Protons, 34–35
Protostomes, 739
Protozoan, 214
Prusiner, Stanley, 592
Pseudocoelom, 738
Pseudopods, 606
Puberty, 988
Public health, 1021
Pulmonary circulation, 950
Punctuated equilibrium, 549
Punnett squares, 315–316
Pupa, 823
Pupil, 912
Pyloric valve, 877
Pyramids of biomass, 78
Pyramids of energy, 77
Pyramids of numbers, 78
Rabies, 589
Radioactive isotopes, 35
Radioactivity, 466
Radiometric dating, 540–541
Ragweed, 694–695
Random mating, 492
Reabsorption, 884
Reactants, 50
Receptors, 217
Red blood cells, 954–955
Red muscle, 933
Red tide, 611
Reflex, 901
Reflex arc, 907
Regional climates, 110
Regulatory proteins, 287
Rejection, organ, 1019
Relative dating, 540
Releasing hormones, 983
Renewable resources, 157
Replication, DNA, 350–353
Reproduction, 19–20. See also Asexual reproduction; Sexual reproduction
Reproductive system, human, 864
Resistance training, 933
Respiration, 249, 251–253, 963, 966–967. See also Cellular respiration
Respiratory system, human, 963–969
Responding variable, 7
Response, 809
Resting potential, 898–899
Retina, 913
Retroviruses, 578
Rh blood group, 394
Rheumatoid arthritis, 1025
Rhizoids, 641
Rhizomes, 644
Ribonucleic acid (RNA). See RNA
Ribose, 362
Rods, 913
Rowland, F. Sherwood, 175
Rubella, 1001
Rumen, 786
Sabin, Albert, 589
Safety studies, 16
Saliva, 876
Salk, Jonas, 589
Sapwood, 678
Sarcomere, 930
Scavengers, 71
Schleiden, Matthias, 191
Schopenhauer, Arthur, 6
Schwann, Theodor, 191
Science, 4–15
Sclerenchyma, 667
Scrotum, 989
Sebaceous glands, 937
Sebum, 937–938
Secondary growth, 676–677
Secondary messengers, 981
Secondary succession, 106–107