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classification of multicellular animalsthe multicellular animals animalia originated from the simpler protozoan protists you know the simpler
polyphyletic theory - metazoathis theory was suggested by greenheig 1959 and some other workers according to this theory sponges coelenterates
colonial theory - metazoa this is the most popular theory on the origin of metazoa the idea was conceived by haeckel 1874 modified by metschnikoff
origin and evolution of metazoamost of the early metazoans were soft bodied and so their fossils are rare the extremely fragmented fossil record does
regional specialisationregional specialisation takes place usually by three processes ndash1 restriction of certain structures to a few segments for
metameric segment - segmentationon the other hand true metameric segment as best observed in annelids has separate schizocoelic body cavity of
body cavity and coelom - metazoavacuoles spaces lacunae and cavities have been of importance in all organisms may it a be plant or animal all animals
germ layers - metazoathe infolding of the blastoderm of the blastula forms a gastrula with two or more layers the outer layer is the ectoderm and the
cleavage - metazoathe unicellular zygote begins cell division cleavage first the single cell divides forming two cells these redivide further to form
developmental patterns - metazoathe metazoans or animalia can be divided into two groups on the basis of body symmetry the bilateral metazoans can be
bilateral - metazoabilaterally symmetrical animals have the major axis running from head anterior to tail posterior they have a ventral lower and
radial and biradial-metazoaradial symmetry is the symmetry in which the parts are so arranged around a central axis or shaft like the spokes of a
asymmetrical and spherical - metazoasome creatures are asymmetrical no matter which way we try to divide them through the middle no two halves would
characteristics of metazoathe unicellular protozoans are highly versatile and successful organisms that show remarkable organization and division of
phylum placozoathe phylum placozoa contains a single species of a minute marine animal trichoplax adharens composed of a dorsal and ventral
metazoain the two kingdom classification the unicellular animals used to be clubbed together under a single phylum protozoa that constituted
life cycle of parasite - protozoanthe life cycle of the parasite in man begins when an infected mosquito while biting and taking a blood meal injects
sporozoans ndash protozoansporozoans of the genus plasmodium are responsible for causing a serious human disease malaria they are among the best
trypanosomes ndash flagellatesthe trypanosomes are among the serious pathogens that cause high mortality among human populations and domestic animals
amoebae- parasitic protozoanthe amoebae of the genus entamoeba vary in their biology entamoeba histolytica or the dysentery amoeba occurs as a
parasitic protozoanout of the thousands of species of protozoa the majority are free living however many species from within the phyla
phylum ciliophora - protozoansimple cilia or compound ciliary organelles typical in at least one stage of life cycle subpellicular cilia present even
classification scheme of protozoaphylum myxozoa parasites of lower vertebrates especially fish and invertebratesphylum microspora parasites of
phylum apicomplexa - protozoancharacteristic set of organelles apical complex asssociated with the anterior end present in some developmental stages
phylum labyrinthomorpha - protozoantrophic stage ectoplasmic network with spindle shaped or spherical nonamoeboid cells small group living on algae