Complex sentence: Some mainly nocturnal or crepuscular animals have been domesticated as pets and have changed into diurnal animals to coincide with the cycle of human life, such ad pet dogs and cats, which are derived from the wolf and the wild cat, respectively.
Split into simpler sentences: Some mainly nocturnal or crepuscular animals have been domesticated as pets and have changed into diurnal animals to coincide with the cycle of human life. Examples are pet dogs and cats, which are derived from the wolf and the wild cat, respectively.