Sedimentary rock, 539–540
Seed, 646
Seed coat, 647
Seed cone, 648
Seedless plants, 639–645
Segmentation, 739
Selection. See Natural selection
Selectively permeable membranes, 205
Self-pollination, 309
Semen, 990
Semicircular canals, 911
Seminal fluid, 990
Seminal vesicles, 990
Seminiferous tubules, 989
Sensation, 935
Sense organs, human, 909–913
Sensory systems, animal, 812–813
Sepals, 696
Septum, 949
Severe acute respiratory syndrome (SARS), 590, 1013, 1022–1023
Sewage, 162
Seward, William H., 1023
Sex chromosomes, 393
Sex hormones, 988
Sex-linked gene, 395
Sexual development, 988
Sexual reproduction, 19, 277–278. See also Plant reproduction
Short-day plants, 713
Shrubland, 112–113
Silencing complex, 380–381
Simard, Suzanne, 625
Single-loop circulatory systems, 792
Single nucleotide polymorphisms (SNPs), 407
Sinuses, 791
Sister chromatid, 282
Skeletal muscle, 928–929
Skeleton, 754
Skepticism, 10
Skinner, B. F., 843
Skinner box, 843
Sliding-filament model, 930–931
Slow-twitch muscle, 933
Smell, 910
Smog, 163
Smoking, 968–969
Smooth muscle, 928–929
Sneezing, 1012
Sodium bicarbonate, 878
Sodium-potassium pump, 899–900
Soil, 671
Soil ecosystems
Solar energy. See also Sunlight
Solute, 42
Solution, 42–43
Solvent, 42
Somatic nervous system, 907
Sound intensity, 910
Southern, Edward, 422
Southern blotting, 422
Species survival plans (SSPs), 170
Spectrum, visible, 230
Sphygmomanometer, 953
Spirilla, 582
Spleen, 957
Spongy bone, 924
Spongy mesophyll, 681
Spores, 607
Squamous cell carcinoma, 939
Stabilizing selection, 489
Staining, cell, 191
Stamens, 697
Stanley, Wendell, 574
Start codon, 367
Statins, 961
Stem cells, 295–297
Stigma, 697
Stomata, 681–683
Stop codon, 367
Strep throat, 587
Stroke, 958
Stroma, 231
Sturtevant, Alfred, 329
Style, 697
Subatomic particles, 34
Substrates, 52–53
Succession, ecological, 106–109
Sucrose, 46