- ablen
- ablet
- abranchiate
- absorbent
- accentor
- aard-wolf
- aardvark
- aasvogel
- abranchial
- acarus
- abrego
- acari
- acarid
- actinia
- actiniae
- aculeate
- adminiculum
- addax
- adjutant
- admiral
- adonis
- aestivate
- aestivation
- aigrette
- agouti
- albacore
- ale-wife
- alate
- aliped
- agouty
- alevin
- alpaca
- alter
- ambulacrum
- amphibia
- amphibious
- amphioxus
- amphipod
- amphipodous
- anaconda
- anchovy
- ancon-sheep
- ant-thrush
- anthophilous
- angler
- annelida
- annulose
- anourous
- ant
- ant-catcher
- ant-lion
- amphibian
- amphidelphic
- amphipoda
- amphipodan
- amphisbaena
- anabas
- anangian
- antelope
- androgynous
- angel-fish
- anisodactylous
- annelid
- ant-eater
- anura
- anurous
- aphides
- aphis
- archangel
- archerfish
- argentine
- arachnid
- archaeopteryx
- asp
- apterous
- arboreous
- arenicolous
- argala
- armadillo
- artiodactylous
- ascidium
- artiodactyl
- astomatous
- arboreal
- argonaut
- arthrobranchiae
- arthropod
- auricle
- auk
- aurelia
- aurelian
- aurochs
- avoset
- axis
- backcross
- aye-aye
- babbler
- babirusa
- baboon
- baccivorous