Part 31

Associated with Darwin's name we must place two other co-workers on heredity and evolution, Alfred Russel Wallace, an Englishman who independently and at about the same time reached many of the conclusions that Darwin came to, and August Weissman, a German. The latter showed that the protoplasm of the germ cells (eggs and sperms) is directly handed down from generation to generation, they being different from the other body cells from the very beginning. In 1883 a German named Boveri discovered that the chromosomes of the egg and the sperm cell were at the time of fertilization just half in number of the other cells (see page 252) so that a _fertilized_ egg was really a _whole cell_ made up of _two half cells_, one from each parent. The chromosomes within the nucleus, we remember, are believed to be the bearers of the hereditary qualities handed down from parent to child. This discovery shows us some of the mechanics of heredity.

Applications to Plant and Animal Breeding.--Turning to the practical applications of the scientific work on the method of heredity, the name of Gregor Mendel, an Austrian monk, stands out most prominently. Mendel lived from 1822 until 1884. His work, of which we already have learned something (see page 258), remained undiscovered until a few years ago. The application of his methods to plant and animal raising are of the utmost importance because the breeder is able to separate the qualities he desires and breed for those qualities only. Another name we have mentioned with reference to plant breeding is Hugo de Vries, the Dutchman who recently showed that in some cases plants arise as new species by sudden and great variations known as _mutations_. And lastly, in our own California, Luther Burbank, by careful hybridizing, is making lasting fame with his new and useful hybrid plants.

REFERENCES

Conn, _Biology_. Silver, Burdett & Co. Darwin, _Life and Letters of Charles Darwin_. Appletons. Galton, _Hereditary Genius_. London (1892). Thompson, _Heredity_. John Murray, London England. Wasmann, _Problem of Evolution_. Kegan Paul, Trench, Truebner and Co., London, E. C.

APPENDIX

A SUGGESTED OUTLINE FOR BIOLOGY BEGINNING IN THE FALL

LIST OF TOPICS

FIRST TERM

First week. WHY STUDY BIOLOGY? Relation to human health, hygiene. Relations existing between plants and animals. Relation of bacteria to man. Uses of plants and animals. Conservation of plants and animals. Relation to life of citizen in the city. Plants and animals in relation to their environment. What is the environment; light, heat, water, soil, food, etc. What plants take out of the environment. What animals take out of the environment. Dependence of plants and animals upon the factors of the environment. _Laboratory_: Study of a plant or an animal in the school or at home to determine what it takes from its environment.

Second week. SOME RELATIONS EXISTING BETWEEN PLANTS (GREEN) AND ANIMALS. Field trip planned to show that insects feed upon plants; make their homes upon plants. That flowers are pollinated by insects. Insects lay eggs upon certain food plants. Green plants make food for animals. Other relations. (Time allotment. One day trip, collecting, etc.; two days' discussion of trip in all its relations.) Make a careful study of the locality you wish to visit, have a plan that the pupils know about beforehand. Review and hygiene of pupil's environment, 2 days.

Third week. STUDY OF A FLOWER, PARTS ESSENTIAL TO POLLINATION NAMED. Adaptations for insect pollination worked out in laboratory. Study of bee or butterfly as an insect carrier of pollen. Names of parts of insect learned. Elementary knowledge of groups of insects seen on field trip. Bees, butterflies, grasshoppers, beetles, possibly flies and bugs. Drawing of a flower, parts labeled. Drawing of an insect, outline only, parts labeled. Careful study of some fall flower fitted for insect pollination with an insect as pollinating agent. Some examples of cross-pollination explained. Practical value of cross-pollination.

Fourth week. LIVING PLANTS AND ANIMALS COMPARED. Parts of plants, functions; organs, tissues, cells. Demonstration cells of onion or elodea. How cells form others. What living matter can do. Reproduction. Growth of pollen tube, fertilization. Development of ovule into seed. Fruits, how formed. Uses, to man.

