MI BIG
The Organization of Living Things III.2
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(Inspiration)
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All students will use classification systems to describe groups of living
things.
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All students will compare and contrast differences in
the life cycles of living things.
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All students will investigate and explain how living
things obtain and use energy.
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All students will analyze how parts of living things are adapted to
carry out specific functions.
Overview
When one thinks of the diversity of living things one immediately thinks
of how to organize and name them all. The process seems to be an outgrowth
of human language and higher order thinking. Children are continually
asking, "Where does it live?" "What does it eat?"
"What is it like?" "What does it do?" These questions
lead them to begin organizing living things. In this strand, the hierarchy
of classification based on internal and external structures, specialized
functions, and energy utilization is the basis for instruction.
Essential Background Narrative
Use classification systems to describe groups of living things.
Compare and contrast differences in the life cycles of living things.
Investigate and explain how living things obtain and use energy.
Analyze how parts of living things are adapted to carry out specific
functions.
With the help of the big yellow bird or the purple dinosaur, children at
an early age sort "which one doesn't belong." There is a
tremendous diversity of life forms. With over 1,500,000 identified
organisms, biologists need some way of organizing these life forms so they
can be studied.
Students informally observe a wide variety of living things in and out of
school. Just like scientists, they note similarities and differences in
their observations. At the elementary level, students focus on observable
characteristics. These informal categories will be challenged with the
acquisition of additional knowledge of anatomical differences, in
particular those characteristics that are not observable.
Just as diversity and change are important features of the continuance of
life on earth, cycles are a recurring theme at all levels of organization
of living things. The "Cycle of Life" is perhaps the most
commonly known of the biological cycles. The birth, growth, reproduction,
and death of organisms within a species occur with regular predictability.
At the elementary level, the life cycles of familiar organisms both plants
and animals are the focus. At the high school level, the life cycle of
organisms associated with human disease can be included in the
investigations.
The relationship between life and energy is complex. While the
generalization that living things need energy to survive is satisfactory
at one level of understanding, it fails to convey the crucial role energy
plays in all aspects of life, from the molecular to the population level.
At the elementary level students can compare and contrast food, energy and
environmental needs of selected organisms, such as beans, corn or aquarium
life.
In the middle and high school, the focus is more specific on the concept
that plants make and store food. Scientists speak of the flow of energy
through the environment. Almost all life on the earth is sustained by
energy from the sun. This energy is transformed and moved from location to
location, but doesn't disappear. Plants capture the sun's energy and use
it to produce energy rich organic molecules that we call food. The food
molecules then serve as energy sources for plants and ultimately animals.
In animals, organic food molecules are chemically broken down and carried
through the circulatory system to cells, cytoplasm, and eventually to
mitochondria. This is, most often the site of final energy release through
the process known as cellular respiration.
The chemical process of photosynthesis occurs at the cellular level and is
capable of converting light energy into molecular energy. Animals are
dependent on plants for this first important step in the flow of energy.
In plants, light energy is captured by chloroplasts or chlorophyll and is
converted to chemical energy through the making of organic food molecules
when water and carbon dioxide are chemically combined to make sugar and
oxygen. These sugars (organic compounds) formed in photosynthesis are used
for the plant's metabolic processes and maybe ultimately be used as food
for animals. The chemical process of respiration is also cellular.
Cellular respiration releases stored molecular energy so the energy can be
used for other life processes. Both plants and animals respire.
The acquisition and use of energy by living things is a very abstract idea
for students at all levels. Students tend to develop a vague and very
broad definition of energy that is inconsistent with the scientific
definition. This imprecise definition interferes with the acquisitions of
the biological understanding of energy and its importance in a living
system.
Multicellular organisms, over a long period of time, have adapted and
become specialized to be efficient at a particular function...for example
the roots, stems, leaves, flowers, fruits, and seeds of a common green
plant have specialized parts that work together to form systems to do
processes which become interdependent within the organism. This
interdependence helps to maintain a stable internal environment in higher
plants and animals. This stable environment can be, in turn, disrupted by
disease and other environmental conditions. The scientifically literate
student should be able to describe how technology can be used in the
prevention, diagnosis, and treatment of diseases in today's world.
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