1. An Introduction to Invertebrates
Chapter 33

2. 1 million species of animals…
95% are invertebrates!

3. 34-36 phyla of the Animal Kingdom

4. Lower Invertebrates

5. Phylum Porifera 5,500 species, mostly marine sponges Parazoans
2 layers unspecialized cells, no tissues
Asymmetrical
Suspension (filter) feeders
Sessile
Hermaphroditic, but cross fertilize
Regenerative abilities
Phylum Porifera

6. : opening
: CaCO3 skeletal fibers

7. Phylum Cnidaria ~10,000 species (jellyfish, sea anemones)
Live in shallow coastal marine waters
Eumetazoa
Organized into tissues
Diploblastic – 2 germ layers
Radially symmetrical
Carnivorous
Have stinging tentacles called cnidocytes
Gastrovascular cavity
Digestive system (only one opening)
Phylum Cnidaria

8. Life Cycle

9. Class Scyphozoa: sea nettle
Class Hydrozoa: hydra
Class Scyphozoa: sea nettle
Class Cubozoa: box jelly
Class Anthozoa: brain coral

10. 3. Phylum Ctenophora All Marine (100 species) Comb Jellies
Resemble Cnidarians
Lack stinging cells; have sticky cells to capture prey
3. Phylum Ctenophora

11. Phylum Platyhelminthes
Bilaterally symmetrical
Triploblastic (all germ layers)
Gastrovascular cavity (both ends)
Sexual and asexual reproduction
Complex tissues: nerves and brain
Acoelomate
Mostly parasitic

12. Class Turberellaria: planaria Class Trematoda: liver fluke
Class Monogenea: Dermophthirius
Class Cestoda: tapeworm

13. Phylum Rotifera Mainly freshwater Pseudocoelomate
Complete digestive system
Use cilia to draw water into mouth
“wheel bearer”
Parthenogenesis: sexual-female dominate
Phylum Rotifera

14. Phylum Braciopoda Bilateral symmetry Coelomates Triploblastic Marine
Lophophores for feeding
Horseshoe-shaped/circular crown of ciliated tentacles surrounding mouth

15. Phylum Nemertea Bilateral symmetry Triploblastic Acoelomate
Mostly marine
Proboscis used to probe environment
Simple circulatory system – no heart, blood movement through body contractions
Complete digestive system

16. Phylum Nematoda 25,000 species Bilateral Symmetrical
Organized into Tissues
Complete digestive tract
Sexual reproduction
Pseudocoelomic
Phylum Nematoda

17. Phylum Annelida Protostome Coelomates Segmented
Complete digestive system
Closed circulatory system
Nervous system
cerebral ganglia and ventral nerve cord
Hermaphrodites
cross fertilized - clitellum

19. Class Oligochaeta: earth worms
Polychaeta:
bristle worms
Class Oligochaeta: earth worms
Class Hirudinea: leeches

20. Higher Invertebrates

21. Phylum Mollusca Some molluscs also have: Protostomes Coelomates
Body plan – 3 parts
Muscular head-foot (soft-bodied) for locomotion
Visceral miss – internal organs
Surrounded by mantle (CaCO3)
Some molluscs also have:
Mantle cavity – contains gills, anus, excretory pores
Radula for scraping food from surfaces
Most dioecious

23. Class Polyplacophora: chitons
Gastropoda:
snails
Class Polyplacophora: chitons
Class Cephalopoda: octopus
Class Bivalvia: clams

24. Phylum Arthropoda
Two out of every three known species of animals are arthropods
Members of the phylum Arthropoda are found in nearly all habitats of the biosphere
Largest phylum (1,000,000 species)
Coelomates
Protostome

25. Segmentation Hard exoskeleton Jointed appendages
allows for specialization of body parts
Head
Thorax
Abdomen
Hard exoskeleton
Cuticle made with chitin
Prevents water loss: move onto land
Organisms must molt (ectdysis)
Jointed appendages
allows for specialization
Walking
Feeding
Copulation

26. centipedes, millipedes
Subphylum Cheliceriformes:
spiders, horseshoe crabs, scorpions, ticks, mites
Subphylum Myriopoda:
centipedes, millipedes

27. Subphylum Hexapoda: insects
Subphylum Crustacea: crabs, lobsters, crayfish, shrimp

28. Phylum Echinodermata Radial symmetry Deuterostomes Coelomates
Sessile or sedentary marine forms
Well developed organs and systems
Have an internal skeleton
Water vascular system
tube feet that function for locomotion, feeding, and gas exchange
Dioecious

30. Class Ophiuroidea: brittle stars
Asteroidea: sea stars
Class Ophiuroidea: brittle stars
Class Echinoidea: sea urchins

31. Class Holothuroidea: sea cucumbers
Crinoidea:
sea lilies
Class Holothuroidea: sea cucumbers
Class Concentriclodea:
sea daisies