Phylum-Coelenterata (Cnideria) Questions in English

(D) Jellyfish,scientifically known as $Aurelia$,belongs to the phylum $Cnidaria$ (also known as $Coelenterata$).
These organisms are characterized by the presence of cnidoblasts or cnidocytes on the tentacles and body,which are used for anchorage,defense,and capturing prey.
They exhibit radial symmetry and are diploblastic animals.

(A) In diploblastic animals,such as those belonging to the phyla $Cnidaria$ and $Ctenophora$,the body is composed of two germinal layers: an external $Ectoderm$ and an internal $Endoderm$.
An undifferentiated,jelly-like layer known as the $Mesoglea$ is present between these two layers.
Therefore,the $Mesoglea$ acts as a non-cellular,gelatinous matrix separating the $Ectoderm$ and the $Endoderm$.

(B) Radial symmetry is a type of body symmetry where the body can be divided into identical halves by any plane passing through the central axis.
This type of symmetry is characteristic of the phyla $Cnidaria$ (also known as $Coelenterata$),$Ctenophora$,and adult $Echinodermata$.
$Platyhelminthes$,$Annelida$,and $Arthropoda$ exhibit bilateral symmetry,where the body can be divided into two identical left and right halves only through a single plane.

(A) In Phylum $Cnidaria$ (Coelenterata),organisms exhibit two main body forms: the $Polyp$ and the $Medusa$.
$1$. The $Polyp$ form is sessile and cylindrical,such as in $Hydra$ and $Adamsia$.
$2$. The $Medusa$ form is umbrella-shaped and free-swimming,such as in $Aurelia$ (jellyfish).
Therefore,the $Medusa$ form is the free-swimming stage.

(A) In the phylum $Cnidaria$ (also known as $Coelenterata$),the characteristic free-swimming,ciliated larva is known as the $Planula$ larva.
This larva develops from the zygote and eventually settles on a substrate to develop into a polyp.
$Amphiblastula$ is characteristic of certain sponges (Porifera),while $Parenchymula$ is another type of sponge larva.
$Morula$ is an early embryonic stage in animal development,not a specific larval form.

(D) The $Cnidoblast$ (also known as a $Cnidocyte$) is a specialized cell found in the phylum $Cnidaria$.
These cells contain a stinging organelle called a $Nematocyst$.
The $Nematocyst$ contains a poisonous fluid known as $Hypnotoxin$,which is used for defense,capturing prey,and anchorage.

(D) The phylum $Cnidaria$ (also known as $Coelenterata$) is characterized by the presence of specialized cells called $Cnidoblasts$ or $Cnidocytes$.
These cells are located on the tentacles and the body surface.
$Cnidoblasts$ contain stinging capsules or nematocysts,which are used for anchorage,defense,and the capture of prey.
Therefore,$Cnidoblasts$ are the structures associated with defense and prey capture.

(B) The phylum $Cnidaria$ (also known as $Coelenterata$) is characterized by the presence of a primitive nervous system known as a nerve net.
This nerve net consists of interconnected neurons that allow the organism to respond to stimuli from all directions.
$Porifera$ lack a nervous system.
$Annelida$ and $Mollusca$ possess more advanced nervous systems with ganglia and nerve cords.

(B) In jellyfish (phylum $Cnidaria$),the gastrovascular cavity is a central digestive cavity. It opens to the exterior through a single opening called the $hypostome$. The $hypostome$ is a conical structure that bears the mouth at its apex. Therefore,the correct answer is $hypostome$.

(C) Cnidoblasts (or cnidocytes) are specialized cells found in the phylum $Cnidaria$.
These cells contain stinging capsules called nematocysts.
Their primary functions include:
$1$. Capture of prey: By injecting toxins to paralyze the prey.
$2$. Defense: Protecting the organism from predators.
$3$. Anchorage: Helping the organism attach to a substrate.
Respiration in $Cnidarians$ occurs via simple diffusion across the body surface,not through cnidoblasts.
Therefore,respiration is the correct answer.

(D) The animals that possess two germ layers (diploblastic) have an undifferentiated layer called mesoglea present between the ectoderm and the endoderm.
Among the given options,the sea anemone belongs to the phylum $Cnidaria$ (or $Coelenterata$),which is characterized by diploblastic organization and the presence of mesoglea.
Sea cucumber $(Echinodermata)$,sea horse $(Chordata)$,and sea lily $(Echinodermata)$ are triploblastic animals.

