Section 2: Roundworms and Rotifers Roundworms and rotifers have a more highly evolved gut than flatworms. K What I Know W What I Want to Find Out L What I Learned

Essential Questions What are the similarities between the features of roundworms and flatworms? How can roundworms be identified based on movement? What are the ways humans risk contracting roundworm parasites? Copyright © McGraw-Hill Education Roundworms and Rotifers

Vocabulary Review New cilia hydrostatic skeleton trichinosis Roundworms and Rotifers Copyright © McGraw-Hill Education

Body Structure of Roundworms Roundworms are in phylum Nematoda, and often called nematodes. Pseudocoelomates, bilaterally symmetric, cylindrical, unsegmented worms. Found in marine, freshwater, and terrestrial environments. Can be parasitic or free-living Copyright © McGraw-Hill Education Roundworms and Rotifers

Body Structure of Roundworms Feeding and digestion Most roundworms are free-living, but some are parasites. Free-living feed on a variety of food sources Have a one-way digestive tract, a major evolutionary step associated with pseudocoelomates. Copyright © McGraw-Hill Education Roundworms and Rotifers

Body Structure of Roundworms Respiration, circulation, excretion, and response to stimuli No circulatory or respiratory organs, depend on diffusion Most roundworms exchange gases/excrete wastes through their outer body coverings. Nematodes have ganglia and associated nerve cords. Respond to touch, chemicals, and some respond to light Copyright © McGraw-Hill Education Roundworms and Rotifers

Body Structure of Roundworms Movement Muscles run the length of the roundworm’s body The muscles pull against the outside body wall and the pseudocoelom, which acts as a hydrostatic skeleton, fluid within a closed space that provides rigid support. Copyright © McGraw-Hill Education Roundworms and Rotifers

Body Structure of Roundworms Reproduction Roundworms reproduce sexually, with internal fertilization. In free-living worms, larvae hatch from eggs and develop into adults. In parasitic worms, larval development is more complicated, and often involves various parts of the host body. Copyright © McGraw-Hill Education Roundworms and Rotifers

Diversity of Roundworms Trichinella worms Cause a disease called trichinosis, contracted by eating raw or undercooked pork products Burrow into the intestines of hosts, such as humans, pigs, and other mammals. Hookworms Commonly contracted in warm climates by humans who walk barefoot over contaminated soils. Travels through the circulatory system to the lungs, then to the esophagus where it is swallowed and transported to the intestines. Copyright © McGraw-Hill Education Roundworms and Rotifers

Diversity of Roundworms Ascarid worms Most common worm infection in humans Contracted through unwashed vegetables or contaminated soils Pinworms Most common nematode parasite in humans in the United States Spread most frequently among children Copyright © McGraw-Hill Education Roundworms and Rotifers

Diversity of Roundworms Filarial worms Tropical parasites spread through mosquito intermediary Causes elephantiasis, swelling of the lymph system, in humans Source of heartworm in cats and dogs Nematodes in plants Some species of roundworm cause disease in plants Most species of nematodes are harmless or beneficial to plants Can be used as biological control for pests. Copyright © McGraw-Hill Education Roundworms and Rotifers

Rotifers Rotifer features and movement Bilaterally symmetric pseudocoelomates with rings of cilia around their mouths Move through the water by means of their cilia Posterior end has “toes” that secrete an adhesive material that allows them to attach themselves to surfaces Copyright © McGraw-Hill Education Roundworms and Rotifers

Rotifers Organ systems of rotifers Gather food with cilia and transfer it to a complete digestive tract Exchange gases and excrete metabolic wastes through diffusion Have sensory bristles and an eyespot Reproduce both sexually and asexually depending on environmental conditions Copyright © McGraw-Hill Education Roundworms and Rotifers

Review Essential Questions Vocabulary What are the similarities between the features of roundworms and flatworms? How can roundworms be identified based on movement? What are the ways humans risk contracting roundworm parasites? Vocabulary hydrostatic skeleton trichinosis Copyright © McGraw-Hill Education Roundworms and Rotifers