Kingdom Animalia

Lower Invertebrates

Characteristics:

• eukaryotic• multicellular• heterotrophic consumers• no cell walls• sexual and asexual reproduction• locomotion• 99% invertebrates

Symmetry of body plan:asymmetry – no symmetryradial – central point; can be divided into equal

sectionsbilateral – can be divided into 2 mirrored halves

•cephalization – concentration of sense organs toward anterior end (associated with development

of a head)

• anterior – region of a bilaterally symmetrical organism toward the head end

• posterior – region of a bilaterally symmetricalorganism toward the tail end

• dorsal – back side of a bilaterally symmetricalorganism

• ventral – under side of a bilaterally symmetrical organism

• lateral – to the side of a bilaterally symmetricalorganism

A. Phylum Porifera• sponges• simplest animals• adults sessile, filter feeders (larvae are free-

swimming)• water vascular system – pumps large amts. of

water through porous body; all aquatic• asymmetrical

A. Phylum Porifera…cont• composed of spicules – framework of the sponge• classified by spicule composition:• reproduce sexually by egg and sperm• asexually by budding

B. Phylum Cnidaria• corals, jellyfish, anemones• radial symmetry• entirely aquatic (marine, few fw)• possess stinging cells (nematocysts) on tentacles• nerve net – simple nervous system

B. Phylum Cnidaria

• classified by life cycle stages:1) medusa – free swimming2) polyp – attached stage

• reproduction:asexually by buddingsexually by egg & sperm

C. Phylum Platyhelminthes• flatworms• incomplete digestive system (one opening)• bilateral symmetry

D. Phylum Nematoda

• roundworms• complete digestive system – 2 openings• bilateral symmetry• tube within a tube body plan• ex: Ascaris, hookworms, filarial worms,

eyeworms, Trichinella – cause trichinosis

E. Phylum Annelida• segmented worms• name means “little ring”• true coelom – fluid-filled body cavity• complete digestive system• all organ systems present• closed circulatory system – blood is confined

to vessels

E. Phylum Annelida• classified by their number of setae – bristles for

locomotion