How to calculate the time of death?

Each trait of a plant is determined a. an allele b. one gene c. a pair of genes d. one dominant gene

Zoo geographic regions are characterized by the presence of specific groups of animals these regions are determined by the taxonomic or phylogenetic relationships of animals. the map shows the zoogeographic regions proposed by the naturalist alfred russel wallace in 1876. the similarities of organisms in which two areas numbered above provide the best evidence for common ancestry between the organisms in both locations ?

How does secondary succession differ from primary succession?