CHARACTERISTICS OF WORMS (See Chapter 34)
Body Symmetry
bilateral (most animals have this type of symmetry) see pg.655 for detail
Key terms for body locations
anterior - head end
posterior - rear end
ventral - belly surface
dorsal - back surface
longitudinal – lengthwise dimension; think North and South
transverse – horizontal dimension: think East and West
lateral – off to the side (like a lateral pass)
Embryology
first group of organisms that have all three tissue
layers: ectoderm, mesoderm and endoderm
Lifestyles
parasitic - organisms that get their energy at the expense of
others.the organism they feed on is called the host.
Free living specie can survive on their own
Body plan
acoelomate, pseudocoelomate, or coelmate.
see pg. 663 -666 for complete explanation.
Three phyla of worms
flatworms, roundworms and segmented worms
THE FLATWORMS (Platyhelminthes)
Tapeworm
- A parasitic flatworm that lives in the intestines of animals.
- long, flat, ribbon like bodies. Nutrients from surrounding fluids of the
digestive juices of their host are absorbed directly through the skin(diffusion).
- the head region is called the scolex. It has hooks and suckers on it to dig into the
host’s intestine
- Its body is made up of repeating units called proglottids. These units contain the
reproductive organs of the worm. Tapeworms are hermaphrodites, meaning they contain
both male and female sexual orgrans.
- Tapeworms can form a protective covering over themselves called a cyst ,
and can exist for years in the muscle tissue of animals. Cysts can be transmitted
to people when they eat undercooked meat.
- The symptoms of a person infected with a tapeworm is loss
of weight, increased appetite, fatigue and anemia (a decrease
in red blood cell counts). Why these symptoms?
Flukes
- Parasitic flatworms, having suckers at the anterior end and ventral surface
of its body. In this way its attached itself and drains blood from its host.
- Transmitted to people from impure drinking water, undercooked fish, and by eggs
burrowing through the skin of the feet
- flukes infect the liver, heart, lungs and blood of an individual. Results in fever, diarrhea and weakness.
- flukes belonging to the group Schistosoma infect millions of people in wet, tropical areas (especially Asia).
Planaria
- Free living flatworm that lives in fresh water
- Moves with muscles and by beating cilia which line the body
- Feeds on decaying matter. Extends a tubelike structure
called the pharynx from its mouth, which is located on the
ventral surface.
- The intestines have branches like a tree to deliver nutrients to
all parts of the body.
- A simple brain is located at the anterior end of the body. This concentration of
nerve tissue at the head end of an organisms known as cephalization , and marks a big
advancement in the evolution of animals.
-Eyespots located at the anterior end of the body are sensitive
to light. (photosensitive)
- Nerves run along the length and width of the body.
- Planarians are hermaphrodites and exchange sex cells with other planarians.
- Planarians can also regenerate themselves
ROUNDWORMS (Nematoda)
Hookworm
- parasitic roundworm that is transmitted to humans by boring
through their feet. Causes internal bleeding and anemia.
Trichina worm
- parasitic roundworm that is transmitted to humans by eating undercooked
pork that has trichina cysts in its tissues. The cysts hatch inside the
intestine, pass into the blood stream and embed themselves in the muscle
tissues. This can cause great pain and muscle stiffness.
Ascaris
Filarial worms
- parasitic roundworm that is transmitted to humans by taking in food or
water contaminated with the eggs of the worm. Worms travel to the lungs where
they are coughed up, swallowed and then mate in the intestines. Left untreated,
Ascaris worms can multiply and block the intestines. They can also cause lung infections.
- a roundworm that it transmitted by a mosquito. Infects the lymphatic system causing
accumulation of fluid and swelling of body parts ( Elephantiasis )
ANNELIDS (segmented worms) See Chapter 35 section 2 for details on this group of worm . Know the
specific features of the earthworm in terms of its structures and what their function is.