After three half-lives, a sample contains 20 grams of parent isotopes. how many grams of the parent isotope were present to start?

Which is not a characteristic of the animal kingdom? a. they include both vertebrates and invertebrates b. their skin is covered with hair or fur c. they are heterotrophs d. they are eukaryotic

Talking listening and reacting non verbally are all part of communicating

Which of the following describes a negative feedback loop? when the heart rate is too high, the body sends hormones that continually increase the heart rate higher. when a pregnant woman is in labor, the body sends hormones that increase the intensity of contractions, which then increases the secretion of the same hormones. when blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows. when a person is jogging, the body sends hormones that continually decrease the rate of oxygen supply to the legs.