1. Worms
Chapters 26.3, 26.4, and 27.2

2. Animal Classification
Sponges
Cnidarians
Worms
Mollusks
Arthropods
Echinoderms
- Phylum Platyhelimenthes
- Phylum Nematoda
- Phylum Annelida
Worms
Invertebrates
Animals
Fishes
Amphibians
Reptiles
Ectotherms
(cold-blooded)
Vertebrates
Birds
Mammals
Endotherms
(warm-blooded)

3. Flatworms Phylum Platyhelimenthes The least complex worm Acoelomates
(Greek) platy = flat
helmins = worm
The least complex worm
Acoelomates
About 14,500 species exist found in marine, freshwater, and land
The most commonly studied flatworm is the planarian

4. Nervous Control Most of the nervous system is located in its head
The nervous system consists of two nerve cords that run the length of the body
Nerve cords

5. Nervous Control Eyespots can detect the presence or absence of light
Sensory cells can detect chemicals and movement in water
Sensory cells
Eyespots
Sensory cells

6. Nervous Control Ganglion A small swelling of the nerve cord
Receives messages from the eyespots and sensory pits, then communicates with the rest of the body
Ganglia

7. Reproduction Most flatworms are hermaphroditic
Can reproduce sexually and asexually
Sexual reproduction
Two planarians will exchange sperm
Internal fertilization occurs
Zygotes are then released in water where they will hatch

8. Reproduction Asexual reproduction
Planarians can regenerate when damaged
Regeneration – The replacement or regrowth of missing body parts

9. Feeding and Digestion in Planarians
A planarian feeds on dead or slow-moving organisms
Planarians are not parasitic
To eat, a planarian extends its pharynx from its mouth
Pharynx – a tube-like, muscular organ (also known as the throat)

10. Extended pharynx

11. Feeding and Digestion in Planarians
Enzymes breakdown the food outside the body, and then food particles are sucked into the digestive tract
Food is digested in individual cells
Waste leaves through its one opening (mouth)

12. Feeding and Digestion in Planarians
Excretory system – eliminates waste from the body
Flame cells – excess water is removed from the body

14. Feeding and Digestion in Parasitic Flatworms
Sucker
Parasitic flatworms have mouthparts with hooks that keep them attached to their hosts
Hook

15. Feeding and Digestion in Parasitic Flatworms
Sucker
Parasitic flatworms don’t need a digestive system because they obtain nutrients from food that has been digested by their host
Hook

16. Tapeworm Scolex – a knob-shaped head
Hook
Scolex – a knob-shaped head
Proglottid – detachable, individual sections that contain muscles, nerves, flame cells, and reproductive organs
Sucker

17. Tapeworm Each proglottid can contain up to 100,000 eggs
Hook
Each proglottid can contain up to 100,000 eggs
Can reach up to 33 ft in length and contain over 2,000 proglottids
Sucker

19. Eggs are passed out the intestines
Fluke larva can bore through the skin, enter the bloodstream, and move to the intestines
Adult flukes
Embryo develops in human waste
Second larval stage
The larva will enter the snail host for further development
First larval stage are found in water

20. Roundworms Phylum Nematoda
Greek word nema = thread
Found in soil, animal, freshwater, and marine environments
More than 12,000 species exist
Nearly all plant and animals are affected by parasitic roundworms

21. Pseudocoelomates
Have a complete digestive system with two openings (mouth and anus)
Free-living species have well-developed eyespots whereas parasitic species have underdeveloped eyespots

22. Roundworm Parasites of Humans
Ascaris is the most common roundworm infection in humans worldwide
More common in subtropical areas
Children become infected more often than adults
Timmy plays in a sandbox…

23. Roundworm Parasites of Humans
Pinworms are the most common roundworm parasites in the U.S.
Children are the commonly infected
Eggs can survive two weeks on the surfaces

24. Roundworm Parasites of Humans
During night, female pinworms lay eggs around the anus of host
Taping the anus before bedtime is one method used to eliminate pinworms

25. Roundworm Parasites of Humans
Trichinella can be ingested in raw or undercooked pork or wild game (turkey)
Trichinella can be controlled by properly cooking meat

26. Roundworm Parasites of Humans
Hookworms are common in warm climates where they walk on contaminated soil in bare feet
Hookworms cause people to feel weak and tired due to blood loss

28. Roundworm Parasites of Humans
Hookworm infection from dogs and cats