In Investigation One students will explore the effect of the refraction of light through lenses. By observing objects with hand-held convex and concave lenses and the convex lenses in a compound microscope, they will discover that refraction of light through lenses produces images that differ in resolution from the object. As students compare the images they will learn that the changes in resolution produced by convex and concave lenses are different. Compared to the object, images produced by convex lenses have increased resolution while those from concave lenses are decreased in resolution. Students’ observations will also enable them to realize that when convex and concave lenses are used, the proportions of the object are maintained in the image.
In Investigation Two, students will build on their experience with lenses as they use the three objectives of the compound microscope to study specimens. Their observation of the specimens will enable them to discover that refraction of light through lenses not only produces changes in magnification and resolution but also in the field of view. As a part of their analysis, students will calculate the total power of magnification produced when specimens viewed with each objective. In addition, students will be introduced to specimen preparation techniques as they prepare their fingerprints for analysis under the microscope.
During Investigation Three, students will be introduced to the concept of a cell and to examples of eukaryotic and prokaryotic cells. Students will learn the procedure for a wet mount preparation of a specimen as they prepare a sample of their own cheek cells for analysis. Through observation of their cheek cells, students will discover that a cell is composed of smaller parts called organelles and that the structure of a cell and its organelles relate to their functions.
Investigation Four introduces students to examples of plant cells. Students will observe specimens of an Elodea leaf and an onion bulb. During their investigation, they will discover that plant cells have a cell wall, an organelle not present in animal cells. Through their observations, students will also realize that chloroplasts, organelles absent in animal cells, are present in some but not all plant cells and that this difference is directly related to the ability of plants to carry out photosynthesis.
In Investigation Five, students will shift the focus of their microscopic exploration from cells to tissues and organs. By observing specimens of the leaves and stems of plants and blood and the colon of the human body, students will come to realize that cells combine within organisms to form larger structures. Through comparison of the cell shapes, sizes, and arrangement within the four specimens students will develop a deeper understanding of how the function of a tissue or organ relates to its structure.