End Show Slide 1 of 33 Copyright Pearson Prentice Hall 27–2 Roundworms

End Show 27–2 Roundworms Slide 2 of 33 Copyright Pearson Prentice Hall What Is a Roundworm? Most species of roundworms are free-living, inhabiting soil, salt flats, aquatic sediments, and water, from polar regions to the tropics. Others are parasitic and live in hosts.

End Show 27–2 Roundworms Slide 3 of 33 Copyright Pearson Prentice Hall What Is a Roundworm? What are the defining features of roundworms?

End Show 27–2 Roundworms Slide 4 of 33 Copyright Pearson Prentice Hall Roundworms are unsegmented worms that have pseudocoeloms and digestive systems with two openings—a mouth and an anus. What Is a Roundworm?

End Show 27–2 Roundworms Slide 5 of 33 Copyright Pearson Prentice Hall Roundworms have a body cavity between the endoderm and mesoderm tissues. What Is a Roundworm?

End Show 27–2 Roundworms Slide 6 of 33 Copyright Pearson Prentice Hall This cavity is partially lined with tissue derived from the mesoderm and is called a pseudocoelom, meaning, “false coelom.” What Is a Roundworm?

End Show 27–2 Roundworms Slide 7 of 33 Copyright Pearson Prentice Hall Roundworms have a digestive tract with two openings. Food moves in one direction through the digestive tract of roundworms. Any food that is not digested leaves the body through the anus. What Is a Roundworm?

End Show 27–2 Roundworms Slide 8 of 33 Copyright Pearson Prentice Hall Form and Function in Roundworms Roundworms have specialized tissues and organ systems that carry out essential physiological functions.

End Show 27–2 Roundworms Slide 9 of 33 Copyright Pearson Prentice Hall Form and Function in Roundworms Feeding Many free-living roundworms use grasping mouthparts and spines to catch and eat other small animals.

End Show 27–2 Roundworms Slide 10 of 33 Copyright Pearson Prentice Hall Form and Function in Roundworms Respiration, Circulation, and Excretion Roundworms exchange gases and excrete metabolic waste through their body walls. They depend on diffusion to carry nutrients and waste through their bodies.

End Show 27–2 Roundworms Slide 11 of 33 Copyright Pearson Prentice Hall Form and Function in Roundworms Response Roundworms have simple nervous systems, consisting of several ganglia. Several nerves extend from ganglia in the head and run the length of the body. These nerves transmit sensory information and control movement.

End Show 27–2 Roundworms Slide 12 of 33 Copyright Pearson Prentice Hall Form and Function in Roundworms Movement Fluid in the pseudocoelom and muscles extending the length of their bodies function as a hydrostatic skeleton. Aquatic roundworms contract muscles to move like snakes through the water. Soil-dwelling roundworms push their way through the soil by thrashing around.

End Show 27–2 Roundworms Slide 13 of 33 Copyright Pearson Prentice Hall Form and Function in Roundworms Reproduction Roundworms reproduce sexually. Most species have separate sexes. Roundworms reproduce using internal fertilization. Parasitic roundworms often have life cycles that involve two or three different hosts or several organs within a single host.

End Show 27–2 Roundworms Slide 14 of 33 Copyright Pearson Prentice Hall What roundworms cause human disease? Roundworms and Human Disease

End Show 27–2 Roundworms Slide 15 of 33 Copyright Pearson Prentice Hall Roundworms and Human Disease Parasitic roundworms include trichinosis-causing worms, filarial worms, ascarid worms, and hookworms. Roundworms and Human Disease

End Show 27–2 Roundworms Slide 16 of 33 Copyright Pearson Prentice Hall Roundworms and Human Disease Trichinosis-Causing Worms Adult Trichinella worms live and mate in the intestines of their hosts. Female worms carrying fertilized eggs burrow into the intestinal wall and release larvae. Larvae travel through the bloodstream and burrow into organs and tissues.

End Show 27–2 Roundworms Slide 17 of 33 Copyright Pearson Prentice Hall The larvae form cysts and become inactive in the host’s muscle tissue. Trichinella completes its life cycle only when another animal eats muscle tissue containing these cysts. Humans can get trichinosis by eating raw or incompletely cooked pork. Roundworms and Human Disease

End Show 27–2 Roundworms Slide 18 of 33 Trichinella Copyright Pearson Prentice Hall

End Show 27–2 Roundworms Slide 19 of 33 Copyright Pearson Prentice Hall Roundworms and Human Disease Filarial Worms Filarial worms are threadlike worms that live in the blood and lymph vessels of birds and mammals. They are transmitted by biting insects. Large numbers of filarial worms may block the passage of fluids within lymph vessels and cause swelling.

End Show 27–2 Roundworms Slide 20 of 33 Elephantitis Copyright Pearson Prentice Hall

End Show 27–2 Roundworms Slide 21 of 33 Copyright Pearson Prentice Hall Roundworms and Human Disease Ascarid Worms Ascaris lumbricoides is a serious parasite of humans and many other vertebrate animals. It absorbs digested food from the host’s small intestine. Ascaris lumbricoides is commonly spread by eating foods that are not washed properly.

End Show 27–2 Roundworms Slide 22 of 33 Ascarid worms Copyright Pearson Prentice Hall

End Show 27–2 Roundworms Slide 23 of 33 Copyright Pearson Prentice Hall Ascaris Life Cycle. Human ingests food or water containing Ascaris eggs. Roundworms and Human Disease 1

End Show 27–2 Roundworms Slide 24 of 33 Copyright Pearson Prentice Hall Ascaris Life Cycle The eggs travel to the small intestine and develop into larvae. Roundworms and Human Disease 2

End Show 27–2 Roundworms Slide 25 of 33 Copyright Pearson Prentice Hall Roundworms and Human Disease Ascaris Life Cycle Larvae enter blood vessels and are carried to the lungs 3

End Show 27–2 Roundworms Slide 26 of 33 Copyright Pearson Prentice Hall Ascaris Life Cycle Larvae are coughed up and swallowed. They then travel to the small intestine where they develop to maturity Roundworms and Human Disease 4

End Show 27–2 Roundworms Slide 27 of 33 Copyright Pearson Prentice Hall Ascaris Life Cycle Eggs are released and leave the host in feces. Roundworms and Human Disease 5

End Show 27–2 Roundworms Slide 28 of 33 Copyright Pearson Prentice Hall Roundworms and Human Disease Hookworms Hookworm eggs hatch and develop in the soil. They use sharp toothlike plates and hooks to burrow into the skin and enter the bloodstream.

End Show 27–2 Roundworms Slide 29 of 33 Copyright Pearson Prentice Hall Hookworms travel through the blood of their host to the lungs and down to the intestines. There, they suck the host’s blood, causing weakness and poor growth. Roundworms and Human Disease

End Show 27–2 Roundworms Slide 30 of 33 Hookworms Copyright Pearson Prentice Hall