MI BIG
Cells III.1
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(Inspiration)
Overview
As a science teacher, I can still remember the eyes of students when they
first observed a cell and cytoplasmic streaming! How excited and engaged
they were in the process of observing life! "Are those green
chloroplasts alive since they are moving?" "Do all onions have
oil droplets?" "That is the nucleus of my cheek cell!"
"Are those my chromosomes?" The understanding of cells as they
relate to the functioning of multicellular organism is the basis of many
real world connections.
Essential Background Narrative
Apply an understanding of cells to the functioning of multicellular
organisms including how cells grow, develop and reproduce
Although most cells are too small to see with the unaided eye, learning
about these units of life is central to our understanding of all
organisms. It is through the study of cells that biologists have come to
understand and interpret the unity that underlies the great diversity of
living things. Biologists sometimes express their understanding of this
unity in terms of the Cell Theory: 1) all organisms are composed of cells;
2) all cells arise from preexisting cells; and 3) the cell is the basic
living unit of organization of all organisms.
Of these three principles, currently in the summer of 2001, none are
assigned to the elementary level articulation of the Michigan Curriculum
Framework Science Standards and Benchmarks. In middle school the
benchmarks address the concept that all organisms are composed of cells
and that cells are the basic living unit of organization. With the use of
tools such as the hand lens and microscope, common living things can be
found to be made up of cells. It becomes increasingly important for the
explanation of why and how selected specialized cells are needed by plants
and animals since students often think incorrectly that there are only
those two types of cells….plant and animal. The specialization of
functions that cells perform will dictate their actual form....i.e.
comparison of a red blood cell to a striated muscle cell.
In high school, students have difficulty discriminating between cell
division, growth/enlargement, and differentiation. Living things do not
simply get larger due to cells growing larger. Growth of the organism is
the result of cell division and resulting increase of number of cells. The
actual trigger for cell division is the ratio of surface area of the cell
to volume but total growth of the organism is not due to just bigger sized
cells.
Specialized cells and organelles carry out life functions and can be tied
to actual classification of organisms by cell type. Scientifically
literate high school students will be able to reason that cells specialize
in order to efficiently divide or share the function needed to keep the
organism alive. The differences in cell type form basic divisions in the
way scientists classify living things.
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