Answer: directional
Explanation:
Because only one trait was favored. When bears are cold, being bigger helps them better adapt to the coldness. Adjusting to the weather is one trait.
The two semilunar valves, the pulmonary and aortic valves, are closed, preventing backflow of blood into the right and left ventricles from the pulmonary trunk on the right and the aorta on the left.
Answer:
The ecosystem will change, maybe, there might be some problems, like some animals will start to die by being food for the alien species, or it might progress more.
Explanation:
