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Topic: Bilaterally symmetrical

In the News (Thu 24 Apr 14)

  development of radial and biradial symmetry: The evolution of bilaterality, The American Zoologist - Find Articles
Perhaps the most profound change that may have occurred in the Metazoa is the appearance of bilaterally symmetrical forms from a presumably radially symmetrical ancestor.
The symmetry properties of bilaterally symmetrical larval and adult metazoans are generally set up during the cleavage period while most "radially" symmetrical cnidarians do not display a stereotyped cleavage program.
Bilaterally symmetrical organisms, the Bilateria, are likely to have evolved from some kind of ancestor with a cnidarian- or ctenophore-like level of body construction, as members of the so-called "Radiata" (Morris, 1993; Wainright et al., 1993; Brusca and Brusca, 1990).
www.findarticles.com /p/articles/mi_qa3746/is_199809/ai_n8812269   (825 words)

  Degenerative Disorders of the Central Nervous System
These lesions were seen as foci of bilateral and symmetrical degeneration in the basal nuclei (caudate nucleus, putamen, and claustrum), midbrain, pons and medulla, in addition to multifocal lesions at the base of sulci in the cerebral cortex and in the gray matter of cerebellar folia in the ventral vermis.
Bilateral and symmetrical foci of malacia were seen grossly in the nuclei of the cerebellum and brainstem (caudal colliculi, lateral vestibular nuclei, lateral cuneate nuclei, and lateral reticular nuclei) and the gray matter of the spinal cord associated with cervical and lumbosacral intumescences.
Microscopically, there is extensive bilaterally symmetrical degeneration of the spinal cord white matter, particularly in the superficial dorsal areas of the lateral funiculi, the fasciculus gracilis of each dorsal funiculus, and the ventral funiculus adjacent to the ventral median fissure.
www.ivis.org /special_books/Braund/braund19/chapter_frm.asp?LA=1   (15382 words)

 KINGDOM ANIMALIA   (Site not responding. Last check: 2007-10-19)
Bilateral symmetry occurs when an organism can be cut into two equal halves by cutting from top to bottom along the long axis of the body.
Nematodes are bilaterally symmetrical, unsegmented, triploblastic, pseudocoelomate animals with a tubular gut with a distinct mouth and anus.
Arthropods are bilaterally symmetrical, triploblastic, coleomate protostomes with regional segmentation (this means parts of the bodies are segmented).
www.colorado.edu /epob/epob1220moreno/ANIMALIA_I.htm   (1706 words)

 Medial Neuroanatomy
The uvula is symmetric and the tongue protruded on the midline.
Bilateral basilar crackles were present in the lungs on inspiration and bilateral jugular venous distention was demonstrable in the neck.
The palate elevated symmetrically and the tongue protruded on the midline.
faculty.une.edu /com/fwillard/Cases/CaseWorkbook.htm   (17316 words)

 Bilateria - Wikipedia, the free encyclopedia
For the most part, Bilateria have bodies that develop from three different germ layers, called the endoderm, mesoderm, and ectoderm.
Nearly all are bilaterally symmetrical, or approximately so.
The most notable exception is the echinoderms, which are radially symmetrical as adults, but are bilaterally symmetrical as larvae.
en.wikipedia.org /wiki/Bilateria   (233 words)

 Introduction to the Invertebrate Laboratory   (Site not responding. Last check: 2007-10-19)
A radially symmetrical animal usually has a mouth at or near the center of one surface, which is consequently known as the oral surface (Fig 1).
Bilaterally symmetrical animals typically are mobile (or derived from mobile ancestors) and have a preferred orientation for meeting and moving through their environment.
The axis of symmetry of a bilaterally symmetrical animal is the anterior/posterior axis.
www.lander.edu /RSFOX/310introLab.html   (4183 words)

 Ad Astra: The Soos'Aer
The annulates are a phylum of the sub-kingdom Elysii Animalia Radiata (radially symmetrical Elysian animals) characterised by a ring-shaped skull with sets of articulated bones attached to both anterior and posterior sides.
The dominant animals were soft-bodied radially symmetrical families and bilaterally symmetrical segmented creatures similar to the largest predators of Terra's early Cambrian.
The bilaterally symmetrical phyla dominated the warm shallows, and the Radiata were the dominant animals in the deep ocean basin that covers approximately one quarter of the planet.
www.theculture.org /adastra/arc/tauceti/SoosAer.html   (1300 words)

