What forms of life were present during earth's first age, the hadean era?
a. crustaceans and fish but no land animals
b. bacteria
c. the same life that is present today
d. none

Some birds look for food near cattle and other livestock. the movement of the cattle churns up the ground, making insects available to the birds. the cattle appear to be unaffected by the presence of the birds. what kind of relationship exists between the birds and the cattle? o a. parasitism o b. commensalism o c. predation o d. mutualism

(amoeba sisters video recap: pedigrees and need

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