Lower and Higher Invertebrates with their differences

Lower and Higher Invertebrates with their differences

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.

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.

Lower and Higher Invertebrates with their differences