 Body Plans Part 2   (Site not responding. Last check: 2007-10-19)
A common ancestor of all bilaterally symmetrical animals is postulated.
The flatworms are bilaterally symmetrical, unsegmented, acoelomate animals.
The phylum Rotifera is comprised of bilaterally symmetrical, pseudocoelomate, unsegmented animals that have three cell layers.
scidiv.bcc.ctc.edu /SL/body_plans_part_ii.htm   (1976 words)

 Bilateral symmetry - Wikipedia, the free encyclopedia
In biology, bilateral symmetry is a characteristic of multicellular organisms, particularly animals.
A bilaterally symmetric, or bilaterian, organism is one that is symmetric about a plane running from its frontal end to its caudal end (head to tail), and has nearly identical right and left halves.
Some exceptions are the sponges (no symmetry), the jellyfish and ctenophores ( radial symmetry), and the echinoderms (partial radial symmetry; starfish exhibit pentamerism).
wikipedia.com /wiki/Bilaterally_symmetrical   (112 words)

 Bilaterally Symmetrical Animals
In bilaterally symmetrical animals, the body is organized along a longitudinal axis, with the right half an approximate mirror image of the left half.
Bilateral symmetry makes possible more efficient movement than does radial symmetry, which is typically found in animals that move slowly or are sedentary.
Bilateral animals are all triploblastic, meaning they have three embryonic tissue layers that give rise to the various specialized tissues of the adult animal.
www.infusion.allconet.org /webquest/BilaterallySymmetricalAnimals.html   (509 words)

 LiveScience.com - Symmetry in Nature: Fundamental Fact or Human Bias?
Bilateral symmetry is so prevalent in the animal kingdom that many scientists think that it can't be a coincidence.
According to one, a body that is bilaterally symmetrical is easier for the brain to recognize while in different orientations and positions, thus making visual perception easier.
In a universe where the natural laws were not symmetrical, experimental results might change depending on where and when and in what direction an experiment was performed.
www.livescience.com /othernews/051221_symmetry_nature.html   (1377 words)

 East Hampton Star - In the News   (Site not responding. Last check: 2007-10-19)
There are a few life forms that one can point to right away and say, "See, they're not symmetrical." Gastropod mollusks, the snails, are all twisted in one way or another with the exception, perhaps, of a few like the limpets.
Crabs are mostly bilaterally symmetrical, but some, like the male fiddler crabs and lobsters, have one claw larger than the other, making them uneven on one side.
Poetry is symmetrical, as in Shakespeare's sonnets or the haiku of the Japanese.
www.easthamptonstar.com /20021212/out1.htm   (1072 words)

 THE WORLD OF LIFE with Douglas Drenkow - Echinoderms   (Site not responding. Last check: 2007-10-19)
They typically have a somewhat bilaterally symmetrical body (the mouth and/or anus are somewhat off-center) and a thinly covered, hard shell, covered with tiny spines.
The larvae of echinoderms are bilaterally symmetrical (as were the presumed ancestors of this group).
In the extremely complicated development of a bilaterally symmetrical larva into a radially symmetrical adult, the mouth forms on one side of the body: The "face" of an echinoderm (such as the disk of a starfish) is technically a "lateral" surface.
theworldoflife.home.att.net /systematics/echinoderms.htm   (1397 words)

 Brief Survey of Animals
With bilateral symmetry, there is only one plane that can divide the organism into two symmetrical halves.
They have bilateral symmetry, a true coelom ("tube within a tube" body plan), a digestive system with two openings (mouth and anus) allowing specialization of digestive organs.
They are the most advanced invertebrates, are bilaterally symmetrical, and have a small coelom.
www.chs.k12.nf.ca /science/b3201/WebCT-Copy/units/unit2-08.htm   (4543 words)

