A(n)is a proposed, testable explanation for an observation. A(n) is a factor that changes during an experiment.
A(n) in an experiment yields data against which other groups are compared.
A(n) differs from the control group by the one variable that is being tested in the experiment.

The construction of phylogenetic trees is a mapping out the proposed divisions and common ancestors of all living species. traditionally, these trees have been built using morphological data, such as appearance and embryology. recently, it has been possible to construct these trees using molecular data. phylogenetic trees based on different types of information agree with each: that there is strong evidence of a real underlying common descent. this phylogenic tree is composed based on molecular data (rrna). what statements can we infer are true about the organisms throughout the tree? because the tree is rooted, all branches share a common ancestor. all organisms have some sort of cellular structure/organization. all eukaryotes evolved from bacteria. since the organisms contain rna, they share the same dna. if the organisms contain rna, the share the same four nitrogen bases.

Blood has traveled from the heart to the toes. which describes the next step of the circulation process?

Of seawater increases with decrease in the temperature. therefore, the cold water sinks to the deeper layers at the bottom