2. Each animal phylum has a unique body plan.
Vertebrates have an internal segmented backbone.
Invertebrates do not have a backbone.
Invertebrates encompass most animal groups.

3. Three criteria are used to categorize animals
Protostomes Deuterostomes
Body plan symmetry
Bilateral: body divides equally along one plane (mirror images)
Radial: body arranged in a circle around a central axis
Tissue layers
Bilateral have 3 distinct layers
Radial have 2 distinct layers
Developmental patterns
Protostomes: mouth first, anus second
Deuterostomes: anus first, mouth second

4. Protostomes and deuterostomes are the two major radiations on the animal phylogenetic tree.
Based on anatomical and molecular evidence
Porifera
Cnidaria
Platyhelminthes
Annelida
Mollusca
Nematoda
Arthropoda
Echinodermata
Chordata
RADIAL
NO TISSUES
PROTOSTOMES
DEUTEROSTOMES
jellyfish, coral, anemones
sponges
flatworms
Segmented
worms
clams, snails,
octopuses
roundworms
insects, spiders
crustaceans,
sea urchins
sea stars,
vertebrates
lancelets,

5. Porifera AKA: Sponges Most primitive animals 570 myo, >9000 species
Specialized cells, but no true tissue
Closely related to protists
Neither protistomes or deuterostomes

6. Shared characteristics
Sessile
Filter feeders
Specialized cells include:
Spicule: skeletal like cells; spongin, silica, or CaCO3
Pinacocytes: outer layer
Choanocytes: inner layer, each has a flagellum
Amoebocytes: middle layer, absorb and digest

7. Sponge Reproduction Reproduce sexually or asexually Sexual Asexual
Hermaphrodites, producing eggs/sperm at different times
Sperm is released, captured by female of same species
Ciliated larvae form from zygote
Asexual
Budding: small piece breaks off, but can still survive

8. Cnidaria AKA: Stinging nettles
Nematocyst: capsule with a poison barb at one end
> 9000 aquatic species
Mobile
Two body forms
Polyp
Medusa
Gastrovascular cavity

9. Cnidarian Reproduction
Sexually: mostly medusa-
Gametes released in water
Zygote develops into free-swimming larva, called planula
Asexually: mostly polyps-budding

10. The four major cnidarian classes are defined by their dominant body form.
Anthozoans such as sea anemones have a dominant polyp stage.
Hydrozoans such as hydra alternate between forms.
Scyphozoans are jellyfish with a dominant medusa form.
Cubozoans such as sea wasps have a dominant medusa form.