Ctenophora - class-XI

Ctenophora is a phylum of animals that live in marine waters worldwide. Their most distinctive feature is the combs, which is groups of cilia they use for swimming. They are the largest animals that swim by means of cilia. Generally, the outer surface bears usually eight comb rows, called as swimming plates, which are used for swimming. Comb plates paddle plates in them are arranged circumferentially like seams in a football. 

Beroe is also known as the mellon jellyfish and is the most common type of species of phylum Ctenophora. Ctenophora is known to have biradial symmetry. Each of the four parts is identical to the opposite side but different from the adjacent side. Cnidoblasts and nematocysts are absent in Ctenophora and are found in cnidarians. 

Ctenophora is a phylum of animals that lives in marine water. Their most distinctive feature is the combs and groups of cilia they use for swimming. They are the largest animals that swim by means of cilia.

Tentacles are the organs which are used to catch the prey. These are present at the opening of the gastrovascular cavity. Colloblasts are a cell type found in ctenophores. They are widespread in the tentacles of these animals and are used to capture prey. These are found in all ctenophores except those of the order Beroida, as they lack tentacles. So, the correct answer is option B.

Ctenophora is a phylum of animals that live in marine waters. The outer surface bears usually eight comb rows. This is called as comb plates or swimming-plates, which are used for swimming. Ctenophora lack stinging nematocysts. Lasso cells are kind of defensive and offensive stinging cells. These are found in great numbers in all coelentrates. 

Ctenophora is a phylum of animals that live in marine waters. The outer surface bears usually eight comb rows. This is called as comb plates or swimming-plates, which are used for swimming. Ctenophora lack stinging nematocysts. Lasso cells are kind of defensive and offensive stinging cells. These are found in great numbers in all coelentrates.  The Beroe or Melon jellyfish and flattened species like Cestum belongs to Ctenophora. Ctenoplana is a genus of comb jellies andPleurobrachia is a common genus of Ctenophora.Thus, the correct answer is option D.

• Ctenophora are also known as comb jellies. This is a phylum of animals that lives in marine waters. 
• Many species in this group have the body which is biradially symmetrical. The main axis is oral to aboral (from the mouth to the opposite end). This gives the bilateral form. 
• The tentacles are present around the mouth. These tentacles radiate outwards. This gives the radial form of symmetry. Thus, the type of symmetry is known as biradial symmetry. 
  
  

Ctenophora shows several affinities with Cnidaria, some of them are:

Ctenophores, commonly known as sea walnuts or comb jellies are exclusively marine, radially symmetrical, diploblastic organisms with tissue level of organization. The germs layers include ectoderm and endoderm. 

Hydra traps its prey by  tentacles which are present at the opening of the gastrovascular cavity. Scattered over the outer layer tentacles are a great many of these stinging cells called cnidoblasts. Each cnidoblast contains a capsule (nematocyst) from which projects a small trigger called a cnidocil. Inside each capsule is a tiny hollow thread. It is inverted like a finger of a glove which is pushed into the hand part. These threads are the food-catching apparatus. 

Ctenophore phylum which includes Comb jellies exhibit Biradial symmetry. It is when the organism can be divided up into equal parts, but with two planes only. Hence option C is correct.

Comb jellies are not strong swimmers. They are typically planktonic animals, transparent and unpigmented and most swim by the synchronous beating of the eight rows of comb plates. Hence, option C is correct.

Ctenophora is considered as a small phylum. The phylum contains very few genera and only about 80 species. This group includes a set of marine animals. These organisms are commonly called as comb jellies. Earlier, this phylum was placed under Coelenterata. Hatschek placed it under a separate phylum. 

Biradial symmetry and lack of cnidoblasts are characteristics of phylum Ctenophora. They have adhesive structure, known as coloblasts instead of cnidoblasts. Both Ctenoplana and Beroe are ctenophores. Hence, option C is correct.

The ctenophores are diploblastic with a biradial symmetry or modified radial  (with an underlying bilateral symmetry), which is a bit different than the radial symmetry typical of cnidarian.

Sea Walnut (Pleurobrachia) belongs to the phylum Ctenophora. These organisms are radially symmetrical, diploblastic, marine, and exhibit bioluminescence.

Boroe is a type of comb jelly and has a body structure that is transparent and sac like with a mouth at one end. The gastrovascular channels are beneath the cilia and the animal lacks any tentacles otherwise. So, the correct answer is 'Boroe.

