phylum porifera: sponges - schoolinsites · 2019-10-22 · figure 15.3 sponges, phylum porifera....
TRANSCRIPT
Marine Animals
• Animals could not evolve until atmospheric oxygen was abundant. Photosynthetic autotrophs (mainly cyanobacteria) changed the composition of the atmosphere
• More than 90% of all living and fossil animals, including all of the earliest multicellular animals, are invertebrates—animals without backbones
Key Concepts
• By nearly any criterion, arthropods are the most successful of Earth’s animals
• The Chordates possess a stiffening scaffold—a notochord—on which they are constructed
• Fishes are Earth’s most abundant and successful vertebrates
• Marine mammals include the whales, the largest animals ever to have lived
Key Concepts (cont’d.)
• Oxygen revolution-mostly cyanobacteria—caused a rapid rise in the amount of oxygen
• Animal –multicellular organism unable to synthesize food
Animals Evolved When Food and Oxygen Became Plentiful
• Phylum Porifera – Sponges
Invertebrates Are the Most Successful and Abundant Animals
• Simple• Asymmetric- have no symmetry• Sessile- permanently attached to a solid
surface
Porifera- “pore bearers”
• Built around a system of water canals
• Full of tiny holes called ostia, through which water carrying oxygen and nutrients flow
• Spacious body cavity called spongocoel
• Opening called osculum
Structure
• No tissues, but specialized cells– Collar cells (choanocytes)- move water through
the sponge’s body with flagellum– Pinacocytes- provide an outer covering for the
sponge– Amoebocytes- resemble amoebas and can
move through the sponge’s body to transport food and other materials
– Other specialized cells produce spongin (elastic fibers) that give support to the sponge’s body; spicules are made of calcium carbonate or silica
Structure
Water out
Central cavity
Water inCollar cell
Flagellum
Flattened surface cells
MesogleaPore
Amoeboid cell
Spicules
Stepped Art
NucleusMicrovilli
• Asconoid (ascon)- most simple; small tubular
• Syconoid (sycon)- increases surface area by folding body wall; most complex
• Leuconoid (leucon)- most body wall folding, several osculums; spongoceol is reduced to a number of large canals; these are the biggest sponges; most common
3 Body Forms
Asconoid
Syconoid
Leuconoid
• Suspension feeders- feed on material
suspended in seawater
• Filter feeders- filter food from seawater
Nutrition and Digestion
• Asexual- budding, fragmentation
• Sexual- hermaphrodites
– Sperm cells- modified collar cells
– Egg cells- modified archaeocytes
Reproduction
• Demospongiae- spongin fibers; includes all commercial sponges
Classes
• Calcarea- calcium carbonate spicules
Classes
• Hexactinellida- silaceous spicules-ancient class
Classes