Fifth week. WHAT MAKES A SEED GROW. Bean seed, a baby plant, and food supply. Food, what is it? Organic nutrients, tests for starch, protein, oil. Show their presence in seeds.

Sixth week. NEED FOR FOODS. Germination of bean due to (_a_) presence of foods, (_b_) outside factors. What is done with the food. Release of energy. Examples of engine, plants, human body. Oxidation in body. Proof by experiment. Test for presence of CO{2}. Oxidation in growing plant, experiment. Respiration a general need for both plants and animals.

Seventh week. NEED FOR DIGESTION. The corn grain. Parts, growth, food supply outside body of plant, how does it get inside. Digestion, need for. Test for grape sugar. Enzymes, their function. Action of diastase on starch.

Eighth week. WHAT PLANTS TAKE FROM THE SOIL, HOW THEY DO THIS. Use of root. Influence of gravity and water. Why? Absorption a function. Root hairs. Demonstration. Pocket gardens, optional home work, but each pupil must work on root hairs from actual specimen. How root absorbs. Osmosis; what substances will osmose. Experiments to demonstrate this.

Ninth week. COMPOSITION OF SOIL. What root hairs take out of soil. Plant needs mineral matter to make living matter. Why? Nitrogen necessary. Sources of nitrogen, the nitrogen-fixing bacteria. Relation of this to man. Rotation of crops.

Tenth week. HOW GREEN PLANTS MAKE FOOD. Passage of liquids up stem. Demonstration. Structure of a green leaf. Cellular structure demonstrated. Microscopic demonstration of cells, stoma, air spaces, chlorophyll bodies. Evaporation of water from green leaf, regulation of transpiration.

Eleventh week. _Midterm Examinations._ Sun a source of energy. Effect of light on green plants. Experimental proof. Starch made in green leaf. Light and air necessary for starch making. Proof. Protein making in leaf. By-products in starch making. Proof. Respiration.

Twelfth week. THE CIRCULATION AND DISTRIBUTION OF FOOD IN GREEN PLANTS. Uses of bark, wood, what part of stem does food pass down. Willow twig experiment. Summary of functions of living matter in plant. Forestry lecture. Economic uses of green plants. Reports.

Thirteenth week. PLANTS WITHOUT CHLOROPHYLL IN THEIR RELATION TO MAN. Saprophytic fungi. Molds. Growth on bread or other substances. Conditions most favorable for growth. Favorite foods. Methods of prevention. Economic importance.

Fourteenth week. YEASTS IN THEIR RELATION TO MAN. Experiments to show fermentation is caused by yeasts. Experiments to show conditions necessary for fermentation. The part played by yeasts in bread making, in wine making, in other industries. Structure of yeast demonstrated. Summary.

Fifteenth week. EXPERIMENTS TO SHOW WHERE BACTERIA MAY BE FOUND AND CONDITIONS NECESSARY TO GROWTH BEGUN. Have cultures collected and placed in a warm room during the holidays. Suggested experiments are exposure to air of quiet room and room with persons moving, dust of floor, knife blade, etc.

Sixteenth, seventeenth, and eighteenth weeks. THE MONTH OF JANUARY SHOULD BE DEVOTED TO THE STUDY OF BACTERIA IN THEIR GENERAL RELATIONS TO MAN. Economically, both directly and indirectly. Especial emphasis placed on the nature and necessity of decay. Bacteria in relation to disease should also be emphasized. The experiments to be performed and the topics expected to be covered follow.

