Adaptation and Acclimation

 

Students typically confuse these two processes, in part because conversational English uses "adapt" interchangeably with "acclimate."  The two pairs of scenarios here attempt to get at this difference.  The first pair of scenarios also addresses the notion of selection against new mutations, thereby selecting against evolutionary change--another difficult concept to grasp.

 

The second set of scenarios are more complicated, and may not be straightforward for some classes.  They were developed for the freshman introductory lab course at Indiana University, and therefore assume background knowledge that students in middle school or high school are in the process of acquiring.

 

 

 


Names: __________________

__________________

__________________

Enzyme Activity in Mountain Fish

The Red Stickleback

 

On Mt. Monadnock, there is a population of Red Stickleback fish.  They live primarily in the streams near the top of the mountain, because An Important Enzyme (AIE) works best at 16C, and they suffer a high degree of stress in the 30C water of the lowlands.

 

Hurricane George comes through, and washes a third of the Red Sticklebacks into the lowlands.  The fish that are left behind have less competition, and quickly replenish the population.

 

All Red Sticklebacks have AIE, but there are occasional mutations.  Sometimes, a fish is born with a mutant AIE that works best at 30C, instead of the normal 16C. 

 

When the fish reproduce here on the heights of Mt. Monadnock, there are 3 new fish for every parent with 16-AIE (which well call 16), but only 2 for every parent with 30-AIE (which well call 30).  At first, all can reproduce effectively, but once the population reaches its capacity, the total number of fish cant increase each year, so some of the young die.  Here, lets say the capacity is 10 fish (if we said 10,000 fish, wed be drawing fish for days).

 

What happens to this population over the course of several years?

 

Starting population of fish:

 

first generation:

 

 

second generation:

 

 

third generation:

 

 

fourth generation:

 

 

fifth generation:

 

 

 

What happened?

 

 

 

 

 


Names: __________________

__________________

__________________

Enzyme Activity in Mountain and Lowland Fish

The Blue Stickleback

 

On Mt. Lyell, there is a population of Blue Stickleback fish.  They live primarily in the streams near the top of the mountain, because An Important Enzyme (AIE) works best at 16C, and they suffer a high degree of stress in the 30C water of the lowlands.

 

Hurricane George comes through, and washes a third of the Blue Sticklebacks into the lowlands.

 

All Blue Sticklebacks have AIE, but there are occasional mutations.  One fish has a mutant AIE that works best at 30C, instead of the normal 16C. 

 

Four of the Blue Sticklebacks are washed into a pond in the lowlands, where they struggle to survive and reproduce.  When the fish reproduce, there are 3 new fish for every parent with 30-AIE (which well call 30), but only 2 for every parent with 16-AIE (which well call 16).  Its a small pond, and can maintain a population of only 10 fish—so some of the young die.

 

What happens to this population over the next few years?

 

Starting population of fish:

 

first generation:

 

 

second generation:

 

 

third generation:

 

 

fourth generation:

 

 

fifth generation:

 

 

What happened?


 

 

 

Brief discussions of the "what happened?" questions at the bottom of each sheet:

 

The following paragraph can be inserted at the bottom of each sheet if we want to give the answer directly to the students.

 

A mutation occurred, creating a 30 fish.  It was able to reproduce, passing its genes to its offspring.  The non-mutant 16 fish also were able to reproduce, passing their genes to their offspring.  The surrounding environment influenced which individual fish had more offspring, resulting in selection ____ for ____ against the mutation (which is it?).  What is this process called?

 

However, it may be more appropriate to lead students through the discussion, allowing them to conclude that natural selection operates in both scenarios. 

 

Caution

 

            Even with experienced educators working through this, the question arises, "why are we doing this?" for the fish that remain at the top  of the mountain.  The scenario "leads nowhere."  There's no change in the population overall.  The expectation is that something should happen, or we wouldn't be doing this.

