The rising phase of the AP is due to opening of voltage dependent Na channels. The falling phase of the AP is due to opening of voltage dependent Na channels. The rising phase of the AP is due to closing of transmitter-dependent K channels. The falling phase of the AP is due to closing of transmitter-dependent K channels. The rising phase of the AP is due to opening of voltage dependent channels other than Na or K. 8.
Flight is a characteristic of all birds and some mammals.
One would perform phylogenetic analysis on intermediate taxa and determine whether flight was present in the common ancestor to birds and mammals. If so, then flight would have likely arisen once for both groups. Otherwise, it arose separately in each group. Male 3 spined stickleback fish are highly aggressive, particularly during mating season. Each male sets up his own individual territory which he vigorously defends from other males.