Snail – Pila globosa
Octopus – Octopus macropus
Mussel – Lamellidens marginalis
Dentalium – Dentalium kernedei
Loligo – Loligo edulis
Cattle fish – Sepia aculeata
Neopilina – Neopilina galatheae
Teredo – Teredo navalis
Mussel – Unio marginalis
Pearl oyster – Pinctada vulgaris
Chiton – Chiton tuberculatus
Chiton – Ischnochiton evanida
Chaetoderma – Chaetoderma nitidulum
Solen – Solen ensis
Garden Snail – Helix pomatia
King Scallop – Pecten maximus
Category: Biology Second Paper
Classification of Mollusca
The order Mollusca is divided into 5 classes.
1. Caudofovita: They are 2–140 mm long. Body covered with chitinous cuticle. They are marine.
2. Polyplacophora: They are 8 mm to 33 cm long. Body covered by chitin.
3. Gastropods: Their bodies are soft, fleshy and unsegmented. Body covered by mantle.
4. Bivalvia: They have hemolymph fluid. There are two shells made of calcium carbonate.
5. Cephalopoda: These are marine animals with eight arms. There is no hard shell on the body. Has eight legs (cephalopods). They are nocturnal.
Characteristics of Mollusca
1. Their bodies are soft, fleshy and unsegmented.
2. They are cylomates, asymmetrical or bilaterally symmetrical and have a conspicuous head.
3. At the base of the body are muscular fleshy legs.
4. The body is covered by a thin covering called mantle. Calcareous material secreted from the mantle forms the shell.
5. Respiration occurs by gills and mantle membrane. Pulmonary sacs are developed in terrestrials.
6. The digestive tract consists of sand-tongues or radulas made of chitin.
7. The body cavity is very short and turned into a hemocele. Circulatory system is semi-free type.
8. The alimentary canal is straight, curved or U-shaped.
9. Blood contains hemocyanin (meat and copper) and amoebocytes.
10. Siloam is limited only to the sides of the heart, the genital cavity and the kidneys.
11. A unisexual or bisexual animal. They have sex.
12. The life cycle consists of trochophore, velizar or gochidium larvae.
13. They live in sea salt water, fresh water, ditches or pits.
Definition of Mollusca
The word Mollusca is derived from the Latin word molluscus meaning soft. Mollusca are the animals whose body is soft, asymmetrical or bilaterally symmetrical, segmentless, ciliated, fleshy legs and exoskeleton made of calcium carbonate. Mollusca is the second largest phylum of fauna. But it is the largest marine episode. 23% of the ocean is molluscs. Precious pearls, Tyrian purple dye, sea silk, lime etc. are obtained from animals of this phase. The giant squid of this episode is 12 meters long and weighs 270 kg. Land snails (Achatina fulica) and snails cause extensive damage to crops and are known as crop pests. The number of species in this category is about 1,00,000. Johnston (1650) named the order Mollusca.
Nematoda : Characteristics, classification and example of Nematoda
The word Nematoda is formed from the Greek words nematos meaning thread, eidos meaning shape and helminth meaning worm. Those organisms whose bodies are cylindrical, cuticular, segmentless, bilaterally symmetrical and have irregular cilia are called nematodes. The animals of this phase are known as threadworms or roundworms. The structure of the body is like a ‘tube within a tube’. They cause ascariasis, elephantiasis, conjunctivitis, abdominal pain, trichuriasis etc. in human body. They play an important role in the nitrogen cycle. 90% of species under the sea are nematodes. The number of species in this category is about 25,033. Previously they were known as Nemathelminthes or Aschelminthes. The order Nemathelminthes was named by scientist Gagenbaur (1851).
Characteristics of Nematoda
1. Body long, cylindrical, bilaterally symmetrical, narrow at both ends and wide in the middle. Known as roundworms.
2. Body unsegmented, ciliated and covered with thick cuticle.
3. The body is flexible and made of elastin.
4. Abnormal cells are present in the body.
5. They are unisexual and sexually dimorphic.
6. The alimentary canal is complete, straight, unbranched and extends from the mouth to the anus. So the structure of the body looks like a tube inside a tube.
7. The mouth opening is surrounded by characteristic mucus.
8. Respiratory and circulatory systems are absent.
9. A rhabditiform or microfilariae larval stage exists in the life cycle.
10. They are terrestrial or aquatic, free-living or parasitic.
Classification of Nematoda
The order Nematoda is divided into 2 classes.
1. Secernentia/Phasmedia: Their phasmids are present. Having pore-like amphids. Excretory system present. For example – round worm (Ascaris lumbricoides).
2. Adenophores/Aphasmedia: Their phasmids are absent. Amphids are not pore-like. Caudal gland present. Eg – Whipworm (Trichinella spiralis).