CONDITIONS FAVORABLE AND UNFAVORABLE FOR GROWTH OF BACTERIA. (Use bouillon cultures.) Effect of intense heat, sterile bouillon exposed to air, effect of boiling, effect of cold, effect of antiseptics (corrosive sublimate, carbolic acid, boric acid, formalin, etc.), effect of large amounts of sugar and salt and the relation of this to preserving, etc. Bring out practical application of principles demonstrated. Discuss sterilization in medicine and surgery, cold storage, canning, sterilization, _e.g._ laundries, etc., use of antiseptics, preserving by means of salt and sugar. Microscopic demonstration of bacteria. Methods of reproduction. Importance in causing organic decay, fixation of nitrogen, various useful forms in cheese making, butter ripening, etc. Harmfulness of bacteria as disease producers. Specific diseases discussed: tuberculosis, typhoid, infective colds, blood poisoning, etc. Vaccination. Antitoxins begun--continued after knowledge of human body is gained. Work of Lister and Pasteur.

Nineteenth and twentieth weeks. REVIEW AND EXAMINATIONS.

SECOND TERM

First week. THE BALANCED AQUARIUM. Carbon and nitrogen cycles. Balanced aquarium and hay infusion compared.

Second week. ONE PROTOZOAN, DEMONSTRATION TO SHOW CHANGES IN SHAPE, RESPONSE TO STIMULI, SUMMARY OF VITAL PROCESSES IN CELL. Food getting, digestion, assimilation, oxidation, excretion, growth, reproduction. Internal structure of protozoan. Protozoa as cause of disease.

Third week. GENERAL SURVEY OF ANIMAL KINGDOM. Survey introduced by museum trip if possible. Protozoa, worm, insect, fish, mammal. Distinction between vertebrate and invertebrate. Character of mammalia. Division of labor emphasized. Man's place in nature.

Fourth week. STUDY OF THE FROG. Relation to habitat, adaptations for locomotion, food getting, respiration, comparison of frog and fish on latter point. Osmotic exchange of gases emphasized. Cell respiration.

Fifth week. METAMORPHOSIS OF FROG. Fertilization, cell division, and differentiation emphasized. Touch on plant and animal breeding. Function of chromosomes as bearers of heredity. Comparison of bird's egg and mammal embryo.

Sixth week. FACTORS IN BREEDING. 1. Variation. 2. Selection. 3. Heredity fixes variation. 4. Hybridizing. 5. Control of environment. Eugenics in relation to (_a_) crime, (_b_) disease, (_c_) genius. Continuity of germ plasm. Work of Darwin, Mendel, De Vries, Burbank.

Seventh week. A BRIEF STUDY OF THE GROSS STRUCTURE OF THE HUMAN BODY. Skin, muscles, bones. Removal of lime from bone by HCl to show other substances and need for lime. Effect of posture, spinal curvature, fractures, sprains.

Eighth week. NEED FOR FOOD. Nutritive value of food. Use of charts to show foods rich in carbohydrates, fats, proteins, minerals, water, refuse. The relation of age, sex, work, and environment to the food requirements. What is a cheap food. Price list of common foods at present time. Efforts of government to secure a cheap food supply for the people. Digestibility of foods.

Ninth week. HOW THE FUEL VALUE OF FOOD HAS BEEN DETERMINED. Meaning of calorie. The 100-caloric portion, its use in determining a daily or weekly dietary. Standard dietary as determined by Atwater. Comparison of standards of Chittenden and Voit with those of Atwater.

Tenth week. STUDY OF PUPIL'S DIETARY. Planning ideal meals. Individual dietaries for one day required from each pupil. Discussions and corrections. The family dietary. Relation to cost.

Eleventh week. DIGESTION. The digestive system in the frog and in man compared. Drawings of each. Glands and enzymes. Internal secretions and their importance. Demonstration of glandular tissues. Experiment to show digestion of starch in mouth.

Twelfth week. DIGESTION CONTINUED. Digestion of white of egg by gastric juice. Digestion of starch with pancreatic fluid. Functions of pancreatic juice. Microscopic examination of emulsion. Reasons for digestion. Part played by osmosis. Demonstration of osmosis. Non-osmosis of non-digested foods, comparison between osmosable qualities of starch and grape sugar.

Thirteenth week. ABSORPTION. Where and how foods are absorbed. The structure of a villus explained. Course taken by foods after absorption. Function of liver. Blood making the result of absorption. Composition of blood, red and colorless corpuscles, plasma, blood plates, antibodies. Microscopic drawing of corpuscles of frog's and man's blood.

