The ld 50 is a number scientists use in research to determine the dose of a toxin required to kill 50% of a population of organisms. biologists in louisiana have become concerned about cadmium levels in the water near new orleans, and the chance that frogs will die out. scientists have performed an experiment on bullfrog tadpoles in louisiana and the results are presented in the graph. the ld 50 for bullfrogs is reached a) at about 6 mg per gallon per day. b) at about 60% of surviving tadpoles. c) somewhere around 11 mg per gallon per day. d) somewhere between 2 mg and 3 mg per gallon per day.

Read the following scenario to answer the following question. in some zoos, rare crosses between a male lion and a female tiger have produced hybrid offspring called "ligers." male ligers are sterile but some female ligers are fertile. in the wild, lion and tiger ranges do not naturally overlap, making such a cross unlikely. furthermore, the solitary behavior of tigers and the social organizations of lions create behavioral differences. applying the biological species concept, the sterility of ligers reveals that a. lions are probably a subspecies of tigers b. tigers and lions are the same species c. a new species called "ligers" is forming d. tigers and lions are separate species

Which beat describes the brain stem

In the water cycle , when does water undergo a chemical change