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

Presenter

Presentation Notes

Figure 15.3 Sponges, Phylum Porifera.

• 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