 97-98 WSC Conference 26   (Site not responding. Last check: 2007-10-19)
The bilateral loss of menace response was interpreted to be loss of vision, but palpebral and corneal reflexes were still present.
Spinal cord, cervical, thoracic, lumbar and sacral: Distended myelin sheaths, bilaterally symmetrical, multifocal, marked, with minimal bilateral neuronal necrosis in the ventral horns.
Occasionally, bilaterally symmetrical areas of malacia are visible in the brain stem, and are associated with lesions in cerebral vessels.
www.afip.org /vetpath/WSC/WSC97/97wsc26.htm   (3273 words)

 Article : Radiological Quiz — Musculoskeletal ; Author : SB Grover ; Co-Author(s) : N Midha,M Gupta,PS Uppal ; Vol / ...   (Site not responding. Last check: 2007-10-19)
Clinically bilaterally symmetrical short limb dwarfism with short, stubby hands and feet, waddling gait with coxa vara, genu valgum/varum and tibiotalar slants are characteristic.
Shortening of long bones with bilaterally symmetrical epiphyseal hypoplasias and epiphyseal irregularities at shoulder, hip and knee joints (figs.1, 4 and 5).
Flaring and irregularity of adjacent metaphyses (figs.1, 4 and 5).
narinder.s7.sleekhost.com /articles/archives/2003-13-1/quiz_115.htm   (1089 words)

A strong bilateral symmetry is not apparent amidst this subparallel pattern.
The band-like character of this elevated lineament is underscored by the lack of internal bilateral symmetry.
The ridges that lie between the midline and the borders are arranged in bilaterally symmetric pairs.
pirlwww.lpl.arizona.edu /HIIPS/Publications/tufts_dilation   (9481 words)

 ARS | Publication request: Evolution of the Tcp Gene Family in Asteridae: Cladistic and Network Approaches to ...   (Site not responding. Last check: 2007-10-19)
Development of bilateral flower symmetry has been shown to be determined by the early acting cycloidea (cyc) and dichotoma (dich) genes in Antirrhinum, a member of the Lamiales.
For the TCP gene family, the use of cladistic phylogenetic analysis to identify orthologous genes is complicated by a paucity of alignable data, frequent gene duplication and extinction, and the possibility of reticulate evolution via intergenic recombination.
Results of analyses are consistent with the hypothesis that the evolution of bilateral floral symmetry in the Lamiales required the origin of a novel gene function subsequent to gene duplication.
www.ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=156028   (566 words)

 Nervous System
Most bilaterally symmetrical animals also have a peripheral nervous system and a central nervous system.
Bilaterally symmetrical with two hemispheres connected by a thick band of fibers (white matter) known as the corpus callosum.
Lateralization (right/left brain) refers to the fact that the association areas of the cerebral cortex are not bilaterally symmetrical; each side of the brain controls different functions.
www.sp.uconn.edu /~bi107vc/sp02am/toedt/Nervousweb.html   (1788 words)

 Evolutionary and developmental Biology Lecture 3
Bauplan: bilaterally symmetrical, segmented, hydrostatic skeleton, cuticle, chaetae, triploblastic external and circular and longitudinal internal muscles, preoral ganglia, paired ventral nerve cords, nephridia, coelomoducts, closed tubular circulatory system.
Bauplan: triploblastic, bilaterally symmetrical, metameric segmentation, paired, jointed appendages, one or more pairs of jaws, chitinous exoskeleton, tubular gut, striated muscles, ventral nerve cord of segmental ganglia, cilia in sense organs, reduced coelom, haemocoel, heart.
Bauplan: bilaterally symmetrical larva, adult lacks head, pentamerous symmetry, tripartite coelom, internal mesodermal skeleton with calcium carbonate spicules, no excretory organs.
www.leeds.ac.uk /chb/lectures/edb03.html   (1646 words)

 Plant_Families A
The flowers are radially symmetrical; three green sepals, three delicate white or pinkish petals, six stamens, six to many separate pistils.
The flowers are radially symmetrical, with five sepals and three petals of uniform color and united below into a tube, often with additional parts in the center forming a crown; six stamens.
Each flower is radially symmetrical in form, with those near the edge of the compound unbel sometimes bilaterally symmetrical; five small sepals, five petals and five stamens.
wildflowers.jdcc.edu /Plant_FamiliesA.html   (2071 words)

