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I recently gave an objective test to my students on an Evolution Unit.  The test consisted of multiple choice questions and short answers.  I know many moan when they hear about multiple choice questions, and their groans are justified. 

 Part I:  You see, multiple choice questions often test isolated facts – a knowledge/comprehension type of assessment, fairly low on Bloom’s Taxonomy.  However, well written multiple choice questions can be more conceptual or analytical.  Students are challenged to apply their knowledge using higher order thinking skills.  This is what I strive for in my assessment strategies.

Part II:  Objective tests are often used as end-points to learning.  Teacher and students engage in learning activities which result in content and concept acquisition, which are then summatively assessed.  Learning stops prior to the assessment.  I’ve often wondered why learning had to stop there and why it couldn’t continue after an assessment was given.  In my case, I allow students to debate and vote for the best answer for multiple choice questions – which allows for even more higher order thinking.  Please note that I say “BEST” answer.  Since the questions are conceptual in nature, sometimes other answer choices are factually accurate, but don’t answer the question in the best possible way.  We get AWAY from right and wrong.  After the debate, some students are not necessarily in agreement with their peers, in which case, they have the option to write a response to justify their disagreement.  At the same time, those who decide that their answers were also not the best have the option to demonstrate their learning in writing, and earn credit back. 

I was recently impressed by this evolution test, and the high-quality thinking that was associated with their understanding of the evolution concepts.  Please note, these questions are short, yet they stimulate deep, sophisticated understanding of concepts.  Don’t believe me?  Read some student responses.  This is about empowering students to be independent, self-directed, critical thinkers.  My role is clearly the facilitator, NOT the knowledge disseminator.

My question:

2. Insects with wing mutations that prevent flight (e.g., in fruit flies, some flies have crumpled wings throughout their lives) usually can’t survive long in nature. Flightlessness is selected against. But in three of the following environments the trait could actually be selected for. In which environment would useless wings NOT be selected for?

     a. an island where stiff winds blow some flying insects out to sea, never to return.

   b. a swamp full of frogs that can see and catch flying insects better than crawling insects.

     c. a forest full of bats that catch and eat insects while in flight.

     d. a cage with predators, who crawl along the base

A student response, indicating that her answer was incorrect 

2.a The original answer selected was A, that insects with useless wings would not be selected for an island where stiff winds blow some flying insects out to sea, to never return. This answer was chosen because it seemed to be the worst environment for an insect with useless wings and the best environment for an insect with functional wings. This means that insects with functional wings would be selected for an environment where stiff winds blow while insects with useless wings would not be selected for this environment. Although insects with flying wings have the chance of flying out to sea in the winds, it was assumed that insects that could not fly would have a harder time escaping this stiff wind. This would make the environment more suitable to insects with functional wings. However this assumption was incorrect.

b. The class discussion involved many possible answers. There were various reasons behind each class member’s choice of answer. However, in the end, the possible answers were narrowed down to D, a cage with no predators, and E, a cage with slippery walls that insects cannot climb and an electrical screen on top that electrocutes insects that touch it. Reasoning behind D was that it was the most neutral answer. This environment would select insects with both functional and useless wings because food is readily available at low places which can be reached by both types of the insects. Reasoning behind E was that insects would have no source of food to survive on and therefore would not be selected. Finally, the class decided that D was the best answer because it suited both insects.

c. The correct answer is D. D is an environment in which both insects, with or without functional wings, would be selected. The question specifically asked in which environment -+–i useless wings would not be selected for. All other choices than D include situations where insects with useless wings would be selected for. In A, an island where stiff winds blow some flying insects out to sea, never to return, useless wings would keep an insect on the ground where it would be safe from the stiff winds. Therefore, the insects would be selected in this environment and A is not a correct choice. In B, a swamp full of frogs that can see and catch flying insects better than crawling insects, the insects with useless wings would have a better chance for survival over the insects with functional wings. Therefore, the insects with useless wings would be selected over insects with functional wings, so B is not a correct answer. In C, a forest full of bats that catch and eat insects while in flight, the insects with useless wings would not risk being caught because they do not fly while insects with wings do. Therefore, the insects with useless wings would be favored in this environment, so C is not the best answer. In E, a cage with slippery walls that insects cannot climb and an electrified screen on the top that electrocutes insects that touch it, insects with functional wings would try to fly to the top and then get electrocuted while insects with useless wings would remain safe on the bottom of the cage. Therefore, this environment would be favorable to insects with useless wings, so E is not the best answer. However, D is the best answer. In this environment, a cage with no predators in which food is provided in low dishes, neither of the insects, with or without functional wings, would be favored. Therefore, in this environment, insects with useless wings would not be selected over insects with functional wings.

My question:

7. A biologist studied a population of squirrels for 15 years. Over that time, the population was never fewer than 30 squirrels and never more than 45. Her data showed that over half of the squirrels born did not survive to reproduce, because of competition for food and predation. Suddenly, the population increased to 80. In a single     generation, 90% of the squirrels that were born lived to reproduce.  What inferences might you make about that population?

          1. The amount of available food probably increased.

          2. The number of predators probably decreased.

          3. The young squirrels in the next generation will show greater levels of variation than in the previous generations because squirrels that would not have survived in the past are now surviving.

     a. 1, 2, and 3 are correct.

     b. 1

     c. 2

     d. 3

     e. Both 1 and 2 are reasonable inferences.

 A student response indicating that she disagreed with the class’ conclusion.

7) a. The original answer chosen was a. 1, 2, and 3 are correct. This answer was chosen based upon the belief that , if a population increases suddenly, reasonable inferences to be drawn from the information given would be that there would be more variation in genes in that population, predation probably decreased, and the amount of food available probably increased.

b. The class discussion focused upon the fact that large populations tend to have a stable gene pool and therefore, according to the class, the correct answer to the question would be e. both 1 and 2 are reasonable inferences. The class agreed with the original answer in that the lack of predation and the increase in food would be reasonable inferences to draw from the information given.

c. The class discussion was not convincing, and the best answer is still a. 1, 2, and 3 are correct for various reasons. The class discussion was based upon the fact that the gene pool of large populations is stable, but this fact does not address the amount of variation within a population.

A large population might have a stable gene pool, but that gene pool will still have a great amount of variation. If a population of squirrels increases sharply due to a lack of predation and an abundance of food, squirrels that might not have favorable characteristics will have a better chance of procreating. This reproduction will increase the amount of genetic variation within the population. Endangered species have reduced genetic variation because the population is so small; this is because many of the traits that were not favorable were lost due to the loss of many of the species. The opposite would be true with a species that was allowed to greatly increase in population. Many unfavorable traits would be allowed to flourish and this would increase genetic variation. Therefore, a. 1, 2, and 3 are correct is the best answer to the question.