1. They are triploblastic animals. That is, the body has cell layers called ectoderm, endoderm and mesoderm.
2. The body is bilaterally symmetrical and flattened like a leaf or ribbon.
3. They are Asilomates. Between different organs are parenchyma or collenchyma cells.
4. Body skin is soft, without cilia or cuticles.
5. The mouth has suckers or hooks or proglottids.
6. The excretory system is made up of flame cells.
7. The nervous system is ladder-like and consists of ganglia and digitorum plexus.
8. Their epidermis is composed of syncytes.
9. Circulatory system and respiratory system are absent.
10. Alimentary system is incomplete, branched and consists of mouth, pharynx and intestine. There is no anus.
11. They self-destruct. The life cycle consists of larvae such as radia, cercoria, sporocysts, cysticercus etc.
[Key words to remember characteristics: triploblastic, flattened, parenchyma, autophagic, sucker, hook, flame cell, syncytial]

The word Platyhelminthes is formed from the Greek words platy meaning flat and helminth meaning worm. Animals of this group are known as flatworms or tapeworms. The number of species in this category is about 29,487. The group Platyhelminthes was named by the scientist Gagenbaur (Gagenbaur, 1859). Some flatworms of the genus cause schistosomiasis or snail fever in humans.

The word Cnidaria is formed by combining the Greek word knide meaning thorn and the Latin word area. Nidarians are called flower of the sea. The former name of the order Nidaria is Cilenterata. The marine animal Chironex fleckeri is the world’s most poisonous jellyfish (it can kill 67 people). Animals of this phase form colonies under the sea like a tropical rain forest. They form reefs or reefs. The number of species in this category is about 10,203. Cnidaria was named by scientist Leuckart (1847).

Characteristics of Cnidaria
1. They are diploblastic animals. That is, their cells have two cell layers called ectoderm and endoderm.
2. Between the ectoderm and endoderm is an acellular layer called mesoglia.
3. Their body shape is filamentous, tubular and umbellate.
4. The body consists of nidoblast cells, which bear nematocysts.
5. There is a body cavity called gastrovascular or cilantern. The cilianteron is called the alimentary canal. It acts as the mouth and anus and participates in digestion and transport.
6. Cellular and organelle division of labor is seen.
7. The life cycle includes genetics, metagenesis and polymorphism.
8. In the life cycle there are stationary polyp dasa and active medusa dasa.
9. Body does not have organ system, respiratory system and circulatory system. The nervous system is underdeveloped.
10. They are multicellular, asymmetrical and headless.
11. Food material is digested extracellularly and intracellularly.
12. Respiration occurs through ciliated planula larvae.
13. Twenty species of Nidaria are freshwater. The remaining Nidaria are marine.
Characteristics Key words to remember: diploblastic, mesoglia, nidoblast, coelenteron, division of labor, metagenesis, polymorphism, polyp, medusa]

Classification of Cnidaria
The order Cnidaria is divided into 4 classes.
1. Hydrozoa: They live in water. Polyp or medusa stages are seen in the life cycle. Mesoglia are cellless. Genitalia arise from ectoderm. Like- Hydra viridis, Obelia geniculata.
2. Scyphozoa: These are cup or bell or umbrella shaped animals. Medusa Dasha is the main one in the life cycle. Genitalia arise from endoderm. Mesoglia are large and composed of cells and fibers. For example, Aurelia aurita
3. Cubozoa: They are storm-like creatures. Their Medusa Dasa is the main one. For example, Metridium
4. Anthozoa: They are flower-shaped organisms. A polyp stage is present in the life cycle. Mesoglia are composed of fibrous connective tissue. Genitalia arise from endoderm. For example, Metridium senil, Gorgoni verrucosa.

Some animals of Cnidaria
Hydra – Hydra vulgaris
Chlorohydra – Chlorohydra viridissima
Jellyfish – Aurelia aurita
Portuguese Man of War – Physalia physalis
Adamsia – Adamsia palliata
Obelia- Obelia geniculata
Sea fan – Gorgonia ventilina
Sea feather – Pennatula aculeata
Sea saffron – Metridium senile
Carydea- Carybdea alata
Cyanea – Cyanea capillata
Chironex – Chironex fleckeri
Brain Coral – Meandrina meandrites
Gorgonia- Gorgonia verrucosa
Red Coral – Corallium rubrum
Kamangola jelly – Stomolophus meleagris

Jelly fish
Jellyfish are marine animals belonging to the order Nidaria. It consists of a hanging part called manubrium. There are four oral arms with shafts. Numerous hollow cores exist. For example – Aurelia aurita.

Jellyfish are marine animals belonging to the order Nidaria. It consists of a hanging part called manubrium. There are four oral arms with shafts. Numerous hollow cores exist. For example – Aurelia aurita.

Hydra – Hydra vulgaris
Chlorohydra – Chlorohydra viridissima
Jellyfish – Aurelia aurita
Portuguese Man of War – Physalia physalis
Adamsia – Adamsia palliata
Obelia- Obelia geniculata
Sea fan – Gorgonia ventilina
Sea feather – Pennatula aculeata
Sea saffron – Metridium senile
Carydea- Carybdea alata
Cyanea – Cyanea capillata
Chironex – Chironex fleckeri
Brain Coral – Meandrina meandrites
Gorgonia- Gorgonia verrucosa
Red Coral – Corallium rubrum
Kamangola jelly – Stomolophus meleagris

The order Cnidaria is divided into 4 classes.
1. Hydrozoa: They live in water. Polyp or medusa stages are seen in the life cycle. Mesoglia are cellless. Genitalia arise from ectoderm. Like- Hydra viridis, Obelia geniculata.
2. Scyphozoa: These are cup or bell or umbrella shaped animals. Medusa Dasha is the main one in the life cycle. Genitalia arise from endoderm. Mesoglia are large and composed of cells and fibers. For example, Aurelia aurita
3. Cubozoa: They are storm-like creatures. Their Medusa Dasa is the main one. For example, Metridium
4. Anthozoa: They are flower-shaped organisms. A polyp stage is present in the life cycle. Mesoglia are composed of fibrous connective tissue. Genitalia arise from endoderm. For example, Metridium senil, Gorgoni verrucosa.

1. They are diploblastic animals. That is, their cells have two cell layers called ectoderm and endoderm.
2. Between the ectoderm and endoderm is an acellular layer called mesoglia.
3. Their body shape is filamentous, tubular and umbellate.
4. The body consists of nidoblast cells, which bear nematocysts.
5. There is a body cavity called gastrovascular or cilantern. The cilianteron is called the alimentary canal. It acts as the mouth and anus and participates in digestion and transport.
6. Cellular and organelle division of labor is seen.
7. The life cycle includes genetics, metagenesis and polymorphism.
8. In the life cycle there are stationary polyp dasa and active medusa dasa.
9. Body does not have organ system, respiratory system and circulatory system. The nervous system is underdeveloped.
10. They are multicellular, asymmetrical and headless.
11. Food material is digested extracellularly and intracellularly.
12. Respiration occurs through ciliated planula larvae.
13. Twenty species of Nidaria are freshwater. The remaining Nidaria are marine.
Characteristics Key words to remember: diploblastic, mesoglia, nidoblast, coelenteron, division of labor, metagenesis, polymorphism, polyp, medusa]

The word Cnidaria is formed by combining the Greek word knide meaning thorn and the Latin word area. Nidarians are called flower of the sea. The former name of the order Nidaria is Cilenterata. The marine animal Chironex fleckeri is the world’s most poisonous jellyfish (it can kill 67 people). Animals of this phase form colonies under the sea like a tropical rain forest. They form reefs or reefs. The number of species in this category is about 10,203. Cnidaria was named by scientist Leuckart (1847).

The word Porifera is derived from the Latin word porous meaning pore and ferro meaning. They are called spore-bearing animals. The animals of this phase are known as sponges. Animals of this phase are called living pumps. The number of species in this category is about 8,659. Robert Grant (1836) named this group Porifera.

Characteristics of the circulation phase
1. They are the simplest multicellular organisms and are immobile.
2. Their body wall has numerous openings called ostia.
3. The body contains flagellated cells called koanocytes.
4. The body has a cavity called spongocele or paragastric. Each spongocele has a single pore called an osculum.
5. The body does not have well-organized organs, organs or systems.
6. They have a duct system in their body. There are three types of canal system. Ascon type, cycon type and leucon type. It functions in respiration and water flow.
7. Endoskeleton composed of spicules or spongy fibers. Spicules are composed of lime and spongy collagen proteins.
8. The body wall consists of 3 layers. Pinoderm on the outside, mesenchyme in the middle and choanoderm on the inside.
9. The matrix in the middle of the body wall contains a gelatinous protein called mesohyl. This matrix contains amoebocytes and skeletal material.
9. Food, oxygen, and sperm enter the ostia through water currents.
10. They are bisexual and reproduce both sexually and asexually. Asexual reproduction occurs by buds or gameules.
11. The life cycle consists of amphiblastula or parenchymula larvae.

[Key words to memorize features: ostia, choanocyte, spongocele, canal system, spicule, mesohyl amphiblastula, parenchymula]

Classification of Porifera
The order Porifera is divided into 3 classes.
1. Calcarea: They are small in size and pale in color. Spongin is less. Their skeleton is made of calcium carbonate. They are quite fragile in nature. For example – Sycon gelatinosum.
2. Hexactinellida: These are cup or vase shaped sponges. Large in size. Their spicules are made of silica. Exopinacoderm absent. For example – Euplectella aspergillus.
3 Demosponges: They look like cups or vases and are large. Their choanocytes are narrow. Spicules are made of silica. For example – Spongilla locustris.
Animals of the order Porifera
Scypha gelatinosum
Spongilla – Spongilla lacustris
Bath sponge – Spongilla officinalis
Freshwater sponge – Spongilla proliferan
Clathrina – Clathrina lacunosa
Leucosolenia – Leucosolenia complicata
Euplectella – Euplectella aspergillus
Chalina – Chalina oculata
Hyalonema – Hyalonema longissimum
Euspongia – Euspongia officinalis
Chiona – Chiona celata
Grantia-Grantia compressa
Neptune Cup – Poterion neptuni

Ostia
Ostia means hole. Ostia are the tiny openings on the outside of the body of peripheric animals. Water enters the body through the ostia. For example – Scypha (Scypha gelatinosum).
spongocoel
A spongocele is called a paragastric cavity. The body cavity of peripheric animals is called spongocele. The opening of spongocele is called osculum. The spongiocele holds water and exits the body through the osculum. For example – Spongilla (Spongilla lacustris).
Choanocyte
Cells with goblet-shaped flagella in the bodies of protozoa are called choanocytes. It resides within the walls of the ducts. It controls the flow of water.

Spicule
The tiny spines that make up the body structure of animals of the peripheries phase are called spicules. It is composed of lime or silica. It is a hard material. Neptune Cup (Poterion neptuni).

The tiny spines that make up the body structure of animals of the peripheries phase are called spicules. It is composed of lime or silica. It is a hard material. Neptune Cup (Poterion neptuni).