The Science Content Standards for Grades Nine through Twelve:
Biology/Life Sciences
Living organisms appear in many variations, yet there are basic similarities among their forms and
functions. For example, all organisms require an outside source of energy to sustain life processes; all
organisms demonstrate patterns of growth and, in many cases, senescence, and the process of
becoming old;
And the continuity of all species requires reproduction. All organisms are con¬structed from the
same types of macromolecules (proteins, nucleic acids, and lipids) and inherit a deoxyribonucleic acid
(DNA) genome from a parent or parents. DNA is always transcribed to yield ribonucleic acid (RNA),
which is translated through the use of a nearly universal genetic code. Environmental factors frequently
regulate and influence the expression of specific genes.
Biologists study life at many levels, and the biology standards for grades nine through twelve reflect
these studies. Organisms are part of an ecosystem and have complex relationships with other
organisms and the physical environment. Ecolo¬gists study these populations and communities, and
many are deeply interested in the physical and behavioral adaptations of organisms. Evolutionary
biologists share these interests because the fitness of an organism is a manifestation of these
adapta¬tions. Adaptations are traits subject to the rules of inheritance; therefore, genetics and
evolutionary biology are closely allied fields.
Physiologists study whole body systems or organs. For example, a neurophysi¬ologist focuses
primarily on the nervous system. Cell biologists study the details of how cells and organelles work,
considering such weighty matters as how cytoskeletal elements segregate chromosomes during mitosis,
how proteins are sorted to differ¬ent compartments of the cell, and how receptors in the cell
membrane communi¬cate with factors that regulate gene expression. Many cell biologists also
consider themselves to be developmental biologists, molecular geneticists, or biochemists. There are
many connections between all the fields and different ways of viewing life.
Biology textbooks typically start with a review of chemistry and energetics; therefore, California
students will be able to make good use of their study of the content standards for “Chemistry of
Living Systems� in the eighth grade. The prin¬ciples of cellular biology, including respiration and
photosynthesis, are usually taught next, followed by instruction in molecular and Mendelian genetics.
Popula¬tion genetics and evolution follow naturally from the study of genetics and lead to a
discussion of diversity of form and physiology. The teaching culminates with ecol¬ogy, a subject that
draws on each of the preceding topics. The teaching comes full circle because ecology is also a starting
point for students in lower elementary school grade levels.

Standard Set 1.  Cell Biology
The first knowledge of cells came form the work of and English scientist, Robert Hooke, who in 1665
used a primitive microscope to study thin sections of cork and called the boxlike cavities he saw â
€œcells.â€�  Anton van Leeuwenhoek later observed one-celled “animalculesâ€� in pond water,
but not until the 1830s did Theodor Schwann view cartilage tissue in Sciences which he discovered
cells resembling plant cells. He published the theory that cells are the basic unit of life. Rudolf Virchow
used the work of Schwann and Matthias Schleiden to advance the cell theory, presenting the concept
that plants and ani¬mals are made of cells that contain fluid and nuclei and arise from preexisting cells.
After the cell theory was established, detailed study of cell structure and func¬tion depended on the
improvement of microscopes and on techniques for prepar¬ing specimens for observation. It is now
understood that cells in plants and animals contain genes to control chemical reactions needed for
survival and organelles to perform those reactions. Living organisms may consist of one cell, as in
bacteria, or of many cells acting in a coordinated and cooperative manner, as in plants, animals, and
fungi. All cells have at least three structures in common: genetic material, a cell or plasma membrane,
and cytoplasm.