A.Mostanimalssurviveandreproducesuccessfullywithoutcoordinatingtheiractivitiestoexternalenvironmentalrhythms.
B.Thecircadianperiodofananimal’sinternalclockisgeneticallydeterminedandbasicallyunchangeabl
e
C.Environmentalcuessuchasachangeintemperatureareenoughtoresetananimal’sclock.
D.Animalshaveinternalclocksthatinfluencetheiractivitiesevenwhenenvironmentalcuesareabsent.
E.Animalsarelessaffectedbylargedifferencesbetweentheirinternalrhythmsandthelocalsolardaythanarehumans.
F.Becauseananimal’sinternalclockdoesnotoperateona24-hourcycle,environmentalstimuliareneededtokeepthebiologicaldayalignedwiththesolarday.