Which role of protists has the most positive effect on maintaining the plant population in an
ecosystem?
A Protists are a major food source for animals.
B Protists produce approximately 75 percent of the oxygen on Earth.
C Protists decompose dead materials, returning nutrients to the soil.
D Protists found in the gut of animals assist in digestion.

How do tides affect the organisms living in intertidal zones? a. no organisms live in intertidal zones due to the tumultuous environment. b. the mechanical forces of the waves keeps the organisms clean. c. only plants live in intertidal zones because the animals float away with the waves and never return. d. the mechanical forces of the waves can dislodge the organisms from their habitat.

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

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis