Example of nematoda *
a)filarial worm
b)planaria
c)hydra
d)jelly fish
Answers
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A}.FILARIAL WORM :—
Filarial worm, any of a group of parasitic worms of the family Filariidae (phylum Nematoda) that usually require two hosts, an arthropod (the intermediate host) and a vertebrate (the primary host), to complete the life cycle. The larval phase occurs within the body of a biting insect. The mature (reproductive) phase occurs in the body of an animal bitten by the insect.
The female worm produces large numbers of microscopic, active embryos called microfilariae that pass into the bloodstream of the primary host. The microfilariae may then enter the body of an insect as the insect bites the infected animal. The microfilariae grow into larvae in the insect’s muscles and may then be passed to the primary host when the insect bites an animal. The larvae reach adulthood within the vertebrate host, and the cycle repeats. In mammals filarial worms cause a group of infectious disorders including heartworm, elephantiasis, and river blindness. These disorders are known collectively as filariasis. At present, more than 200 million people are infected with filarial parasites.
B}.PLANARIA:—
Platyhelminthes are commonly known as flatworms or tapeworms. They are a group of soft-bodied invertebrate animals. As a matter of fact, there are around 20,000 species of these animals. A few of these live as parasites on humans and other animals. Furthermore, it is because of this parasitic nature that they do cause some amount of trouble for the host animal. A few species belonging to this phylum can be a major cause of certain diseases. For example, Schistosomiasis, or bilharzia or bilharziasis, is a disease caused by these parasitic flatworms. They belong to the family Schistosomatidae.
The most distinguishing feature of these invertebrates is their flat body. As the body does not have any cavity, they are flat. The body is also not segmented and they do not have specialized systems. Around eighty percent of the flatworms are parasitic in nature, while a few free-form flatworms are also present. The free-living forms are scavengers or predators. The parasitic species feed on the tissues of the host organism in which they live.
The animals in this phylum have a diverse range in size. Some are microscopic, while a few go up to two feet long. They are also hermaphrodites, which mean that both the sexes are present in the same organism
D}.JELLY FISH :—
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, which produces planula larva that disperse widely and enter a sedentary polyp phase before reaching sexual maturity.Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the "true jellyfish") are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal group.[2]
Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomae order are pressed and salted to remove excess water. Australian researchers have descibed them as a "perfect food", sustainable, and protein-rich but relatively low-calorie.[3]
They are also used in research, where the green fluorescent protein used by some species to cause bioluminescence has been adapted as a fluorescent marker for genes inserted into other cells or organisms.
The stinging cells used by jellyfish to subdue their prey can injure humans. Many thousands of swimmers are stung every year, with effects ranging from mild discomfort to serious injury or even death; small box jellyfish are responsible for many of these deaths. When conditions are favourable, jellyfish can form vast swarms, which can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea.