BASIC BIOLOGY & METHODS of SCIENCE

Introduces fundamental biological mechan-
isms that are basic to an understanding of
how organisms live and function. Presents
some of the fundamental intellectual, phys-
ical & conceptual tools of scientific study.

VIRUSES, BACTERIA, NEMATODES, etc.
Introduces these diverse and myriad microscopic creatures that play such a large role in mankind's health and well-being. 4 pgms.75 slides and guides.
EPSS-1095X SLIDES
$129.95

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SAVE OVER $32.00 ON 4 SLIDE SET BUNDLE ORDER EP#SS-1095X..........$129.95
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INTRODUCTION TO VIRUSES Slides order #SS-1100S.......$34.95

A comprehensive visual examination of this unique and obscure group of
organisms. Topics include reproduction, diseases caused by viruses, culturing,
vaccinations, and electron microscopy. Provides numerous examples. 15 frames and
guide. (Filmstrip order SS-1100F.........$15.00.)

CONTENT SAMPLE: 3. A typical virus is made up of a protein shell or capsule
around a nucleic acid core. Often proteins (enzymes) are found associated with the nucleic
acid. The shells provide protection as well as a mechanism for invading susceptible cells.
Viruses range in size between 10 and 200 microns (0.0000004 to 0.000008 inch). They may be
simple isometric colloids of protein with a high degree of structural symmetry, or complex
multilayered enveloped particles. Virus structures are so much like crystalline solids in
appearance that we seem to be looking at molecules straddling a narrow gap between animate
and inanimate.

Virus shapes can be divided into five categories. The simplest shape is the naked helix.
Tobacco mosaic virus, illustrated in this frame, is a good example of this form. There is a
protein capsid surrounding a helical core of RNA. The term "naked" is used because there is no
envelope, only the protein coat (capsid) on the nucleic acid. Notice the distinctive rod shape of
TMV; other plant viruses may have a similar shape.

The second category is composed of the naked icosahedral viruses. Adenovirus, shown
here, is an example of this structural form. Like TMV, Adenovirus has no envelope, only the
naked protein capsid. In this case the capsid is a highly symmetric solid called an icosahedron.
This is a 20-sided regular solid of equilateral triangles, with 12 vertices and 30 edges. The
capsid is made up of repeating protein subunits called capsomeres. The size and shape of the
capsomeres determine the fine structure of the capsid. In the case of Adenovirus there are 252
spherical capsomeres arranged in the icosahedral shape. Note the slender rods extending out
from the twelve vertices.
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INTRODUCTION TO BACTERIA Slides order #SS-1095S.......$42.50

Surveys the bacteria phyla: diversity of form and function within this extensive
but usually unseen world of microscopic organisms. Includes anatomy, physiology,
reproduction, evolution, behavior and significance to man and nature. 2O frames and
guide. (Filmstrip order SS-1095F.........$15.00.)

CONTENT SAMPLE: 3. Most commonly, bacteria are of three general shapes:
spherical, rod-shaped or spiral. Eight of the many types of known varieties are shown here.

Spherical bacteria are the cocci. They may be true spheres, like the staphylococci;
helmet-shaped, like pneumococci or kidney-shaped like Neisseriae. The cocci may occur
singly or in groups. If found in pairs they are called diplococci; triads, if in a group of three.
There are tetrads, cuboidal packets of eight cells, grape-like clusters such as the well known
staphylococci and chains of spheres as in the streptococci.

The rod-shaped bacteria are the bacilli. These do not show the same arrangements as
the cocci but they may be found in pairs (diplobacilli), or end to end in chains (streptobacilli).
Certain species, such as Corynebacterium diphtheriae, form picket-fence or cuneiform patterns
which look like stacks of wood.

Spiral shapes, or spirilla, are distinguished by their length, the number and size of the
spirals, and direction of the coil. Short segments or incomplete spirals are common, such as
the comma-shaped Vibrios. The spirochetes of syphilis are typical spiral bacteria. Spirilla are
solitary bacteria, rarely found in chains or clusters.

Other types of bacterial shapes include the filamentous branching bacteria, such as
Actinomyces scabies, which resemble fungal mycelia. Specialized reproductive elements
produce conidia (functioning similar to spores), eventually released for aerial distribution.

Many bacterial forms other than those described are known, and doubtless thousands of
individual species will eventually be added to the already burgeoning list of microbes.
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NEMATODE STRUCTURE AND DEVELOPMENT Order #414.....$42.50

Although more than 5O,OOO species are known, nematodes are one of the
most obscure animal groups. They are found in almost every ecological niche and cause
untold economic loss and numerous diseases to man. The life cycle of Pelodera
strongyloides is presented here. 2O slides and detailed guide.

CONTENT SAMPLE: 26919 Male and Female Copulating. 22x mag. Sexes are
separate with the female being somewhat larger than the male. In this copulating pair, the male is
1,200 microns long and the female is 1,500 microns.

REVIEWS: "...best for more advanced high school and college biology classes.
Recommended." Booklist.
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PARASITIC ORGANISMS Slides order #SS-0225S.....$42.50

Illustrates parasites common to man and domestic animals, with selected
adults, and their life cycles. Includes amoebas, mosquito, flatworm, flukes, tape and
bladder worms, itch mite, etc. 2O frames & guide. (Filmstrip SS-0225F......$15.00.)

CONTENT SAMPLE: 20. This is Sarcoptes scabiei, the itch mite of man, and is
responsible for scabies. The females lay eggs subcutaneously, and the larvae tunnel through the
integument. The feces of S. scabiei are responsible for much of their pathogenicity.
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~0723-79~ Nematodes copulating. photo by William C. Marquardt, Ph.D.

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