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الموضوع: Worms

  1. #1
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    افتراضي Worms










    Dirt eaters!

    Worms have a highly developed process for digesting food.

    Dead plant matter in the soil is the primary food of worms.

    Worms will tunnel in the soil and the soil is moved by the worm not only by their movement but also through their digestion.

    As worms tunnel they ingest the soil. This soil passes through two parts in their bodies.

    The parts are the crop and the gizzard.

    In these parts, soil is turned into a form that can be digested by the aid of digestive juices. Then it is passed to the intestine.

    Nutrients are absorbed in the intestine and anything that is not wanted will pass out the back end.

    The soil is passed out as a worm cast. Worm casts look like small, curled worms made of mud.

    Worms are among the most common of a all invertebrates! Despite their sometimes slimy nature, worms are a vital part of our ecology








    Despite the common myth that a worm split in two will eventually grow into two worms, they don't actually have that ability.
    Still, earthworms very resilient! An earthworm can survive being cut almost in half! The tail will die, but the head section will grow a new tail, thinner and sometimes a different color than the original.







    Worms

    A worm is an elongated soft-bodied invertebrate animal. The best-known is the earthworm, a member of phylum Annelida, but there are hundreds of thousands of different species that live in a wide variety of habitats other than soil.
    Originally the word referred to any creeping or a crawling animal of any kind or size, such as a serpent, caterpillar, snail, or the like (this old usage is preserved in the name "slow worm", actually a lizard). Later this definition was narrowed to the modern definition which still includes several different animal groups.
    Other invertebrate groups may be called worms, especially colloquially. Many insect larvae are called worms, such as the railroad worm, woodworm, glowworm, or bloodworms.
    Worms may also be called helminths, especially in medical or terminology when referring to parasitic worms, especially the Nematoda (roundworms) and Cestoda (tapeworms). Hence helminthology is the study of parasitic worms.
    When an animal, such as a dog, is said to have worms, it means that the dog is infested with parasitic worms, typically roundworm or tapeworm.
    Worm species differ in their abilities to move about on their own. Many species have bodies with no major muscles, and cannot move on their own. They must be moved by forces or other animals in their environment. Many species have bodies with major muscles, that let them move on their own. They are a type of muscular hydrostat.
    The fear of worms is known as 'scoleciphobia'.











    The flatworms (Platyhelminthes, Greek "platy"': flat; "helminth": worm) are a phylum of relatively simple soft-bodied invertebrate animals. Flatworms are found in marine, freshwater, and even damp terrestrial environments. Most are free-living forms, but many are parasitic on other animals. There are four classes: Trematoda (Flukes), Cestoda (Tapeworms), Monogenea, and Turbellaria.






    The flatworm’s cephalized soft body is ribbon-shaped, flattened from top to bottom, and bilaterally symmetric. Flatworms are the simplest triploblastic animals with organs. This means their organ systems form out of three germ layers: an outer ectoderm and an inner endoderm with a mesoderm between them.


    There is also no true body cavity except the gut. The interior of the body is filled with somewhat loosely spaced mesodermal tissue called parenchyma tissue. There is no true circulatory or respiratory system, but as a requirement of all organisms, flatworms do take in oxygen. Extracellular body fluids percolate between cells to help distribute nutrients, gases, and waste products.
    Depending on species and age, individuals can range in size from almost microscopic to over 20 m long (some tapeworms can attain this length).


    Flatworms respire at their integument; gasses diffuse directly across their moist outer surface. This type of system is called integumentary exchange. However, flatworms do have a bilateral nervous system; they are the simplest animals to have one. Two cordlike nerves branch repeatedly in an array resembling a ladder. The head end of some species even has a collection of ganglia acting as a rudimentary brain to integrate signals from sensory organs such as eyespots.

    Usually the digestive tract has one opening, so the animal can't feed, digest, and eliminate undigested particles of food simultaneously, as most animals with tubular guts can. Despite the simplicity of the digestive chamber, they are significantly more complex than cnidarians in that they possess numerous organs, and are therefore said to show an organ level or organization. Mesoderm allows for the development of these organs, and true muscle. Major sense organs are concentrated in the front end of the animals for species who possess these organs.
    Muscular contraction in the upper end of the gut causes a strong sucking force allowing flatworms to ingest their food and tear it into small bits. The gut is branched and extends throughout the body, functioning in both digestion and transport of food. Flatworms exhibit an undulating form of locomotion.

