Biology Two DOL38 - 41

III. Phylum Platyhelminthes A. General characteristics All About Worms! 1. flat worms a. distinct head & tail ends 2. bilateral symmetry 3. habitat = free-living aquatic or parasitic *a. Parasite = heterotroph that gets its nutrients from the living organisms in/on which they live Ph. Platyhelminthes Ph. Nematoda Ph. Annelida 4. motile 5. carnivores or detritivores 6. reproduce sexually & asexually Biology Two DOL38 - 41 7/4/2016 B. Anatomy 3. Simple nervous system 1. have 3 body layers w/ true tissues a. brain-like ganglia in head & organs b. 2 longitudinal nerves with a. inner = endoderm transverse nerves across body b. middle = mesoderm 4. Lack respiratory, circulatory systems c. outer = ectoderm 5. Parasitic forms lack digestive & excretory systems 2. are acoelomates - lack a coelom around internal organs a. use diffusion to supply needs from host organisms a. digestive tract is formed of endoderm 6. Planaria anat. 7. Tapeworm anat. a. flat body w/ arrow-shaped head & a. head = scolex tapered tail 1) has hooks to help hold onto host b. light-sensitive eyespots on head 2) has suckers to ingest food c. body covered in cilia & mucus to aid b. body segments = proglottids movement 1) new ones form right behind head d. digestive tract only open at mouth 2) each segment produces gametes 1) in center of ventral surface 3) each houses excretory organs 2) used for feeding, excretion C. Physiology 1. Digestion (free-living) a. pharynx extends out of mouth b. sucks food into intestines for digestion c. excretory pores & mouth/pharynx remove wastes 2. Reproduction varies a. Sexual for free-living (& some parasites) 1) hermaphrodites a) cross-fertilize or self-fertilize internally b. Asexual – most parasites 1) by fission c. Parasites have complex development usually w/ multiple hosts D. Classes 1. Class Turbellaria a. free-living flatworms 1) free-living 2) ex: Planaria, Blue Pseudoceros Flatworm 2. Class Cestoda a. tapeworms 1) internally parasitic 2) may grow up to 10m long! 3) ex: fish tapeworm, dwarf tapeworm 3. Class Trematoda IV. Phylum Nematoda Nema = Greek for a. flukes A. General characteristics “thread” 1) internally parasitic 1. unsegmented round worms 2) ex: sheep liver fluke, blood fluke a. slender body, tapered ends 4. Class Monogenea 2. bilateral symmetry 3. habitat = free-living aquatic or a. flukes terrestrial or parasitic on plants & 1) external parasites animals 2) ex: Frog bladder fluke 4. motile 5. carnivores 6. females typically larger 7. reproduce sexually B. Anatomy 1. 1 mm – 1+ m long 2. protective cuticle covers body 3. are pseudocoelomates – cavity between mesoderm & endoderm 4. “tube-within-a-tube” body a. inner = digestive tract 1) separate mouth & anus b. outer = muscles 5. respiration, excretion through body walls 6. circulation by diffusion 7. simple nervous sys. w/ ganglia, nerves & sense organs 8. move using muscles & hydrostatic skeleton 9. Reproduction Dioecious – separate genders C. Classes & Examples a. sexual 1. Two major classes 1) most are separate sexes a. Cl. Rhabditea a) a few hermaphrodite species 1) most round worms 2) internal fertilization 2) ex: Trichinella, C. elegans, 3) eggs laid outside body hookworms, pinworms, heart 4) juveniles molt 4-5 times while worms, filaria growing b. Cl. Enoplea 1) more ancestral form V. Phylum Annelida Latin = annelus – little ring A. General characteristics 1. segmented worms a. ex: earthworms, leeches, sandworms 2. bilateral symmetry 3. habitat = aquatic, land a. only a few are parasitic 4. motile 5. carnivores or detritivores 6. reproduce sexually B. Anatomy 1. are true coelomates – cavity lined w/ mesoderm, suspending internal organs 2. “tube-within-a-tube” body a. separate mouth & anus 3. closed circulatory sys. a. blood vessels & aortic arches pump blood b. blood has hemoglobin 4. well-developed muscles, repro sys. 5. digestive tract has a crop & gizzard to store, grind food 6. Movement 7. Reproduction a. 2 sets of muscles work together w/ a. sexual hydrostatic skeleton b. separate genders or hermaphrodites 1) longitudinal c. external or internal fertilization 2) circular 1) internal - line up at clitellum to b. many have setae on segments to exchange sperm anchor part of body while 2) fertilized eggs are placed in a stretching, pushing mucus cocoon and laid externally C. Classes “few hairs” 1. Class Oligochaeta a. fresh water or terrestrial b. ex: earthworm, Queensland Turquoise Earthworm 2. Class Polychaeta a. marine “many hairs” b. ex: Orange Christmas Tree worm 3. Class Hirudinea a. aquatic or terrestrial b. ex: Tiger leech, ribbon leech.

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