1. End Show Slide 1 of 33 Copyright Pearson Prentice Hall Biology

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

3. End Show 27–2 Roundworms Slide 3 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.

4. 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?

5. End Show 27–2 Roundworms Slide 5 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?

6. End Show 27–2 Roundworms Slide 6 of 33 Copyright Pearson Prentice Hall Food moves in one direction through the digestive tract, Any food that is not digested leaves the body through the anus. What Is a Roundworm?

7. End Show 27–2 Roundworms Slide 7 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.

8. End Show 27–2 Roundworms Slide 8 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.

9. End Show 27–2 Roundworms Slide 9 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.

10. End Show 27–2 Roundworms Slide 10 of 33 Copyright Pearson Prentice Hall Form and Function in Roundworms Reproduction Roundworms reproduce sexually. Most have separate sexes. Parasitic roundworms often have life cycles that involve two or three different hosts or several organs within a single host.

11. End Show 27–2 Roundworms Slide 11 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

12. End Show 27–2 Roundworms Slide 12 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. Larvae travel through the bloodstream and burrow into organs and tissues. 50 µm Encysted juveniles Muscle tissue

13. End Show 27–2 Roundworms Slide 13 of 33 Copyright Pearson Prentice Hall 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. Get Ready, the next slide is gross. Roundworms and Human Disease

14. End Show 27–2 Roundworms Slide 14 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 mosquitoes. Causes Elephantiasis

15. End Show 27–2 Roundworms Slide 15 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. May block intestine.

16. End Show 27–2 Roundworms Slide 16 of 33 Copyright Pearson Prentice Hall Ascaris Life Cycle. Human ingests food or water containing Ascaris eggs. Roundworms and Human Disease 1

17. End Show 27–2 Roundworms Slide 17 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

18. End Show 27–2 Roundworms Slide 18 of 33 Copyright Pearson Prentice Hall Roundworms and Human Disease Ascaris Life Cycle Larvae enter blood vessels and are carried to the lungs 3

19. End Show 27–2 Roundworms Slide 19 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

20. End Show 27–2 Roundworms Slide 20 of 33 Copyright Pearson Prentice Hall Ascaris Life Cycle Eggs are released and leave the host in faces. Roundworms and Human Disease 5

21. End Show 27–2 Roundworms Slide 21 of 33 Human Ascarid Reproduction Copyright Pearson Prentice Hall

22. End Show 27–2 Roundworms Slide 22 of 33 Ascarids Copyright Pearson Prentice Hall Ascarids taken from children of one village.

23. End Show 27–2 Roundworms Slide 23 of 33 Heartworm Copyright Pearson Prentice Hall

24. End Show 27–2 Roundworms Slide 24 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. http://www.youtube.com/watch?v=44aq2A6NkUw

25. End Show 27–2 Roundworms Slide 25 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

26. End Show - or - Continue to: Click to Launch: Slide 26 of 33 Copyright Pearson Prentice Hall 27–2

27. End Show Slide 27 of 33 Copyright Pearson Prentice Hall 27–2 In roundworms, the body cavity that forms between the endoderm and mesoderm is the a.ganglion. b.hydrostatic skeleton. c.pseudocoelom. d.coelom.

28. End Show Slide 28 of 33 Copyright Pearson Prentice Hall 27–2 All of the following are parasitic roundworms EXCEPT a.tapeworms b.filarial worms c.hookworms d.ascarid worms

29. End Show Slide 29 of 33 Copyright Pearson Prentice Hall 27–2 Characteristics of roundworms include a digestive system with a.one opening and a pseudocoelom. b.one opening but no pseudocoelom. c.two openings and a pseudocoelom. d.two openings but no pseudocoelom.

30. End Show Slide 30 of 33 Copyright Pearson Prentice Hall 27–2 Gas exchange and excretion of metabolic wastes in roundworms occurs a.via a complex system of alveoli. b.through their body walls by diffusion. c.through excretory tubules. d.by flame cells.

31. End Show Slide 31 of 33 Copyright Pearson Prentice Hall 27–2 The roundworms called ascarids cause harm by a.causing serious body swelling. b.burrowing into body tissues and causing pain. c.causing malnutrition. d.causing internal bleeding.

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