One of the major specifications to categorize plants into Thallophytes and Bryophytes is the basic cell structure.
Gymnosperms and Angiosperms are classified on the basis of visibility of seeds. Hence, morphological characteristics play a key role in plant classification. In animal classification, cytology is considered primarily as more minute structural variations are taken into account.
The cell layers, cytology, morphology are significant features to be considered in the classification of animals.
The presence and absence of various features decide the classification of higher hierarchies.