    Flatworm reproduction is hermaphroditic, meaning each individual produces eggs and sperm. When two flatworms mate, they exchange sperm so both become fertilized. They usually do not fertilize their own eggs. Turbellarians classified as planarians (usually freshwater, non-parasitic) can also reproduce asexually by transverse fission. The body constricts at the midsection, and the posterior end grips a substrate. After a few hours of tugging, the body rips apart at the constriction. Each half grows replacements of the missing pieces to form two whole flatworms. This also means that if one of these flatworms is cut in half, each half will regenerate into two separate fully-functioning flatworms.



    Brainless:

    The flatworm is the simplest animal with a nervous system in the world. Flatworms have two cordlike nerves that branch throughout their bodies, which look similar in ladders.

    The head end of the flatworm has ganglia, which acts like a very simple brain. The ganglia pass messages and signals down the nerve cords to the rest their body.





    Kingdom: Animalia
    SubKingdom: Eumetazoa
    Superphylum: Platyzoa
    Subphylum: Platyhelminthes






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  2. #2
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    افتراضي رد: Worms










    Earthworm is the common name for the larger members of the Oligochaeta in the phylum Annelida. Folk names for earthworm include "dew-worm", "night crawler" and "angleworm".





    Earthworms have a closed circulatory system. They have two main blood vessels that extend through the length of their body: a ventral blood vessel which leads the blood to the posterior end, and a dorsal blood vessel which leads to the anterior end. The dorsal vessel is contractile and pumps blood forward, where it is pumped into the ventral vessel by a series of "hearts" which vary in number in the different taxa. A typical lumbricid will have 5 pairs of hearts. The blood is distributed from the ventral vessel into capillaries on the body wall and other organs and into a vascular sinus in the gut wall where gases and nutrients are exchanged.


    One often sees earthworms come to the surface in large numbers after a rainstorm. There are two theories for this behavior:
    The first is that the waterlogged soil has insufficient oxygen for the worms, therefore, earthworms come to the surface to get the oxygen they need and breathe more easily. However, earthworms can survive underwater for several weeks if there is oxygen in it, so this theory is rejected by some.
    Secondly, the worms may be using the moist conditions on the surface to travel more quickly than they can underground, thus colonizing new areas more quickly. Since the relative humidity is higher during and after rain, they do not become dehydrated. This is a dangerous activity in the daytime, since earthworms die quickly when exposed to direct sunlight with its strong UV content, and are more vulnerable to predators such as birds.

    Earthworms are hermaphrodites (both female and male organs within the same individual) but generally cannot fertilize their own eggs. They have testes, seminal vesicles and male pores which produce, store and release the sperm, and ovaries and ovipores. However, they also have one or more pairs of spermathecae (depending on the species) that are internal sacs which receive and store sperm from the other worm in copulation. Copulation and reproduction are separate processes in earthworms. The mating pair overlap front ends ventrally and each exchanges sperm with the other. The cocoon, or egg case, is secreted by the clitellum, the external glandular band which is near the front of the worm, but behind the spermathecae. Some indefinite time after copulation, long after the worms have separated, the clitellum secretes the cocoon which forms a ring around the worm. The worm then backs out of the ring, and as it does so, injects its own eggs and the other worm's sperm into it. As the worm slips out, the ends of the cocoon seal to form a vaguely lemon-shaped incubator (cocoon) in which the embryonic worms develop. They emerge as small, but fully formed earthworms, except for sexual structures, which develop later. Some earthworm species are mostly parthenogenetic, in which case the male structures and spermathecae may become abnormal, or missing.



    Worm: invertebrate environmentalist.

    The earthworm (also called a night crawler) travels through the ground adding valuable nutrients to the soil.




    Kingdom: Animalia
    Phylum: Annelida
    Class: Clitellata
    Subclass: Oligochaeta
    Order: Haplotaxida
    Suborder: Lumbricina













    Leeches are annelids comprising the subclass Hirudinea. There are freshwater, terrestrial and marine leeches. Like earthworms, leeches are hermaphrodites. The medicinal leech, Hirudo medicinalis, which is native to Europe, and its congeners have been used for clinical bloodletting for thousands of years.



