The animal kingdom is characterized by heterotrophic eukaryotic organisms that are multicellular and their cell lack cell wall. In animals, certain fundamental features are common to various individuals, which forms the basis of their classification.
The level of organization also called grades of arrangement cellular level(Poriferans), tissue level (coelenterates and ctenophores), tissue organ level (Platyhelminthes) and organ system level (Ascheiminthes to chordates) in the animal kingdom.
In Porifera (sponges), bodies are asymmetrical. The body lacks tissue or organs but forms a meshwork of cells surrounding channels that open to the outside through pores and that expand into internal cavities lined with food filtering flagellated cells (Choanocytes) [CBSE AIPMT RE-EXAM 2015].
The third stage larva of Wuchereria bancrofti carried by Culex mosquito is microfilariae, which are discharged in lymph vessels of man and soon reaches the bloodstream [WB JEE 2015].
Nematocysts are the stinging capsules produced by the cnidocytes or cnidoblasts present on the tentacles and the body of the animals belonging to the Phylum – Coelenterata (Cnidaria). Cnidoblasts are used for anchorage, defense and for the capture of prey [WB JEE 2015].
Comb plates are the characteristic feature of phylum – Ctenophora. These animals have cilia in each toe arranged to form a stack of combs called comb plates [AMU 2015].
Metagenesis is the phenomenon, in which one generation of certain plants and animals reproducing generations. It is found in coelenterates (Hydra), a number of worms, and certain lower chordates (Salpa) [AMU 2015].
Cnidarian members of the animal kingdom are found both in freshwater and marine environments, while members of Ctenophora, Cephalochordata, and Echinodermata are found exclusively in marine environment [CBSE AIPMT 2014].
The coelom given in the diagram is of roundworm (Ascaris), which belongs to the phylum – Aschelminthes. The body cavity in the diagram is not lined by mesoderm instead, the mesoderm is present in the form of scattered patches in between the ectoderm and endoderm [KCET 2014].
Polyps produce medusae through vegetative budding and medusae form polyp after sexual reproduction [Kerela CEE 2014].
Euplectella is referred to as Venus flower basket. Its skeleton is a very costly marriage gift in Japan [Kerela CEE 2014].
Choanocytes form the lining of the para gastral cavity in sponges. By constant beating of flagella of choanocytes cells, a water current is produced, which has a fixed direction [J & K CET 2014].
Ctenoplana and Berore lack cnidoblasts and have biradial symmetry. These belong to phylum- Ctenophora [BCECE 2015].
Scleroblasts are skeleton manufacturing cells and may be calciblasts, silicioblasts or spongioblasts depennding upon the skeletal element these are producing [OJEE 2012].
Gemmules formation is the characteristic feature of water sponges. In sponges, reproduction is of asexual type mainly by gemmules or budding or reduction bodies or fission [HPMT 2012].
The sponges possess an endoskeleton in the form of calcareous spicules, siliceous spicules, and spongin fibers, But no by chitin [Kerela CEE 2011].
Fasciola hepatica (Sheep liver fluke) belongs phylum – Platyhelminthes. These worms have the incomplete alimentary canal, there is a single opening for both digestion and egestion. This is also called as blind sac body plan [CBSE AIPMT 2010].
Planaria (Dugesia) has a remarkable power of regeneration. If an individual is cut transversely into two parts, the anterior fragment will regenerate a new tail and a posterior piece will develop a new head.
Aschelminthes are triploblastic, bilaterally symmetrical pseudocoelomate (false coelom derived from embryonic blastocoel. and is not lined by mesoderm), unsegmented organisms [Kerela CEE 2010].
Flatworms (Planaria) are devoid of cavities in between the alimentary canal and body wall, hence are acoelomate [UP CPMT 2008].
Turbellaria is a class of phylum – Platyhelminthes. Turbellarians are mostly free-living flatworms, majorly aquatic (marine), having cilia, body unsegmented, mouth ventral, suckers absent with tango, chemo, and photoreceptors, e.g. Planaria (Dugesia), Bipalium, etc [UP CPMT 2008].
Platyhelminthes are bilaterally symmetrical animals. The body of the animal can be divided into two equal halves through only one plane, e.g. liver fluke (Fasciola hepatica) [DUMET 2008].
The posterior end to the male Ancylostoma is the form of a broad, umbrella-like structure, the copulatory bursa, which surrounds the cloaca [UK PMT 2007].
Life Cycle of Ascaris lumbricoides – Animal kingdom
In the life cycle of Ascaris lumbricoides, rhabditiform larvae are the infective stage of man. It reaches the alimentary canal through contaminated food and water. In the small intestine, the shell gets dissolved to release second stage larva. Now, it reaches liver through the hepatic portal vein and the heart through post vena cava vein. It goes to lungs through the pulmonary arteries. In the alveoli of lungs, it undergoes the second molting and produces the third molting in the alveoli only and then enters the small intestine again. In the small intestine, it undergoes forth and fifth molting to become a young one attaining sexual maturity within 8-10 weeks [EAMCET 2014].