Low-density lipoprotein (LDL), 959–961
“Lucy,” 769, 773
Lupus, 1025
Luteal phase, 993
Lymph, 956
Lymph nodes, 957
Lyon, Mary, 396
Lysogenic infections, 577
Lysosomes, 198
Lytic infections, 576–577
Macleod, Colin, 349
Macroevolution, 546–547
Macrophages, 955
Magnetic Resonance Imaging (MRI), 962
Male cone, 648
Male reproductive system, 988–990. See also Reproductive system, human
Malignant tumors, 289
Malpighian tubules, 797
Mammals, 764
Mammary glands, 825
Manipulated variable, 7
Marcus, Rudolph, 229
Margulis, Lynn, 557
Marine biologist, 105
Marine ecosystems, 120–121
Marsupium, 826
Mass extinction, 548
Mass number, 35
Mast cells, 1014
Matrix, 256
Mayer, Julius Robert, 229
McCarty, Maclyn, 349
MC1R gene, 394
Measurement, scientific, 24
Medications, 1021
Medicine, 430–432
Melanin, 936
Melanocytes, 936
Melanocyte-stimulating hormone (MSH), 983
Melanoma, 938–939
Mello, Craig, 381
Membranes
Memory B cells, 1017–1019
Meningitis, 587
Menopause, 993
Menstrual cycle, 991–993
Menstruation, 993
Mercury, 161
Mesophyll, 680–681
Methamphetamine, 904
Methicillin-resistant Staphylococcus aureus (MRSA), 591
Methionine, 369
Metric system, 24
Microclimates, 96
Microfilaments, 199
Microfossils, 555
Micrographs, 192
MicroRNA (miRNA), 380–381
Microscopes, 190–192
Microscopist, 195
Microspheres, 554
Microtubules, 199
Microvilli, 880
Midbrain, 903
Miller, Stanley, 554
Minerals, 872
Mitochondrial DNA (mtDNA), 434
Mitosis, 282–285. See also Asexual reproduction
Mitotic spindle, 199
Mixture, 42
Modeling, ecological, 68
Model systems, 308
Molars, 785
Molecular clocks, 498–499
Molecular evolution, 498–501
Molecular transport, 212
Molecules, 37
Molina, Mario, 175
Molting, 815
Monera, 523–524
Monkeys, 766–767