    All leech species are carnivorous and have evolved from detritus-eating earthworms/oligochaete ancestors. Some are predatory, feeding on a variety of invertebrates such as worms, snails, insect larvae, crustaceans, while a very few are blood-sucking leeches, feeding on the blood of vertebrates such as amphibians, reptiles, waterfowl, fish, and mammals. Given the opportunity, they will also feed on human blood. The most important predators on leeches are fish, aquatic insects, crayfish and other leeches.

    Haemophagic leeches attach to their hosts and remain there until they become full, at which point they fall off to digest. Leeches' bodies are composed of 34 segments. They all have a anterior (oral) sucker formed from the last six segments of their body, which is used to connect to a host for feeding, and are known to release an anaesthetic to remain unnoticed by the host. They use a combination of mucus and suction (caused by concentric muscles in those six segments) to stay attached and secrete an anti-clotting enzyme into the host's blood stream.
    Some species of leech will nurture their young, providing food, transport, and protection, which is unusual behavior in an invertebrate.
    The anatomy of medicinal leeches may look simple, but more details are found beyond the macro level. Externally, medicinal leeches tend to have a brown and red striped design on an olive colored background. These organisms have two suckers, one at each end, called the anterior and posterior sucker. The posterior is mainly used for leverage while the anterior sucker, consisting of the jaw and teeth, is where the feeding takes place. Medicinal leeches have three jaws that look like little saws, and on them are about 100 sharp teeth used to incise the host.

    Lots-a-Leech:

    In the tropics of South America, leeches live in dense populations of 50 per square yard.




    Kingdom: Animalia
    Phylum: Annelida
    Class: Clitellata
    Subclass: Hirudinea











    nematodes (Phylum Nematoda from Gr. nema, nematos "thread" + ode "like") are one of the most common phyla of animals, with over 20,000 different described species (over 15,000 are parasitic). They are ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in locations as diverse as Antarctica and oceanic trenches. Further, there are a great many parasitic forms, including pathogens in most plants and animals, humans included. Only the Arthropoda are more diverse.



    R
    oundworms are triploblastic protostomes with a complete digestive system. Roundworms have no circulatory or respiratory systems so they use diffusion to breathe and for circulation of substances around their body. They are thin and are round in cross section, though they are actually bilaterally symmetric. Nematodes are one of the simplest animal groups to have a complete digestive system, with a separate orifice for food intake and waste excretion, a pattern followed by all subsequent, more complex animals. The mouth is often surrounded by various flaps or projections used in feeding and sensation. The portion of the body past the anus or cloaca is called the "tail." The epidermis secretes a layered cuticle made of keratin that protects the body from drying out, from digestive juices, or from other harsh environments, as well as in some forms sporting projections such as cilia that aid in locomotion. Although this cuticle allows movement and shape changes via a hydrostatic skeletal system, it is very inelastic so does not allow the volume of the worm to increase. Therefore, as the worm grows, it has to moult and form new cuticles.



    Most free-living nematodes are microscopic, though a few parasitic forms can grow to several meters in length. There are no circular muscles, so the body can only undulate from side to side. Contact with solid objects is necessary for locomotion; its thrashing motions vary from mostly to completely ineffective at swimming.

    Roundworms generally eat bacteria, algae, fungi and protozoans, although some are filter feeders. Excretion is through a separate excretory pore.
    Reproduction is usually sexual. Males are usually smaller than females (often very much smaller) and often have a characteristically bent tail for holding the female for copulation. During copulation, one or more chitinized spicules move out of the cloaca and are inserted into genital pore of the female. Amoeboid sperm crawl along the spicule into the female worm.
    Eggs may be embryonated or unembryonated when passed by the female, meaning that their fertilized eggs may not yet be developed. In free-living roundworms, the eggs hatch into larva, which eventually grow into adults; in parasitic roundworms, the life cycle is often much more complicated.
    Roundworms have a simple nervous system, with a main nerve cord running along the ventral side. Sensory structures at the anterior end are called amphids, while sensory structures at the posterior end are called phasmids.
    Parasitic forms often have quite complicated life cycles, moving between several different hosts or locations in the host's body. Infection occurs variously by eating uncooked meat with larvae in it, by entrance into unprotected cuts or directly through the skin, by transfer via blood-sucking insects, and so forth.
    Nematodes commonly parasitic on humans include whipworms, hookworms, pinworms, ascarids, and filarids. The species Trichinella spiralis, commonly known as the trichina worm, occurs in rats, pigs, and humans, and is responsible for the disease trichinosis. Baylisascaris usually infests wild animals but can be deadly to humans as well. Haemonchus contortus is one of the most abundant infectious agents in sheep around the world, causing great economic damage to sheep farms. In contrast, entomopathogenic nematodes parasitize insects and are considered by humans to be beneficial.
    One form of nematode is entirely dependent upon the wasps which are the sole source of fig fertilization. They prey upon the wasps, riding them from the ripe fig of the wasp's birth to the fig flower of its death, where they kill the wasp, and their offspring await the birth of the next generation of wasps as the fig ripens.


