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Oral poliovirus vaccine or Sabin vaccine, named for its inventor American physician and microbiologist Albert Sabin, was developed. OPV contains live attenuated (weakened) virus and is given orally.
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Prokaryotes are the most primitive organism that exists on earth. They have the simplest form of body organization and they do not perform complex tasks.
The eukaryotic cell has nucleus in it and they have more complex machinery in their body to perform various tasks accordingly.
The nucleus of the prokaryotes are not enclosed in the nuclear membrane and it is dissolve in the cytoplasm. It lacks true nucleus.
Eukaryotes have nucleus enclosed inside nuclear membrane.
DDT stands for dichloro-diphenyl-trichloroethane. The first kind of synthetic/artificial insecticides came into use in the 1940s. The earlier usage of DDT include: a) Killing of malarial vectors, b) Combatting Typhus and other insect borne human diseases, c) As a pest control in crops d) as a pest control in garden, live stock production and even at homes.
The negative impact of DDT could be felt for the first time when the pests that were earlier killed by use of DDT have now become pesticides resistant. In the 1950s in USA, the regulatory measures were adopted to reduce the usage of DDTs as its effects as a pesticides were no more long significant and also it was creating detrimental physical and psychological impacts on the human and environment.
It was in 1972 that the U.S. Environmental Protection Agency cancelled the order for banning the usage of DDT based on the adverse impact it produced on the environment, human and other life forms. Since then continuous studies are being conducted to analyse the impact of DDTs. In some later years it was established that DDT is the cause of producing tumors in liver.
Some of the common negative impacts produced by DDT as per the U.S. Department of Agriculture :
a) The non destructive nature – DDT can not be destroyed and thus it remains persistent in the atmosphere
b) It attacks the tissues of living organisms especially the animals and humans ( fatty tissue)
c) It can penetrate the atmosphere to deeper extent.
Now as per the current stuation, The use of DDT is controlled and other alternatives of pest control organisms is being deduced. As per the treaty of Stockholm Convention on POPs (Persistent organic pollutants) , usage of DDT for malarial control is justified but it puts a restrictive use of DDT as pesticides in other areas.
You can use the volume displacement method. If you had the alligator in a tank and you knew how much the volume of water in the tank was before the alligator was in there you could subtract that from the volume of the water with the alligator in the tank.
