Which best describes a centromere? sister chromosomes that are held together by a chromatid
paired chromosomes that have genes arranged in the same order
the part of a chromosome that joins the sister chromatids
the material that makes up a chromosome

Which of the following is a possible reason for sleep? a) growth b)digestive c)speed d)intelligence

Can you identify which of the following groups of organisms are, or are not, populations? a. the american bison (bison bison) and grey wolves (canis lupus) currently living in yellowstone national parkb. all of the rainbow trout (oncorhynchus mykiss that) that have ever lived in lake eriec. the group of american bison (bison bison) currently living in yellowstone national parkd. a group of calliope hummingbirds (selasphorus calliope) and a group of rufous hummingbirds (selasphorus rufus) living in the same new hampshire woodse. the northern cardinals (cardinalis cardinalis) living on opposite shores of lake champlain f. all of the whales currently living in the atlantic ocean off cape cod, massachusetts

In sexual reproducing animals once fertilization of the egg takes place, the exists as a single cell until cell division begins. a) egg b) larva c) sperm d) zygote