Gil rides a bike. His younger brother, Jess, rides a skateboard. They both had to return a book to the library, which is 2 km from their home. Gil rode to the library in 12 minutes and home in 8 minutes. Jess skateboarded to the library in 10 minutes and home in 20. Whose leg—to or from the library—was the fastest? Show the equations you use and calculate the average speed of each leg.

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.

Apart of an ecosystem that can restrict the growth of a population is referred to as

The transport tubes from food came down the plant are called?