British Prosobranch Molluscs: Their Functional Anatomy and

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In a majority of chordates, the notochord is replaced by a series of interlocking bones — vertebrae — during early development. Reproduction and larval ecology of marine bottom invertebrates. Once achieved, the selective ad- vantages of a multilayered body plan may have led to a gradual early metazoan diversification in the late Precambrian, and then to a more rapid radiation of ani- mals in the early Cambrian.* Molecular data also support the hypothesis that metazoans arose from choanoflagellates (or from a com- mon ancestor), a protist phylum that probably originat- ed over a billion years ago.

Platyhelminthes and Nemertinea, Volume 3, Microscopic

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Note that searching for common (vernacular) names may not yield the expected results. The gas exchange organs of xiphosurans are unique among the chelicerates. ANIMAL ARCHITECTURE AND THE BAUPLAN CONCEPT 69UNCORRECTED PAGE PROOFS Figure 3.22 Water expulsion vesicles (WEV), or “con- tractile vacuoles.” (A) An ameba with a single WEV. Polyps are tubular structures with an outer epidermis, an inner gut sac (coelenteron) lined with gastrodermis, and a layer of jelly-like mesoglea or mesenchyme in be- tween.

Pollution Ecology of Freshwater Invertebrates (Water

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Unlike the Cnidaria, ctenophores have true subepider- mal (mesenchymal) musculature and acetylcholine/ cholinesterase nerve impulse transmission. They are known from all oceans but are especially abundant in tropical and sub- tropical waters. If we start with a generalized, rather homono- mous arthropod prototype with a fairly high number of segments, and with paired appendages on each of those segments, we can set the stage for just such a dramatic diversification.

Nervous System Regeneration in the Invertebrates

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The hatching forms of some of these nemerteans resemble macrosto- mids (Figure 11.14). In any case, the evi- dence is strong that the Metazoa had their origin in a flagella-bearing protist. Other comparisons between the vestimentiferans and the other beard worms are noted in Box 13B. These collections provide the basis for understanding the ocean's biodiversity, the evolutionary history of life on Earth, and the rates and characteristics of climate change. PHYLUM OPALINIDA: Opalinids; previously classified in the old phylum “Sarcomastigophora” (e.g., Cepedea, Opalina, Pro- topalina).

Bionomics And Identification Of Rotylenchus Species

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Our cladogram is only one of many possible sets of hypotheses, and like all hypotheses and ideas in biol- ogy, it is certainly open to a host of challenges.‡ You will notice that we have not included three “mesozoan” phyla (Monoblastozoa, Rhombozoa, Ortho- nectida) in our analysis, simply because too little is known about these odd groups to code them into our data set. In their retention of these ancestral features, sipunculans and echiurans have remained as largely infaunal burrowers, using the large trunk coelom for peristalsis.

HANDBOOK OF GENETICS [5 VOLUME SET].

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These two forms of calcium are chemically identical, but they crystallize differently and can be identified by microscopic examination of sections of the shell. Acorn worms fragment small pieces from the trunk, and each one is able to grow into a new individual. Behavioral hypothermia and sur- vival of hypoxic protozoans Paramecium caudatum. Searle in 1913 and thereafter dramatically slowed her publication output, apparently due to having to care for her handicapped son born in 1914.

The Nepticulidae and Opostegidae (Lepidoptera) of North and

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Jointed legs are a synapomorphy of the Arthropoda, but within the arthropods jointed legs are a symplesiomorphy. Of course, it is better not to use a character at all than to use it, but score it incorrectly. In fact, in many groups this type of system has assumed a variety of functions be- yond circulation. Orphan worm finds a home: Buddenbrockia is a Myxozoan. In future years, ongoing taxonomic and biogeographical studies are expected to yield additional specimens, including newly reported non-native species, tissue samples, and taxa from remote regions of British Columbia.

The Irish Pearl

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Some syconoid sponges appear radial- ly symmetrical, but their complex internal organization is largely asymmetrical. Supplemental Photo Collection: This collection of over 900 photographs depicts organisms that span the entire range of phyla covered in the textbook. You will have to look the information up online. Separate letters (or groups of letters) have been added. These cells were also suggested to function in the synthesis and secretion of a protein product. The head may bear various sensory structures, most notably eyes, statocysts, and tentacles.

The Trematoda

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In the latter phenomenon, the pedal disc spreads, and the anemone simply moves away, leav- ing behind small fragments from the disc, each of which develops into a young sea anemone. Each link not only has the pieces but also the information (or links to the information) that you need. Variability in the reproductive cycle of Stichopus mollis (Echinodermata: Holothuroidea). Hickman's early research concentrated on renal physiology in fish, but he later focused on the fauna of the Galapagos Islands.

Manual of Medical Entomology

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In both hexapods and crustaceans, longitudinal connectives of the CNS originate in the segmental neu- rons, whereas in myriapods they derive from neurons in the cerebral ganglia that send their axons posteriorly to set up long parallel connectives. Dahl proposed the class Maxillopoda for these taxa. Are Aschelminthes pseudocoelomates or acoelmates. The study was published in the online edition of the journal Evolution. Paired sacciform gonads lie in the trunk, outside the peritoneum; they are often very elongate in the acorn worms.