Fourteenth week. CIRCULATION OF BLOOD. The heart and lungs of frog demonstrated. Heart of man a force pump, explain with use of force pump. Demonstration of beef's heart. Circulation and changes of blood in various parts of body. Work of cells with reference to blood made clear. Capillary circulation (demonstration of circulation in tadpole's tail or web of frog's foot).

Fifteenth week. RESPIRATION AND EXCRETION. Necessity for taking of oxygen to cells and removal of wastes from cells. Part played by blood and lymph. Mechanics of breathing (use of experiments). Changes of air and blood in lungs (experiments). Best methods of ventilation (experiments). Elimination of wastes from blood by lungs, skin, and kidneys. Cell respiration.

Sixteenth week. HYGIENE OF ORGANS OF EXCRETION, especially care of skin. The general structure and functions of the central nervous system. Sensory and motor nerves. Reflexes, instincts, habits. Habit formation, importance of right habits. Rules for habit formation. Habit-forming drugs and other agents. Lecture.

Seventeenth, eighteenth, nineteenth weeks. CIVIC HYGIENE AND SANITATION. Hygiene of special senses, eye and ear. A well citizen an efficient citizen. Public health is purchasable. Improvement of environment a means of obtaining this. Civic hygiene and sanitation. Cleaning up neighborhood, inquiry into home and street conditions. Fighting the fly. Conditions of milk and water supply. Relation of above to disease. Work of Board of Health, etc. Review and Examinations.

SUGGESTED SYLLABUS FOR COURSE BEGINNING FEBRUARY 1 AND ENDING THE FOLLOWING JANUARY

FIRST TERM

First week. WHY STUDY BIOLOGY? Relation to human health, hygiene. Relations existing between plants and animals. Relation of bacteria to man. Uses of plants and animals. Conservation of plants and animals. Relation to life of citizen in this city. Needs of plants and animals: (1) food, (2) water, (3) air, (4) proper temperature. Study of a single plant or animal in relation to its environment. Problems of city government: (_a_) storage, preservation and distribution of foods, (_b_) water supply, (_c_) overcrowded tenements, (_d_) street cleaning, (_e_) clean schools. Biological problems in city government.

Second week. INTERRELATIONS BETWEEN PLANTS AND ANIMALS. Plants furnish food, clothing, shelter, and medicine. Animals use food, shelter. Man's use of plants as above. Man's use of animals as above. Plant and animal industries. Use of balanced aquarium as illustrative material.

Third week. DESTRUCTION OF FOOD AND OTHER THINGS BY MOLD. Home experiment. Conditions favorable to growth of mold. Food, moisture, temperature. Destruction of commodities by mold: food, leather, clothing.

Fourth week, fifth week. DESTRUCTION OF FOODS BY BACTERIA. Experiment. To show where bacteria are found. Soil, dust, water, milk, hands, mouth. Use and harm of decay. Relation to agriculture. Experiment. Conditions favorable and unfavorable to growth of bacteria: boiling, cold, sugar, salt. Bacteria in relation to disease briefly mentioned. Bacteria in industries.

Sixth week. USE OF STORED FOOD BY YOUNG GREEN PLANT: (_a_) for energy, (_b_) for construction of tissue. Experiment. Structure of bean seed. Draw to show outer coat, cotyledon, hypocotyl, and plumule. Test for starch and sugar (grape). Test for oil, protein, water, mineral matter. Use of all nutrients to seedling.

Seventh week. OTHER NEEDS OF YOUNG PLANTS. Home experiments to show (_a_) temperature, (_b_) amount of water most favorable to germination. Experiment. To show need of oxygen. To show that germinating seeds give off carbon dioxide. Proof of presence of carbon dioxide in breath. The needs of a young plant compared with those of a boy or girl.

