What is the average temperature in the polar zones?

Which element provides strength to the exoskeleton of clams and oysters

In some plants, pointed leaves (p) are dominant over rounded leaves (p). a plant with a genotype of pp

The ancestors of plants that lived in water had plenty of water for the young. angiosperms are a group of land plants that evolved a reproductive trait for living on land. this trait protect young plants by allowing them to grow only when water is present and the conditions for healthy development are right. what trait most likely young angiosperms in this way?