Chum salmon (oncorhynchus keta) are born in freshwater environments and then migrate to the sea near the end of their lives, they return to the freshwater stream where they were born to spawn. in freshwater, water constantly diffuses into the body and ions are lost from the body. in salt water, body water diffuses out of the body and excess ions are gained from the water. a salmon's gills have special cells to pump salt in or out of the body to maintain homeostasis. in response to the salmon's moves between freshwater and salt water, some cells in the gills are produced and others are destroyed. these changes made in the cells of the gills during the lifetime of an individual salmon are an example of?a. trade offb. evolutionc. acclimatizationd. adaptation

c. Acclimatization

Explanation:

Acclimatization : Various physiological readjustments and compensatory mechanisms in body that reduces the effects of hypoxia in permanent residents at high altitude. These are basically the respiratory and hematopoetic adjustments to long-term move to high altitude.

As the Chum Salmon (oncorhynchus keta) are born in freshwater water constantly diffuses into the body and ions are lost from the body while in the sea water, they lose water.

As alot of changes are occrun in the cells of the gills of chum salmon, that is acclimatization as various physiological readjustments are being made.

C.

Explanation:

If an organism has ability to tolerate and survive  the effects of  varied  environmental factors  in its environments, by adjusting  its  body systems to  the fluctuations in these factors  to  improve its performance for  survival , such organism is said to undergo acclimatization.

it usually occur over a short period of time, and it is reversible.

These varied or changing environmental factors are  temperature,humidity, pH, water current etc, And the mechanisms for  adjustment of the body systems(homeostasis)  to tolerate and  adjust to  theses factors   may involve changes in the body structure, biochemical reactions, or behaviours.

Note it is different from adaptation, which  takes longer time, which  may be permanent and therefore affects the Genotype of the organisms.Acclimatization in most cases affects phenotype of the organism involved.