(B) Animals belonging to the phylum $Coelenterata$ (also known as $Cnidaria$) are characterized by the presence of tentacles.
These tentacles are used for capturing prey,defense,and locomotion.
$A$. Hypostome is a structure found in $Cnidaria$ but it is not the defining characteristic feature compared to tentacles.
$B$. Tentacles are a characteristic feature of $Cnidaria$.
$C$. Flame cells are the excretory structures found in the phylum $Platyhelminthes$.
$D$. Choanocytes (collar cells) are the characteristic cells found in the phylum $Porifera$.

(D) Metagenesis is the phenomenon of alternation of generation between the asexual polyp form and the sexual medusa form in the life cycle of certain Cnidarians. $Obelia$ is a classic example of an organism that exhibits metagenesis,where polyps produce medusae asexually and medusae produce polyps sexually.

(A) The phylum $Cnidaria$ (also known as $Coelenterata$) is characterized by the presence of specialized stinging cells called $Cnidoblasts$ or $Cnidocytes$.
These cells are used for anchorage, defense, and capturing prey.
While $Tentacles$ and $Gastrovascular cavity$ are also present in $Cnidarians$, the $Cnidoblasts$ are the unique, diagnostic feature that defines the phylum.
$Choanocytes$ are characteristic of the phylum $Porifera$.

(A) Polymorphism is a phenomenon where an organism exists in more than one morphological form. In the phylum $Coelenterata$ (also known as $Cnidaria$),many species exhibit polymorphism,where individuals of the same species exist in different forms such as polyps and medusae. For example,in $Obelia$,both polyp and medusa forms are present in the life cycle.

(B) The $Coelenteron$ (also known as the gastrovascular cavity) is a central cavity found in the phylum $Cnidaria$ (Coelenterata).
It serves a dual purpose: it acts as a digestive system (extracellular digestion) and as a circulatory system (distributing nutrients throughout the body).
$Spongocoel$ is the central cavity of sponges.
$Coelom$ is the body cavity lined by mesoderm.
$Mantle cavity$ is the space between the mantle and the body in mollusks.

(B) Radial symmetry is a body plan where an organism can be divided into identical halves by any plane passing through the central axis.
In the animal kingdom,members of the phyla $Coelenterata$ (also known as $Cnidaria$) and $Ctenophora$,as well as adult $Echinodermata$,exhibit radial symmetry.
$Platyhelminthes$,$Annelida$,and $Mollusca$ typically exhibit bilateral symmetry.

(A) The provided diagram represents a cross-section of a diploblastic organism (like Cnidaria).
$P$ points to the outer layer, which is the Ectoderm.
$Q$ points to the undifferentiated, jelly-like layer between the two germ layers, known as the Mesoglea.
$R$ points to the inner layer, which is the Endoderm.
$S$ points to the central cavity, which is the Gastrovascular cavity (coelenteron).
Therefore, the correct labeling is $P - \text{Ectoderm}, Q - \text{Mesoglea}, R - \text{Endoderm}, S - \text{Gastrovascular cavity}$.

(B) Figure $A$ shows a diploblastic organization,where the body consists of two germ layers: an external ectoderm and an internal endoderm,with an undifferentiated mesoglea in between. This type of organization is characteristic of the phylum Cnidaria (Coelenterata). Among the given options,$Hydra$ belongs to the phylum Cnidaria. Therefore,the correct option is $B$.

(D) Metagenesis is the phenomenon of alternation of generation between asexual and sexual phases in the life cycle of an organism.
In the phylum $Coelenterata$ (also known as $Cnidaria$),certain species like $Obelia$ exhibit metagenesis.
In this process,polyps produce medusae asexually,and medusae form the polyps sexually.
Therefore,the correct option is $D$.

(A) In the phylum Coelenterata (Cnidaria),there are two main body forms: polyp and medusa.
$1$. The polyp form is typically cylindrical and sessile (fixed),such as in Hydra and Adamsia.
$2$. The medusa form is umbrella-shaped and free-swimming,such as in Aurelia.
$3$. Polyp forms reproduce asexually to produce medusa forms,while medusa forms reproduce sexually to produce polyp forms (a phenomenon known as metagenesis or alternation of generations).
Therefore,the correct statement for the polyp form is that it reproduces asexually.

