Blood moves into and then out of a heart chamber because 1. the veins and arteries constrict and dilate to propel and attract blood. 2. it moves along its pressure gradient, and that gradient depends on contraction and relaxation during the cardiac cycle. 3. it is under constant pressure, but its movement is dictated by the control of valve openings and closures. 4. All of the choices are correct.

And give a detailed description! scientist observes the boundary between two tectonic plates for a decade and finds that no new volcanoes have formed over the course of her investigation. does this result support the theory of plate tectonics? why or why not?

The graph shows the amount of global warming happening in different ecosystems. which populations of organisms will likely decline the most as a result of climate change, and why? a.coral reefs because of the loss of the symbiotic algae living within their bodies b.penguin populations because the fish they eat will move into warmer waters c.mountain-dwelling birds because rising sea levels will relocate their food sources d.large cats in the rainforest because of decreased habitat loss for their prey

Which process is represented a.) deletion b.) nondisjunction c.) translocation d.) insertion