• Anthus pratensis (Linnaeus, 1758) graspieper
  meadow pipit
  
• Antidorcas marsupialis (Zimmermann, 1780) springbok
  springbok
  
• Antilope cervicapra (Linnaeus, 1758) Indische antilope
  blackbuck
  
• Aonyx cinerea (Illiger, 1815) Asian small-clawed otter
  Aziatische kleine klauwotter
  
• Aphrocallistes beatrix Gray, 1858
• Aphrodita aculeata Linnaeus, 1758 fluwelen zeemuis
  sea mouse
  
• Apis mellifera Linnaeus, 1758 honingbij
  western honey bee
  
• Apodemus agrarius (Pallas, 1771) brandmuis
  striped field mouse
  
• Apodemus sylvaticus (Linnaeus, 1758) bosmuis
  wood mouse
  
• Aptenodytes forsteri G. R. Gray, 1844 keizerspinguïn
  emperor penguin
  
• Aptenodytes patagonicus Miller, 1778 koningspinguïn
  king penguin
  
• Aptera fusca (Thunberg, 1784) kakkerlak
  cockroach
  
• Apteryx australis Shaw, 1813 southern brown kiwi
  zuidelijke bruine kiwi
  
• Apteryx mantelli Bartlett, 1852 noordelijke bruine kiwi
  northern brown kiwi
  
• Apus apus (Linnaeus, 1758) gierzwaluw
  common swift
  
• aquamarijn aquamarijn
  
• Aquila audax (Latham, 1801) wigstaartarend
  wedge-tailed eagle
  
• Aquila nipalensis Hodgson, 1833 steppearend
  steppe eagle
  
• Ara ararauna (Linnaeus, 1758) blauwgele ara
  blue-and-yellow macaw
  
• Ara chloropterus G. R. Gray, 1859 groenvleugelara
  red-and-green macaw
  
• aragoniet aragoniet
  aragonite
  
• Arapaima gigas (Schinz, 1822) arapaima
  arapaima
  
• Araucaria araucana (Molina) K. Koch slangenden
  monkey puzzle tree
  
• Archaeopteryx lithographica Meyer 1861 archaeopteryx
  archaeopteryx
  
• Architectonica carocollata (Lamarck,1822)
• Arctica islandica (Linnaeus, 1767) noordkromp
  ocean quahog
  
• Ardea cinerea Linnaeus, 1758 blauwe reiger
  grey heron
  
• Ardea purpurea Linnaeus, 1766 purperreiger
  purple heron
  
• Ardenna gravis (O'Reilly, 1818) grote pijlstormvogel
  great shearwater
  
• Ardeotis kori (Burchell, 1822) koritrap
  kori bustard
  
• Ardipithecus ramidus (White, Suwa & Asfaw, 1994)
• Arenaria interpres (Linnaeus, 1758) steenloper
  ruddy turnstone
  
• Argiope bruennichi (Scopoli, 1772) wespspin
  wasp spider
  
• Arion rufus Linnaeus, 1758 wegslak
  large red slug
  
• Armillaria mellea (Vahl) P.Kumm. echte honingzwam
  honey fungus
  
• Artibeus jamaicensis Leach, 1821 jamaicavruchtenvampier
  Jamaican fruit bat
  
• Artocarpus integer (Thunb.) Merr. tjampedak
  chempedak
  
• Arvicola amphibius (Linnaeus, 1758) woelrat
  Eurasian water vole,
  
• Asaphus kowalewskii (Lawrow 1856) trilobiet
  trilobite
  
• Ascaris leptoptera Rudolphi, 1809 rondworm
  roundworm
  
• Aschiphasma annulipes Westwood, 1835 wandelende tak
  stick insect
  
• Asio flammeus (Pontoppidan, 1763) velduil
  short-eared owl
  
• Asio otus (Linnaeus, 1758) ransuil
  long-eared owl
  
• Aspidella terranovica Billings 1872 Aspidella
  Aspidella
  
• Aspidimorpha miliaris (Fabricius, 1775) schildpadkever
  tortoise beetle
  
• Aspidosperma sp.
• Astarte borealis (Schumacher, 1817) grote astarte
  boreal astarte
  
• Astarte goldfussi Hinsch,1952
• Asterias rubens Linnaeus, 1758 gewone zeester
  common starfish
  
• Astrapia nigra (Gmelin, 1788) arfakastrapia
  Arfak astrapia