A little bit about invertebrates

What is an invertebrate?

          Simply put an invertebrate is an animal that lacks a backbone. This is a very broad statement and includes around 95 percent of the entire animal kingdom and is made up of around 30 phyla (Phyla is the plural of the word phylum which describes a large group of organisms that are related to eachother. It is the next division after kingdom and before class.). 

What are the phyla?

          Here is a list of the phylums for invertebrates and the estimated number of describe species:

Porifera - 5500

Placozoa - 1

Monoblastozoa - 1

Rhombozoa - 70

Orthonectida - 20

Cnidaria - 10,000

Ctenophora - 100

Platyheminthes - 20,000

Nemertea - 900

Rotifera - 1,800

Gastrotricha - 450

Kinorhyncha - 150

Nemata/ Nematoda - 25,000

Nematophora - 320

Acanthcephala - 1,100

Entoprocta - 150

Gnathostomulida - 80

Priapula - 16

Loricifera - 10

Cycliophora - 1

Sipuncula - 320

Echiura - 135

Annelida - 16,500

Onychophora - 110

Tardigrada - 800

Arthropoda - 1,093,514 (This comes from a book published in 2003 so this has likely jumped to closer to 2,000,000)

Mollusca - 93,195

Phoronida - 20

Ectoprocta - 4,500

Brachiopoda - 335

Echinodermata - 7,00

Chaetognatha - 100

Hemichordata - 85

What does this tell us?

          From this list alone we can see that the largest invertebrate phyla is Arthropoda with close to 2,000,000 identified species. If we compare this to the phylum Chordata, (Everything that isn't an invertebrate) which has has approximately 50,00 describe individuals, we can see that just one one invertebrate phylum comprises most of the planets animals.

          The phylum Arthropoda has 13 classes in it which include spiders, scorpions, millipedes, centipedes, crustaceans and insects. So Arthropoda is what people colloquially refer to as bugs, micro beasts and insects.

I hope this has been a useful little look into the invertebrate world, and hope to see you next time.

Heyze.