Platyhelminthes General characteristics: Known as “flat worms.” Body plan: acoelomate, bilateral symmetry Habitat: aquatic or in host’s body

Platyhelminthes Nutrition: Parasitic - (blood, tissue, or predigested materials from host’s intestines) OR Scavengers and Saprobes

Platyhelminthes Feeding: Planarians extend pharynx from mouth Parasites have specialized mouth parts to attach to their host.

Platyhelminthes Digestion: Excretion: diffusion through the body wall Extracellular: food is pumped into digestive cavity or gut and cells digest and absorb nutrients, digested food is then diffused into the other body tissue Excretion: diffusion through the body wall planarians have flame cells to excrete water and wastes through pores

Platyhelminthes Respiration and Circulation: Diffusion of gases through the skin, skin must remain moist

Platyhelminthes Nervous: most have ganglia (mass of nervous tissue), eyespots, sensory lobes and respond to touch and chemicals Demostrates cephalization, nervous tissue is concentrated in the head region.

Platyhelminthes Reproduction: Sexual Reproduction: Hermaphrodites Parasitic worms require hosts to reproduce Sexual reproduction exchange sperm, internal fertilization

Schistosome Life Cycle Section 27-1 Primary host (human) Intermediate host (snail) Flukes mature and reproduce sexually in the blood vessels of human intestines. Embryos are released and passed out with feces. Adult fluke Human intestine Embryo Ciliated larva Tailed larva After asexual reproduction, new larvae are released from the snail into the water. They then infect humans, the primary host, by boring through their skin. Once in the water, embryos develop into swimming larvae that infect an intermediate host (snail). Shistosomiasis

Tapeworm Life Cycle

DON’T DO THIS!! GROSS!

Platyhelminthes Reproduction: Asexual reproduction through fragmentation or fission.

Platyhelminthes Mobility: Cilia for gliding Muscle cells controlled by nervous system to react to stimuli

The Anatomy of a Flatworm Eyespot Ganglia Freshwater flatworms have simple ganglia and nerve cords that run the length of the body. The excretory system consists of a network of tubules connected to flame cells that remove excess water and cell wastes. Head Nerve cords Gastrovascular cavity Flatworms use a pharynx to suck food into the gastrovascular cavity. Digested food diffuses from the cavity into other cells of the body. Eyespots in some species detect light. Excretory system Ovary Testes Mouth Pharynx Most flatworms are hermaphrodites, having male reproductive organs (testes) and female reproductive organs (ovaries) in the same organism. Flame cell Excretory tubule

Platyhelminthes Common Examples: Turbellaria (Planarian) Trematoda (Fluke) Cestoda (Tapeworm)

Nematoda General characteristics: Known as “round worms”. Pseudocoleomate long and slender, tapered at both ends protostomes bilateral symmetry Body is covered in a complex cuticle

Nematoda Habitat/Nutrition: Parasites Feeding Both mouth and anus connected by digestive tube Digestion: takes place in digestive cavity, digested food diffuses into other body tissue. May also have digestive sacs that food is pumped into for digestion.

Nematoda

Nematoda Circulation and Respiration: Diffusion of gases through the skin Excretion: Canal system, diffusion through body wall or out through mouth Nervous: simple nervous system, with a main ventral (belly) nerve cord and smaller dorsal (back) nerve cord

Nematoda Reproduction: Sexual usually dioescious (separate sexes) internal fertilization genders differ in size, shape and color Parasitic worms require host

Life Cycle of Hookworm

Life Cycle of Whipworm

Nematoda Mobility: Muscles along body wall for movement

Nematoda Examples: Hookworms Pinworms Guinea worms

Annelida General characteristics: Habitat: aquatic and moist soil Known as “segmented worms” Coelomates Habitat: aquatic and moist soil

Annelida Nutrition: heterotrophic, filter feeders, parasites, scavengers, and saprobes Feeding: Pharynx used to obtain food Carnivorous species have two or more sharp jaws

Annelida Digestive wastes pass out through the anus Excretion: Digestive wastes pass out through the anus Cellular wastes containing nitrogen is passed out by the nephridia (simple kidney)

Annelida Digestion: extracellular, takes place in intestine Earthworm: pharynx → esophagus→ crop (storage) → gizzard (ground) → intestines (absorption)

Annelida Circulation: closed (blood contained in vessels)

Annelida Respiration: Aquatic: breathe through gills Land dwellers: diffusion through skin (must stay moist) typically secrete a mucus to keep skin moist

Annelida Nervous: Best developed sense organs in free living marine organism Well developed nervous systems consisting of brain and spinal cord Two or more pairs of eyes, sensory tentacles, chemical receptors and statocysts that help detect gravity

Annelida Reproduction Most sexually Some use external fertilization and have separate sexes Earth worms and leeches are hermaphroditic, but rarely fertilize their own eggs

Annelida Mobility Two major groups of muscles that function as part of the hydrostatic skeleton Longitudinal and circular muscles, move by alternating contractions Earthworms have hair-like structures called setae that allow them to easily grip a surface. Marine worms have parapodia to use for swimming and crawling

Section 27-3 Anus Setae Clitellum Circular muscle Longitudinal muscle Nephridia Ganglia Ring vessels Reproductive organs Ventral blood vessel Ganglion Brain Mouth Dorsal blood vessel Crop Gizzard Body segments Setae

Annelida Examples: Earthworms Leeches Marine worms