Chapter 33 Notes

Invertebrates

Concept 33.1

Phylum porifera:- asymmetric- ex. sponges- sessile adults, larva may swim- have no nerves or muscles; individual cells can sense and react to environmental changes

Concept 33.1

- filter-feeders; choanocytes, or collar cells, ingest food filtered through the sponge- most are hermaphrodites

Concept 33.1

Concept 33.1

Concept 33.2

Phylum Cnidaria:- radial symmetry- ex. jellyfish, hydra, sea anemones, coral- have stinging cells called nematocysts or cnidocysts; eject a barbed thread- contain a gastrovascular cavity; single opening

Concept 33.2

Concept 33.2

- sessile forms are called polyp; free-floating are called medusa- diploblastic (epidermis and gastrodermis); between layers is the mesogloea

Concept 33.2

Concept 33.2

Concept 33.2

Concept 33.2

There are 3 classes of Cnidarians:Hydrozoa:

- ex. hydra, Portuguese man-of-war- most marine- both polyp and medusa stages; polyp is often colonial

Concept 33.2

Scyphozoa:- ex. jellies- all marine- polyp stage is reduced- free-swimming

Concept 33.2

Concept 33.2

Anthozoa:- ex. sea anemones, coral- all marine- medusa stage absent- sessile

Concept 33.2

Concept 33.2

Phylum Ctenophora:- means “comb-bearer” for the eight rows of fused cilia- ex. comb jellies- tentacles contain colloblasts to capture prey

Concept 33.3

Phylum Platyhelminthes:- ex. Flatworms, flukes, tapeworms- bilateral symmetry- unsegmented- triploblastic; acoelomates (no body cavity)

Concept 33.3

Class Turbellaria:- flatworms- free-living- rely on diffusion for movement of food, oxygen, and waste- asexual and sexual reproduction; can regenerate lost parts

Concept 33.3

Concept 33.3

Concept 33.3

Class Trematoda:- ex. blood flukes, liver flukes- all parasitic: feed on veins/organs of host- hermaphroditic

Concept 33.3

Class Cestoidea:- ex. tapeworms- all are parasites- attach to intestinal wall with scolex and absorb food from host

Concept 33.3

Concept 33.3

Phylum Rotifera:- psuedocoelomates- freshwater- complete digestive tract- fluid in psuedocoelom acts as a hydrostatic skeleton

Concept 33.3

Concept 33.3

Phylum Nematoda:- ex. roundworms- complete digestive system and closed circulatory system: blood is contained in vessels- decomposers and parasites

Concept 33.4

Phylum Mollusca:- ex. snails, slugs, clams, squids, octopuses- body consists of three parts: foot, visceral mass, mantle- open circulatory system- gas exchange is via gills, lungs, or the body surface (diffusion)

Concept 33.4

Concept 33.4

Class Polyplacophora:- ex. chitons- use foot to cling to rocks- simple nervous system and sense organs

Concept 33.4

Concept 33.4

Class Gastropoda:- “stomach-foot”- ex. snails and slugs- torsion: uneven growth in the visceral mass; rotates 180 degrees- exchange gases via gills; use mantle cavity

Concept 33.4

Concept 33.4

Class Bivalvia:- “hatchet-foot”- ex. clams, oysters, mussels- foot used for motility or anchorage- suspension feeders- no distinct head

Concept 33.4

Concept 33.4

Class Cephalopoda:- “head-foot”- ex. squid and octopus- carnivores; beak-like jaw to crush prey- have chromatophores to allow them to change colors- shell is reduced or absent

Concept 33.4

Concept 33.5

Phylum Annelida:- ex. earthworms, leeches- all are segmented- setae project from cuticle- closed circulatory system; aortic arches

Concept 33.5

- developed nervous system with two ventral, solid nerve cords and cerebral ganglia- complete digestive system: mouth-crop-gizzard-intestine-anus- sexual and asexual reproduction- tactile organs, chemoreceptors, balance receptors, and photoreceptors

Concept 33.5

Concept 33.5

Concept 33.5

Class Oligochaeta:- ex. earthworm- all have setae- help aerate soil and cycle nutrients

Concept 33.5

Class Hirudinea:- ex. leeches- mostly freshwater- either carnivorous or parasitic

Protosomia

Class Polychaeta:- primarily marine- parapodia with bristles; can be used for locomotion and gas exchange- largest class

Protosomia