Did John Dalton use an observational study, a controlled experiment, or a mathematical model?

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important

Which of the following produces carbon dioxide? a. plants b. animals c. decomposers d. all of the above

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.