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Comparison in Locomotion of Planarians and Earthworms

Bibliography

  • in class notes*
  • http://www.ucmp.berkeley.edu/platyhelminthes/platyhelminthes.html
  • http://www.earthlife.net/inverts/annelida.html
  • http://userwww.sfsu.edu/biol240/labs/lab_17hydrostaticsk/pages/nematode.html
  • http://www.ehow.com/about_6533407_cephalization-earthworms.html
  • http://www.ehow.com/about_6533407_cephalization-earthworms.html
  • http://www.biology-questions-and-answers.com/nematoda.html
  • http://www.cdc.gov/parasites/taeniasis/biology.html
  • http://www.biologycorner.com/bio1/notes_flatworms.html
  • http://www.jstor.org/stable/83790?seq=1#page_scan_tab_contents
  • http://www.biology.ualberta.ca/courses.hp/zool250/animations/Earthworm.swf

In some ways, the locomotion of these two species is similar, other parts are a bit different. Obviously some of the ideas in the pictures above give a basic idea of how they both get around. For the earth worm, while some parts of it's body act as anchors, it pushes against these parts while squeezing the anterior end into the soil. After a pull forward the anterior end expands and then becomes the newanchors as it pulls the other segments forward through the soil. What parts are responsible for creating these wave like movements are the hydrostatic skeleton and the circular and longitudinal muscles. As for the planarians, their mobility takes place both in and out of water. For the in water movement, true swimming movements are used to swim through the water, also known as undulation(up and down motion...similar to that of waves). Over a supporting surface it seems like planarians move at ease and with no effort. This is suspected be done by the constant beating of ventral cilia. The last form of movement for planarians is crawling, which is simply made possible by the clear muscular constrictions it makes.

Sexual Reproduction in Earthworms

Body Cavities found in Worms

Earthworms are hermaphroditic. They reproduce through cross fertilization. The reproduction for earthworms though is actually a bit complex. Even though they are hermaphroditic and most of this kind can reproduce asexually, earthworms still have to engage in sexual intercourse for the purpose that they must mix together their gametes.

Free-living digestive system difference from parasitic worm

Flat worms are carnivores or scavengers. Unlike parasitic worms, the have a complete digestive cavity. They however do need it, because the material they consume is not already digested, unlike what the parasitic worms digest.

Parasitic worms feed on blood, tissue fluid, and pieces of cell within the host they are living in. The majority of parasitic worms don't have and don't really particularly need a complete digestive system. The reason for this is what they directly absorb from the host is digested material.

Comparison of Worm Phyla

By:Seth Rathjen

May 4th, 2015

Block D

Phylum plathelminthes

Phylum Annelida

Phylum Nematoda

As mentioned before, flat worms are acoelmates, which means they do not have a coelom. Other than a gut cavity, flat worms do not contain any other body cavities. When it comes to expelling waste from the body, since they do not have an anus, all waste must be transferred out through the same opening that takes in food. Their flat bodies are made possible by the lack of body cavities within them. They do also possess a gastrovascular cavity and a primitive organ system for digestion and excretion.

Annelids have a true coelom, which allows the to have muscular layers and also a true organ system. The body cavity is often divided by internal septa. This class, having a true coelom, do not have to expel waste and take food in from the same opening, instead they have a separate mouth and anus.

Nematodes are pseudocoelomates. This allows them to have a complete one way digestive tube, which implies that they have a mouth and anus that are separate from each other. Nematodes possess a flattened gut and other reproductive organs. Their reproductive systems are developed. Through a pore is how they excrete their waste.

Different Worm Phyla

Pylum Platyhelminthes

Phylum platyhelminthes(also known as The flat worms) is made up of 4 classes, which are: Trematoda(flukes), Cestoda(tapeworms), Monogenea, and Turbellaria. The characteristics that help identify an organism to be under Phylum Platyhelminthes are that they are acoelomates, they exhibit bilateral symmetry, take in oxygen by integumentary exchange, and use undalation as a form of motion as they are motile. They have multiple ways of reproduction: sexually or asexually by regeneration, as they are hermaphroditic. They can be found in a few types of habitats such as marine, freshwater, and terrestrial.

The life cycle of a Tapeworm

Phylum Annelida

Phylum Nematoda

Phylum nematoda(also known as The round worms)are a class which contain three parasitic species: whipworms, hookworms, and ascarids. There are some specific characteristics that can help classify nematodes. They all have a complete one way digestive tube, which is able to happen since they are pseudocelomates. The only form of reproduction is through sexual reproduction, as nematodes are separate sexes.

The last phyla that worms are broken into are Phylum annelida(also known as The segmented worms). This phyla's major classes include class oligochaeta(the earth worms), class hirudinea(the leeches), and class polycheata(the marine worms. Some of the specific characteristics that are shown to help identify this class are: they have a true coelom, they are segmented into different compartments by septa, they can reproduce both sexually and asexually(by regeneration and fission), as they are hermaphroditic. Terrestrial, fresh water, and marine environments is where species of this phyla can be found.

Cephalization in different Worms

The life cycle of a tapeworm begins when feces containing eggs or gravid is passed on into the environment. Next pigs or humans will ingest the embryonated eggs. Following the ingestion of the eggs, oncospheres hatch and penetrate the intestinal wall. After they circulate to the musculature in either the pig or human. Most of the time, humans would not have ingested the infection before acquiring it from an animal host, like a pig. With that being said, by ingesting raw or undercooked meat from an infected animal host, humans will receive this infection. In a human, an adult tapeworm can last two years, after reaching adult from developing for over two months from the cysticercus. By their scolex, adults attach to the small intestine. Once the tape worm produce proglottids, which eventually mature to eggs, the human passes the eggs in their stool and the cycle then again repeats itself.

Nematoda

  • Nematodes exhibit cephalization with a ventral nerve chord

Platyhelminthes

  • flat worms have a bilateral nervous system. Cephalization is at the head end. Eye spots sensitive to light is exhibited by some species.

Annelida

  • the nervous systems in annelids includes a ventral nerve chord and cephalization with a primitive brain. The nervous system also possess a anterior nerve ring and a ganglia. It is easy to say that earthworms have no cephalization since the nervous system is distributed throughout a segmented body along a nerve chord, but there is a large ganglion in this nervous system that does not just act as a simple brain. It is located in the anterior portion of an earthworms anatomy. They do not however have any defined sensory organs. Compared to flat worms and nematodes, cephalization in annelids is considered much more outstanding.
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