Invertebrates Biosystematics Taxonomy of Invertebrates

1. Invertebrates

2. Classification of the Phylum Annelida
✘The animal group who are triploblastic, coelomate and
bodies are segmented and covered with soft cuticle is
known as annelida.
✘3 Classes of Annelids
✗Class I: Polychaeta
✗Class II: Oligochaeta
✗Class III: Hirudinea

3. Class I: Polychaeta
Characteristics:
✘1. Most of them are marine and variously
colored.
✘2. Each segment bears a lateral fleshy
outgrowth help in swimming. These appendages
are known as parapodia.
✘3Body is with a distinct head, head with eyes,
pulp and tentacles.
✘4. Clitellum is absent.
✘5. Generally unisexual, fertilization external.
✘6. Development through trochophore larva.
Myrianida pachyceraAphrodita aculeata

4. Class II: Oligochaeta
Characteristics:
✘1. Either freshwater or terrestrial forms.
✘2. Head indistinct and without head
appendages.
✘3. Parapodia and bristles absent and setae
remain embedded in the skin.
✘4. Clitellum present.
✘5. Sexes united, gonads few, development
direct
Eisenia andreiPerionyx
excavatus

5. Class III: Hirudinea
Characteristics:
✘1. Mostly aquatic forms but a few may be terrestrial.
✘2. Body dorsoventrally flattened
✘3. Head distinct, without head appendages, may bear eyes.
✘4. Parapodia, absent.
✘5. Two sucker
✗Posterior used for adhesion
✗Anterior one suction.
✘7. Fertilization internal, development direct, and are
hermaphrodite.
Hirudo medicinalisErpobdella obscura

6. Class Habitat Reproduction Development Clitellum
Polychaeta Marine Hermaphrodite
Trochophore
larva
Absent
Oligochaeta
Freshwater or
terrestrial
Hermaphrodite Direct
Present
Hirudinea
Aquatic but
Few terrestrial
Hermaphrodite Direct
Present

7. Arthropod
✘Is an invertebrate animal having an exoskeleton, a
segmented body, and jointed appendages
✘5 Classes of Arthropod
✗Class I: Diplopoda
✗Class II: Chilopoda
✗Class III: Crustacea
✗Class IV: Arachnida
✗Class V: Insecta

8. Class I: Diplopoda
Characteristics:
✘Round body
✘Segented body
✘Two pairs of legs per segment
✘Also known as myriapods
✘"Thousand feet"
✘Example: millipedes
Ommatoiulus sabulosus
Narceus americanus

9. Class II: Chilopoda
Characteristics:
✘Flattened body
✘Segmented body
✘One pair of legs per segmet
✘"Hundred feet“
✘Example: centipedes
Scolopendra polymorpha
Scolopendra morsitans

10. Class III: Crustacea
Characteristics:
✘Hard
✘Flexible exoskeleton
✘Gills
✘Branched antenna
✘Two body sections - abdomen, cephalothorax
✘Mostly aquatic
Planes minutusNephropidae

11. Class IV: Arachnida
Characteristics:
✘Two body sections - abdomen, cephalothorax
✘No antennae
✘Four pairs of legs
✘Chelicerae
✘Pedipalps
✘Spinnerets
Araneus diadematusEuscorpius carpathicus

12. Class V: Insecta
Characteristics:
✘Three body sections (Head, Thorax, Abdomen)
✘One pair of antennae (unbranched)
✘Three pairs of legs
✘Mandible
Schistocerca gregaria
Musca domestica

13. ECHINODERMS
✘The Echinoderms are triploblastic, coelomate
animals.
✘They possess a water vascular system.
✘Their endoskeleton is covered by epithelium
✘5 Classes of Echinoderms
✗Class I: Asteroidea
✗Class II: Ophiuroidea
✗Class III: Echinoidea
✗Class IV: Holothuroidea
✗Class V: Crinoidea

14. Class I: Asteroidea
Characteristics:
✘Body is star-like.
✘Five arms are usually present which are not
sharply marked off from the central disc.

15. Class II: Ophiuroidea
Characteristics:
✘Body is star-like
✘The arms are not joined to each other and the
body and arms are clearly separated.
✘Example Brittle Star

16. Class III: Echinoidea
Characteristics:
✘Body is globular or disk like.
✘They have a specialized mouth part with teeth
to scrape food from rocks.

17. Class IV: Holothuroidea
Characteristics:
✘Body is elongated and cylindrical.
✘Oral end has mouth surrounded by tentacles.

18. Class V: Crinoidea
Characteristics:
✘Body has a central disc which is attached to the
substratum.
✘They are free living or they are attached by an
aboral stalk of ossicles.

19. Hemichordate
✘Is a phylum of marine animals, generally
considered the sister group of the echinoderms.
✘ They appear in the Lower or Middle Cambrian
✘2 Classes of Hemichordate
✗Class I: Enteropneusta
✗Class II: Pterobranchia

20. Class I: Enteropneusta
Characteristics:
✘They live in shallow water.
✘They are worm like animals.
✘They live in burrows on sandy shorelines.
✘Their body is divided into three regions:
✗Proboscis
✗Collar
✗Trunk.
✘Example: Acorn Worm

21. Class II: Pterobranchia
Characteristics
✘They have two or more arms.
✘They are often colonial.
✘They live in an externally secreted encasement.