Transcript Invertebrates

The Invertebrates
• Animals are multicelled
heterotrophs that move about for
at least part of their life cycle
• Animals develop in a series of
stages
– Ectoderm, endoderm, and
often mesoderm form in the
early embryo
– Cells interact in functional
units (epithelium and
connective tissues)
Comparing Key Groups
• Evolutionary trends
toward
– Greater size
– Compartmentalization
(division of labor
among cells, tissues,
and organs)
– Integration of
specialized activities
that keep the organism
alive
• Most animals are bilateral
– Mouth
– anus
Body Organization
• Cephalization
– Sensory cells concentrated at the head
• Segmentation
– Repetition of body units, front-to-back
Body Cavities
• Most bilateral animals
have a coelom and a
complete gut
Sponges (Phylum Porifera)
• Sponges
– No symmetry, tissues, or organs
– Flattened cells line the body wall (many
pores; spikes of silica and/or proteins)
– Skeleton of silicon, calcium, or spongin
(protein fibers)
– Filter feeders (flagellated collar cells
absorb food; amoeboid cells digest and
distribute it)
– Hermaphrodites
– Zygote develops into free-living larva
Cnidarians (Phylum Cnidaria)
• Jellyfishes, corals, and sea anemones
– Radial, tentacled carnivores (bag
like with only one opening
– Gastrovascular cavity (respiration
and digestion)
– True epithelial tissues with a
jellylike matrix in between
(mesoglea)
– Simple nervous system (nerve net)
– Hydrostatic skeleton
– Some are commercial, some
symbiotic with algae
Eaten by molluscs
and flatworms for
nematodes. Base of
food web.
Unique Cnidarian Weapons
• Nematocysts
– Used to capture prey
and for defense
Flatworms (Phylum Platyhelminthes)
• Free-living turbellarians
(planarians), parasitic
tapeworms and flukes
– Simplest animals with
organ systems
– Bilateral protostomes
– Paired nerve cords,
ganglia
– Hermaphrodites
Annelids
• Segmented worms (earthworms,
polychaetes) and leeches
– Closed circulatory system
– Digestive and excretory systems,
solute-regulating nephridia
– Nervous system, ganglia in each
segment
– Muscles and fluid in chambers act
as a hydrostatic skeleton
– Hermaphrodites
Mollusks (Phylum Mollusca)
• Soft body with mantle.
• Including gastropods (snails), bivalves (scallops),
chitons, nudibranchs, cephalopods
– 100,000 named species
Cephalopods
• Another class of molluscs.
• The fastest (squids), largest
(giant squids), and smartest
(octopuses) invertebrates
• Have a mantle
– Sheetlike part of the
body mass, draped back
on itself
Echinoderms
• Sea stars, sea urchins, sea
cucumbers, etc.
– Invertebrates of the
deuterostome lineage
– Exoskeleton with spines,
spicules, or plates of calcium
carbonate
– Water-vascular system with
tube feet
– Adults are radial, but bilateral
traits appear in larval stages
and other features