How your teeth are shaped and formed
100,000 years ago is your answer
Bird migrations began with the recession of the glaciers during the ice age. You will notice a great increase in insects in the spring time and early summer.The birds moved North to take advantage of this increase in the food supply that followed the warming in the spring and early summer. Their reproductive organs temporarily developed so they could lay eggs and raise a family. Look at the early flush of Night crawlers in the moist times of the early rains. By mid summer most of the insects have matured, mated and died. Their eggs have hatched and turned to larva and moved underground until next spring. The shortening of the days causes the reproductive functions to decrease and signals the birds that the food will soon become scarce. They move back to the area that makes it the easiest to find food and avoid freezing. which of course is the warmer climates nearer the equator. Not all birds move past the Tropics at approximately 30 degrees. Some like Chickadees may move down from Mi or Mn or Canada only as far south as Indiana. Some migrations may be quite short. For example from the mountains down to the plains. They don't generally reproduce in the warmer winter climes they migrate to. In the spring time they migrate along paths of the retreating glaciers. As the climate warms away from the tropics the birds follow the emerging insects etc to the birds selected breeding grounds.with increased insects and longer days to feed the hatching's. It is necesary to understand why they move to cooler climates in the summer to under stand why they move to eh warmer ones in the fall. As the days shorten the food supply dwindles and the babies have fledged. They move to warmer climates in winter to rest and refuel for the next years migration.
Answer:
<u>Active transport across membranes is like refilling an empty soda can after pouring the soda into a cup. It takes effort (energy in the form of ATP) to pour the soda back into the can, it wouldn't typically happen on its own.</u>
Explanation:
Cells use several transport mechanisms to move substances across their plasma membranes. Plasma membranes control all movement of substances through passive transport, which does not use energy; and active transport which requires chemical energy in the form of ATP.
Active transport moves substances out of cells against their gradients. In the cell, glucose can be transported inwards for respiration. However, because the internal environment is typically concentrated, (and glucose is needed in high amounts) this requires the use of transport enzymes and ATP.
One characteristic is that they make energy