Eighth week. DIGESTION IN SEEDLING. Structure of corn grain. Experiment. To show that starch is digested in a growing seedling (corn). Experiment. To show that diastase digests starch. Discussion of experiments.

Ninth week. WHAT PLANTS TAKE FROM THE SOIL AND HOW THEY DO THIS. Use of roots. Proof that it holds plant in position, takes in water and mineral matter, and in some cases stores food. Influence of gravity and water. Labeled drawing of root hair. Root hair as a _cell_ emphasized. Osmosis demonstrated.

Tenth week. COMPOSITION OF THE SOIL. Demonstration of presence of mineral and organic substances in the soil. What root hairs take from the soil. Mineral matter necessary and why. Importance and sources of nitrogen. Soil exhaustion and its prevention. Nitrogen-fixing bacteria. Review bacteria of decay. Rotation of crops.

Eleventh week. UPWARD COURSE OF MATERIALS IN THE STEM. Demonstration of pea seedlings with eosin to show above. Demonstration of evaporation of water from a leaf. Action of stomata in control of transpiration. Cellular structure of leaf. Demonstration of elodea to show cell.

Twelfth week. SUN A SOURCE OF ENERGY. Heliotropism. Demonstration. Necessity of sunlight for starch manufacture. Necessity of air for starch manufacture. By-products in starch making. Oil manufacture in leaf. Protein manufacture in plant. Respiration.

Thirteenth week. REPRODUCTION. Necessity for (_a_) perpetuation, (_b_) regeneration. Study of a typical flower to show sepals, petals, stamens, pistil. Functions of each part. Cross and longitudinal sections of ovary shown and drawn. Emphasis on essential organs. Pollination, self and cross. (NOTE. At least one field trip must be planned for the month of May. This trip will take up the following topics: The relations between flowers and insects. The food and shelter relation between plants and animals. Recognition of 5 to 10 common trees. Need of conservation of forests. An extra trip could well be taken to give child a little knowledge and love for spring flowers and awakening nature.)

Fourteenth week. STUDY OF THE BEE OR BUTTERFLY WITH REFERENCE TO ADAPTATIONS FOR INSECT POLLINATION. Study of an irregular flower to show adaptations for insect visitors. Fertilization begun. Growth of pollen tubes.

Fifteenth week. FERTILIZATION COMPLETED. Use of chart to show part played by egg and sperm cell. Ultimate result the formation of embryo and its growth under favorable conditions into young plant. Relation of flower and fruit, pea, or bean used for this purpose. Development of fleshy fruit. Apple used for this purpose.

Sixteenth week. MATURING OF PARTS AND STORING OF FOOD IN SEED AND FRUIT. The devices for scattering the seeds and relation to future plants. Resume of processes of nutrition to show how materials found in fruit and seed are obtained by the plant.

Seventeenth week. PLANT BREEDING. Factors: (_a_) selective planting, (_b_) cross-pollination, (_c_) hybridizing. Heredity and variation begun. Darwin and Burbank mentioned.

Eighteenth and nineteenth weeks. THE NATURAL RESOURCES OF MAN: SOIL, WATER, PLANTS, ANIMALS. The relation of plant life to the above factors of the environment. The relation of insects to plants (forage and other crops) and the relation of birds to insects. Need for conservation of the helpful factors in the environment of plants. Attention called to some native birds as insect and wood destroyers.

Twentieth week. REVIEW AND EXAMINATIONS.

SECOND TERM

First week. THE BALANCED AQUARIUM. Study of conditions producing this. The role of green plants, the role of animals. What causes the balance. How the balance may be upset. The nitrogen cycle. What it means in the world outside the aquarium. Symbiosis as opposed to parasitism. Examples.

Second week. STUDY OF THE PARAMOECIUM. Study of a hay infusion to show how environment reacts upon animals. Relation to environment. Study of cell under microscope to show reactions. Structure of cell. Response to stimuli, function of cilia, gullet, nucleus, contractile vacuoles, food vacuoles, asexual reproduction. Drawings to show how locomotion is performed, general structure. Copy chart for fine structure.

