Including the Phyla: Rotifera, Nematoda, Rhynchocoela, and Platyhelminthes

 Also called Nemertinea  Commonly referred to as ribbon or bootlace worms  Over 900 different species  They live in marine habitats including: sand, mud, or under shells and rocks  Mostly ocean dwelling  Often brightly colored  Can reach lengths of feet long  Carnivorous  Uses proboscis to capture prey ▪ Eats segmented worms, and crustaceans  Simplest animal with a circulatory system  Contains Nervous system  Sensory nerve cells located in epidermis  Respiration occurs through epidermis

 Reproduce asexually or sexually  When sexual, fertilization occurs externally, forming a larvae called pilidium  When asexual, ribbon worms regenerate themselves  The larvae pilidium develops into adult

 Common name Roundworm  Has a bilaterally symmetrical body, surrounded by a cuticle  Characterized by pseodocoelom  Moves by contraction of muscles, producing a back and forth motion  Muscles run in a longitudinal direction, along with nerve cords  Can be decomposers, predators, or parasites  Inhabit a wide variety of places, from beer coasters to mud, from humans to the placentas of sperm whales  Extremely abundant, about 12,000 known species  An rotting apple could have 90,000 individuals living on it  236 species could live in a few cubic centimeters of mud

 Sexual  Males fertilize eggs by using copulatory spines to open a females reproductive tracts, and inject sperm into them  Sperm do not have flagellae, it uses pseudopodia to move around ▪ Eggs develop directly into adult  Roundworms infest half of the worlds humans  Hookworms  Worms that cause trichinosis  Pinworms  A worm whose eggs can be transmitted in household dust  Filarial worms  Can cause filariasis and onchocerciasis

 Rotifer: Latin for “Wheel bearer”  The cilia round the mouth resembles a wheel  Microscopic  Found in marine environments  Can vary in length from micrometers, to one millimeter  Omnivorous  Sometimes cannibalistic ▪ Eats things from decomposing materials, to algae and phytoplankton

 Many Rotifers use parthenogenesis  Asexual reproduction  Two types of parthenogenesis  The formation of only females  The formation of males and females, where males are degenerate ▪ Condition is know as sexual dimorphism  Males in the second type of parthenogenesis survive only long enough to produce sperm to fertilize eggs ▪ Eggs that are formed either hatch and release into water, or stay attached to the posterior end of the rotifer until enough water is available for it to hatch

 Lack both circulatory and respiratory systems  Not necessary because of cells located near the animal’s exterior  No body cavity  About 20,000 species  Consists of three major classes  Turbellaria  Trematoda  Cestoda  A common flatworm that can be found worldwide, is the Dugesia, otherwise known as the planarian

 Over 3,000 species in its class  Live in marine environments  Body resembles a piece of tape  Moves by flexing its body, producing a wavelike motion that propels it through water  Produce asexually  All are predatory, feeding upon: bacteria, algae, protozoans and invertebrates

 Over 6,000 species in its class  Mostly parasitic  Also known as flukes  Flukes can be endoparasites, or ectoparasites ▪ Endoparasites are covered by a tegument  Simple bodies, due to parasitic lifestyle  Contain multiple suckers to attach to hosts  Reproduce asexually, allows for an exponential population growth  Some flukes can be found in the blood, liver, or intestinal wall  Common fluke found in humans: Clonorchis Sinensis (Liver fluke)

 About 1,500 species  Parasitic  Commonly referred to as tapeworms  Cestoda attach themselves permanently to intestinal walls of hosts, absorbing food through their skin  Grown in sections called proglottids  May grow to reach a length of 40 feet. Imagine that in your intestine!  About a dozen types of tapeworm infect humans, one of them being Taenia Saginata (beef tapeworm)  They are hermaphrodites, but cannot reproduce asexually  Each proglotid produces sperm and eggs