Some animals of Nematoda
Roundworm – Ascaris lumbricoides
Eye worm – Loa loa
Hook worm – Ancylostoma doudenale
Hook worm – Necator americanus
Mealworm – Enterobius vermicularis
Ringworm- Wuchereria bancroftis
Whipworm – Trichinella spiralis
Trichuris trichiura
Dioctophyme – Dioctophyme renale
Free-living roundworm – Caenorhabditis elegans
Some animals of Nematoda
Roundworm – Ascaris lumbricoides
Eye worm – Loa loa
Hook worm – Ancylostoma doudenale
Hook worm – Necator americanus
Mealworm – Enterobius vermicularis
Ringworm- Wuchereria bancroftis
Whipworm – Trichinella spiralis
Trichuris trichiura
Dioctophyme – Dioctophyme renale
Free-living roundworm – Caenorhabditis elegans
Classification of Nematoda
The order Nematoda is divided into 2 classes.
1. Secernentia/Phasmedia: Their phasmids are present. Having pore-like amphids. Excretory system present. For example – round worm (Ascaris lumbricoides).
2. Adenophores/Aphasmedia: Their phasmids are absent. Amphids are not pore-like. Caudal gland present. Eg – Whipworm (Trichinella spiralis).
Characteristics of Nematoda
1. Body long, cylindrical, bilaterally symmetrical, narrow at both ends and wide in the middle. Known as roundworms.
2. Body unsegmented, ciliated and covered with thick cuticle.
3. The body is flexible and made of elastin.
4. Abnormal cells are present in the body.
5. They are unisexual and sexually dimorphic.
6. The alimentary canal is complete, straight, unbranched and extends from the mouth to the anus. So the structure of the body looks like a tube inside a tube.
7. The mouth opening is surrounded by characteristic mucus.
8. Respiratory and circulatory systems are absent.
9. A rhabditiform or microfilariae larval stage exists in the life cycle.
10. They are terrestrial or aquatic, free-living or parasitic.
Definition of Nematoda
The word Nematoda is formed from the Greek words nematos meaning thread, eidos meaning shape and helminth meaning worm. Those organisms whose bodies are cylindrical, cuticular, segmentless, bilaterally symmetrical and have irregular cilia are called nematodes. The animals of this phase are known as threadworms or roundworms. The structure of the body is like a ‘tube within a tube’. They cause ascariasis, elephantiasis, conjunctivitis, abdominal pain, trichuriasis etc. in human body. They play an important role in the nitrogen cycle. 90% of species under the sea are nematodes. The number of species in this category is about 25,033. Previously they were known as Nemathelminthes or Aschelminthes. The order Nemathelminthes was named by scientist Gagenbaur (1851).
Platyhelminthes : Characteristics, classification and example
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.
Characteristics of Platyhelminthes
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]
Classification of Platyhelminthes
The order Platyhelminthes is divided into 4 classes.
1. Turbellaria: Their bodies are flat like leaves. Cuticle is absent on the body. The epidermis is ciliated and rhabdite in nature. Suction is missing. Larval stage absent. They are known as Edewam. Such as Planaria (Dugesia tigrina).
2. Trematoda: They are cylindrical or flat like leaves. Cilia are absent on the body. The mouth has suckers or hooks. Larval stage present. They are known as Fluke. For example- liver worm (Fasciola hepatica).
3. Monogenia: These are small parasites. Their heads contain nerve cells and sensory organs. Alimentary canal is simple in nature. They are known as flatworms. Such as Planaria (Dugesia tigrina).
4. Cestoda: Their bodies are long and flattened like ribbons. Composed of 800-900 proglottid segments. Each segment has one or two sets of male or female reproductive organs. The mouth has suckers and curved hooks. Mouth opening and esophagus absent. They are known as tapeworms. For example, tapeworm (Taenia solium).
Flame cell
The cyst is a part of the excretory organ. Cells are bulbous with holes. It is attached to the tube of mesoderm. It has cilia in clusters. The cilia vibrate violently inside the tube, creating a current of water. As a result, the waste material is released through the excretory hole. Thus it helps in digestion.
Some animals of Platyhelminthes
Liver worm- Fasciola hepatica
Tape worm – Taenia solium
Dog tapeworm – Echinococcus granulosus
Free-living flatworm – Dugesia tigrina
Hammer head worm- Bipalium kewense
Human bloodworm – Schistosoma mansoni
Frog worm- Polystoma integrimum
Gyrodactylus- Gyrodactylus corti
Dactylogyrus alatus
Convoluta- Convoluta convoluta
Microstomum- Microstomum lineare
Thysanozoon – Thysanozoon brocchii
Sheep worm- Dicrocoelium dendriticum