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WJEC BY2 2.6 Adaptations for parasitism
Parasites are organisms that live on or in another organism, called the host, and obtain nourishment at the
expense of the host.
The cestode (tapeworm) Taenia solium (pork tapeworm) is the main cause of human cysticercosis.
Life cycle of T. solium with resulting cysticercosis
o Cysticercosis is an infection of both humans and pigs
with the larval stages of the parasitic cestode, Taenia
solium. This infection is caused by ingestion of eggs shed
in the faeces of a human tapeworm carrier .
o Humans and pigs are infected by ingestion of food contaminated
with faeces, which contains eggs.
o Once eggs are ingested, the tapeworms hatch in the intestine, and
penetrate the intestinal wall, where they are
able to attach to it because on their scolex (head)
Two rows of hooks
The following are the problems that the gut parasite has to
overcome in order to survive:
It lives surrounded by digestive juices and mucus.
Food, mixed with digestive juices, is in constant motion as it is churned about as well as being propelled
along the length of the gut by peristaltic contractions of the muscular wall.
It lives in extremes conditions of pH along the length of the gut.
The immune system of the host.
If the host dies then so does the parasite.
In order to survive the tapeworm must adapt by:
Have a means of penetrating the host
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Have a means of attachment to the host
Protect itself against the immune responses of the host
Develop only those organs that are essential for survival no need for digestive system as is already
surrounded by digested food
Produce many eggs
Have an intermediate host
Have resistant stages to overcome the period away from a host
They have evolved the following structural modifications for their parasitic way of life:
Suckers and a double row of curved hooks for attachment to the wall of the…read more