We can identify only a small fraction of all the pulsars that exist in our galaxy because

the fossil record provides evidence of a common ancestor to many species.

a researcher conducts an experiment on the secretion of a particular hormone in mice. scientists inject mice with a substance that stimulates the production of the hormone. the scientists then test the levels of hormones produced by the mice. the tool used to measure the hormones consistently detects the levels at 10 points lower than the actual hormone levels in the mice. this tool makes measurements, but the measurements aren't .

explanation:

no u

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.