UNit 9 Lecture 2

asymmetrical

no symmetry

radial symmetry

multiple planes of identical pieces

bilateral symmetry

one plane creating only 2 identical pieces

endoderm

innermost layer of the embryo

mesoderm

middle layer of the embryo

ectoderm

outer most layer of the embryo

coelom

body cavity between the digestive tract and outer body wall

acoelomates

do not have a cavity, it is completely filled with mesoderm tissue

psuedocoelomates

has a cavity that is not surrounded by mesoderm tissue. along the outer body wall is mesoderm tissue.

coelomates

body cavity that is completely surrounded by mesoderm

protostomes

the blastopore forms the mouth

dueterosomes

blastopore forms the anus

porifera

* 4-5 cell types


* asymmetrical
* filter feeders
* intracellular digestion
* lack any germ
* asexual and sexual reproduction with external fertilization
* Ways to increase chances
* most are marine, but a few are fresh water

cnidaria

\
* all are aquatic
* carnivorous, filter feeders, many have symbiotic algae
* radial symmetry
* 2 germ layers, endoderm and ectoderm w/ mesoglea b/w them
* tentacles containing cnidocytes used to capture prey
* digestive sac
* nerve net
* polyp (for sessile species) and Medusa (for free species)
* asexual and sexual reproduction with external fertilization

ctenophora

\
* radial symmetry (some evidence of bilateral symmetry)
* all aquatic most are predatory
* 2 germ layers; ecto- and endo- w mesoglea b/w them
* digestive sac
* have cilia along their body that propels them
* most have **colloblasts**
* nerve net
* asex. and sex. rep. with ext. fert.
* bioluminescent!!

platyhelminthes

\
* aquatic and terrestrial; free living and parasitic
* “Triploblastic” ecto- meso- endo-
* acoelomate
* bilateral symmetry (cephalization)
* digestive sac
* concentration of nervous tissue in the head area, some eyespots can detect light/dark
* asex. and sex. rep. with ext. and int. fert.
* some move through muscular contractions, others “glide” along with cilia

rotifera

\
* aquatic
* bilateral symmetry with cephalization
* psuedocoelomate
* protosomal digestive tube
* ciliated structure known as the corona at the “head”
* simple nerve system with a “Brain”
* sexual reproduction w/ internal fertilization

nematoda

\
* aquatic or terrestrial, many are parasitic
* a lot of human diseases are caused by round worms
* 3 germ layers
* psueocoelomate
* bilateral symmetry with cephalization
* protosomal digestive tube development
* primarily sexual with internal fert.

annelida

\
* aquatic or terrestrial
* 3 germ layers
* coelomate
* bilateral symmetry with cephalization
* protosomal digestive tube development
* closed circulatory system
* primarily sexual reproduction with internal fertilization
* trochophore larva

Mollusca

* aquatic or terrestrial
* 3 germ layers
* Coelomate
* Bilateral symmetry with cephalization
* protosomal digestive tube development
* soft body, some form a shell of of calcium carbonate
* trochophore larvae
* primarily sexual reproduction
* 3 body parts: the foot, the mantle, the visceral mass

3 Major Classes of Mollusca

Cephalopoda, Gastropoda, Bivalvia

Cephalopoda

“Head Foot” Squid and Octopi

* closed circulatory system
* internal fertilization
* most intelligent of “invertebrates”

Gastropoda

“Stomach-Foot” Slugs and Snails

* open circulatory system
* internal fertilization with many being hermaphrodites

Bivalvia

“Two Shells” Clams, Mussels, Oysters

* open circulatory system
* external fertilization

Arthropoda

* 3 germ layers
* coelomate
* bilateral symmetry with cephalization
* protostomal digestive tube
* 3 specific traits: segmented body, exoskeleton (chitin), jointed appendages
* open circulatory system
* sex. rep. with both int. and ext. fert.

3 different classes in Arthropoda

crustacea, chelicerae, insecta

Crustacea

(Crabs, Crayfish, Barnacles)

* 10 legs

Chelicerae

(spiders, scorpions, ticks)

* 8 legs

Insecta

(ants, butterflies, bees)

* 6 legs

Echinodermata

(Sea stars, sea urchins, sea cucumbers, crinoids)

* aquatic
* 3 germ layers
* coelomate
* bilateral symmetry as a larva, as an adult, radial symmetry
* deuterostomal digestive tube development
* endoskeleton
* water vascular system instead of blood
* Tube feet which aid in movement, respiration, and excretion (inflates with water)
* sex. rep. with ext. fert.