Which of the following is a limiting factor in lotic ecosystems?
a. pH
b. salinity
C. light intensity
d. all of the above

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

In a lab, scientists grew several generations of offspring of a plant using the method shown. what conclusion can you make about the offspring? a. they formed from meiosis and mitosis. b. they have half the number of chromosomes as their parent. c. they have low genetic variability among them. d. they will be able to reproduce only after they grow flowers.

How are fossils most commonly formed