Transcript Chapter 28
Chapter 28
Simple Invertebrates
28-1: Sponges
Domain: Eukarya
Kingdom: Animalia
Phylum: Porifera
General Characteristics
No symmetry
No tissues / organs
Cells can recognize other cells
Reorganize when separated
Sessile: do not move as adults
Diameter ranges from 1cm to 2m
Body Characteristics
Ostia: Pores on outer wall
Osculum: Large hole for water to exit
Choanocytes: cells with flagella that line
internal cavity
Move water through body cavity
Trap food particles and digest
Also called Collar Cells
Amoebocytes: cells that move around in
sponge body to transport nutrients / wastes
Pore cells = Ostia
Collar cell = choanocyte
Sponge Feeding
Sponge “Skeletons”
Most have Spicules: tiny needles made
of calcium carbonate or silica
Some sponges have spongin: flexible
protein fibers
3 Classes of Sponges
1. Calcareous Sponges
•
Skeletons made of
calcium carbonate
spicules
2. Glass Sponges
•
Spicules made of silica
3. Demosponges
•
Skeletons made of
spicules and spongin
Asexual Reproduction
Can regenerate when cut into pieces
Fragmentation
Budding: smaller individuals grow off
sides of larger individual
Form gemmules: when living conditions
become too poor, amoebocytes encase
in protective shells to survive
Sexual Reproduction
Most sponges are hermaphrodites
Sperm released into water
Sperm cells from another sponge enter
through pores
Larvae develop from fertilized eggs and
swim away
Sponge Defenses
Sponges are soft (easily eaten)
Sponges are sessile (can’t swim away)
Protect selves by producing chemicals
These chemicals have been used by
humans for
Antibiotics
Pain killers / Sedatives
Cancer treatments
28-2: Cnidarians
Two body forms:
Medusa: free-floating umbrella-like
Polyp: tubelike and attached at base
Polyps are sessile…
Attach to floor / object with Basal Disk
Both show radial symmetry
Tentacles surround mouth
Enters into gastrovascular cavity
2 layers of cells
Ectoderm on outside
Endoderm on inside
Mesoglea: layer of “jelly” between the 2
layers
Cells arranged into tissues
Cnidocytes
Cnidocytes: Stinging cells on tentacles
Contain Nematocysts: small, barbed
harpoons
Some nematocysts have deadly toxin, some
with chemicals to just stun
Used for defense and to spear prey
Tentacles pull food into mouth
3 classes
Hydrozoans
Ex: Hydra, Portuguese-Man-of- War
Scyphozoans
Ex: Jellyfish
Anthozoans
Ex: Sea Anemones, Corals
Hydrozoans
Most are Colonial
Life cycle includes both polyp and
medusa forms
Live in freshwater and marine
Freshwater example: Hydra
Marine hydrozoans are among most toxic
(deadly to humans)
Hydra: freshwater
Hydrozoans
Most of life is individual polyp
Stick to surfaces with sticky secretion
from basal disk (bottom)
Can glide on basal disk or tumble
Reproduction in
Hydrozoans
Most capable of sexual reproduction
Some are hermaphrodites
Can reproduce asexually also
budding
Scyphozoans
“True” Jellyfish
Can be small (thimble-sized) to extremely
large (queen-sized mattress)
Go through polyp stage at some point in
life cycle
Anthozoans
Corals and Sea Anemones
Have symbiotic algae living in cells to help
provide energy
Sea Anemones are soft-bodied
Corals secrete calcium carbonate outer
skeletons
Only top layer is alive, rest is old skeletons of dead
corals
Build up into reefs
28-3: Flatworms &
Roundworms
Flatworms
Flatworms
Phylum Platyhelminthes
More complex than sponges and
cnidarians
Have middle tissue layer
Tissues organized into organs
Bilateral symmetry
Cephalization
Since they are flat…
Each cell close enough to outside to get
O2 and release CO2
Gastrovascular cavity branched and
close to all tissues (nutrients to cells
easily)
Still have just 1 opening
3 classes
1. Turbellaria:
Free-living
Most marine
Freshwater: Planaria
Planarian Feeding
Use muscular tube
that extends from
center of GVC
Called Pharynx
Eat small protists or
dead / dying animals
Planaria Reproduction
Attach posterior end to rock, pull apart
into 2
Regenerate
Sexually reproduce by exchanging sperm
with another planarian
Hermaphrodites
2. Cestoda
Parasitic
Commonly called Tapeworms
Hooks and suckers on head to attach
inside host’s intestine
Absorb nutrients from host
Produce proglottids: string of rectangular
body segments that break off in
reproduction
Can grow to be 40 ft. long
3. Trematoda
AKA “Flukes”
Parasites:
Live in host (endoparasites)
Live on host (ectoparasites)
Ex: Schistosoma
Disease: Schistosomiasis
•Enter
through skin
(hookworm)
and burrows
to blood
vessels to lay
eggs
•Block blood
vessels
(internal
bleeding and
liver damage)
Roundworms
Phylum Nematoda
Have pseudocoelom
Simplest animals with one-way digestive
tract (mouth and anus!)
Most microscopic
One square yard of forest soil can have 3
million nematodes
Pseudocoelom
“False” body cavity
Filled with fluid to act as simple
respiratory and circulatory systems
O2, CO2, nutrients flow through body
Can be human parasites…
Ascaris lumbricoides
Infects lungs, gall bladder,
pancreas
Trichinella spiralis
Infects muscles
Elephantitis: blockage of
lymph system by
nematode
•enters through skin in
water