Ecosystem diversity is: A. variety of interactions among organisms in natural communities. B. the number of different species in a given area. C. the variety of abiotic characteristics within a given area. D. the genetic variety within all populations of a given species. E. synonymous with ecosystem services.

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.