A variety of microorganisms live as symbionts in the human digestive tract. What determines whether their relationship with the human is parasitic or mutualistic?
a their size compared to human cells
b their reproductive rate compared to the replication rate of human cells
c. whether or not they gain energy from food that the human eats
d whether their actions harm or benefit the human host

Describe the response the kidneys have to dehydration and excessive water intake. what happens to the concentration of urine in each case ?

Which statements describe resources? one of the factors people use when deciding where they will live is the availability of resources. renewable resources have little value for people. resources are unevenly distributed throughout the world. energy is the world resource which has the highest use. the use of nonrenewable resources has decreased in recent history. the use of resources is evenly distributed throughout the world. the world's oil supply will last for the next forty years if its use continues as expected.

What environmental cues and landmarks do the geese use to determine the timing and direction of their migration over the mountains? how do they find their way?