Biology 11 – Kingdom Animalia Study of the Primitive Worms

Biology 11 – Kingdom AnimaliaStudy of the Primitive Worms Phylum Platyhelminthes: Flatworms Phylum Nematoda: Roundworms Phylum Platyhelminthes

The Flukes The Planarians The Tapeworms Phylum Platyhelminthes – the Flatworms Phylum Platyhelminthes

Importance of the Flatworms to Evolution • Bilateral body plan – left side mirror image of right • Cephalization – development of the head • sense organs and nerves concentrated in head region • Centralization of nervous system: • Nerve cord accompanies cephalization and bilateral symmetry. • Advanced muscle tissue present; • Primitiveexcretory system • allows removal of metabolic wastes Phylum Platyhelminthes

Phylum Platyhelminthes

Phylum Platyhelminthes Characteristics • Bilateral symmetry; anterior and posterior ends. • Body flattened • Well developed Epidermis • No internal body cavity other than digestive tube (acoelomate) • Parenchyma (connective tissue) fills space between organs. • Incomplete digestive system • Still one opening • This critter eats and poops out of its mouth – mmmm, pass the popcorn Phylum Platyhelminthes

Flatworm Nervous System and Excretory System Characteristics • Nervous system with ganglia and longitudinal nerve cords and branches • Simple sense organs; eyespots in some. • Excretory system • Lack circulatory, respiratory, and skeletal systems. • Reproductive system complex; • Well-developed gonads and accessory organs. • Free-living (eg Planarians) have well developed digestive and nervous systems to seek-out and process food • Parasitic Tapeworms – rely on host’s digestive system to process food, which absorb. No need for advancement of nervous system – not needed. Phylum Platyhelminthes

Nervous System and Sense Organs • Have a Nerve-net. • Most have more complex system. • Cerebral ganglion = primitive brain coordinates impulses. • “Ladder” system carries impulses throughout body • Many sense organs present • Eyespots • Chemoreceptors, touch sensors and rheoreceptors (sense direction) also common Phylum Platyhelminthes

3mm 3mm 3mm Volume = 3 x 3 x 3 = 27mm2 Area = 6(3 x 3) = 54mm3 3mm 1mm 9mm Volume = 9 x 3 x 1 = 27mm2 Area = 2(9 x 1) + 2(3 x 1) + 2(3x9) = 78mm3 Advantage of Being Flat • Surface area to volume ratio is important for organisms. • many substances enter and leave through body surface. • Faster absorption and release of wastes Phylum Platyhelminthes

Cross Section of a Flatworm Phylum Platyhelminthes

Nutrition and Digestion • Typical digestive system includes a mouth, a pharynx, and an intestine. • Parasitic Tapeworms and Flukes lack a digestive system • Free living flatworms (Planarians) are carnivorous; suck prey into pharynx with mouth. • Undigested food goes out mouth. Yes, folks, they eat and excrete out the same hole  • Parasitic flatworms, such as the Tapeworm absorb molecules from host. Phylum Platyhelminthes

Reproduction – in Free-living Flatwormssuch as Planarians • May reproduce sexually or asexually • Asexual: • Binary fission – split in two • Sexual: • Both sexes present in same flatworm (hermaphrodites). • Fertilization internal, eggs produced • Embryos emerge as juveniles resembling adults. Phylum Platyhelminthes

Reproduction in theTapeworm! • Lack digestive system • Sucker and hooks on anterior end for attachment • Neck produces new segments • Called proglottids • Each proglottid contains male and female gonads • Reproductive output high • Many proglottids per worm • Many eggs per proglottid Phylum Platyhelminthes

Tapeworm - Life Cycle Phylum Platyhelminthes

Flukes -- Life Cycle of a Liver Fluke Phylum Platyhelminthes

The Coelom or Body Cavity Advances Phylum Platyhelminthes

Another Look at the Coelom Phylum Platyhelminthes

Roundworms Phylum Nematoda Non-segmented; have smooth body wall Generally colorless, less than 5 cm in length, occur almost everywhere Parasitic roundworms Live anaerobically in every type of animal and many plants Have tube-within-a-tube body plan Digestive tract is complete; has both mouth & anus Phylum Platyhelminthes

Roundworm Ecological Roles • Carnivores that catch and eat algae, fungi, decaying matter • Recyclers • Parasites of Plants – eg. The Golden Nematode attacks potato crops, causing severe devastation • Parasites of animals - Phylum Platyhelminthes

Ascaris – Parasitic Roundworm of Pigs and Humans Phylum Platyhelminthes

Unfortunately, they can Grow quite Big! Phylum Platyhelminthes

Parasites: Your Pet's EnemiesTiny parasites that pose a gigantic threat Phylum Platyhelminthes

Adult roundworms live in the dog's small intestine.What they do:Cause diarrhea, vomiting, stunted growth, rough coat, bloated belly.How they spread:Almost all puppies get roundworms from their mothers. Dogs can also pick up roundworms from the soil.Defending against them: Once a month prevention is recommended, contact your local veterinarian for advice. Phylum Platyhelminthes

Enlarged hook worm mouth showing 'teeth'.What they do:Attach to the dog's intestinal lining, leaving bleeding internal wounds. Cause blood loss, anemia, and diarrhea. As few as 100 hook worms can kill a puppy.How they spread:Eggs pass through the feces of an infected dog into the soil where they are easily swallowed or can penetrate through a dog's feet.Defending against them: Once a month prevention is recommended, contact your local veterinarian for advice. Phylum Platyhelminthes

Symptoms: Larvae digested enter bloodstream and burrow into organs, causing absolutely horrendous pain and in some cases death. Phylum Platyhelminthes

Filarial (threadlike worms) are nematodes that may block the passage of Fluids in the Body • Disease: Elephantitis • The disease is caused by parasitic worms, including Wuchereria bancrofti, Brugia malayi, and B. timori, all transmitted by mosquitoes. Lymphatic filariasis currently affects 120 million people worldwide, and 40 million • Blocks Lymphatic nodes which drain fluid to and from the blood. • Tropics, Africa and Asia Phylum Platyhelminthes

Biology 11 – Kingdom Animalia Study of the Primitive Worms