Why is dna replication said to be semi-conservative

In "the man in the water," what was the remarkable occurrence that rosenblatt reported?

Residential construction is expanding in florida, the expansion has caused fragmentation of habitats, one of the results of the increased construction is a decrease in the number of large predators such as the coyote, black bear and pool panther, which will be the most immediate local result of this fragmentation? 1)large predators will become extinct 2)decrease in middle sized predators 3)increase in population of top carnivores 4)increase in population of prey species

Which material is commonly used as a culture medium for living cells