Question

Phylum Annelida Sipuncula common name(s) of organisms chaetae parapodia (+/-) structures and modes of locomotion structures and ways that they feed Structures/modes of defense internal/external fertilization, reproduction Synapomorphies

Answer 1

Annelida

•common name(s) of oganisms:- ringed worms or segmented worms

•chaetae:- epidermal extracellular structures that are in general clearly visible from the exterior. Their structure is highly diverse, especially within the Polychaeta, and each species shows a specific pattern of chaetae.

•parapodia(+/-):- In annelids, parapodia are paired, un-jointed lateral outgrowths that bear the chaetae. In several groups of sea snails and sea slugs, 'parapodium' refers to lateral fleshy protrusions.

•Structures and modes of locomotion:- The basic features of locomotion in annelids are most easily observed in the earthworm because it lacks appendages and parapodia. Movement involves extending the body, anchoring it to a surface with setae, and contracting body muscles. The setae are retracted during the circular contraction period.

•Structures and ways that they feed:- The digestive system of annelids can be explained as a "tube within a tube body plan." An earthworm obtains its food by feeding on live and dead organic matter in soil. When food enters the earthworm's mouth, its pharynx pumps the food into its esophagus where it is then passed into the gizzard.

•Structures/modes of defense:- The setae stick to dirt and the worm then contracts its body to force itself through soil. The worm also secretes a mucus that helps it slide through dirt more quickly. In fact, to escape the cold of winter or an eager predator, the earthworm can burrow dozens of feet below the surface.

•internal/external fertilization, reproduction:- Once the cocoon is ready, they deposit their eggs and sperm, stored from the mating process, into the cocoon where fertilization takes place. In this way, oligochaetes have external fertilization. Once they are fertilized, the eggs are then deposited into the cocoon. Therefore, leeches have internal fertilization.

•Synapomorphies:- They have a long and segmented body. Annelids are bilaterally symmetrical. They are triploblastic. Also, they exhibit organ system grade of organisation, showing organ differentiation.

Sipuncula

•Common name(s) of organisms:- sipunculid worms or peanut worms

•chaetae:- Unsegmented marine worms lacking chaetae. The body is divided into a trunk and a slender, retractable introvert. The mouth is located at the tip of the introvert and in some taxa is surrounded by tentacles.

•Parapodia(+/-):- The body may be divided into a head and a trunk region; a distinct prostomium and a pygidium are lacking. The head carries a ventral mouth opening and a large brain and is not clearly separated posteriorly from the uniform trunk or anteriorly from the elongated rostrum, which makes up 20–30% of the total body length.

•Structures and modes of locomotion:- Most peanut worms quickly withdraw their introverts when disturbed and avoid light by retreating into their burrows or rock crevices. They use their introvert hooks and muscles to pull their bodies forward. Swimming is not common and is accomplished by simply jerking the body trunk in all directions.

•Structures and ways that they feed:- Most sipunculans are deposit feeders, employing a number of different methods to obtain their foods. Those living in burrows extend their tentacles over the surface of the sediment. Food particles get trapped in mucous secretions and the beating of cilia transport the particles to the mouth.

•Structures/modes of defense:- In neither cellular nor humoral immune re sponses has an immunological memory been demonstrated. Thus the sipunculan defense system is relatively simple and as such is of interest as a model in the elucidation of the phylogeny of invertebrate and vertebrate defense mechanisms. The role of ciliated urns in defense is considered later.

•internal/external fertilization, reproduction:- The sexes are identical to each other, and their reproductive organs are present only while they reproduce. Eggs and sperm are released into the coelom, where they are collected by the kidneylike organs and expelled into the water. Fertilization takes place outside of the body.

•Synapomorphies:- 1)Bilaterally symmetrical and vermiform. 3)Body cavity is a true coelom. 4)Body possesses a U shaped gut with a mouth and anus. 5)Body covered in a rubbery cuticle.