Transcript phylum porifera and cnidaria

PHYLUM PORIFERA AND CNIDARIA
Aquatic Science – Mrs. Walker
PHYLUM PORIFERA (sponges)
I. General
A. extremely simple animals
B. benthic
C. mobile larval stage/sessile adult form
D. some live alone/some live in colonies
E. variety of colors and sizes (1cm to 2m)
F. no nervous system
a. mycocytes: muscle-like cells near outside pores and top of sponge that
close openings to protect sponge from toxic substances in the water.
G. no circulatory system: all cells must be close to water in order to take in
O2 and eliminate CO2
a. folding allows all cells to contact water as the sponge increases in size
II. Body Plan
A. loosely organized groups of cells
B. no true tissues or organs
C. 3 layers:
1. endoderm: inner layer of cells (choanocytes)
a. choanocytes (collar cells) whip flagella to create a current inside the
sponge (make own current) and food is also trapped in their stickiness
and nutrients are passed on to the mesenchyme
2. mesenchyme: middle noncellular layer of jelly-like material
a. amoebocytes: cells in mesenchyme that ingest and digest food
b. spongin: proteinaceous elastic-like mesh for support in soft sponges
c. CaCO3 and silicon spicules: give hard sponges their rigid structure
3. ectoderm: outer layer of cells
a. contains small pores (ostia) which are surrounded by pore cells
(porocytes)
D. atria (body cavities): have 1 – many to keep all cells in contact with water
E. osculum: where water and waste exit at top of sponge
F. water path: porocytes -> atria -> osculum
III. Feeding
A. filter feeders
B. feed on bacteria, protists, organic debris
C. digestion happens in individual cell food vacuoles
D. can filter 100 liters of seawater in an hour
IV. Respiration
A. Water coming in contains dissolved O2 which diffuses into the sponge’s cells
B. Carbon dioxide diffuses out fo the cells and is expelled through the osculum
with the water
V. Reproduction
A. asexual (increases numbers)
a. budding: bits of sponge pinch off and grow into new sponges
b. regeneration: any piece broken off of a sponge can regenerate into a new
sponge
c. gemmules: protective cell packets designed to withstand conditions that
kill the “parent” sponge. Gemmules grow into a new sponge.
B. sexual (increases variety)
1. most are hermaphroditic (both sperm and eggs but can’t self-fertilize)
2. sperm emitted into currents and taken in by another sponge to fertilize eggs
3. fertilized eggs develop into larvae, leave sponge, settle and grow_
PHYLUM CNIDERIA (stinging organisms)
I. General
A. organisms such as hydroids, jellyfish, corals, and anemones
B. more than 9,000 species
C. have cnidocytes (stinging cells)
D. larvae are meroplankton
II. Cnidocytes
A. cells specialized for capturing prey and defense
B. located on tentacles
C. nematocyst: coiled, thread-like structure with a barb housed in a capsule in each
cnidocyte
D. chemical or tactile stimuli causes firing
E. used only once and new nematocyst is produced by cnidocyte
III. Body Plan
A. radial symmetry
B. composed of tissues but lack organs
C. 3 body layers
1. outer epidermis: outer membrane
2. inner gastrodermis: inner membrane
3. noncellular mesoglea: jelly-like mass between the other two layers
D. shape and thinness of the membranes and the low density of the mesoglea
between them allow the jellyfish to float with ease
E. move by using muscles to contract their medusa in a rhythmic fashion causing
them to pulsate gently through the water (weak so often washed up)
IV. Respiration
1. O2 and CO2 diffuse directly into and out of all cells
V. Feeding
1. tentacles and medusa cilia bring food to mouth under medusa
2. digestion is extracelluar (coelenteron: digestive sac) and intracellular (food
vacuoles)
3. waste: expelled through mouth
VI. Nervous system
1. nerve net: network of nerve cells and receptors
VII. Life Cycle
1. alternation of generations
a. sexual phase:
- sperm out of male mouth into female mouth into digestive sac
to ovaries to eggs. Eggs are laid and grow into larvae and then into
polyp - OR- sperm and eggs expelled into water for external fertilization
2. two body forms (generations)
A. polyp
1. benthic
2. sessile
3. mouth and tentacles point up
b. asexual phase:
- immature jellyfish are “budded” from the polyp
B. medusa Ex. jellyfish
1. weak free swimmer
2. mouth and tentacles hang down from bell
VIII. Classes: based on differences in life cycle and body structure
1. Hydrozoa: alternation of generations and colony of polyps is dominant stage
Ex. Portuguese Man-of War, fire coral
2. Scyphozoa: alternation of generations and medusa is dominant
Ex. true jelly fish
3. Anthozoa: only polyp stage
Ex. Sea anemones and corals
4. Ctenophora: “catch-all” phylum
Ex. Jelly-fish like organisms with gelatinous medusae (including comb jellies)
- most do not have nematocysts