standards
Grade 6
Ecology (Life Sciences)
5. Organisms in ecosystems exchange energy and nutrients among themselves and with the environment. As a basis for understanding this concept:
a. Students know energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis and then from organism to organism through food webs.
e. Students know the number and types of organisms an ecosystem can support depends on the resources available and on abiotic factors, such as quantities of light and water, a range of temperatures, and soil composition.
Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope. As a basis for understanding this concept:
f. Students know that as multicellular organisms develop, their cells differentiate.
Genetics
2. A typical cell of any organism contains genetic instructions that specify its traits. Those traits may be modified by environmental influences. As a basis for understanding this concept:
a. Students know the differences between the life cycles and reproduction methods of sexual and asexual organisms.
Evolution
3. Biological evolution accounts for the diversity of species developed through gradual processes over many generations. As a basis for understanding this concept:
a. Students know both genetic variation and environmental factors are causes of evolution and diversity of organisms.
e. Students know that extinction of a species occurs when the environment changes and the adaptive characteristics of a species are insufficient for its survival.
Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
b. Students know organ systems function because of the contributions of individual organs, tissues, and cells. The failure of any part can affect the entire system.
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations.
Mars Exploration Rovers: This special-effects image combines a model of the Mars rover Opportunity and 46 photogrpahs that Opportunity took of "Burns cliffs" near the edge of "Endurance Crater". Image courtesy of NASA/JPL-Caltech/Cornell.
Summary
In the summer of 2003, NASA’s Jet Propulsion Laboratory launched two Mars Exploration Rovers - Spirit and Opportunity - towards Mars. They landed on January 3rd and 4th, 2004. Their primary scientific goal was to study the geology of Mars and search for signs of water. Although they were expected to last only 3 months, they have been vigorously sending back data for over 2 years and are still going strong! In this activity, students receive simulated Martian soils and are given the task of designing 3 tests to determine whether the soil sample contains something alive or something that was once alive. They may use any of the tools from the previous lessons – agar plates, tests for organic molecules, microscopes, or something of their own design. This assignment allows students an opportunity to demonstrate what they have learned throughout the unit, both about scientific experimentation and about the special characteristics of living things.
Objectives
Can describe the necessary characteristics of life.
Can categorize objects as alive or not alive using self-generated data.
Can demonstrate that all living things will grow and reproduce when provided with the proper nutrients and environmental conditions.
Can demonstrate that living things are made of organic molecules.
Can test for the presence of protein, glucose and starch.
Can design an experiment.
Can make observations and keep track of data over several days.
Can interpret the results of an experiment.
Vocabulary
Characteristic
Agar
Nutrients
Yeast
Organic molecule
Protein
Biuret solution
Carbohydrates
Glucose
Benedict’s solution
Starch
Iodine
Microscope
Attachment | Size |
---|---|
assess_life_on_mars.doc | 68 KB |
mars_soil_handout.doc | 2.13 MB |
mars_soil_handout.pdf | 1.62 MB |
Time
10 min introduction
20-30 min design experiments
35-50 min conduct experiments (some tests may need to be left overnight)
20-30 min discuss experiments
Grouping
Groups of 2-3 students
Materials
For all tests:
For soil samples, enough for a class of 30 students in teams of 3:
For nutrient milkshake:
For agar plates (see Life Trap activity for ordering information):
For organic molecules tests (see Testing for Life activity for ordering information):
For microscope test:
Optional for introduction:
Setting
Classroom
Teacher Background
Mars, Blueberries, and Hematite
Mars Rover - Spirit: This special effects image of the Mars Exploration Rover Spirit was created using a rover model and an image taken by the Spirit navigation camera. Image courtesy of NASA/JPL-Caltech.The Mars Exploration Rover mission provides the inspiration for exciting science experiences. These two rovers represent incredible feats of engineering and have contributed vast piles of data for geology and astrobiology research.
This lesson is built around the discovery of Martian “blueberries” by the rover Opportunity in Meridiani Planum. The blueberries aren’t really blue – they’re actually grey – nor are they the size of blueberries – they are only around 3 millimeters in diameter. When they were first observed scattered across the floor of Meridiani Planum, their composition was an enticing mystery.
Closeup of "blueberries": This image, taken by the rover's microscopic imager, clearly shows the sphere-like grains or "blueberries" that fill Berry Bowl. Image courtesy of NASA/JPL-Caltech.What are they? Their uniformity and symmetrical shape calls to mind the bacterial and fungal colonies grown on agar plates. Could they once have been living things, now frozen or fossilized on the surface of Mars? What about the 3 fused berries in the picture? Does this capture the process by which berries reproduce? That is the question posed to students in this activity, however, this is not a theory supported by scientists. Scientists guessed that the blueberries were concretions, formed when water rich in minerals permeates into porous rock then evaporates, leaving behind the hardened minerals in the spaces. Although originally buried within the rock, as the surrounding rock weathered away, the concretions were freed and left to roll around on the Martian surface.