 Cephalization Summary
The larval stage remains bilaterally symmetrical and is characterized by cephalization.
The cephalization / bilateral symmetry combination allowed animals to have sensory organs facing the direction of movement, allowing a more focused assessment of the environment into which they are moving.
A notable exception to the trend of cephalization throughout evolutionary advancement is phylum Echinodermata, which, although having a bilateral ancestor (as evidenced by their embryology), develop into a pentaradial animal with no concentrated neural ganglia or sensory head region.
www.bookrags.com /Cephalization   (1222 words)

 Introduction CVA   (Site not responding. Last check: 2007-10-19)
In contrast are radially symmetrical groups such as the Coelenterates and Echinoderms (the latter group start off as bilaterally symmetric larvae).
One of the features of bilaterally symmetrical animals is that they tend to be relatively active in comparison to those that are radially symmetrical.
Various bilaterally symmetric invertebrate groups do have longitudinal nerve cords, but these are frequently paired and may be lateral or ventral in position; further, these nerve cords are generally solid clusters of nerve cells running between equally solid masses of nerve fibers.
www.uta.edu /biology/restricted/3452intro.htm   (1786 words)

 Unit J — Simple Invertebrates
radially symmetrical and hermaphroditic and reproduce by broadcasting.
bilaterally symmetrical, have separate sexes and reproduce by mating.
bilaterally symmetrical and hermaphroditic and reproduce by broadcasting.
www.biology-study-guides.com /selftests/11_j_j.html   (380 words)

 tate etc. ISSUE 1
Since most living organisms and many natural objects are bilaterally symmetrical, symmetry perception probably has an evolutionary basis – you don’t want to stare too long or hard to make out the tiger’s eyes amid the tousled asymmetry of the foliage around them.
In cultural terms, symmetrical binaries structure almost every system of thought; they are often mythologised as twins – male and female, day and night, good and evil, life and death.
The bilateral and rotational symmetries of Duchamp’s readymades – the snow shovel, bicycle wheel, bottle rack, urinal – simultaneously indicate their industrial origin and their upstart but impeccable claim to classical aesthetic credentials.
www.tate.org.uk /tateetc/issue1/article7.htm   (2687 words)

 COA :: Conchology   (Site not responding. Last check: 2007-10-19)
They were once thought to represent a link to the annelid worms, in having several pairs of foot retractor muscles, gills, and hearts, but unlike annelids, their bodies are not truly segmented.
The animal is bilaterally symmetrical, with a well-developed foot surrounded by a groove in which there are 6 to 88 pairs of gills.
also known as tusk shells, are bilaterally symmetrical and have elongate, tubular, tapering shells that are open at both ends.
www.conchologistsofamerica.org /conchology/classes.asp   (888 words)

 Untitled Document   (Site not responding. Last check: 2007-10-19)
As Jaume Baguñà, a geneticist at the University of Barcelona in Spain, and his colleagues report on page 1919, tiny marine worms called acoels may be one of the closest living representatives of the first bilaterally symmetrical organisms on Earth.
By moving into this prime spot on the animal tree of life--close to the first bilateral animal--the acoels and their idiosyncrasies take on new meaning for evolutionary biologists, offering a living link between primitive and more complex animals.
That suggests that acoels branched off from all other bilateral animals very early indeed, and that their cleavage pattern represents an early experiment in the evolution of body form.
www.ummz.lsa.umich.edu /courses/bio288/flatw.html   (1385 words)

Bilaterally symmetrical body plan (body is divisible only along one central axis, into mirror image left and right halves)
Cephalization- sensory modalities concentrated in the anterior region, with a centralized nervous system including a primitive "brain" and two ventral nerve cords running parallel anterior to posteriorly..
Extant planaria are attributed as being the living descendants of the first truly bilaterally symmetrical organisms with cephalization.
www.drmichaellevin.org /Planaria/biology/Biology.htm   (132 words)

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