Basis of classification (brief account)-:
Locomotion
Nutrition and digestion
Respiration
Excretion
Trends in Neural Evolution
Invertebrate larvae
Minor Phyla (Ctenophora,Rhyncocoela,Entoprocta,Rotifera,Bryozoa,Phoronida)
Links:
[1] https://www.zoology.iisuniv.ac.in/courses/subjects/structure-and-function-invertebrates
[2] https://www.zoology.iisuniv.ac.in/academic-year/2018-2019