(D) : Metagenesis refers to the alternation of generation between asexual and sexual phases of an organism.
In this process,the organism exists in two different forms.
For example,in $Obelia$ (a coelenterate),the polyp form reproduces asexually to produce medusae,and the medusa form reproduces sexually to produce polyps.

(D) : Cnidarians are sac-like animals that are aquatic. They are mostly marine,but some species like $Hydra$ are found in fresh water. They are the simplest organisms that have attained a tissue level of organization. Members of $Ctenophora$,$Cephalochordata$,and $Echinodermata$ are exclusively marine.

(B) : $Gorgonia$ (sea fan) is an animal belonging to the phylum $Coelenterata$ (also known as $Cnidaria$).
All animals lack a cell wall,as their cells are bounded only by a plasma membrane.
$Cyanobacteria$ and blue-green algae (which are the same) have a peptidoglycan cell wall.
$Saccharomyces$ (yeast) is a fungus and possesses a chitinous cell wall.

(B) $Physalia$ (Portuguese man-of-war) belongs to the phylum $Cnidaria$ (Coelenterata).
$1$. $Cnidarians$ are diploblastic animals,so option $A$ is correct.
$2$. $Cnidarians$ exhibit tissue level of organization,not cellular level. Thus,option $B$ is incorrect.
$3$. $Cnidarians$ possess cnidoblasts or cnidocytes containing nematocysts on their tentacles for defense and prey capture,making option $C$ correct.
$4$. The gastro-vascular cavity in $Cnidarians$ opens to the outside through a single opening called the hypostome,making option $D$ correct.
Therefore,the incorrect statement is $B$.

(D) Nematocysts (or cnidoblasts) are specialized stinging cells found in the tentacles and body of organisms in the phylum $Cnidaria$.
These cells contain a coiled,thread-like structure that can be everted rapidly.
The primary functions of nematocysts are:
$1$. Defence against predators.
$2$. Capture of prey by injecting toxins to paralyze them.
Therefore,the correct option is $D$.

(D) Metagenesis,also known as alternation of generations,is a phenomenon where a life cycle involves both asexual and sexual phases.
In the phylum $Cnidaria$,certain organisms exhibit this phenomenon.
$Obelia$ is a classic example of a cnidarian that shows metagenesis,where the polyp form reproduces asexually to produce medusae,and the medusae reproduce sexually to produce polyps.

(C) Animals in which the cells are arranged in two embryonic layers,an external ectoderm and an internal endoderm,are called diploblastic animals.
Examples of diploblastic animals include phylum $Cnidaria$ (also known as $Coelenterata$) and $Ctenophora$.
$Chordates$,$Aschelminthes$,and $Platyhelminthes$ are triploblastic,meaning they possess three germ layers: ectoderm,mesoderm,and endoderm.

(A) The correct matches are as follows:
$a$. Pennatula is commonly known as Sea-pen $(3)$.
$b$. Meandrina is commonly known as Brain coral $(1)$.
$c$. Gorgonia is commonly known as Sea-fan $(2)$.
$d$. Adamsia is commonly known as Sea-anemone $(4)$.
Therefore,the correct sequence is $a-3, b-1, c-2, d-4$.

(B) In the phylum $Cnidaria$,certain species exhibit a phenomenon known as metagenesis or alternation of generations.
$Obelia$ is a classic example of this,where the organism exists in two body forms: the polyp and the medusa.
The polyp is the sessile,asexual form,while the medusa is the free-swimming,sexual form.
The medusa produces gametes,which fuse to form a zygote,eventually developing into a new polyp,thus acting as the reproductive structure.

(A) The organ-pipe coral is scientifically known as $Tubipora$ $musica$. It belongs to the phylum $Cnidaria$ (or $Coelenterata$). It is named 'organ-pipe coral' because its skeletal structure consists of parallel tubes that resemble the pipes of a musical organ. Therefore,the correct option is $A$.

(B) Jellyfish,scientifically known as $Aurelia$,belongs to the phylum $Cnidaria$ (or $Coelenterata$).
Within this phylum,the class $Scyphozoa$ is commonly referred to as the 'true jellyfish' class.
Members of the class $Hydrozoa$ include organisms like $Hydra$ and $Obelia$,while the class $Anthozoa$ includes corals and sea anemones.
Therefore,the correct classification for jellyfish is $Scyphozoa$.

