Which phylum has pseudocoelomates

Which of the following phyla is Pseudocoelomate phylum? What is the largest phylum of Pseudocoelomates? The Pseudocoelomates or Aschelmiths are a heterogenous assemblage of marine and freshwater animals, with the Nematoda forming the largest phyla with over 12, species. Arthropod, phylum Arthropoda , any member of the phylum Arthropoda, the largest phylum in the animal kingdom, which includes such familiar forms as lobsters, crabs, spiders, mites, insects, centipedes, and millipedes.

About 84 percent of all known species of animals are members of this phylum. The pseudocoelomates include the nematodes, rotifers, gastrotrichs, and introverts. Some members of some other phyla are also, strictly speaking, pseudocoelomate. These four phyla of tiny body size many species no larger than the bigger protozoans are placed together in part because they…. This phylum consists of leeches, polychaete worms and earthworms.

The presence or absence of Coelom is a feature which is used to classify animals. Pseudocoelomates derive their body cavity partly from endoderm tissue and partly from mesoderm. Roundworms and not Annelids are pseudocoelomates. Type of Coelom: Animals in Mollusca are coelomates.

Note: In acoelomate, Coelom is absent. Pseudocoelomate animals have a pseudocoelom. They have a body cavity but it is not lined with mesodermal cells. These animals are known as pseudocoelomates. A pseudocoelom is a body cavity that lies between mesodermal and endodermal tissue and is, therefore, not completely surrounded by mesodermal tissue. The consensus view among taxonomists has long been that the sponges Porifera represent the oldest surviving animal phylum. So it is the largest kingdom in the animal kingdom.

The organisms that have a coelom have a complex structure and higher in taxonomic order, and are known as Coelomates. Human beings are Eucoelomates and that means they have a true coelom. Lying inner to the mesodermal wall, coelom surrounds the body track of humans and is divided into three parts.

For example, animals belonging to Class Insecta have three distinct segments: the head, the thorax sometimes grouped together with the head as the cephalothorax , and the abdomen.

The rhinoceros beetle Fig. Typically, these different body regions have distinct functions and often contain various types of jointed appendages. Jointed appendages afford the animal with a greater degree of movement. In addition to locomotion, the appendages may be adapted for other functions e. A Rhinoceros Beetle. An arthropod member of the Insecta Click image to enlarge. Some jointed appendages, such as the swimming appendages of this candy cane shrimp Fig. A Candy Cane Shrimp.

An arthropod that is a crustacean. Figure 24 shows the body segmentation cephalothorax and abdomen and specialized appendages of a representative arthropod, a lobster. A Lobster. The arthropods are traditionally divided into five subgroups or subphyla: trilobites an exclusively marine group whose members all are extinct; the fossil record indicates that they were once the dominant subgroup , chelicerates, myriapods, crustaceans, and hexapods.

As is the case for many groups of organisms, new molecular datasets are providing additional information on relationships. The groups presented here may change as future molecular data provide a clearer insight into arthropod relationships. A Scorpion. An arthropod that is a chelicerate, and also an arachnid. The majority of modern chelicerates e. As with the trilobites, most of the marine chelicerates are extinct, even though a few marine members e.

The arachnids Figs 25 and 26 are best distinguished by their claw-like feeding appendages chelicerae , from which this subgroup gets its name. Another characteristic of the chelicerates is the presence of two body segments a cephalothorax and an abdomen.

The cephalothorax has six pairs of appendages, including four pairs of walking legs, one pair of chelicerae, and one pair of pedipalps, which have either a feeding or sensory function. Chelicerates lack antennae and have simple eyes. The crustaceans make up the second largest arthropod subgroup.

Extant species are mainly aquatic animals, although some terrestrial species e. Animals in this class include crabs, lobsters, crayfish and shrimp, and they are the only arthropods with two pairs of antennae. Their appendages have two branches at the tips see the crab claw in Fig. Segmentation is obvious and extensive in these animals. In contrast to the chelicerates, crustaceans have jaw-like mandibles and compound eyes. The fiddler crab Fig. The myriapods include the centipedes and millipedes.

All of the members of this group are terrestrial, and they have long bodies with many segments, although the segments lack specialization. They have a single pair of antennae and usually have simple eyes Fig.

