Answer:
Indicator species, organism—often a microorganism or a plant—that serves as a measure of the environmental conditions that exist in a given locale. ... For example, greasewood indicates saline soil; mosses often indicate acid soil. Tubifex worms indicate oxygen-poor and stagnant water unfit to drink.
I think the correct answer would be mass of the shells. According to the law of conservation of mass, mass can never be created not destroyed. Therefore, mass here should be constant before the transformation and after the process. Hope this helps.
This process is known as synaptic pruning.
Synapse pruning is the process when the synapses are eliminated and it occurs usually in the early childhood. Synapses that are eliminated are the ones that organism no longer needs. Synaptic pruning process is regulated and influenced by environmental factors.
