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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 symmetry radial – central point; can be divided into equal
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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 symmetry radial – central point; can be divided into equal sections bilateral – 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 symmetrical organism toward the tail end • dorsal – back side of a bilaterally symmetrical organism • ventral – under side of a bilaterally symmetrical organism • lateral – to the side of a bilaterally symmetrical organism
A. Phylum Porifera • sponges • simplest animals • invertebrates • adults sessile, filter feeders (larvae are free-swimming) • water vascular system – pumps large amts. of water through porous body; all aquatic • asymmetrical • 2 cell types: amoebocytes choanocytes – (collared cells)
A. Phylum Porifera • osculum – opening at top of sponge; water exits • atrium – open chamber • composed of spicules – framework of the sponge • classified by spicule composition: 1) Class Calcarea – calcium carbonate spicules 2) Class Hexactinella – siliceous spicules 3) Class Demospongia – spongin • 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 • 3 classes: 1) Class Hydrozoa – ex: Hydra 2) Class Scyphozoa – ex: most jellyfish 3) Class Anthozoa – ex: corals, anemones
B. Phylum Cnidaria • classified by life cycle stages: 1) medusa – free swimming 2) polyp – attached stage • reproduction: asexually by budding sexually by egg & sperm
C. Phylum Platyhelminthes • flatworms • incomplete digestive system (one opening) • bilateral symmetry • flame cells for excretion (nephridia) 1) Class Turbellaria – free-living ex: planarian 2) Class Trematoda – parasitic ex: liver fluke 3) Class Cestoda – parasitic ex: tapeworm
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” • fw, sw, terrestrial • 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 • 3 classes: 1) Class Hirudinea – no setae ex: leeches *parasitic, fw or sw 2) Class Polychaeta – many setae ex: bristleworm *most marine 3) Class Oligochaeta – few setae ex: earthworms *terrestrial
Earthworm • prostomium – liplike covering over mouth; pushes soil into mouth • clitellum – banded structure that functions in reproduction by secreting a mucus ring which carries fertilized eggs and is left behind as a cocoon • reproductive system: hermaphrodite – has both male & female sex organs ovaries – produce eggs testes – produce sperm seminal vesicles – store worm’s own sperm seminal receptacles – receive other worm’s sperm
Earthworm • digestive system: complete (mouth & anus) mouth – takes in food pharynx – sucks in soil esophagus – transports food to crop crop – stores food gizzard – grinds food intestine – absorbs nutrients anus – releases wastes
Earthworm • circulatory system: closed; will be black no heart; has aortic arches (pump blood) dorsal blood vessel – carries blood to aortic arches ventral blood vessel – carries blood to posterior end • respiratory system: O2 & CO2 (gases) exchanged through moist skin; kept moist by secreting mucus
Earthworm • excretory system: nephridia – “little kidneys” remove wastes from blood • cuticle – outer skin-like covering on worm that secretes mucus • nervous system: fused nerve cells (ganglia) simple brain that sends/receives messages ventral nerve cord – carries messages to/from body from/to ganglia