Unsegmented worms (flatworms & roundworms)

Kingdom Animalia Overview First animals with bilateral symmetry and cephalization!

General Characteristics Eukaryotic, multicellular, heterotrophic Includes Planaria (free-living) and parasites: fluke and tapeworm 3 germ layers: endoderm, mesoderm & ectoderm Acoelomates (no central body cavity) Bilateral symmetry – has symmetry in only one direction Cephalization! Nervous tissue is concentrated in one end of organism. Two way digestive system (one opening) Hermaphrodites Regeneration/Fragmentation

3 Classes of Planarians Turbellaria – free-living Trematoda – Parasites Flukes Cestoda – Parasites Tapeworms

Structure Planaria

Structure - Planaria Pharynx  sucks food into gastrovascular cavity Mouth  takes in and expels digested food. On stomach, not on head! Brain control centre of nervous system – collection of ganglia Eyespot  senses light, lateral flaps allow smelling Gastrovascular cavity  enzymes break down food, diffuses into cells (many branches along body) Nerve cord control muscles

Structure Tapeworm structure Prot0glottid = unit of the reproductive system Scolex = head region

Feeding & Excretion Carnivores (feed on aquatic animals) or scavengers (feed on dead animals) Use pharynx to suck food into gastrovascular cavity GV cavity forms branching intestine Enzymes in GV cavity breakdown food, then diffuses into tissues Waste expelled through mouth Parasitic forms have no digestive tract (food is digested already by host). Food absorbed via diffusion

Response Movement simple “brain” (collection of ganglia) Nerve cords down length of body Ocelli (eye spots) – detect light & dark Cells to detect food source, direction of water flow Parasitic forms – no nervous system Cilia on epidermal cells glide along a film of mucus they secrete Muscle cells controlled by nervous system allows twisting and turning Parasitic – no need for movement (constant supply of food) Movement

Circulation & Respiration Rely on diffusion for transport and for gas exchange Some use flame cells for reproduction Reproduction Most free-living (non-parasitic) are hermaphrodites (sexual reproduction) Some: asexual reproduction through fission Parasites – complicated life cycles. Sexual reproduction, no fission

Reproduction – tapeworm

Reproduction – liver fluke

Swimmer’s itch

What are at least 3 ways flatworms are more complicated than Cnidarians? What is the scolex? How do tapeworms attach to a host? Where do they attach? How does the shape of the flatworm allow it to rely on diffusion for respiration? Describe fragmentation in the planarian. What is meant by cephalization? Do flatworms show this? What are the 3 groups of flatworms? Which ones are free-living? Name the hosts involved in a fluke’s life cycle. Explain why Platyhelminthes are called flatworms. How many germ layers do flatworms have? Name them. Name 2 parasitic flatworms. What type of digestive system do flatworms have? How many body openings do they have? Planarians are hermaphrodites. What does this mean? Do planarians fertilize their own eggs? Describe the nervous system and sensory structures of the planarian. Do tapeworms fertilize their own eggs? Why do tapeworms not need a digestive system? What are proglottids?

Kingdom Animalia Overview Two-way digestive system pseudocoelomates

General Characteristics Well defined digestive system with TWO openings Most are free-living and some parasitic Unsegmented worms with tapering ends Bilateral symmetry and cephalization

Structure

General Characteristics Well defined digestive system with TWO openings Most are free-living and some parasitic Unsegmented worms with tapering ends Bilateral symmetry and cephalization

Feeding Long tube-shaped digestive tract with a separate mouth and anus creates a one-way digestive system. food goes in through the mouth, and undigested food is expelled from the anus   Free-living roundworms are often carnivores that eat tiny animals Some eat algae, fungi, or rotting organic matter Some attach to the roots of plants and suck out the plant juices

Response simple nervous systems: several ganglia (groups of nerve cells) in head region but no real brain Nerves attached to the ganglia run the length of the body Simple sense organs detect chemicals given off by prey or hosts

Movement Internal Transport Longitudinal muscles run in strips down their bodies, and when contracted allow them to move similar to snakes to push their way forward Internal Transport Breathe and excrete metabolic wastes through their body walls using diffusion, just like flatworms

Reproduction Roundworms reproduce sexually, and most species have separate male and female sexes few are hermaphroditic Fertilization happens inside the female   Parasitic roundworms often have complex life cycles involving two or three hosts