Index precipitation–temperature relationship 1:59F protected area systems 5:444T, 6:492T, 6:499T Serengeti ecosystem 2:487–488, 2:488F South America 6:607T tropical Africa 1:49–51 woodlice 3:226 wood mouse 1:367 wood-pasture ecosystems 4:574–577, 4:575F, 4:576F, 4:581F woodpecker finches 1:27–28, 1:28F, 4:33, 4:34F woodpeckers beak shape 1:604F guilds 4:33–35, 4:34F woodpigeons 2:541F wood turtles 7:390 wood wasps 4:177–178 woolly adelgids 4:361 woolly lemurs 6:251T woolly mammoths 5:231–233 woolly monkeys 6:251T wooly spider monkey 4:692 workflow systems 1:445 World Association of Zoos and Aquariums (WAZA) 1:662–663, 4:325–326 world-at-night map 4:561F World Bank 2:231–232, 4:324–325, 7:18–19, 7:207–208 World Climate Research Program 4:326–327 World Conference on Education for All 3:136 World Conservation Monitoring Centre (WCMC) 4:327 World Conservation Union 3:209, 4:664–666 World Database on Protected Areas (WDPAs) 6:489 World Education 2:231–232 world energy use 3:251, 3:251F, 3:252T, 3:253T World Flora online database 6:509 World Health Organization (WHO) 5:670–672 World Heritage Convention 4:325, 6:489 World Heritage Sites program 4:325, 6:489, 6:506, 7:18–19 World Network of Biosphere Reserves (WNBR) 4:325–326 World Resources Institute (WRI) 4:324–325, 4:664–666 World Trade Organization (WTO) 7:18–19 worldwide commerce and travel 2:532 World Wide Web Consortium (W3C) 1:444 World Wide Web (WWW) 1:444 World Wildlife Fund (WWF) 2:231–232, 3:139, 4:271T, 4:325–326 Wormaldia kisoensis 7:345, 7:346F Wormaldia mohri 7:346F worm-lizards 3:216T worms classifications 4:381T mangrove ecosystems 4:337 river ecosystems 6:478T worm–whale nutrient conversion 5:121, 5:121F see also Platyhelminthes woundfin 4:364 Wrangel Island 4:723F wrasse 3:467–471 Wrightea tomentosa 1:70 Wright, Sewall 3:675, 4:245–246, 6:2 Wright’s F-statistical method 4:510 Wular Lake 1:276T Wulff, Evgenii 2:539–540 Wuliang black crested gibbon 6:256–258T Wyeomyia smithii 5:724–725 wyerone 1:590 Wyoming Basins Ecoregion (WBE) study 2:503–505, 2:504–505F Wyoming toad 3:696 Wytham Wood (England) 7:266–268, 7:266F, 7:267T X Xanthoma sagittifolium 4:289T Xanthopan morganii preadicta 5:398 Xanthopan morgani praedicta 2:138 Xanthophyceae 3:571T, 6:478T xanthorhodopsins 6:281F, 6:283 Xanthorhoeă fluctuata 6:159F Xanthorrhoea caespitosa 1:304F Xanthosoma sagittifolium 6:553 Xanthotis macleayana 2:75F xanthotoxin 5:712T Xenarthra characteristics 4:689 evolutionary history 2:583F late Quaternary extinction event (LQEE) 4:727T mammalian evolution 4:685 number of species 4:690T tropical rain forests 6:309T Xenasteiidae 3:489–491T Xenicus longipes 1:621 Xenicus lyalli 1:621 Xenicus lyallii 5:366–367 xenoestrogens (XEs) 3:118–119 Xenophyophora 5:48, 6:292 Xenopus laevis 3:695–696 Xenoturbellida 7:434F Xenungulata 2:583F xeric formations 3:111F, 3:115–116, 6:600–604T xeric shrublands 5:526T, 6:492T, 6:495T, 6:499T xerophytes 2:471 Xeropicta vestalis 5:466–467, 5:469–470 Xerus inauris 2:473–474, 2:474F Xi Jiang Delta 1:276T Xingu River, Brazil 1:159T, 1:161F Xiphias gladius 2:8–13, 2:12F, 3:410 Xiphinema 7:422–424, 7:430 Xiphocaris elongata 3:247 Xiphophorus cladistic analysis 7:348, 7:348F, 7:349–351, 7:350F 849 endemic analysis 7:349–351, 7:350F geographical distribution 7:348F Xiphosura arthropod radiation ecology 2:400 number of species 5:669–670T phylogenetic relationships 1:203F Xiphydrioidea 4:178 X-ray crystallography 5:708 X-rays 7:297F Xyeloidea 4:178 Xylia kerrii 1:70 Xylocarpus 1:277, 5:11T Xylomyidae 3:489–491T Xylophagidae 3:489–491T Xylophagomorpha 3:489–491T xylose 6:113T Y yaks 1:640, 1:644F, 3:191 yams intercropping patterns 2:383 native crops Southeast Asia 2:663 Sub-Saharan Africa 2:663 regional cultivars 3:32F slash-and-burn systems 6:553 Yancheng Biosphere Reserve 3:374 Yancheng Marshes 1:276T yang 6:565 Yangtze River 7:150 Yangtze River dolphin 5:75 Yangtze River finless porpoise 5:81T Yanomono, Peru 1:159T yeast infections 3:634, 3:634T yeasts bread baking 3:638 growth processes 3:626 interspecific competition 2:182–184, 2:183T nonseed gene banks 3:652T wine and beer making 3:638 yellow-bellied marmots 5:722 yellow-billed hornbills 5:603 yellow-billed magpie 5:215 yellow birch 1:610 yellow-breasted capuchin 6:256–258T yellow-cheeked crested gibbon 6:256–258T yellow clover aphid 4:362 yellowfin tuna 6:422T yellow–green algae 3:571–572, 3:571T yellowhead 7:184 yellow-legged frogs 3:695–696 yellow perch 1:10T, 1:12F, 4:517, 6:153F yellow pitcher plants 7:396F yellow rail 7:182 Yellow River 7:150–151 yellow rocket 1:75 Yellow Sea 3:171–173T Yellowstone National Park Act (1872) 2:289–292, 5:442, 6:77–78, 6:486 Yellowstone National Park ecosystem 4:113, 5:449 Yellowstone to Yukon initiative 2:258 yellowtail 1:190T