SPONGES AND CNIDARIANS
Sponges
•Phylum Porifera
•“Pore bearing”
Defining Characteristics
• sessile – remain attached to
single place as adults.
• No mouth or gut, no
muscles, no nervous system.
• No tissues or organ systems.
Collection of specialized
cells.
• Could run through a blender,
cells would re-assemble to
make new sponge.
Body Plan
BODY PLAN
osculum
choanocyte
Epidermal cell
Archaeocyte or
amoebocyte
pore
spicule
Spicules
Feeding: How do sponges get food and digest it?
•
Filter feeders. Flagella (tails) whip around, making currents that draw
water in through pores.
•
Archaeocytes pick up and digest bits of dead animal and plant material
(detritis) from incoming water.
RESPIRATION: HOW DO SPONGES
EXCHANGE OXYGEN AND CARBON
DIOXIDE?
• Oxygen in water diffuses into cells, carbon dioxide in cells
diffuses out into water.
• Diffusion = movement of molecules from area of high
concentration to low
CIRCULATION: HOW DO SPONGES TRANSPORT OXYGEN,
CARBON DIOXIDE, AND NUTRIENTS TO WHEREVER
THEY ARE NEEDED?
– Oxygen and carbon dioxide carried by diffusion and water
currents created by flagella.
– Nutrients carried by archaeocytes.
EXCRETION: HOW DO SPONGES GET
RID OF WASTE PRODUCTS?
 Passes from cells into central cavity, carried out
osculum (opening at top) by water currents.
RESPONSE: WHAT KIND OF NERVOUS
SYSTEM DO SPONGES HAVE?
 No brain, no nervous system, no senses
 Very basic response, all “automatic”
REPRODUCTION
•Asexually by budding. A piece of
sponge breaks off and grows into
new sponge.
REPRODUCTION
•Asexually by budding. A piece of
sponge breaks off and grows into
new sponge.
•Sexually. Sponges makes both
sperm and eggs. Sperm released
into water, where taken in by
another sponge. Sperm fertilizes
egg inside sponge. Larvae grow
and are carried away by water
currents.
ECOLOGY: HOW ARE SPONGES INTERCONNECTED
AND INTERDEPENDENT ON THEIR
ENVIRONMENT?
– Sponges contain photosynthetic bacteria and
algae, which provide food and oxygen for sponge.
Sponge provides shelter.
– Mutualism = relationship where both benefit.
– Sponges provide shelter for snails, shrimp, sea
stars, and other small sea animals.
corals
jellyfish
Sea anemone
CNIDARIANS
hydra
Sea pens
DEFINING CHARACTERISTICS: WHAT
ANIMALS ARE CLASSIFIED AS
CNIDARIANS? WHAT DO THEY
HAVE IN COMMON?
– Jellyfish, sea anemones, coral, hydra, sea
pens
– Soft bodied and carnivorous
– Have tentacles with stinging cells
(nematocysts)
Cnidarian
Body Plan
•Radial symmetry
•Central mouth
surrounded by
tentacles
•Body wall surrounds
gastrovascular cavity
(digestive chamber)
•2-way digestive tract:
Food and waste go
through same
opening.
NEMATOCYSTS: STINGING CELLS
Feeding: How do
cnidarians get food and
digest it?
Use nematocysts to
sting and paralyze prey.
Tentacles pull prey into
mouth. Digested in
gastrovascular cavity.
Respiration: How do cnidarians exchange oxygen and carbon
dioxide?
Diffusion between cells and water outside and in gastrovascular cavity.
No cells more than a few centimeters away from water.
HOW DOES DIFFUSION WORK?
• Oxygen in water diffuses into cells, carbon dioxide in cells
diffuses out into water.
• Diffusion = movement of molecules from area of high
concentration to low
Circulation: How do cnidarians transport oxygen, carbon dioxide, and
nutrients to wherever they are needed?
Diffusion through water in and out of cells.
Excretion: How do cnidarians get rid of waste products?
Diffusion through cell walls into gastrovascular cavity,
then out mouth/anus into surrounding water.
RESPONSE: WHAT KIND OF NERVOUS
SYSTEM DO CNIDARIANS HAVE?
• No brain; only a network
of interconnected nerve
cells (nerve net)
• Also have eyespots and
other sensory cells.
REPRODUCTION: HOW DO CNIDARIANS
REPRODUCE?
Stage 1: Medusa is motile (can move around). Reproduces sexually. Males and
females release sperm and egg into water. Fertilization happens in
water.
Stage 2: Fertilized egg grows into larva, which turns into polyp.
Stage 3: Polyp is sessile (stays in one place like plant). Reproduces asexually by
budding.
ECOLOGY: HOW ARE CNIDARIANS
INTERCONNECTED AND INTERDEPENDENT
ON THEIR ENVIRONMENT? HOW ARE
CORAL REEF ECOSYSTEMS ENDANGERED?
– Most corals contain photosynthetic algae that provide food
for coral. Coral provides shelter for algae.
– Coral reefs endangered by human activity: divers, sediment
from industry and farming, overfishing.
– Global warming may also be causing ocean temperatures to
rise, killing the algae inside corals. This causes bleaching;
they turn pale and die.
CORAL BLEACHING
CORAL REEFS WITH SEVERE BLEACHING
WHY ARE CORAL REEFS IMPORTANT?
• Among oldest and most diverse of Earth’s ecosystems.
“Rainforests of the sea”
• Breeding ground for many fish and other marine life.
• Food, jobs for millions of people. Billions of dollars each year
from tourism.
• Protect shorelines from waves, storms, floods.
VIDEOS
Sponges
http://www.youtube.com/watch?v=laJgUrSsO_k
Sea pens
http://www.youtube.com/watch?v=kthxHa3Hats
Giant jellyfish
http://www.youtube.com/watch?v=u0I-3wkH37w
Questions?