What is phylum annelida - segmented worms, Biology

Assignment Help:

What is Phylum Annelida - Segmented Worms?

Members of this Phylum are commonly known as the segmented worms. The body of a segmented worm is made of many individual ring-like segments. The Latin word for "little ring" is "annellus," hence the name "Annelida."

Segmentation here and in the arthropods represents a distinct and significant departure from the Mollusk body plan. In terms of evolution, segmentation provides a built-in redundancy of systems. The embryo of segmented animals can develop identical segments, so that if one segment becomes damaged, other segments can take over the damaged segment's functions. Body movement is also improved, because many independent segments offer a wider range of motion than one segment by itself.

Most of the segments that form the body of annelids are for the most part identical. The anterior segments are modified to perform specific functions, depending on the type of annelid. Special functions found here would include the brain, light-sensitive eyes or antennae. Each individual segment is compartmentalized by cross walls called septa (singular: septum).

Even though each segment is partitioned, the digestive system, the nervous system and blood vessels extend along the length of the annelid body. The digestive system takes full advantage of a coelom and reflects the segmentation, in that it is divided into specialized parts called the pharynx, esophagus, crop, gizzard, and intestine. Each segment contains a pair of ganglia, or cluster of nerve cells that connect to a ventral nerve cord, providing coordination. Annelids have closed circulatory systems that use small muscular "hearts" toward the anterior of the body. A pair of organs called nephridia in each segment carries out waste excretion.

Annelids have two types of muscles. One muscle group runs longitudinally along the body from the anterior to the posterior. These muscles serve to shorten the length of the worm when they contract. The other muscle groups circle the cylindrical body rings. These circular muscles make the worm smaller in diameter when they contract. The two groups of muscles work together to move the worm's body.

Annelids can exchange gases with their surrounding medium either through gill-like structures, or directly through their skin. The digestive tracts of annelids is a complete tube that opens through a mouth and empties through an anus at the rear.

There are three classes of Annelids: Oligochaeta, Hirudinea, and the Polychaeta.


Related Discussions:- What is phylum annelida - segmented worms

Difference between hazard and disaster, 1.      Hazard Is An Extreme Event ...

1.      Hazard Is An Extreme Event Whereas Disaster Is Its Consequence. 2.      A hazard can occur without human interference but it may become a disaster on account of careless

Why is the dietary obtainment of iodine so important, Why is the dietary ob...

Why is the dietary obtainment of iodine so important for thyroid functioning? The obtainment of iodine from the diet is significant for the thyroid because this chemical elemen

What is hydrogenqted fat, Q. What is Hydrogenqted Fat? All vanaspati pr...

Q. What is Hydrogenqted Fat? All vanaspati preparations are the result of hydrogenation of oils, where unsaturated fat is converted to saturated fat for its favour and long she

What are the advantages of yoga, What are the advantages of Yoga Yoga h...

What are the advantages of Yoga Yoga has been derived from the Sanskrit word Yuj which means union. It is popular since ancient times. It is also one of the means to maintain f

Cytological approach, Write an essay on cytological approach in taxonomy.

Write an essay on cytological approach in taxonomy.

Evaluate the claim of sodium-dependent vitamin C transporter, Problem-solvi...

Problem-solving essay. Maximum 800 words. Deadline 12th of March. Show me you understand what this essay requires

What is the probability that their child have alkaptonuria, A recently marr...

A recently married man and woman discover that each had an uncle with alkaptonuria, otherwise known as "black urine disease," a rare disease caused by an auto somal recessive allel

Fragmentation, Normal 0 false false false EN-IN X-NON...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Leishmaniasis, Leishmaniasis Leishmaniasis is a group of disease cause...

Leishmaniasis Leishmaniasis is a group of disease caused by protozoa of the group Leishmania, and are transmitted to man by the bite of female sandfly (Phlebotomus). Three typ

Experiment of a study of broken rock, A study of broken rock Break open...

A study of broken rock Break open several rock specimens. Compare the appearance of freshly broken surfaces with the Heather-worn outside of the rock. The rocks may be safely b

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd