What is Biology?--_Biology is the study of living beings, both plant and
animal._ Inasmuch as man is an animal, the study of biology includes the
study of man in his relations to the plants and the animals which surround
him. Most important of all is that branch of biology which treats of the
mechanism we call the human body,--of its parts and their uses, and its
repair. This subject we call _human physiology_.
Why study Biology?--Although biology is a very modern science, it has found
its way into most high schools; and an increasingly large number of girls
and boys are yearly engaged in its study. These questions might well be
asked by any of the students: Why do I take up the study of biology? Of
what practical value is it to me? Besides the discipline it gives me, is
there anything that I can take away which will help me in my future life?
Human Physiology.--The answer to this question is plain. If the study of
biology will give us a better understanding of our own bodies and their
care, then it certainly is of use to us. That phase of biology known as
_physiology_ deals with the uses of the parts of a plant or animal; human
physiology and hygiene deal with the uses and care of the parts of the
human animal. The prevention of sickness is due in a large part to the
study of hygiene. It is estimated that over twenty-five per cent of the
deaths that occur yearly in this country could be averted if _all_ people
lived in a hygienic manner. In its application to the lives of each of us,
as a member of our family, as a member of the school we attend, and as a
future citizen, a knowledge of hygiene is of the greatest importance.
Relations of Plants to Animals.--But there are other reasons why an
educated person should know something about biology. We do not always
realize that if it were not for the green plants, there would be no animals
on the earth. Green plants furnish food to animals. Even the meat-eating
animals feed upon those that feed upon plants. How the plants manufacture
this food and the relation they bear to animals will be discussed in later
chapters. Plants furnish man with the greater part of his food in the form
of grains and cereals, fruits and nuts, edible roots and leaves; they
provide his domesticated animals with food; they give him timber for his
houses and wood and coal for his fires; they provide him with pulp wood,
from which he makes his paper, and oak galls, from which he may make ink.
Much of man's clothing and the thread with which it is sewed together come
from fiber-producing plants. Most medicines, beverages, flavoring extracts,
and spices are plant products, while plants are made use of in hundreds of
ways in the useful arts and trades, producing varnishes, dyestuffs, rubber,
and other products.
Bacteria in their Relation to Man.--In still another way, certain plants
vitally affect mankind. Tiny plants, called _bacteria_, so small that
millions can exist in a single drop of fluid, exist almost everywhere about
us,--in water, soil, food, and the air. They play a tremendous part in
shaping the destiny of man on the earth. They help him in that they act as
scavengers, causing things to decay; thus they remove the dead bodies of
plants and animals from the surface of the earth, and turn this material
back to the ground; they assist the tanner; they help make cheese and
butter; they improve the soil for crop growing; so the farmer cannot do
without them. But they likewise sometimes spoil our meat and fish, and our
vegetables and fruits; they sour our milk, and may make our canned goods
spoil. Worst of all, they cause diseases, among others tuberculosis, a
disease so harmful as to be called the "white plague." Fully one half of
all yearly deaths are caused by these plants. So important are the bacteria
that a sub-division of biology, called _bacteriology_, has been named
after them, and hundreds of scientists are devoting their lives to the
study of bacteria and their control. The greatest of all bacteriologists,
Louis Pasteur, once said, "It is within the power of man to cause all
parasitic diseases (diseases mostly caused by bacteria) to disappear from
the world." His prophecy is gradually being fulfilled, and it may be the
lot of some boys or girls who read this book to do their share in helping
to bring this condition of affairs about.
The Relation of Animals to Man.--Animals also play an important part in the
world in causing and carrying disease. Animals that cause disease are
usually tiny, and live in other animals as _parasites_; that is, they get
their living from their hosts on which they feed. Among the diseases caused
by parasitic animals are malaria, yellow fever, the sleeping sickness, and
the hookworm disease. Animals also _carry_ disease, especially the flies
and mosquitoes; rats and other animals are also well known as spreaders of
disease.
From a money standpoint, animals called insects do much harm. It is
estimated that in this country alone they are annually responsible for
$800,000,000 worth of damage by eating crops, forest trees, stored food,
and other material wealth.
The Uses of Animals to Man.--We all know the uses man has made of the
domesticated animals for food and as beasts of burden. But many other uses
are found for animal products, and materials made from animals. Wool, furs,
leather, hides, feathers, and silk are examples. The arts make use of
ivory, tortoise shell, corals, and mother-of-pearl; from animals come
perfumes and oils, glue, lard, and butter; animals produce honey, wax,
milk, eggs, and various other commodities.
The Conservation of our Natural Resources.--Still another reason why we
should study biology is that we may work understandingly for the
conservation of our natural resources, especially of our forests. The
forest, aside from its beauty and its health-giving properties, holds
water in the earth. It keeps the water from drying out of the earth on hot
days and from running off on rainy days. Thus a more even supply of water
is given to our rivers, and thus freshets are prevented. Countries that
have been deforested, such as China, Italy, and parts of France, are now
subject to floods, and are in many places barren. On the forests depend our
supply of timber, our future water power, and the future commercial
importance of cities which, like New York, are located at the mouths of our
navigable rivers.
Plants and Animals mutually Helpful.--Most plants and animals stand in an
attitude of mutual helpfulness to one another, plants providing food and
shelter for animals; animals giving off waste materials useful to plants in
the making of food. We also learn that plants and animals need the same
conditions in their surroundings in order to live: water, air, food, a
favorable temperature, and usually light. The life processes of both plants
and animals are essentially the same, and the living matter of a tree is as
much alive as is the living matter in a fish, a dog, or a man.
Biology in its Relation to Society.--Again, the study of biology should be
part of the education of every boy and girl, because society itself is
founded upon the principles which biology teaches. Plants and animals are
living things, taking what they can from their surroundings; they enter
into competition with one another, and those which are the best fitted for
life outstrip the others. Animals and plants tend to vary each from its
nearest relative in all details of structure. The strong may thus hand down
to their offspring the characteristics which make them the winners. Health
and strength of body and mind are factors which tell in winning.
Man has made use of this message of nature, and has developed improved
breeds of horses, cattle, and other domestic animals. Plant breeders have
likewise selected the plants or seeds that have varied toward better
plants, and thus have stocked the earth with hardier and more fruitful
domesticated plants. Man's dominion over the living things of the earth is
tremendous. This is due to his understanding the principles which underlie
the science of biology.
Finally the study of biology ought to make us better men and women by
teaching us that unselfishness exists in the natural world as well as among
the highest members of society. Animals, lowly and complex, sacrifice their
comfort and their very lives for their young. In the insect communities the
welfare of the individual is given up for the best interests of the
community. The law of mutual give and take, of sacrifice for the common
good, is seen everywhere. This should teach us, as we come to take our
places in society, to be willing to give up our individual pleasure or
selfish gain for the good of the community in which we live. Thus the
application of biological principles will benefit society.