Related by context. Frequent words. (Click for all words.) 58 circadian clocks 55 humans 55 endothermic 55 fruitflies 54 Circadian rhythms 53 evolutionary adaptation 53 hibernators 52 single celled organisms 52 primitive organisms 52 metabolisms 52 contagious yawning 52 gastrointestinal tracts 51 sexual dimorphism 51 reproduce asexually 51 respire 51 nonhuman primate 51 cold blooded creatures 51 reproductive hormones 51 mammals 51 thermoregulation 51 organismal 51 Sea otters 51 decomposers 51 crocodilians 50 photoperiod 50 prokaryotes 50 Cyanobacteria 50 coral polyps 50 neurochemicals 50 nematode worms 50 predator prey relationships 50 Dust mites 50 symbiotic bacteria 50 frogs salamanders 50 biochemical processes 50 evolutionary origins 50 Migrating birds 50 phytoplankton blooms 50 planktonic 50 neural crest cells 50 fatty acid metabolism 50 endocrine disruption 50 photosynthetic organisms 49 painful stimuli 49 vertebrate animals 49 diapause 49 exquisitely sensitive 49 metabolise 49 echidnas 49 multicellular organisms 49 mammals reptiles 49 Physiologically 49 pigment melanin 49 hydrologic cycle 49 organisms 49 methylation patterns 49 biologically programmed 48 vocalisations 48 voracious predators 48 genetically programmed 48 gut microbes 48 cone snails 48 digestive tracts 48 nonhuman animals 48 neuronal circuits 48 developmental abnormalities 48 insect populations 48 habituate 48 reef ecosystems 48 sicken humans 48 microscopic bugs 48 Calorie restriction 48 amphipods 48 gut microbiota 48 serotonin neurotransmitter 48 synapse formation 48 eukaryotic cells 48 mutant proteins 48 metacognition 47 thermohaline circulation 47 insect eaters 47 locomotor 47 biological molecules 47 biting midges 47 physiological 47 platypuses 47 neurone 47 emotional reactivity 47 Scientists theorize 47 roundworms 47 Fruit flies 47 Evolutionary biologists 47 mammalian 47 quantum tunneling 47 synchrony 47 temperate forests 47 microgravity environment 47 voracious eaters 47 sensory receptors 47 unicellular 47 daphnia