What does retreating mean in geography?

How many types of tissues are there in a human bone? How are genesand alleles related to genotype and phenotype? What molecule contains uranium? In what era did the first crustaceans appear? What allows the old strand and the new strand to come back together? What is the noble gas configuration of O2? What is the ability to adapt important for specie's survival? Why do penguins and grebes have similarities although they are not related? Can aspies be sympathetic? The first and largest category in the classification system commonly used today to group organisms? What is the chemical in the atmosphere that is responsible for absorbing ultraviolet light from the Sun? What will happen in the savanna if animals keep overgrazing? North pole south pole can they ever be separated? Is the definitive nucleus in plants haploid in number? Means knowing how to find analyze and use information.? What type of lines can indicate strength and stability but in certain circumstances may appear awkward or stiff? What is an archival science? Which of the following terms describes the spread of influenza across Europe after the war? What is a large non rounded rock in outer space called? Is there anything in nature that grows in pairs?