Invertebrates Flashcards
What is the disadvantage to not having a coelom?
They have no fluid filled cavity to protect their vital organs from any exterior forces.
Give a basic description of the Platyhelminthes.
They are flat, bilaterian, unsegmented, soft bodied invertebrates. They are acoelomates, that is they have no body cavity.
The Platyhelminthes express cephalisation, that is their nervous system is concentrated at one end.
What are the four classes of flat worms?
Cestoda,
Turbellaria,
Monogena,
Trematoda.
Give an example organism from the Turbellaria class.
Describe how this organism generates motion.
An example is the planaria.
Circular and longitudinal muscles contract to generate pedal waves that push the organism along the surface. Circular muscles contract just in advance of the wave while longitudinal muscles contract after the wave.
What is a disease caused by organisms of the class Trematoda? What is a name given to organisms of the Trematoda class? They can exist as what two structures?
Schistomiasis,
Flukes,
Sporocysts and mobile cercaria
When can Cestoda infection be serious?
Give an example of a Cestoda parasite that if ingested by humans can pose a serious health risk.
When the parasite is ingested by the wrong host the infection can be serious. Echinococcus granulosus is a small tapeworm that lives in dogs however if eaten by humans it develops into hydatid cyst.
Cestodes have what attachment organ?
What do they invest heavily in?
They have a scolex and invest heavily into reproduction.
Parasitic flatworms have free-swimming larval stages. What are the characteristics of these larvae?
Some larvae go into a resting stage and are reactivated by a chemical stimulus.
Some mimic the prey of their next host and some are chemically attracted by their host.
Describe what the monogenea are?
They are ectoparasites of fish, develop on the gills.
What are the nermetea? Describe their defining feature.
These are a phylum of invertebrate animals known as ribbon worms. All species of nermetea possess a proboscis which is used to capture the animal prey with venom. The sphincter muscle is used to evert the proboscis. The nermetea possess a rhynchocoel which the proboscis is in.
Compare both the Platyhelminthes and the nermetea.
The Platyhelminthes rely on diffusion for respiration while the nermetea rely on a circulatory system. Also flatworms have a single opening to the gut while the nermetea have a through gut. Both however are flat and accoelomate and move with muscles and cilia.
What sort or gut cavity do the Rotifera have?
What does their foot contain?
What helps in both feeding and locomotion?
They have a pseudocoelom.
Their foot contains adhesive glands which enable adhesion to the substrate, contributing to their locomotion.
Coronal cilia.
What phylum of invertebrate worms has a characteristic feature of segmentation?
What do some of these worms possess for locomotion?
The Annelida- they are bilaterally symmetrical, triploblastic, coelomate organisms.
They possess parapodia for locomotion.
What are the three classes of the Annelida?
The Polychaeta, oligochaeta and hirudinea.
Describe the Polychaeta class.
These possess parapodia for locomotion. They also possess a through gut with septum separating each section of the worm. Like molluscs, the Polychaeta have trochophore larvae.
