A. Zoology: the study of animals.
B. Fascinating Facts.
1. Two million species of animals –
four times as many as plants.
2. 97% of animal species are
invertebrates.
C. Definition: Multicellular heterotrophic eukaryotes that
produce gametes in multicellular structures.
D. Characteristics.
1. Ingest food.
2. No cell walls.
3. Most mobile.
4. Zygote formed directly from
gametes.
E. Anatomical terms (p. 339).
1. Cephalic – concerning the head.
2. Caudal – concerning the tail.
3. Anterior – toward the front.
4. Posterior – toward the rear.
5. Dorsal – upper surface; back.
6. Ventral – lower surface; front.
7. Lateral – side.
8. Medial – middle.
9. Median – midline.
10. Transverse – perpendicular to
the midline
II. The Kingdom "Animalia".
Note: Italics indicates Phylum, Sub-phylum, or Class name.
III. Sponges (Porifera).
A. General Characteristics.
1. Primitive tissues, little
interdependence among cells.
a. H. V.
Wilson's experiment, 1907.
b. Forced a
living sponge through fine silk so individual cells were separated.
c. Cells
start crawling around and forming aggregate masses.
d. In about 3
weeks a functional sponge has re-formed.
2. As small as a grain of rice, as
large as a barrel.
3. Some independent, some colonial.
4. Body shape maintained by either:
a. Spongin -
fibrous protein.
b. Spicules -
calcium carbonate.
5. Brightly colored.
6. Sessile.
7. Filter feeders: protists, algae,
bacteria.
8. What makes them animals rather
than plants.
a. Animal
cells; i.e. no cell walls.
b.
Development; i.e. no alternation of generation.
B. Structure.
1. Three body types.
a. Barrel.
b. Cloister.
c. Branched
2. Tissues:
a. Outer
epithelium – epidermal cells.
b. Inner
epithelium – choanocytes.
c. Mesenchyme
(middle layer).
3. Pores.
a. Incurrent
– pore cells punctuate the body.
b. Excurrent
(osculum).
4. Choanocytes.
a. Flagellum
– creates a current that pulls in food particles.
b. Collar –
traps the food particles.
5. Mesenchyme.
a. Gelatinous
matrix.
b.
Amoebocytes – moveable cells.
c. Structural
materials that maintain body shape.
i. Produced by the amoebocytes.
ii. Spongin - fibrous protein.
iii. Spicules - needles made of calcium carbonate or silicon.
C. Feeding.
1. Choanocyte flagella create a
current that pulls in food particles through the incurrent pores.
2. The incurrent pores can open or
close to regulate the flow of sea water through the sponge.
3. The choanocyte collar traps
protists, algae, and bacteria from the sea water that moves past.
4. Food is then ingested into the
cell by endocytosis and digested inside the cell.
5. Nutrients are passed to the
amoebocytes, and from them to the epidermal cells.
D. Reproduction.
1. Asexual
a. Budding.
b. Gemules
– dormant state.
c.
Regeneration.
2. Sexual
a.
Hermaphroditic.
b. No sex
organs; sperm and egg produced in the mesenchyme.
c. Sperm
dispersed through the sea, engulfed by a choanocyte.
d. Choanocyte
transfers it to an amoebocyte
e. Amoebocyte
transfers sperm to an ovum where fertilization occurs.
f. Zygote
develops into a ciliated larval form which swims to another location.
g. Larva
attaches to a substrate and begins to grow into an adult sponge.
E. Four groups.
1. Calcarea - bristly,
shallow water, 1, 3, or 4 rays.
2. Hexactinellida - marine, 300 feet
under water, 6 rays.
3. Demospongiae - siliceous skeleton,
bath sponges.
4. Sclerospongiae - mostly CaCO
skeleton, thin tissue coating.
IV. Coelenterates (Cnidaria).
A. General Characteristics.
1. Radial symmetry.
2. Two body forms:
a. Polyp -
sessile.
b. Medusa -
free-swimming.
3. True tissues, but no real organs.
4. Most carnivores.
5. Most marine.
B. Structure.
1. Central gut, one opening.
a. Old phylum
name coelenterata = “hollow gut.”
b. Gut called
the “gastrovascular cavity” or the “coelenteron.”
2. Mouth surrounded by tentacles.
3. Tissues.
a. Epidermis
– “outer skin”.
b. Mesoglea
– “middle glue”.
i. Gelatinous layer.
ii. Sometimes contains cells.
c.
Gastrodermis – “stomach skin”.
4. Cnidocyte.
a. Located on
epidermis and tentacles.
b. Cnidocil
– trigger.
c. Nematocyst
– stinging organelle.
5. Epitheliomuscular cells
a. Long
contractile fibers at their base.
b. Enable
primitive movement.
6. Nerve cells.
C. Feeding.
1. Cnidocil is triggered by an animal
brushing past.
2. Nematocyst shoots out its
filament.
a. Barb-like,
for hooking fish.
b. Rope-like,
for lassoing prey.
c. Sticky,
for ensnaring food.
d. Often
coated with poison.
e. Dozens of
these can trap, paralyze, and kill the prey.
3. Tentacles draw the prey through
the mouth into the coelenteron.
4. Partial digestion occurs in the
coelenteron.
5. Nutrients are then absorbed by the
cells of the gastrodermis.
D. Reproduction.
1. Asexual.
a. Polyps
typically produce buds that grow into new polyps.
b.
Regeneration.
2. Sexual.
a. Polyps can
also produce buds that mature into medusas which develop gonads.
b. Medusas
release eggs and sperm into the sea where fertilization occurs.
c. Embryo
develops into a larva propelled by cilia – “planula.”
d. The
planula attaches to a substrate and grows into a polyp.
e. Both polyp
and medusa forms are diploid.
E. Classes.
1. Hydrozoa.
a. Hydra is a
freshwater genus.
b. It has
brief medusa and planula stages.
c. Some
hydrozoa lack the polyp stage entirely.
d. Potuguese
man-of-war has both stages.
2. Scyphozoa (Jellyfish).
a. Greatly
reduced polyp stage.
b. Muscle
fibers around bell allow some species to swim quite rapidly.
c. Body
almost transparent.
d. Tentacles
can reach 40m.
3. Anthozoa (Sea Anemone and Coral).
a. Sessile.
b. No medusa
stage.
c. Spread by
the planula stage.
d. Sea
anemone are large.
e. Coral are
colonial.
f. Coral
secrete limestone shells.
