Why doesn't penicillin work on all bacteria?

The law of superposition states that in horizontal rock layers, the oldest layers are at the bottom. Which statements explain why this is a law and not a theory? Check all that apply It has changed as technology advanced.

Which of the following is involved in "double fertilization"? a-sperm b-endosperm c-embryo sac d-all of the above

The Permian-Triassic extinction 250 million years ago wiped out about ninety percent of Earth's animal species. Some scientists are predicting a sixth mass extinction in the future, due to A) acid rain. B) air pollution. C) global warming.

Neurotransmitters are molecules that cross the synapse. True or False?

The passage of salts into and out of cells is most closely associated with the life process of A) transport B) respiration C) reproduction D) digestion

What indicates a positive test for the presence of salt?

Explain how deep water currents affect the number of organisms found in the area by circulating nutrients.

If an element has a mass number of 244 and an atomic number of 94, how many neutrons does the element have? A. 94 B. 244 C. 155 D. 150

The concentration of atmospheric carbon dioxide is currently decreasing due to human activities. t or f?

What do the data suggest about the effects of cane toads on the predatory behavior of black snakes in areas where the toads have been present for 40-60 years? a.