Berry Bowl with "blueberries": This image from the Mars Exploration Rover Opportunity's camera shows the rock called "Berry Bowl" in the "Eagle Crater" outcrop. Image courtesy of NASA/JPL-Caltech.For several long weeks, the blueberries were too small and scattered to be analyzed accurately with Opportunity’s scientific instruments. Thus the scientists’ theory could not be confirmed. Finally the rover reached a spot nicknamed the “Berry Bowl”. There, enough blueberries had collected in one place for the rover to use its Mössbauer, thermal emission, and alpha particle X-ray spectrometers to decipher its chemical make-up. By comparing the berry cluster in the Berry Bowl with a berry-free patch nearby, scientists were able to determine that the blueberries are composed of hematite (or haematite).
Hematite is the mineral form of iron oxide (rust). It is very common on Earth and is generally found in places where there has been standing water or mineral hot springs. However, it may also be formed volcanically. So, does the hematite blueberries on Mars indicate the former presence of water or were the blueberries formed volcanically? The presence of fused blueberries, like the triplet berry near the center of the image strongly argues that these blueberries were formed through the action of liquid water. Volcanically formed beads are unlikely to fuse along a line in this fashion.
More information on the Mars Exploration Rover mission is available on the NASA/JPL website and specific links of interest to this lesson are provided in the Sources section.
Tips for Teachers
Be aware of several tips as you embark on this open-ended experiment.
The yeast will remain active when added to the nutrient milkshake for a few hours until they run out of nutrients to sustain their growth. Adding more milkshake will reinvigorate the culture.
For students to grow yeast on agar plates, the nutrient agar must include sugars for the yeast to digest. This differs from the agar plates described in the Life Trap activity in which no sugar was required. In addition, it is best to dissolve the yeast-soil sample in water first (approximately 1 part yeast-soil to 2 parts water) and seed the plates with a Q tip dipped in the solution. Dry yeast get too little moisture from the plates alone to grow effectively.
To test for organic molecules, it is important to dissolve the yeast-soil sample in water first (approximately 1 part yeast-soil to 2 parts water). Only the protein test will yield a positive result. If you want to increase the rate of positive results, add 2 tablespoons of flour to the yeast-soil mixture. This will make the starch test give a positive result as well without interfering with any of the other tests the students might conduct.
Student Prerequisites
Students need a thorough understanding of the characteristics of life and must be equipped with several means of testing for life such as growing microbes on agar plates or nutrient-rich solutions, testing for organic molecules, observing cells under the microscope, etc. See the Life Trap, Testing for Life, and Seeing Cells activities.
Getting Ready
For soil samples:
For nutrient milkshake: combine 500 ml distilled water, 85 g table sugar, and 85 g all purpose white flour in a 1 liter bottle or flask.
For agar plates: see Life Trap activity for directions on how to mix nutrient agar and pour plates.
For organic molecules tests: see Testing for Life activity for directions on how to set up test stations.
Lesson Plan
Going Further
Sources
This lesson was inspired by a workshop by Steve Ribisi of the University of Massachusetts and Mission 10 from the Life in the Universe curriculum, published by the SETI Institute.
To learn more about the Mars Rovers, go to the NASA/JPL website. The following are some of the highlights from this site that may be used in conjunction with this lesson:
To learn more about blueberries and hematite, see:
Standards
Grade 6
5. Organisms in ecosystems exchange energy and nutrients among themselves and with the environment. As a basis for understanding this concept:
e. Students know the number and types of organisms an ecosystem can support depends on the resources available and on abiotic factors, such as quantities of light and water, a range of temperatures, and soil composition.
Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope.
Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
Grade 8
Chemistry of Living Systems (Life Sciences)
6. Principles of chemistry underlie the functioning of biological systems. As a basis for understanding this concept:
a. Students know that carbon, because of its ability to combine in many ways with itself and other elements, has a central role in the chemistry of living organisms.
b. Students know that living organisms are made of molecules consisting largely of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
c. Students know that living organisms have many different kinds of molecules, including small ones, such as water and salt, and very large ones, such as carbohydrates, fats, proteins, and DNA.
Grades 9-12 Biology
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:
a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.
b. Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings.
h. Students know most macromolecules (polysaccharides, nucleic acids, proteins, lipids) in cells and organisms are synthesized from a small collection of simple precursors.
Grades 9-12 Chemistry
Organic Chemistry and Biochemistry
10. The bonding characteristics of carbon allow the formation of many different organic molecules of varied sizes, shapes, and chemical properties and provide the biochemical basis of life. As a basis for understanding this concept:
a. Students know large molecules (polymers), such as proteins, nucleic acids, and starch, are formed by repetitive combinations of simple subunits.
b. Students know the bonding characteristics of carbon that result in the formation of a large variety of structures ranging from simple hydrocarbons to complex polymers and biological molecules.
c. Students know amino acids are the building blocks of proteins.
All Grades
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
a. Select and use appropriate tools and technology (including calculators, computers, balances, spring scales, microscopes, and binoculars) to perform tests, collect data, and display data.
e. Communicate the steps and results from an investigation in written reports and oral presentations.