A Fiddler Crab. A millipede. An arthropod that is a myriapod. The hexapods have mandibles and compound eyes as do the crustaceans. Uniquely, they have only one pair of sensory antennae and their appendages are unbranched or uniramous the name unirames is sometimes used for this group.

The hexapods include Class Insecta, with its twenty-six described orders. Insects first appear in the fossil record about million years ago. Insects have three distinct segments head, thorax, and abdomen.

Two pairs of wings and three pairs of legs are typical. Scientists who study insects are called entomologists. Class Insecta is the largest class in the phylum Arthropoda, and their diversity is unmatched in the animal kingdom. Flight evolved independently in this group what other types of animals can fly?

Why would flight be correlated with species diversity? Several respresentative hexapods. A cricket B. A solitary bee C. A leafhopper D. A butterfly. This tutorial continued our discussion of the bilateria branch of the kingdom Animalia.

When you think about this character bilateral symmetry , keep in mind that it is observed in animals that actively move through their environment. Bilaterally symmetrical animals not only have a single plane of symmetry, but their sensory and cephalic areas are usually displaced toward the anterior end of the animal. There are two lineages of pseudocoelomates.

The nematodes include free-living species as well as many species that are parasites of mammals, while the mostly free-living rotifers are an important part of the zooplankton.

The mollucs are very diverse morphologically, ranging from the shell-less slugs to the bivalves with two large shells that are joined at a hinge.

Some cephalopods show remarkable levels of intelligence for an invertebrate. The annelids show true segmentation, although their segments do not show extensive specialization. Arthropods fall into one of five subphyla.

Segmentation, and subsequent specialization, is one of the hallmarks of each of these five groups. Trilobites were a very successful group that became extinct about million years ago. Although these animals were segmented, they had very little diversification in their segments.

The chelicerates include spiders. These animals have two major body segments: the cephalothorax and the abdomen. Their appendages are all clustered in the cephalothorax. Typically there are six pairs of appendages.

These include the chelicerae, which are involved in feeding, and the pedipalps, which may have a feeding function. The remaining appendages are walking legs. The members of this group do not have antennae but do have simple eyes. Crustaceans, the second largest extant subgroup, include mostly aquatic species, however, there are some terrestrial species.

They have two pairs of sensory antennae, jaw-like mandibles, and compound eyes. The millipedes and centipedes are myriapods. They have many unspecialized segments, and many pairs of legs. The usually have one pair of antennae and simple eyes. The body has a single opening, the hypostome, surrounded by sensory tentacles equipped with either nematocysts or colloblasts to capture mostly planktonic prey.

The flatworms are acoelomate organisms that include free-living and parasitic forms. The nematodes, or roundworms, possess a pseudocoelom and consist of both free-living and parasitic forms. The bodies of the organisms belonging to this group are bilaterally symmetrical and triploblastic.

These organisms have tissues but no real organs. They have body cavity or a pseudocoelom in their body. Examples of animals belonging to this group are Ascaris, Wuchereria.

Annelids have two sets of muscles that are used to contract and elongate the body. Annelid worms are excellent examples of a hydrostatic skeleton in the form of a coelom in action. In earthworms , the hydrostatic skeleton or coelom is surrounded by sheaths of longitudinal and circular muscles.

Those with two embryonic germ layers are diploblastic ; those with three embryonic germ layers are triploblastic. Are nematodes diploblastic or triploblastic animals? Just like platyhelminthes, nematodes are triploblastic organisms, meaning that they have three germ layers the ectoderm, mesoderm and endoderm.

All complex animals have a true coelom, including the mollusks , annelids , arthropods , echinoderms and chordates. They have a true coelom that is completely lined by the mesoderm layer. The internal organs in a true coelom are more complex, and they are held in place by mesentaries. Finally, the arthropods , one of the most successful taxonomic groups on the planet, are coelomate organisms with a hard exoskeleton and jointed appendages.

In coelomates, body space is a true coelom enclosed by mesoderm on both sides. Remaining phyla of bilateria, from annelida to arthropoda are coelomates. Molluses and insects are coelomates while flatworms are acoelomates.

So, the correct answer is 'Round worms are pseudocoelomates. The cockroach is a coelomate animal but its coelom is greatly reduced in the adults. The original coelom is represented by the cavities of the reproductive organs.

The space between the body wall and gut represents the haemocoel which is filled with blood. Hence true coelom of Cockroach occurs around the gonads.