Some animals can produce a potassium ion concentration inside their cells that is twenty times greater than that of their environment. this ion concentration gradient is maintained by the plasma membrane. identify the process in the cell membrane that produces this difference in concentration.

Invasive species are one of the major threats to biodiversity. these species multiply quickly and compete with native species for food, sunlight, spac and other resources. on the map, determine the area where native species will have limited resources available to them due to invasion threat from invasive species threat very low low medium high very high

The table shows dates and appearance of index fossils. which rock layers can be dated most precisely? a) a layer containing both a fossil 4 and a fossil 3 b) a layer containing both a fossil 2 and a fossil 3 c) a layer containing both a fossil 1 and a fossil 4 d) a layer containing both a fossil 1 and a fossil 2

As a small change in a person's dna can cause a genetic disorder