(A) Hydra belongs to the phylum $Cnidaria$.
It possesses a primitive nervous system consisting of a network of neurons (nerve net) spread throughout the body.
However, it lacks a centralized nervous system, such as a brain or distinct nerve cords, which are characteristic of higher animals like flatworms $(Platyhelminthes)$, annelids $(Earthworm)$, and chordates $(Frog$ tadpole).
Therefore, among the given options, $Hydra$ is the most primitive organism with a diffuse nerve net rather than a complex nervous system.

(B) The phylum $Cnidaria$ (also known as $Coelenterata$) is characterized by the presence of specialized cells called $Cnidoblasts$ or $Cnidocytes$.
These cells contain stinging capsules known as $nematocysts$, which are used for anchorage, defense, and capturing prey.
$Flame$ $cells$ are characteristic of Phylum $Platyhelminthes$ (excretion).
$Polymorphism$ is seen in some $Cnidarians$ but is not the defining characteristic of the entire phylum.
$Hermaphroditism$ is found in various phyla and is not a unique feature of $Cnidaria$.

(D) $1$. Tapeworms $(Taenia)$ are endoparasites that live in the intestine of humans.
$2$. Mosquitoes are ectoparasites that feed on the blood of vertebrates.
$3$. Leeches $(Hirudinaria)$ are ectoparasites that feed on the blood of various animals.
$4$. Sea Anemones $(Adamsia)$ are marine cnidarians that are free-living and predatory,not parasitic. Therefore,the Sea Anemone is the non-parasitic organism.

(B) $Obelia$ exhibits an alternation of generations between the asexual polyp form and the sexual medusa form. This phenomenon,where the asexual phase alternates with the sexual phase in the life cycle of certain cnidarians,is specifically termed as Metagenesis.

(D) The phylum $Cnidaria$ (also known as $Coelenterata$) includes organisms that are mostly marine,but some species,such as $Hydra$,are found in freshwater. $Echinodermata$,$Ctenophora$,and $Cephalochordata$ are exclusively marine.

(A) The cell wall is a characteristic feature of plants,fungi,and most bacteria.
$A$. $Gorgonia$ (Sea-fan) belongs to the phylum $Cnidaria$ (Kingdom $Animalia$). Animals do not possess a cell wall.
$B$. $Cyanobacteria$ are prokaryotes that possess a peptidoglycan cell wall.
$C$. $Saccharomyces$ (Yeast) is a fungus and possesses a chitinous cell wall.
$D$. Blue-green algae are $Cyanobacteria$ and possess a cell wall.
Therefore,$Gorgonia$ is the correct answer.

(B) Metagenesis is a phenomenon observed in certain members of the phylum $Cnidaria$ (e.g.,$Obelia$).
It refers to the alternation of generation between the asexual polyp form and the sexual medusa form.
In this process,polyps produce medusae asexually,and medusae produce polyps sexually.
Therefore,it represents the alternation of generation between asexual and sexual phases.

(C) In $Hydra$,the digestive system is incomplete,meaning it has only one opening which acts as both the mouth and the anus. Therefore,undigested food is egested through the mouth. Nitrogenous waste products,such as ammonia,are primarily removed via simple diffusion through the general body surface (body wall) into the surrounding water.

(D) The $Hydra$ belongs to the phylum $Cnidaria$ (or $Coelenterata$).
These organisms possess a primitive nervous system consisting of a network of neurons (nerve net) spread throughout the body.
Unlike higher animals,$Hydra$ does not have a centralized brain or a central nervous system to process information.
Therefore,it is the correct answer.

(D) "Portuguese man of war" is a polymorphic, colonial coelenterate known as $Physalia \ physalis$.
It is named so due to its appearance, which resembles Portuguese warships (caravels) sailing in the sea during the $15^{th}$ and $16^{th}$ centuries.

