The diagram below shows the layers in a rock having a brachiopod: a rock column labeled rock is shown. the column has three layers. the bottommost layer of the rock has two identical organisms marked as, brachiopod, in the key and one shaded circle, the middle layer has a two squares, the top layer has one star shape. in the key the shaded circle is marked as x, the square is marked as y and the star is marked as z which statement about the rock fossils is true?

I know I'm late but I htought I'd give the answer for anyone in the future. The answer is  "Organism X existed for a short period of time." I got it right on a test and I saw that there was no right answer here so I thought I'd help out Hope it helps!

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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mientras se trata la anorexia o la bulimia, es importante buscar ayuda antes que nada. un profesional de la salud mental será el más útil para aquellos que sufren anorexia o bulimia. este es un buen lugar para comenzar, sin embargo, ver a otros profesionales como dietistas registrados, especialistas médicos y dentistas podría ayudar a alguien a recuperarse de un trastorno alimentario. después de la ayuda profesional, o si la ayuda profesional no es una opción, alguien que se recupere de la anorexia o la bulimia debe rodearse de compañeros de apoyo, padres u otros miembros de la familia que también estén comprometidos con el proceso de recuperación.

hope this you! : )

(i popped my answer into google translate so it may be a bit wonky)