A punnet square can be described as a diagram which depicts the outcomes of the genotype and phenotype of offsprings from a cross between parents. A cross in which a single trait is being considered is a monohybrid cross. A cross in which two traits are being studied is considered as a dihybrid cross.
The punnet square for such a cross can be made as follows:
A.) Pollen are well preserved in the sediment layers because they are highly resistant to decay.
B.) Other indicators that can be used to determine past climates are through the analysis of the width of tree rings and the coral reefs formed underwater.