- •In mineral deposits, in sea water, or in the atmosphere.
- •Viewed as a whole.
- •In general, life processes cease at about the freezing
- •Insects to polar bears, have camouflaging colours at one
- •In those days without anesthetics. So he left the medical
- •Instruments. Since the space alloted him was so small,
- •Voyage was spent along the coast of South America.
- •Is developing by leaps and bounds, the genetics of
- •It follows that a study of the mechanisms which allow
- •Vulpian expressed the opinion that Pasteur's
- •Is some action, which is becoming mote intense as we
- •Infectious agent of the rabies received from the dog bite
TEXTS FOR HOME—READING
THE SCIENCE OF BIOLOGY
Biology is the science of living organisms. It is
concerned with their nature, functions, reproduction, and
place in their environment. It is a ramifying science,
but it aims to be a precise one. It is ruoted in physics
138
--page0138--
and chemistry and many of its interpretations are made
in terms of these sciences and of mathematics. It is bound
closely with geology and meteorology, and applications
of its principles are found in anthropology, psychology,
sociology, agriculture, medicine, industry, and indeed,
in everyday living. Inasmuch as one of its ultimate aims
is thorough understanding of living organisms including
man, biology is entitled to be called the most vital of
. the sciences.
composition of living bodies. Chemical analyses show
that living materials consist of carbon, hydrogen, oxygen,
nitrogen, sulfur, phosphorus,, potassium, iron, ancj
magnesium. In addition, they usually contain sodium, chlorine,
and lesser amounts of such elements as manganese,
copper, iodine and fluorine. Everything can be.identified.
There is no residue of unidentifiable stuff. But the
elements present in living matter are all found in abundance
In mineral deposits, in sea water, or in the atmosphere.
Hence we can conclude that there is nothing peculiar in
the elemental composition of living matter.
But what of the wdy in which these elemental blocks
are put together? We know, for instance, that hydrogen
and oxygen combined in one proportion (H2O) constitute
water, a specific substance; in another (H2O2), hydrogen
peroxide have quite different properties, associated with
their differences in composition. Is living matter
distinguished from nonliving matter by its chemical
organization? With reference to many of chemical compounds
found in living matter the answer to this question is no.
With reference to the sum total of the compounds which
together make up any living body the answer is yes.
A major part* 65 to 90 percent, of every living body
is composed of hydrogen and oxygen combined as water.
Water is an inorganic substance, chemically simple and
obviously not confined to living organisms. The bodies
of plants and animals contain numerous other inorganic
substances—acids, bases, and salts. None of them differ
from the acids, bases, and salts with which the inorganic
chemist works daily in his laboratory.
Other substances, the so-called carbon or organic
compounds; are restricted, in nature, to living bodies or the
products of living bodies. They include the carbohydrates,
139
.
--page0139--
fats, and proteins. All contain carbon, hydrogen* and
oxygen. In.addition, the proteins contain nitrogen and often
suffur and other elements. ^
The carbohydrates are generally considered the
simplest organic substances. Their stru<^ure is adequately
known and many of them can be synthesized. In Tiving
organisms they are important as energy compounds.
Nearly all the energy used by living organisms, plant,
and animal, is light energy derived from the sun. This
light energy is converted to other energy forms by a
process called photosynthesis. It is in carbohydrates
that green plants first store this energy. It is primarily
in carbohydrates that the energy is distributed to,all
parts of the plant, and it is from carbohydrates that much
of the energy used by animals is obtained.\"
Fats resemble carbohydrates in composition but are
chemically more complex and contain more stored energy.
Like the carbohydrates, many fats can be synthesized Fn
the laboratory.
Proteins differ considerably from fats and
carbohydrates. Chemically they are much more complicated than
all except a few carbohydrates and fats. So far no
proteins have been synthesized. Proteins are more closely
xelated to certain of the activities which characterize
the living state than are the carbohydrates and fats.
Proteins have a specific character which the other organic
compouns lack. Whereas the same carbohydrates and fats
are found in thousand's of different kinds of organisms,
among the proteins there is a high degree of specificity.
Each protein tends to be characteristic of only one kind
of organism, sometimes of only certain organs or of
particular stages in development. Hence, the differences
among living things seem to be in some way correlated
with differences in the nature of their proteins.
subdivisions of biology. We shall consider plants and
animals together, both in the discussion of fundamental
biological principles and with respect to their natural
associations with each other. They will be treated
separately when this appears desirable for purposes of
emphasizing basic differences and when the problems of
approach are different.
140
.
--page0140--
Plants and animals are, similar in the their
fundamental composition. They are made up of the same group of
elements combined in essentially the same way. Both are
composed of cells as the fundamental structural units,
but their tissue systems, organ systems, and general
construction are very different. Animals are usually
more complicated than- plants, and with this greater
structural complexity are associated with more highly
developed coordination and greater activity. Plants lack the
power of locomotion; animals have various means of
moving about. The nutritional activity of a plant is
circumscribed by its inability to move; that of an animal is fairly
brqad. This difference is associated with the expenditure of
far more energy by animals and with more intricate
mechanisms for the liberation and use of energy. Partly as
a result of such differences, evolution has brought about
greater diversity among animals, the types of animals
being much widely different than the types of plants.
Biology may be divided in either of two ways,
depending upon whether thfe emphasis is placed on type of
organisms or on processes, structures, and functions.
With the first system there are two principal divisions:
botany, which deals with plants, and zoology, which
deals with animals.
Botany may be subdivided as follows:
Bacteriology — study of bacteria.
Mycology — study of fungi. -
Algology (sometimes called phycology)—study of algae.
Bryology — study of mosses.
Pteridology — study of ferns.
All these branches may be grouped together as
mic botany, the study of plants which do not produce seed.
Study oi the seed plants (actually two groups — the
nosperms, which bear cones, and the angiosperms, which
bear flowers) covers a single field, phanerogamic botany.
Zoology is similarly divided as follows:
Protozoology — study of single-celled animals. ,
Entomology — study of insects. ' •
Ichthyology — study of fishes.
Herpetology — study of amphibians and reptiles.
Ornithology — study of birds.
Mammalogy — study of mammals.
141
.
--page0141--
Anthropology — study of man (with reference to physical
rather than cultural characteristics).
This botany-zoology system grew up naturally as
biological science developed, the emphasis during its early years
being placed on structure and relationships.
As it became more arid more of a precise experimental
science and emphasis was given to finer aspects of
structure and function, another system of classification based
upon the parts or prpcesses studied came into use. In this
system there are such subdivisions as the following:
Cytology — study of cells.
Histology — study of tissues.
Anatomy — study of internal structure as revealed by
dissection.
Morphology — study of gross structure, the organism