What are the positive or negative effects on survival and reproduction of individuals as relating to their expression of a variable trait in a population?

Transmission electron microscope are best for viewing a) microorganisms in pond water b) internal organs of a mouse c)internal structures of a cell d) surface features of a specimen

Hormones are chemical molecules produced by endocrine glands. one such endocrine gland is the thyroid gland, which synthesizes the thyroid hormone, which in turn affects the heart muscles. which two statements describe the probable reason for the function of the hormone? the cells in the heart have specific receptors that allow for the intake of hormones. the heart and the endocrine glands have the exact same types of cells. all cells make the same types of hormones. thyroid hormones show their effect on the heart by means of specialized cells. thyroid cells and cardiac cells have different dna.

Which of these is one of the nitrogenous bases in dna? a. proline b. leucine c. glycine d. thymine