Comb jellies are oval-shaped animals with eight rows of tiny comb-like plates that they beat to move through the water.  They are gelatinous animals belonging to the phylum of animals that live in marine waters worldwide, ctenophora.
Thus, the correct answer is option D.

Ctenophores, also called the comb-jellies, exhibit bioluminescence. The enzyme called photoprotein is present in them in which luciferin is combined with oxygen. When the calcium changes the shape of the ptotoprotein, light is given off.

Some animals are three layered with ectoderm, endoderm and mesoderm called triploblastic.  Ctenophores have two main layers of cells that sandwich a middle layer of jelly-like material, which is called the mesoglea. So, even though the layers of tisse are diploblastic the presence of the third jelly-like layer gives them an intermediate stage.

Ctenophores have colloblast in their tentacles to capture/ disarm their prey as opposed to cnidarians like jelly fish having Cnidoblasts doing the same function.

The loose layer of jelly-like substance in Ctenophores is mesoglea which are composed of muscle bundles and nerve fibres that lie under the epethelial cells. They are hydrostatic and have elastic cells along with amoebocytes that have a role in phagocytosis, 

Comb plates are the characteristic feature of phylum Ctenophora. Pleurobrachia is a well-known example of a ctenophore.

Biradial symmetry is a combination of radial and bilateral symmetry, as in the ctenophores. Here, the body components are arranged with similar parts on either side of a central axis, and each of the four sides of the body is identical to the opposite side but different from the adjacent side. Also, Cnidblasts being exclusive Cnidarian character does not exist in Ctenophora.

In Ctenophores, the digestion is predominantly completed in the stomadaeum(extracellular). The undigested food passes out either throught the mouth or the anal pores. 

Statocysts are a balance organ present in ctenophores. This provides equilibriuim for the organism while swimming. These statocysts are situated away from the oral or mouth region also called the aboral region. 

Ctenophores are cylindrical/flat with a biradially symmetrical body along an oral-aboral axis. Biradial symmetry refers to the type of symmetry which is the combination of both radial and bilateral.

Boroe is a transparent comb jelly with sac-like body with a mouth on one side and gonads internally present. However, it lacks any tentacles. So, the correct answer is 'Tentacles'.

Ctenophores reproduce only by sexual means. Porifera, Protozoa, and Cnidaria all exhibit various forms of asexual reproduction.

The tentacles of Ctenophores have meridonial bands with transversely arranged combs like structures. Comb-like eight ciliary plates on the body serve the purpose of locomotion. 

Ctenophores use their tentacles to capture their prey and these tentacles are made of specialized cells called colloblast. These colloblast are made of axial filaments and a granular sticky dome.

While Beroe have a sac like transparent body, Hormiphora have a pear shaped body. Ctenoplana has a circular and flattened body. So, the correct answer is 'Flat bilobed body'.

A locomotor organ consisting of a row of strong cilia whose bases are fused are called Comb plates. These  are found in 'Pleurobrachia'.

So, the correct option is 'Pleurobrachia'.

The correct matching is: Ctenophora-Pleurobrachia-bioluminescence, Platyhelminthes-Planaria-acoelomate, Cyclostomata-Hog fishes-migration, Aschelminthes-Ancylostoma-endoparasite, Echinodermata-Ophiura-coelomate. This follows taxonomic classification and characteristic traits.

Adamsia, Astraea and Physalia belong to the phylum Cnidaria (Coelenterata). Cnidarians are aquatic, mostly marine, solitary or colonial sessile or free swimming, radially symmetrical animals. These phyla are divided into three classes Hydrozoa, Scyphozoa, and Anthozoa. Pleurobrachia belongs to the phylum Ctenophora.

Beroe (comb jellyfish) belong to the Ctenophora. Monocystis is an endoparasite found in the seminal vesicles and coelom of earthworm (Annelida). Wuchereria is a human parasitic roundworm (Aschelminthes) known to cause lymphatic filariasis. Pennatula is colonial marine cnidarian. Cleiona belongs to Porifera.

Ctenophores are commonly known as sea whales or comb jellies, radially symmetry, diploblastic organisms with tissue level of organization. The body bears eight external rows of ciliated comb plates which help in locomotion, hence the name Ctenophora. Cnidocytes are absent.

a) Tape worm and liver fluke belongs to phylum platyhelminthes, having dorsoventrally flattened body hence are flat worms.