Amorph allele
An allele of a gene that appears to code for no detectable product. It can be produced by a deletion mutation.

Amphibia
A class of vertebrates. That contains frogs, toads (Anura); newts, salamanders (Urodela); tropical burrowing worm-like Apoda. In the course of evolution they were the first vertebrates to inhabit the land (late Devonian, about 370 million years ago), being descended immediately from fish (Choanichtyes).
Early Amphibia were immediate ancestors of the reptiles which themselves gave rise to mammals and birds. Amphibia differ from fish in having the four pentadactyl (q.v.) legs typical of tetrapods, hip girdle jointed to the vertebral column at the sacrum, and an ear-drum connected to the inner ear by a rod of bone (columella auris), which corsses the middle ear and is effective for hearing in air. Though differ from reptiles in that fertilization is not accomplished by coition and the eggs are unprotected by a shell and embryonic membranes.
Consequently most Amphibia have to become temporarily aquatic for the purpose of reproduction. Fossil Amphibia are distinguished from fossil reptiles by, e.g. having a single vertebra concerned in the sacrum, instead of two. Modern Amphibia have diverged far from those which were ancestral to Reptilia, losing much of their bony skeleton.

Amphiblastula
It refers to the flagellated larva found in porifera.

Amphidiploid
A tetraploid individual having two sets of chromosomes from each of two known ancestral species, i.e. in which source of the two different gnomes is clearly known.

Amphimixis
True sexual reproduction involving the fusion of male and female gametes and formation of a zygote.