Which of the following are not found in sponges
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Sponges have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. Sponges do not have nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes. Sponges were first to branch off the evolutionary treefrom the common ancestor of all animals, making them the sister group of all other animals.
Movement
Although adult sponges are fundamentally sessile animals, some marine and freshwater species can move across the sea bed at speeds of 1–4 mm (0.039–0.157 in) per day, as a result of amoeba-like movements of pinacocytes and other cells. A few species can contract their whole bodies, and many can close their oscula and ostia. Juveniles drift or swim freely, while adults are stationary.
Respiration, feeding and excretion
Sponges do not have distinct circulatory, respiratory, digestive, and excretory systems – instead the water flow system supports all these functions. They filter food particles out of the water flowing through them. Particles larger than 50 micrometers cannot enter the ostia and pinacocytes consume them by phagocytosis (engulfing and internal digestion). Particles from 0.5 μm to 50 μm are trapped in the ostia, which taper from the outer to inner ends. These particles are consumed by pinacocytes or by archaeocyteswhich partially extrude themselves through the walls of the ostia. Bacteria-sized particles, below 0.5 micrometers, pass through the ostia and are caught and consumed by choanocytes.Since the smallest particles are by far the most common, choanocytes typically capture 80% of a sponge's food supply. Archaeocytes transport food packaged in vesicles from cells that directly digest food to those that do not. At least one species of sponge has internal fibers that function as tracks for use by nutrient-carrying archaeocytes, and these tracks also move inert objects.
Euplectella aspergillum, a glass spongeknown as "Venus' flower basket"
It used to be claimed that glass spongescould live on nutrients dissolved in sea water and were very averse to silt.However, a study in 2007 found no evidence of this and concluded that they extract bacteria and other micro-organisms from water very efficiently (about 79%) and process suspended sediment grains to extract such prey. Collar bodies digest food and distribute it wrapped in vesicles that are transported by dynein"motor" molecules along bundles of microtubules that run throughout the syncytium.[22]
Sponges' cells absorb oxygen by diffusionfrom water into cells as water flows through body, into which carbon dioxide and other soluble waste products such as ammoniaalso diffuse. Archeocytes remove mineral particles that threaten to block the ostia, transport them through the mesohyl and generally dump them into the outgoing water current, although some species incorporate them into their skeletons.[22]
Carnivorous sponges
A few species that live in waters where the supply of food particles is very poor prey on crustaceans and other small animals. So far only 137 species have been discovered.[36]Most belong to the family Cladorhizidae, but a few members of the Guitarridae and Esperiopsidae are also carnivores.In most cases little is known about how they actually capture prey, although some species are thought to use either sticky threads or hooked spicules. Most carnivorous sponges live in deep waters, up to 8,840 m (5.49 mi),and the development of deep-ocean exploration techniques is expected to lead to the discovery of several more. However, one species has been found in Mediterraneancaves at depths of 17–23 m (56–75 ft), alongside the more usual filter feedingsponges. The cave-dwelling predators capture crustaceans under 1 mm (0.039 in) long by entangling them with fine threads, digest them by enveloping them with further threads over the course of a few days, and then return to their normal shape; there is no evidence that they use venom.
Most known carnivorous sponges have completely lost the water flow system and choanocytes. However, the genusChondrocladia uses a highly modified water flow system to inflate balloon-like structures that are used for capturing prey.
Endosymbionts
Freshwater sponges often host green algaeas endosymbionts within archaeocytes and other cells, and benefit from nutrients produced by the algae. Many marine species host other photosynthesizing organisms, most commonly cyanobacteria but in some cases dinoflagellates. Symbiotic cyanobacteria may form a third of the total mass of living tissue in some sponges, and some sponges gain 48% to 80% of their energy supply from these micro-organisms.In 2008 a University of Stuttgart team reported that spicules made of silica conduct light into the mesohyl, where the photosynthesizing endosymbionts live.
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Movement
Although adult sponges are fundamentally sessile animals, some marine and freshwater species can move across the sea bed at speeds of 1–4 mm (0.039–0.157 in) per day, as a result of amoeba-like movements of pinacocytes and other cells. A few species can contract their whole bodies, and many can close their oscula and ostia. Juveniles drift or swim freely, while adults are stationary.
