what is the Smallest animal in the world?
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Your question has a number of difficult aspects to it, but I have asked a friend of mine to help me do some research into the answer for you and I think he has included a great number of pieces of information that you may find interesting.\nHere is what I eventually decided was the most productive answer to give you. I hope it helps you out! (after all, it is 99% his answer I have included below. He generally gives me such good feedback that I try to quote him directly as much as possible.)\nHere we go: An animal is:\nAn organized living being endowed with sensation and the power of voluntary motion, and also characterized by taking its food into an internal cavity or stomach for digestion; by giving carbonic acid to the air and taking oxygen in the process of respiration; and by increasing in motive power or active aggressive force with progress to maturity.\nOR:\nAny of a kingdom (Animalia) of living things including many-celled organisms and often many of the single-celled ones (as protozoans) that typically differ from plants in having cells without cellulose walls, in lacking chlorophyll and the capacity for photosynthesis, in requiring more complex food materials (as proteins), in being organized to a greater degree of complexity, and in having the capacity for spontaneous movement and rapid motor responses to stimulation" These are the animal subkingdoms, and the principal classes under them:\n* Vertebrata, including Mammalia or Mammals, Aves or Birds, Reptilia, Amphibia, Pisces or Fishes, Marsipobranchiata (Craniota); and Leptocardia (Acrania).\n* Tunicata, including the Thaliacea, and Ascidioidea or Ascidians.\n* Articulata or Annulosa, including Insecta, Myriapoda, Malacapoda, Arachnida, Pycnogonida, Merostomata, Crustacea (Arthropoda); and Annelida, Gehyrea (Anarthropoda).\n* Helminthes or Vermes, including Rotifera, Ch�tognatha, Nematoidea, Acanthocephala, Nemertina, Turbellaria, Trematoda, Cestoidea, Mesozea.\n* Molluscoidea, including Brachiopoda and Bryozoa.\n* Mollusca, including Cephalopoda, Gastropoda, Pteropoda, Scaphopoda, Lamellibranchiata or Acephala.\n* Echinodermata, including Holothurioidea, Echinoidea, Asterioidea, Ophiuroidea, and Crinoidea.\n* Coelenterata, including Anthozoa or Polyps, Ctenophora, and Hydrozoa or Acalephs.\n* Spongiozoa or Porifera, including the sponges.\n* Protozoa, including Infusoria and Rhizopoda.
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the largest living creature on Earth is the Blue Whale. Which incidentally is also the largest mammal
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lower level animals IE protozoans, flagellates
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An amoeba is the smallest animal in the world. It is a single cell organism. This means it has ONLY one cell in its whole body and insides.
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The smallest unit of living entities are viruses (nothing but packets of DNA).
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The smallest cell is a type of bacteria known as mycoplasma. Its diameter is 0.0001 mm. The smallest cell in the human body is the sperm cell.
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Amoeba are among the largest single celled organisms, far larger than any bacteria.  Some amoeba are large enough to be seen without needing a microscope!\n\nBacteria are the smallest living things and mycoplasms are the smallest living bacteria (known as nanobacteria).\n\nIf by creatures you mean animals, then the smallest depends a bit on your definition of "small".  The shortest is probably little Trichoplax adhaerens, which looks a bit like a hairy, multi-cellular amoeba.\n\nThe smallest animal in terms of number of cells is probably some kind of Mesozoa, a set of worms famous for being very short and only a few cells across, so much thinner than Tricoplax and less massive.\n\nThe smallest vertebrate is a species of fish that was just discovered recently, though I forget the name of it, sorry.  :-)\n\nIt's recently been discovered that a few single-celled organisms are, in fact, evolved from animals.  If you would count these as animals, they would be the smallest animals, though that would be merely a technicality.\n\nAll of this applies only to adult forms, of course.  We're all very very small to begin with!
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Researchers have found one of the smallest known fish on record in the peat swamps of the Indonesian island of Sumatra. \n\nIndividuals of the Paedocypris genus can be just 7.9mm long at maturity, scientists write in a journal published by the UK's Royal Society. \n\nBut they warn long-term prospects for the fish are poor, because of rapid destruction of Indonesian peat swamps. \n\nThe fish have to survive in pools of acid water in a tropical forest swamp.\n\nThe new fish was discovered by Maurice Kottelat (from Switzerland) and Tan Heok Hui from the Raffles Museum of Biodiversity Research in Singapore, while working with colleagues from Indonesia and with Kai-Erik Witte from the Max Planck Institute in Germany. \n\nRalf Britz helped analyse the animal's skeleton and the complex structure of the pelvic fin.\n\nFor more information about the Paedocypris genus check this site...\n\nhttp://news.bbc.co.uk/1/hi/sci/tech/4645708.stm
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Vatican City has a total land area of 0.44 square kilometers, making it the smallest country in the world.
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Kitti's hognosed bat, also known as the bumblebee bat is generally considered the smallest mammal (as asdf... said).  This record is based on skull length, with the bat having the shortest skull of any mammal.\n\nIf you take the smallest mammal as being the one with the lowest average adult body mass, then the smallest mammal is the Etruscan pygmy shrew.  It weighs less than the bat, but because it has a long nose, its skull is longer.
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animal cells are smaller and more numrous
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There are a few basic body types among mustelids: ferrets, weasels, minks, fishers, otters and martens all have that cylindrical long sinuous body and do the fast inchworm-hop run; badgers, wolverines, and skunks have broad flat heads and bodies and trundle or waddle along.\nSo if it runs like a ferret but is all-over dark, it may be a stoat or a polecat--depends on where you live and the size of the animal. See link as well.
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Smallest Ocean:\n\nThe Arctic Ocean, with an area of 9,485,000 sq km (3,662,000 sq miles), is the smallest ocean. It has a maximum depth of 5,450 m (17,880 ft). The Arctic Ocean is not completely enclosed by land, however, and so is sometimes referred to as an arm of the Atlantic. It is also connected to the waters of the Pacific Ocean by the Bering Strait.\n\nThe Arctic Ocean is ten times smaller than the Pacific Ocean, and has about 1.5 times the surface area of the United States. It is the smallest of the four oceans, and is almost completely surrounded by land at the top of the globe.
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The smallest spider in the world is the Samoan moss spider, Patu marplesi, which has a leg span of only 0.017 inches.
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The smallest rainforest is on Sentosa Island in Singapore Zoo.
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Both the largest and the smallest fish in the world are found in the Philippines\n\nPandaka pygmaea  (dwarf pygmy) is the smallest\n\nhttp://members.tripod.com/a_yee/pgi/fish.html
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The blue whale. It has been dubbed the largest animal that has ever lived on Earth; it bigger than even the biggest dinosaurs. It is on average between 80 and 100 ft. long. Females are bigger than males. The largest ever recorded when measurements were accepted world wide was 102ft. But befor there was standard world wide measurement, whaler claimed to have recorded a 108 foot blue whale, and a 110 foot blue whale; but scientist aren't sure how accurate those last two measerments are.\nThe baby is aslo the largest baby in the world.