A) Tetrahymena
B) Radiolaria
C) Paramecium
D) Trichonympha.
Correct Answer: B
Solution :
: Radiolarians (also radiolaria) are amoeboid protozoa that produce intricate mineral skeletons, typically with a central capsule dividing the cell into inner and outer portions, called endoplasm and ectoplasm. They are found as plankton throughout the ocean, and their shells are important fossils found from the Cambrian onwards. Radiolarians have many needle-like pseudopods supported by microtubules, called axopods, which aid in flotation. The nuclei and most other organelles are in the endoplasm, while the ectoplasm is filled with frothy vacuoles and lipid droplets, keeping them buoyant. Often it also contains symbiotic algae, especially zooxanthellae, that provide most of the cells energy. Some of this organization is found among the heliozoa, but those lack central capsules and only produce simple scales and spines. Radiolaria are present in the fossil record from as early as the Lower Cambrian, but the earliest well-preserved specimens are from the Lower Ordovician limestones of Spitsbergen. Most petroleum bearing regions show the presence of these organisms (like radiolaria and foraminiferans) in the fossil state. Their study has been found useful in the oil bearing strata of the earth in different regions of the world.
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