Respiration, feeding and excretion
Sponges do not have distinct circulatory, respiratory, digestive, and excretory systems – instead the water flow system supports all these functions. They filter food particles out of the water flowing through them. Particles larger than 50 micrometers cannot enter the ostia and pinacocytes consume them by phagocytosis (engulfing and internal digestion). Particles from 0.5 μm to 50 μm are trapped in the ostia, which taper from the outer to inner ends. These particles are consumed by pinacocytes or by archaeocyteswhich partially extrude themselves through the walls of the ostia. Bacteria-sized particles, below 0.5 micrometers, pass through the ostia and are caught and consumed by choanocytes.Since the smallest particles are by far the most common, choanocytes typically capture 80% of a sponge's food supply. Archaeocytes transport food packaged in vesicles from cells that directly digest food to those that do not. At least one species of sponge has internal fibers that function as tracks for use by nutrient-carrying archaeocytes, and these tracks also move inert objects.
Euplectella aspergillum, a glass spongeknown as "Venus' flower basket"
It used to be claimed that glass spongescould live on nutrients dissolved in sea water and were very averse to silt.However, a study in 2007 found no evidence of this and concluded that they extract bacteria and other micro-organisms from water very efficiently (about 79%) and process suspended sediment grains to extract such prey. Collar bodies digest food and distribute it wrapped in vesicles that are transported by dynein"motor" molecules along bundles of microtubules that run throughout the syncytium.[22]
Sponges' cells absorb oxygen by diffusionfrom water into cells as water flows through body, into which carbon dioxide and other soluble waste products such as ammoniaalso diffuse. Archeocytes remove mineral particles that threaten to block the ostia, transport them through the mesohyl and generally dump them into the outgoing water current, although some species incorporate them into their skeletons.[22]
Carnivorous sponges
A few species that live in waters where the supply of food particles is very poor prey on crustaceans and other small animals. So far only 137 species have been discovered.[36]Most belong to the family Cladorhizidae, but a few members of the Guitarridae and Esperiopsidae are also carnivores.In most cases little is known about how they actually capture prey, although some species are thought to use either sticky threads or hooked spicules. Most carnivorous sponges live in deep waters, up to 8,840 m (5.49 mi),and the development of deep-ocean exploration techniques is expected to lead to the discovery of several more. However, one species has been found in Mediterraneancaves at depths of 17–23 m (56–75 ft), alongside the more usual filter feedingsponges. The cave-dwelling predators capture crustaceans under 1 mm (0.039 in) long by entangling them with fine threads, digest them by enveloping them with further threads over the course of a few days, and then return to their normal shape; there is no evidence that they use venom.
Most known carnivorous sponges have completely lost the water flow system and choanocytes. However, the genusChondrocladia uses a highly modified water flow system to inflate balloon-like structures that are used for capturing prey.
Endosymbionts
Freshwater sponges often host green algaeas endosymbionts within archaeocytes and other cells, and benefit from nutrients produced by the algae. Many marine species host other photosynthesizing organisms, most commonly cyanobacteria but in some cases dinoflagellates. Symbiotic cyanobacteria may form a third of the total mass of living tissue in some sponges, and some sponges gain 48% to 80% of their energy supply from these micro-organisms.In 2008 a University of Stuttgart team reported that spicules made of silica conduct light into the mesohyl, where the photosynthesizing endosymbionts live.
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COMPLETE QUESTION
Which of the following are not found in sponges?
A. oscula.
B. Spongocoels.
C. Cnidocytes.
D. Spicules.
E. Amoebocytes.
ANSWER
(c) Cnidocytes are not found in sponges
EXPLANATION -
- Sponges belong to the group Porifera, are sessile multicellular organisms that are characterized by the presence of pores all over the body.
- Out of all the given options, Cnidocytes are not found in sponges.
- The presence of Cnidocytes is the definitive feature of the members of the phylum Cnidaria. Cynodyctes shoot a sting-like structure containing toxins as a defense against their predators.
- Oscula (singular Osculum) is the excretory organ present at the top of the body of a sponge that expels water and wastes out of the body.
- The size of the opening of the osculum determines the amount of water it will expel.
- Spongocoels, also known as paragastric cavity, is the central cavity present on the body of sponges through which waters enters through multiple tiny openings called Ostia.
- The spongocel is lined by collar cells called choanocytes, pushing water inside the body, producing currents.
- Ameobcytes are phagocytic motile cells that are responsible for the transport of nutrients in the body and excreting waste outside the body.
- Spicules are one of the structural elements of sponges providing structural support and defense against predators.
Hence, The correct option is (c) Cnidocytes.
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