Suggestions for instructional improvement are provided in two topic areas. Explains the use of models in helping students to visualize selected concepts in genetic engineering and recommends the use of tropical tuber crops for encouraging students to conduct practical investigations. (ML)

Presents information that gives a methodological background to the concept of food webs. Stresses the importance of calibrated techniques in ecological research and explains direct methods for studying animal diets. Exercises for gathering first-hand data on bird diets and analyzing secondary data on mammal diets are suggested. (ML)

Clearing is a simple and rapid technique in which 75 percent lactic acid is used to remove pigments and cytoplasmic contents of fresh leaves, enabling microscopic view of various internal leaf layers. Procedures for using the technique (which helps students gain a more thorough understanding of plant anatomy) are given. (DH)

Presents a classroom experiment that demonstrates the directional sensitivity of the human ear. Outlines the activity's procedures and provides a diagrammatical view of the experimental arrangement. Also included is an analysis of the expected results. (ML)

Explains how simple models of easily assembled materials can help teach the workings of human joints. Provides specific suggestions for demonstrating the structure and operation of fixed joints, slightly movable joints, and freely movable joints. (ML)

Thin slices of potato can be used to demonstrate the presence of protein, carbohydrates, and nucleic acids at the cellular level. Procedures and materials are provided for these simple tests. Also indicates that the presence of fat can be readily seen by staining avocado with Sudan red or Sudan black. (Author/DH)

Background information on the biology of aphids is supplied. Using this information in a wide variety of investigations, many involving equipment and techniques available in the school laboratory, can be carried out. An appendix lists possible projects. (Author)

Describes a field exercise which links ecology and taxonomy in the teaching of the species concept. Two common hedgerow plants (red and white campions) are used as a pair of "species" that are normally distinct. Plants of intermediate character can be encountered, and the status of these plants is investigated. (Author/JN)

Briefly describes some of the more recent developments in the use of human hairs for such instructional purposes as observing barr bodies and chromosomes, and for culturing to produce cells of both epithelial and fibroblastic morphology. Three main hair categories are also described. (JN)

Described is a method of rearing common house flies in a biology laboratory. Included are 16 suggested biological investigations utilizing the house-fly. (SL)

Described is an experiment investigating carbon dioxide fixation in the dark and the diurnal rhythm of acid production in plants exhibiting Crassulacean Acid Metabolism. Included are suggestions for four further investigations. (SL)

Described are embryology experiments demonstrating effects of lithium on the nervous system and the use of hypertonic salt solutions to produce exogastrulation in the eggs of Xenopus laevis. (SL)

Described are science experiments which utilize methylene blue to demonstrate the effects of pH, temperature inhibitors, and concentration on enzyme reactions in yeast enzyme systems. (SL)

Describes the experimental procedures used for detecting DNA and RNA synthesis in xenopus cells by autoradiography. The method described is suitable for senior high school laboratory classes or biology projects, if supervised by a teacher qualified to handle radioisotopes. (JR)

Describes an exercise in which senior high school biology students used a computer to simulate genetic mapping. The exercise was designed to enhance the students' grasp of the concepts of linkage and crossing-over. (JR)