Third week. A BIRD'S-EYE VIEW OF THE ANIMAL KINGDOM. One day. Development of a multicellular organism. (Use models.) One day. Physiological division of labor. Tissues, organs. Functions common to all animals. Illustrative material. Optional trip to museum for use of illustrative material to illustrate the principal characteristics of (_a_) a simple metazoan, sponge, or hydrazoan, (_b_) a segmented worm, (_c_) a crustacean (Decapod), (_d_) an insect, (_e_) a mollusk and echinoderm, (_f_) vertebrates. (Differences between vertebrates and invertebrates.) The characteristics of the vertebrates. Distinguish between fishes, amphibia, reptiles, birds, mammals. Two days for discussion. Man's place in the animal series, elementary discussion of what evolution means.

Fourth week. THE ECONOMIC IMPORTANCE OF ANIMALS. Uses of animals: (1) As food. Directly: fish, shellfish, birds, domesticated mammals. (2) Indirectly as food: protozoa, crustacea. (3) They destroy harmful animals and plants. Snakes--birds; birds--insects; birds--weed seeds; herbivorous animals--weeds. (4) Furnish clothing, etc. Pearl buttons, etc. (5) Animal industries, silkworm culture, etc. (6) Domesticated animals.

Animals do harm: (1) To gardens. (2) To crops. (3) To stored food; examples, rats, insects, etc. (4) To forest and shade trees. (5) To human life. Disease: parasitism and its results,--examples, from worms, etc.; disease carriers fly, etc. Preventive measures. Methods of extermination.

References to Toothaker's _Commercial Raw Materials_. Use one day for laboratory work from references.

Fifth week. THE STUDY OF A WATER-BREATHING VERTEBRATE. Two days. The fish, adaptations in body, fins, for food getting, for breathing. Structure of gills shown. Laboratory demonstration to show how water gets to the gills. Drawings. Outline of fish, gills. Required trip to aquarium. Object, to see fish in environment. One day. Home work at market. Why are some fish more expensive than others. Economic importance of fish. Relation of habits of (_a_) food getting, (_b_) spawning to catching and extermination of fish. Two days. Means of preventing overfishing, stocking, fishing laws, artificial fertilization of eggs, methods. Development of fish egg. Comparison with that of frog and bird.

Sixth week. THE FACTORS UNDERLYING PLANT AND ANIMAL BREEDING. Study of pupils in class to show heredity and variation. Conclusion. Animals tend to vary and to be like their ancestors. Heredity, role of sex cells, chromosomes. Principles of plant breeding. Selective planting, hybridizing, work of Darwin, Mendel, De Vries, and Burbank. Methods and results. Animal breeding, examples given, results. Improvement of man: (1) by control of environment, (_a_) example of clean-up campaign, 1913; (2) by control of individual, personal hygiene, and control of heredity. Eugenics. Examples from Davenport, Goddard, etc.

Seventh week. THE HUMAN MACHINE. Skin, bones and muscles, function of each. Examples and demonstration with skeleton. Organs of body cavity; show manikin. Work done by cells in body.

Eighth week. STUDY OF FOODS to determine: (_a_) nutritive value. Exercise with food charts to determine foods rich in water, starch, sugar, fats, proteins, mineral salts, refuse. One day. (_b_) Nutritive value of foods as related to work, age, sex, environment, cost, and digestibility. Foods compared to determine what is really a cheap food.

Ninth week. HOW THE FUEL VALUE OF FOOD HAS BEEN DETERMINED. The dietaries of Atwater, Chittenden, and Voit. The 100-calorie portion table and its use.

Tenth week. THE APPLICATION OF THE 100-CALORIE PORTION TO THE MAKING OF THE DAILY DIETARIES. Luncheon dietaries. A balanced dietary for pupil for one day. Family dietaries. Relation to cost. Reasons for this.