Some aquatic organisms that live in cold environments similar to that of the crabs have multiple forms of certain enzymes that catalyze reactions at various temperatures. Explain how having multiple forms of the enzymes would contribute to the fitness of these organisms. Both adult and juvenile red king crabs can be found in ocean water of a different salinity and osmolarity than their body tissues are. Explain why it is important to the crabs that they can regulate the osmolarity of their tissues.

1. emigration the movement of people from one place to another 2. immigration a situation in which resources are being used up at a faster rate than they can be replenished 3. migration the leaving of one's homeland to settle in a new place 4. overpopulation the movement of people to a new country 5. sustainable development a situation in which the birth rate is not sufficient to replace the existing population 6. underpopulation the ability to meet current needs without reducing the ability to meet future needs 7. unsustainable development the increase in the population of a city 8. urbanization a situation in which the number of people exceeds the available natural resources in an area

Which locations on the map are low-pressure areas? a b c d e

This is a situation in which genes are attached to an organism's sex chromosomes; the sex of an organism influences the expression of a gene.