This document summarizes information about 9 different phyla: Porifera, Cnidaria, Nematoda, Arthropoda, Platyhelminthes, Annelida, Mollusca, Echinodermata, and Chordata. It addresses which phyla lack organs and symmetry, which show cephalization, which have fewer than three germ layers, the phylum with the most species examples, differences in fish skeletal structures, and the three types of mammals based on young development - monotremes, marsupials, and placental. The Arthropoda phylum contains the most species, including examples like crabs, shrimp, spiders, butterflies and beetles. Fish skeletal structures

1. Unit 5 IP: Part 2
Victoria Rock
September 25, 2011
Part 2: Answer the following questions as they relate to the nine phyla in
the assignment table. (Porifera, Cnidaria, Nematoda, Athropoda,
Platyhelminthes, Annelida, Mollusca, Echinodermata, and Chordata.)
1. a.) Which phyla lack organs?
Porifera and Cnidaria
b.) What type of symmetry do they have?
Porifera has no symmetry
Cnidaria has radial symmetry
2. List all of the phyla that show cephalization.
Mollusca
Annelida
Chordata
Chordata
Playhelminther
Nematod
3. Do all organisms on the table have 3 germ layers (endoderm,
ectoderm, and mesoderm)? If not, which phyla have fewer than three
germ layers?
No; Porifera has no germ layers and Cnidaria has two germ
layers.
4. One phylum on the table has more species than all the others. State
the name of this phylum, and provide several different examples of
species found in this phylum.

2. Phylum Arthropoda has the most species which include the
crustaceans, arachnids, and insects. Examples include: crabs,
shrimps, spiders, butterflies, beetles, and grasshoppers.
5. Fish do not all have the same skeletal structure. Describe the
differences among fish from the most primitive to more advanced
types of fish.
Fish are divided into three classes; Agnatha, Chondrichthyes, and
Osteichthyes.
Agnatha, referred to as “jawless-fish”, is the most primitive, not
only do they lack a jaw, they also have no bone skeleton.
Examples of this primitive fish is; the hagfish and lamprey.
(Buchheim)
Chondrichthyes, referred to as “cartilage-fish”, have a
cartilaginous skeleton. Their jaw is also cartilaginous with a
loosely attached lower jaw and an array of teeth which they use
to attack their prey or defend themselves. Examples of this fish
are the shark, rays, and rat-fish. (Buchheim)
Osteichthyes, or “boney-fish”, have calcified skeletons. They
have great maneuverability and speed, as well as highly
specialized mouths equipped with protrusible jaws. This group is
the largest of all three groups with 20,000 species ranging from
trout, bass, salmon, and perch, just to name a few. (Buchheim)
6. Describe the three types of mammals based on how their young
develop.
The three types of mammals are the Monotremes, Marsupials,
and the Placental.
Monotremes, the most primitive, contains only three species’ the
duck-billed platypus and tow species of echidna. Although these
mammals have hair and produce milk, they lay their eggs, which
are similar to a reptile’s egg. After hatching, the baby clings to

3. the mothers belly fur and sucks the milk, which comes from
pores in the skin instead of nipples. (Animal Bytes: Mammals)
Marsupials young grow inside the mother’s body. When born,
they climb up the mother’s fur into a pouch on her belly. They
continually nourish themselves by latching onto a nipple until
they are old enough to come out of the pouch. (Animal Bytes:
Mammals)
Placental young develop inside the mother’s body, in the uterus
which is attached to a placenta giving the growing baby
nourishments to develop. Examples of this mammal are; cats,
dogs, monkeys, and yes humans. (Animal Bytes: Mammals)

4. Reference
Audersirk, T. (2011). Chapter 23: Animal Diversity I: Invertebrates . In T.
Audersirk, Biology:Life on Earth with Physiology (9th Ed.) (pp. 420-445). San
Franciso:Benjamin Cummings.
Animal Bytes: Mammals. (n.d.). Retrieved September 24, 2011, from San
Diego Zoo: www.sandiegozoo.org/animalbytes/a-mammal.html
Buchheim, J. (n.d.). A Quick Course in Ichthyology. Retrieved September 24,
2011, from Odyssey Expeditions: Tropical Marine Biology Voyages:
www.marinebiology.org/fish.htm