BIOLOGY 11
Kingdom Animalia:
Phylum Nematoda:
The Roundworms
Phylum Nematoda Objectives
• Advances over Platyhelminthes
• Body plan and body systems
• 2 broad types and their example animals
• Parasitic worms (enter, live, hosts, effects)
The Pseudocoelomates
Characteristics and Advances
1. Evolution of the anus allows for a complete digestive
system - tube within a tube body plan
2. A pseudocoelom between mesoderm and endoderm
Phylum Nematoda
The Roundworms
• A very large phylum,
found in almost all
habitats
• most are small to
microscopic
• Reproduction is mostly
sexual
Hookworms
Phylum Nematoda
A. Free living nematodes
• Most nematodes live in
water or soil
• They are important in the
ecology of soil decomposers
A Soil Nematode
Phylum Nematoda
B. Parasitic Nematodes
Some of the worst worm parasites are members of this
phylum
1. Ascaris sp. the Intestinal Roundworm
• Most common world wide worm parasite - over 1 billion
people have it
• Lives in small intestine but travels through the body as a
juvenile
Phylum Nematoda
2. Hookworm
• Human hookworm (Necator sp.) feeds on blood from
inside of intestine
• A single worm can drain 20 ml of blood per day
• Most serious in children as can lead to physical and
mental retardation
• Enters as “Itch worm” between toes
Phylum Nematoda
3. Pinworm (Enterobius sp.)
• Lives in lower bowel
• Female migrates out anus
each night to lay eggs
• Secretes irritating toxin to
get person to scratch
• Re-infection is oral
Phylum Nematoda
4. Trichinella
• From eating
undercooked pork
• Invades selected
muscles forming painful
cysts
• Causes Trichanosis
Phylum Nematoda
5. Filarial Worm
• Small nematode that lives
in human lymph ducts and
blocks them
• As a result, fluids can’t
drain so accumulate
resulting in severe,
grotesque swelling below
Causes Elephantiasis where the worm is
Phylum Nematoda
6. The Guinea Stick Worm (Dracunculus sp.)
• In Africa only
• Enters while a person is in contaminated water and
burrows through skin and grows
• No cure - is removed by wrapping around a stick - one
turn per day
• Contains deadly toxin if broken it can kill its victim
Nematoda Video
• Video 1