    Why Breath When You Can Eat?

    Roundworms lack circulatory and respiratory systems, but they are among the simplest animals on earth to have a complete digestive system!




    Kingdom: Animalia
    Phylum: Nematoda










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  3. #3
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    افتراضي رد: Worms












    In biology, Cestoda is the class of parasitic flatworms, called tapeworms, that live in the digestive tracts of vertebrates as adults and often in the bodies of various animals as juveniles. In a tapeworm infection, adults absorb food predigested by the host, so the worms have no need for a digestive tract or a mouth. Large tapeworms are made almost entirely of reproductive structures with a small "head" for attachment. Symptoms vary widely, depending on the species causing the infection. Symptoms may include upper abdominal discomfort, diarrhea, and loss of appetite. However, infestations are usually asymptomatic. Worm segments or eggs may be found in the stool of an infected person.







    The largest tapeworms can be 80 feet or longer. Tapeworms harm their host by stealing vital nutrients, causing malnutrition and if left untreated can cause intestinal blockages.




    Adult tapeworms share a basic body plan. All have a scolex, sometimes colloquially referred to as the "head," a "neck," and one or more proglottids, which are sometimes called "segments," and which are the source of the name "tapeworm," because they look like a strip of tape. All cestodes have a nerve ring in the scolex with lateral trunks passing through the rest of the body.
    The Scolex or "head" of the worm attaches to the intestine of the definitive host. In some groups, the scolex is dominated by bothria, which are sometimes called "sucking grooves," and which function like suction cups. Other groups have hooks and suckers that aid in attachment. Cyclophyllid cestodes can be identified by the presence of four suckers on their scolex, though they may have other structures as well.
    While the scolex is often the most distinctive part of an adult tapeworm, it is often unavailable in a clinical setting, as it is inside the patient. Thus, identifying eggs and proglottids in feces is important.
    The Neck of a tapeworm is a relatively undifferentiated mass of cells that divide to form new proglottid "segments." This is where all growth in an adult tapeworm occurs.
    Posterior to the scolex, they have one or more proglottids that hold the reproductive structures. The sum of the proglottids is called a strobila. It is shaped thin like a strip of tape, which is the source of the common name tapeworm. Like some other flatworms, cestodes use flame cells (protonephridia) for excretion, which are located in proglottids.
    Mature or gravid proglottids are released from the mature tapeworm and leave the host in its feces.

    Because each proglottid can reproduce independently, it has been suggested by some biologists that each should be considered a single organism, and that the tapeworm is actually a colony of proglottids.
    Tapeworms can be effectively cured with antiparasitic (antihelmintic) medication once it is detected. Current Centers for Disease Control and Prevention guidelines for treatment is a prescription drug called praziquantel. The medication causes the tapeworm to dissolve within the intestines. Praziquantel is generally well tolerated. Sometimes more than one treatment is necessary.


    Uninvited Guests!

    Tapeworms can inhabit the intestines of humans and other animals, including cats, dogs and livestock. With suckers and hocks on their heads, tapeworms attach themselves along the intestinal walls of these sorry animals.

    They can live a fairly long time and will often continue to grow. The fish tapeworm may very well be the largest tapeworm, capable of reaching over 60 feet. Some even claim that tapeworms are capable of growing to over 100 feet.




    Kingdom: Animalia
    Phylum: Platyhelminthes
    Class: Cestoda









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