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Genetics
Teaching Vignettes: Elementary School
Title:
Teaching Genetics in a Kit-based Elementary School Curriculum
Teacher: Julie Blystad
School: Bertschi School, Seattle, WA
Grade Level: 3-5
Instructional Materials:
Science and Technology for Children
(STC) Kits: Plant Growth and Development and Microworlds
(available from Carolina Biological, 800-334-5551). Useful supplementary
books that focus on genetics include the Cells Are Us
series (Cells Are Us, Amazing Schemes Within Your Genes,
Cell Wars, and DNA is Here to Stay) and the Microexplorers
series (Ingenious Genes, How the Y makes the Guy,
and The Cell Works). Reviews of these books can be found
in Appendix I, Guide to Instructional
Materials. Books that are particularly strong in supporting
the Microworlds kit are Microscopic Explorations and Magnificent
Microworld Adventures.
Classroom Activities:
Many activities are included in
the Plant Growth and Development and Microworlds
kits. Three lessons/activities from the kits are described below:
Interdependence of Bees and Flowers, Observation and
Description of Onion Cells, and Observation of a Microscopic
Organism: Volvox.
Description:
Even at the elementary level, students
are learning basic genetics concepts or their forerunners. In
a science kit-based curriculum, many of the units do touch on
the building blocks of genetics even though the "language"
of genetics may never be used. Thus, some teachers at this level,
having little genetics familiarity, may not realize that they
are indeed laying the foundation for subsequent study of genetics
that will occur in more depth in middle and high school. In the
two kits described here, Plant Growth and Development
and Microworlds, both from the STC curriculum, a number
of genetics concepts are covered. Some of the concepts addressed
include: Reproduction and Inheritance (#1), Cells (#6), Variation
(#7), Technology (#8), and Ethics (#9). Even when a kit curriculum
is used, additional materials can be brought in to support and
extend the kit lessons. For example, two series of books relating
to genetics that are especially suitable for elementary students
are the Cells Are Us series and the Microexplorers
series.
Plant Growth and Development
In this unit, students observe
the life cycle of the simple plant Brassica rapa (Wisconsin
Fast PlantTM). They observe and describe the distinct stages
of the life cycle, starting from seed germination through seed
production. They learn that flowering plants must be pollinated
in order to produce seeds and that in many cases, plants are
pollinated by bees. The honeybee-Brassica relationship
provides an example of the interdependence of living things.
Students also learn that in order to grow and thrive, plants
need light, water, and nutrients from the soil. These requirements
illustrate how plants depend on their environment for survival.
Through hands-on activities, students reinforce these concepts
as well as learn basic scientific skills such as observation
and measurement.
Lesson: Interdependence of Bees and
Flowers
In nature, there are many examples
of symbiotic relationships, where each partner is dependent on
the other. Between bees and flowering plants, the symbiotic relationship
is complex. In order for the ovule of a flower to develop into
a seed, it must be fertilized by a pollen grain from the same
species. For Brassica Fast Plants, the pollen cannot come
from the same flower or from a flower on the same plant. The
Brassica blossoms must be cross-pollinated—fertilized
by pollen from another plant. Bees are the means that Brassicas
use to achieve the required cross-pollination. In return, the
bees obtain nectar from the Brassica flowers. In this
activity, students use "bee sticks" (dead worker bees
glued to toothpicks) to cross-pollinate Brassicas. Through
discussions and readings, they come to appreciate the interdependent
relationship of the bee and the Brassica.
Microworlds
In this unit, students investigate
both living and non-living specimens with a variety of magnifiers,
including the microscope. They learn about the properties of
lenses—transparency and curvature—and the relationship
between magnification and the lens. They develop skills such
as focusing and lighting adjustment and learn to prepare specimens
for viewing on microscope slides. Students learn that all living
things are made up of cells and observe firsthand in their microscopes
the cells of an onion, as well as subcellular structures such
as the nucleus and cell wall. Observation of living microorganisms
such as Volvox allows students to understand how these
organisms grow and reproduce. Several fine supplementary books
are available on this topic (see previous page under Instructional
Materials).
Lesson: Observation and Description
of Onion Cells
In previous Microworlds
activities, students will have investigated magnification and
learned how to prepare microscope slides for viewing. In this
lesson, students will move from the outside of the onion in,
until they reach the smallest living unit, the cell. Students
will examine and describe the internal structure of an onion
and observe and describe onion cells. Onions are ideal subjects
for students’ first observations of cells because it is
possible to remove a thin skin from the onion that is actually
a single layer of large cells. Students will be able to observe
several cellular structures, including the cell wall, which supports
and gives shape to the cell; the cell membrane, which lies just
inside the wall; and the nucleus, the cell’s control center.
Lesson: Observation of a Microscopic
Organism: Volvox
Students should already be
familiar with magnification and how to prepare microscope slides
for viewing. This lesson provides another opportunity for students
to view individual cells. In this case, the cells are from the
unicellular green alga Volvox. Volvox is interesting
because unicellular Volvox individuals live together in
colonies of 1000-3000 similar cells, arranged in a hollow sphere.
Each individual cell has two flagella, or whiplike tails, which
work together to propel the colony through the water. Visible
inside many of the colonial spheres are smaller daughter colonies.
After the daughter colonies become big enough, they will be released
through an opening in the parent colony to become new, independent
colonies.
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