Explain why a leaf kept in the light for 24 hours will turn an iodine solution blue-black, whereas a leaf kept in light for 24 hours and then in the dark for 24 hours will have no effect on an iodine solution

The circles, or orbits, for electrons are called energy levels. each level can hold only a certain number of electrons. add electrons to each level until you can't add any more. how many electrons can each level hold?

Which statement best describes the relationship between an allele and a gene? question 1 a. an allele is a variation of a gene that can be expressed as a phenotype. b. an allele is the part of a gene that attaches to messenger rna molecules. c. an allele is a segment of a dna molecule that controls replication of a gene.

Which characteristics are typical of a human population in the postindustrial stage?