            That is exactly the point that this scenario makes.  When the environment is stable, new mutations are usually selected against.  This is the same thing as a mutant individual dying because they are "sick," which we typically do not associate with natural selection.  Yet, that is precisely why evolutionary change commonly occurs non-linearly (or as Gould put it, as "punctuated equilibrium").  A constant environment tends to select for the status quo.  A changed environment has the opportunity to select for mutations that would have been selected against, until a new environmental equilibrium, and a new status quo, are established.

 

 


Names: __________________

__________________

__________________

Enzyme Activity in Mountain and Lowland Fish

The Red Stickleback

 

On Mt. Monadnock, there is a population of Red Stickleback fish.  They live primarily in the streams near the top of the mountain, because An Important Enzyme (AIE) works best at 16C, and they suffer a high degree of stress in the 30C water of the lowlands.

 

Hurricane George comes through, and washes a third of the Red Sticklebacks into the lowlands.

 

All Red Sticklebacks have AIE, but there are occasional mutations.  One fish has a mutant AIE that works best at 30C, instead of the normal 16C.  All fish have 50,000 AIE molecules per gram of fish.

 

Four of the Red Sticklebacks are washed into a pond where they struggle to survive and reproduce.  When the fish reproduce, there are 3 new fish for every parent with 30-AIE (which well call 30), but only 2 for every parent with 16-AIE (which well call 16).  Its a small pond, and can maintain a population of only 10 fish—so some of the young die.

 

What happens to this population over the next few years?

 


Starting population of fish:

first generation:

 

 

second generation:

 

 

third generation:

 

 

fourth generation:

 

 

fifth generation:

 

 

Years later, we analyze the fish from the pond, and 10 fish from the heights of Mt. Monadnock.  Using a clever method that doesnt hurt the fish, we measure AIE, then put the fish in a tank at room temperature (25C).  We measure AIE again after two weeks.  What do we find?

We conclude that these fish handle the temperature difference by

                        _____Acclimation (physiological adjustment) OR

                        _____Adaptation (genetic change due to selection for a particular version of AIE)


Names: __________________

__________________

__________________

Enzyme Activity in Mountain and Lowland Fish

The Blue Stickleback

 

On Mt. Wilson, there is a population of Blue Stickleback fish.  They spawn in the streams near the top of the mountain, where the water is cool.  After three months in the cool alpine water, they migrate to the marshes of the lowlands.  They migrate back to the mountains to spawn.

 

The higher temperature in the lowlands increases the metabolic rate of the Blue Sticklebacks.  They need more of An Important Enzyme (AIE) in the marshes than in the mountains.

 

The AIE in the Blue Sticklebacks works best 25C.  It can work, although less well, in the 16C water of the mountains and in the 30C water of the lowlands.  Physiological systems increase the amount of AIE per fish; at 16C, they produce 16,000 molecules per gram of fish;  every degree increase in temperature makes them produce 1,000 molecules more per gram. 

 

We can probably make a graph of amount of AIE vs temperature.  It would look like this:

 

 

You would expect that young fish, from high in the mountains (16), should have _________ molecules of AIE per gram of fish.

 

You would expect that older fish, from the lowlands (30), should have _________molecules of AIE per gram of fish.

 

We collect 10 fish from the lowlands, and 10 fish from the heights of Mt. Wilson. Using a clever method that doesnt hurt the fish, we measure AIE, then put the fish in a tank at room temperature (25C).  We measure AIE again after two weeks.  What do we find?

 

We conclude that these fish handle the temperature difference by

                        _____Acclimation (physiological adjustment) OR

                        _____Adaptation (genetic change due to selection for a particular version of AIE)

 

 


 

Discussion afterwards

We looked at two groups of fish, mountain and lowland.  We looked at temperature optimum and amount of enzyme.  What did we see?

 

 

 

Mechanism      differential survival                 physiological feedback

                        = evolutionary adaptation        = acclimation