The organism shown is a free-living one that is anchored to the bottom of ponds and streams during the first part if its life cycle. what is the common name of the group to which this organism belongs? a. comb jellies b. arthropods c. echinoderms d. cnidarians

Plz plz plz quick! 49 points for whoever which of the following statements about greenhouse effect is true? *life on earth is suffering because of greenhouse effect *the greenhouse effect is caused by human activity *all greenhouse gases are harmful *life on earth would not exist without the greenhouse effect

Veins have a much lower blood pressure than arteries. which of these prevents backflow of blood in veins? a. pressure applied by the heart b. one–way valves in veins c. thin muscular walls of veins

Ecology can best be described as the study of what