Related by context. Frequent words. (Click for all words.) 63 megafauna 58 amphibian populations 57 terrestrial ecosystems 56 species extinctions 55 marine invertebrates 54 temperate forests 53 ecosystems 53 paleoclimate 53 biogeography 53 species 53 mammals 52 fossilization 52 microfossils 52 overhunting 52 vertebrate species 52 relict 51 Indohyus 51 freshwater ecosystems 51 toothed whales 51 trilobites 51 extinctions 51 systematics 51 mammal species 51 prehistory 51 diatom 51 planktonic 50 biosphere 50 caribou herds 50 biogeochemical 50 speciation 50 taxa 50 mammal 50 Cambrian explosion 50 marine sediments 50 genetic diversity 50 feathered dinosaurs 50 avian species 50 bee populations 50 hydrothermal vent 50 prokaryotes 50 forest ecosystems 50 diatoms 49 Late Cretaceous 49 plate tectonics 49 methanogens 49 Beringia 49 coprolites 49 mammoths 49 habitat fragmentation 49 ecologies 49 multicellular organisms 49 thylacine 49 marine ecosystems 49 tetrapod 49 biodiversity hotspot 49 genetic variability 49 Pleistocene 49 continental drift 49 Snowball Earth 48 marine reptiles 48 carnivorous dinosaurs 48 H. erectus 48 mass extinctions 48 frog species 48 glacial retreat 48 anthropoids 48 Younger Dryas 48 arthropod 48 foraminifera 48 palaeontology 48 marine organisms 48 hominins 48 platypuses 48 Palaeolithic 47 middens 47 extinct species 47 biome 47 Mesolithic 47 symbionts 47 biota 47 subarctic 47 evolutionary adaptation 47 humans 47 phylogeny 47 atmospheric methane 47 theropod 47 benthic 47 ocean ecosystems 47 ocean acidity 47 amphibian species 47 Ordovician 47 caribou herd 47 chytrid fungus 47 volcanism 47 Cyanobacteria 47 Burgess Shale 47 honey bee colonies 47 tyrannosaur 47 crocodilians 47 vertebrate 46 glaciation