Lower and Higher Invertebrates with their differences

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The invertebrates are usually classified as Lower Invertebrates and Higher Invertebrates.

Lower Invertebrates

  • The lower invertebrates are simple in body organization.
  • They are generally small in size.
  • These are thought to have originated in the main lines of evolution, near the base of the phylogenetic tree of Animal kingdom.
  • Lower Invertebrates includes Protozoa, Porifera, Coelenterata (Cnidaria), Platyhelminthes and Nematoda.

Higher Invertebrates

  • They possess a complex body organization.
  • They are generally larger in size.
  • These occupy a higher position in the phylogenetic tree of Animal kingdom.
  • Higher Invertebrates include Mollusca, Annelida, Arthropoda, and Echinodermata.

Lower and Higher Invertebrates

On the basis of some important features, there are some differences between lower and higher invertebrates as shown below:

Table 1: Differences between Lower Invertebrates and Higher Invertebrates

S.N.

Characteristics

Lower Invertebrates

Higher Invertebrates
1. Size Smaller in size Larger in size
2. Body organization Body organization simple Body organization complex
3. Symmetry Radial, biradial or no symmetry Bilateral symmetry
4. Germ Layers Germ layers wanting or 2 or 3 germ layers Three germ layers present
5. Coelom No Coelom or a pseudo-coelom True Coelom
6. Mouth and Anus Generally, no separate mouth and anus Mouth and Anus are separate
7. Muscular Gut Absent Present
8. Blood Vascular System Not well developed Well developed

 References

  1. Kotpal RL. 2017. Modern Text Book of Zoology- Invertebrates. 11th Edition. Rastogi Publications.
  2. Jordan EL and Verma PS. 2018. Invertebrate Zoology. 14th Edition. S Chand Publishing.

About Author

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Sagar Aryal, PhD

Dr. Sagar Aryal is a microbiologist, researcher, and science communicator from Nepal. He is also co-founder and Research Head of the Department of Natural Products at the Kathmandu Research Institute for Biological Sciences (KRIBS), where he leads research on natural product discovery and microbial biodiversity. Dr. Aryal earned his Ph.D. in Microbiology from Tribhuvan University, Kathmandu, Nepal, in 2025, supported by a DAAD Research Grant and a University Grants Commission (UGC) Nepal Ph.D. Fellowship. His research interests include Actinomycetes, Myxobacteria, microbial taxonomy, and natural products, particularly the discovery of bioactive compounds with potential pharmaceutical applications. He isolated and identified Nocardia nepalensis, a novel bacterial species from Nepal, contributing to understanding microbial diversity in the region. Dr. Aryal has published more than 16 research articles in international journals and contributed three book chapters to established academic publications. He has presented scientific research findings and developed international research collaborations through visits to more than 18 countries across Asia, Europe, North America, and Oceania. From 2023 to 2025, he served as the American Society for Microbiology (ASM) Young Ambassador to Nepal. Since December 2025, he has served as an Editorial Board Member of Scientific Reports, a Nature Portfolio journal. In recognition of his scientific contributions, Dr. Aryal received the NAST Science and Technology Youth Award 2025 from the Nepal Academy of Science and Technology. He previously received the Frs. Locke and Stiller Research Award (LSRA) for the 2017-2018 cycle from St. Xavier's College, Kathmandu, and a Nepal Academy of Science and Technology (NAST) Research Grant for 2017-2018. Alongside his scientific career, Dr. Aryal has more than 15 years of experience in blogging, content writing, and search engine optimization (SEO).