(N/A) The characteristics of Phylum $Coelenterata$ (also known as $Cnidaria$) are as follows:
$1$. Habitat: They are mostly aquatic,mostly marine,sessile or free-swimming,and radially symmetrical animals.
$2$. Body Organization: They exhibit tissue-level organization and are diploblastic (composed of two germ layers: ectoderm and endoderm).
$3$. Body Cavity: They possess a central gastro-vascular cavity with a single opening called the $hypostome$ (mouth on the oral surface).
$4$. Specialized Cells: They contain $cnidoblasts$ or $cnidocytes$ (stinging cells) on the tentacles and body,which are used for anchorage,defense,and capturing prey.
$5$. Digestion: Digestion is both extracellular and intracellular.
$6$. Body Forms: They exhibit two basic body forms: the polyp (sessile and cylindrical,e.g.,$Hydra$,$Adamsia$) and the medusa (umbrella-shaped and free-swimming,e.g.,$Aurelia$ or jellyfish).
$7$. Alternation of Generation: Some species exhibit $metagenesis$ (alternation of generation),where polyps produce medusae asexually and medusae produce polyps sexually.

(N/A) The polyp form is a sessile and cylindrical body form found in the phylum $Cnidaria$.
Key characteristics include:
$1$. Body Shape: It has a cylindrical body shape.
$2$. Lifestyle: It is a sessile form,meaning it remains attached to a substrate.
$3$. Mouth Position: The mouth is directed upwards and is surrounded by tentacles.
$4$. Examples: Common examples include $Hydra$ and $Adamsia$ (sea anemone).
$5$. Reproduction: It typically reproduces asexually by budding.

(N/A) $(i)$ Tentacles:
Location: In Coelenterata (Cnidaria),the mouth is surrounded by many thin,long,slender,and hollow structures known as tentacles.
Function: They are used for capturing prey,paralyzing prey using cnidoblasts,attachment to surfaces,and for defense and offense.
$(ii)$ Hypostome:
Location: It is a conical,elevated structure located at the center of the oral end of the body,bearing the mouth at its apex.
Function: It acts as the mouth-bearing region and helps in the ingestion of food.

(N/A)

Polyp	Medusa
$(1)$ Polyps are sessile and resemble a cylindrical stalk with mouth and tentacles.	$(1)$ Medusae are free-floating,umbrella-like structures with tentacles.
$(2)$ Polyps reproduce asexually by budding.	$(2)$ Medusae reproduce sexually by liberating gametes into the water.

(B) The neural system was developed for the first time in the phylum $Cnidaria$ (also known as $Coelenterata$).
In these organisms,it consists of a simple network of neurons dispersed throughout the body,which helps in coordinating the activities of the organism.

(N/A) $\rightarrow$ There are about $9000$ species of Cnidarians.
$\rightarrow$ The name Cnidaria (Knide-nettle or sting cells) is derived from the stinging cells or Cnidoblasts present on the ectoderm of tentacles and the body of these animals.
$\rightarrow$ Cnidoblasts are used for anchorage, defense, and for the capture of prey.
$\rightarrow$ Cnidarians exhibit tissue level of organization and are diploblastic.
$\rightarrow$ They have a central gastro-vascular cavity with a single opening, the hypostome.
$\rightarrow$ Digestion is extracellular and intracellular. Some of the cnidarians, e.g., corals, have a skeleton composed of calcium carbonate $(CaCO_{3})$.
$\rightarrow$ Cnidarians exhibit two basic body forms called polyp and medusa.
$\rightarrow$ Polyp is a sessile and cylindrical form like Hydra, Adamsia, etc., whereas the medusa is umbrella-shaped and free-swimming like Aurelia or jelly fish.
$\rightarrow$ Those cnidarians which exist in both forms exhibit alternation of generation (Metagenesis), i.e., polyps produce medusae asexually and medusae form the polyps sexually (e.g., Obelia).
$\rightarrow$ Examples: Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Pennatula (Sea-pen), Gorgonia (Sea-fan), Meandrina (Brain coral), Aurelia (Jelly fish), Obelia (Sea fur).

(A) The animals belonging to the phylum $Coelenterata$ (also known as $Cnidaria$) are characterized by being free-swimming or sessile,exhibiting radial symmetry,and possessing specialized cells called $cnidocytes$ or $cnidoblasts$.
These $cnidocytes$ contain stinging capsules called $nematocysts$,which are used for anchorage,defense,and capturing prey.

(C) Cnidarians exhibit two basic body forms: the $Polyp$ and the $Medusa$.
$Polyp$ is a sessile and cylindrical form,like $Hydra$ and $Adamsia$.
$Medusa$ is an umbrella-shaped and free-swimming form,like $Aurelia$ (jellyfish).