Misconception Monday: Is Our Readers Learnin? Answers! Part 1
Let’s find out how you did on the first part of our quiz!
1. A volcano erupted on an island. The ash released from the volcano changed the acidity (pH) of the soil from the level it had been for hundreds of years. This significant change resulted in new environmental pressures on species in the soil. Which of the following is a likely outcome of these pressures?
- Some species will disappear from the soil because they do not have individuals with traits that allow them to survive in more acidic soil.
- Only some species will generate the needed mutations to adapt to the change in pH; other species will become extinct.
- Most species gain additional genetically-based traits, and this increase in complexity allows them to live in the more acidic soil.
- Individuals in each species will evolve the traits necessary to survive under these new conditions.
- Option B should have been a no-go because of the dreaded “needed”—remember, there is no need in evolution! But if you didn’t read B as saying, “Only some species will respond to the need caused by the new changes by generating mutations…” then this answer might have looked quite tasty. However, I contend that it’d still be problematic because it suggests that after the change, the species will generate the mutations. In reality, the mutations need to be present before the changes occur—especially when it comes to rapid changes like this one.
- Option C is wrong because it implies that new traits will arise on demand. That’s not how it works! Evolution only works on existing variations. If no members of the population had the traits that would enable them to survive the environmental change (and note that this question deals with a sudden change), then the population is out of luck. This is why genetic diversity is a major concern for wildlife ecologists—the more diversity there is, the better the chances a population can survive an environmental change. Also, note that this option had the pitfall of assuming that more complicated is necessarily better. Tell that to a bacterium or a parasite.
- Option D—ugh. Individuals don’t evolve, and (as with B, at least on its objectionable reading) they certainly don’t get what they need on demand.
2. A ship that had been used for many years in arctic exploration was sold and moved to a harbor in the warm waters of the Caribbean. Worms that had lived on the ship bottom crawled off in the warm waters and attempted to attach to other ships in this tropical area where there were no similar worms. Some of the worms were able to survive and reproduce. What would you expect to happen to this group of worms over many generations in this new environment?
- The worms will mate and produce offspring just as they did in their previous environment, and the group’s traits will likely remain unchanged after many generations.
- The worms will gain new, more complex traits through natural selection that will help them better adapt to the warmer waters because natural selection leads to more complex and better adapted organisms.
- Worms possessing genetic variations that help them to survive and thrive in the new environment will leave more offspring than others lacking those traits. Over time, the proportion of the worm population with these adaptive traits will likely increase.
- The mutation rate will increase in this group of worms in order to promote evolution.
- Option A is, well, just wrong—there’s no specific misconception here, but organisms all have tolerance ranges, and a big shift in environment will almost always lead to some kind of change. Not many organisms have a cockroach’s ability to live nearly anywhere—even without a head.
- Option B is a mess. There are two problems with it that we’ve seen before: the idea of traits appearing on demand and equating complexity with superiority.
- As for option D, if you weren’t dissuaded by the mutation rate’s suddenly increasing in the new environment (was this Caribbean ocean full of radioactive material? Or was it the malign mutagenic influence of the Bermuda Triangle?), then hopefully you were tipped off by the phrase “in order to promote evolution.” Beneficial mutations do not appear because they’re needed. Say it with me, people: there is no need in evolution!
3. A scientist is studying a species of gopher found in North America. Some of the areas where these gophers live and burrow have hard packed soil. Other areas contain soil that is more lightly packed and loose, and still other areas contain both types of soil. The animals that live in the area with hard packed soil have thick short claws. Those in the areas with more loosely packed soil have long thin claws. There is wide variation in claw shape among animals living in areas where both types of soil exist. Which statement best explains this distribution of gopher types?
- Both the areas with hard packed soil and the areas with looser soil were colonized by animals from the mixed soil area. The hard packed soil area happened to be colonized by animals that by chance had thicker claws, and those with thinner longer claws happened to colonize the areas with less densely packed soil.
- Each type of environment was probably colonized by gophers with variation in claw type, but over time each individual changed its traits to ones needed to live best in each area so all the gophers in the hard packed soil had only the traits needed to live there and, similarly, because the gophers in the loosely packed soil needed particular traits, they changed their traits to suit that environment.
- Animals with thick short claws are better able to burrow in dense soil, so in hard packed soil areas those animals with thicker claws were better able to survive and reproduce. In areas with loose soil, animals that thin long claws better for moving larger amounts of soil were the ones most likely to survive and produce offspring.
- The animals in the hard packed soil areas needed to have claws adapted to hard soil, so a mutation arose to provide that trait. The animals in the less dense soil areas also needed to adapt, so they had a mutation that made their claws suitable for soil in their area.
- While there are obviously some things about evolution that come down to chance, I think we can agree Option A doesn’t look like one of them. Nature is not this organized.
- Options B and D are immediately wrong due to the “needed”s, plus option B seems to attribute evolution to individuals rather than to populations.
4. Bacillus thuringienses (Bt) bacteria produce a natural insecticide. Widespread use of Bt has led to Bt resistance among insects. Why is this occurring?
- Individual insects that have mutations providing resistance to Bt can survive in the presence of Bt. The survivors pass this Bt resistance on to their offspring.
- Bt-resistant insects increase in the population by chance. There are so many insects that some of them are resistant to each type of insecticide.
- In the presence of Bt, individual insects evolve to become Bt resistant.
- Natural selection causes insects to generate genes providing resistance to Bt
- So there is no directed need in evolution, but nor is there complete randomness. Option B is out.
- In Option C, did you catch the no-no phrase of Xs evolve to do Y? No, no. Also, individuals don’t evolve, full stop.
- As for option D, no needed mutations (or any mutations for that matter) on demand!
5. A chef sprays antimicrobial cleaner on her counter top. At first, the bacteria population declines significantly. However, even though she continues to spray in following weeks, the number of bacteria begins to increase again. Why did this happen?
- Some bacteria had traits that allowed them to survive the initial antimicrobial application. They produced offspring also carrying those traits.
- After the application of antimicrobial spray, the bacteria needed to adapt by developing antimicrobial spray-resistant traits.
- The antimicrobial compound caused a mutation for resistance to it. This trait increased in the population over time.
- The bacteria that tried hardest to become resistant left more offspring, who were also resistant.
- Option B has “needed” so it’s out.
- Option C has beneficial mutations on demand.
- Yoda knows why Option D is wrong. There is no “try” in evolution—Reproduce, or reproduce not. There is no try.
6. A population of a particular shoreline plant has existed for a long period of time under conditions of stable temperature and sea level. Years ago, these plants were tall with very long roots and thin leaves, traits adapted for windy conditions well above the high tide line. Due to global climate change, a significant rise in sea level occurs and persists over multiple plant generations. A group of scientists measures this same population of plants, and finds that they are now on average shorter with much thicker leaves and even longer roots, traits adapted for being submerged at each high tide. Explain the change in the population.
- The traits in the plant population randomly changed, and would have done so regardless of an increase in rainfall.
- Due to the increased sea level, mutations occurred that led to some of the plants being shorter with thicker leaves, allowing them to withstand submergence at high tide.
- Each plant evolved to become shorter with thicker leaves in order to thrive in this wetter environment. They then passed these traits on to their offspring.
- Shorter plants with thicker leaves that already existed in the population were better able to thrive and generate offspring under the new conditions.
- Option A has the “evolution is totally random” problem.
- Option B has beneficial mutations arising on demand.
- Option C has an unprecedented trifecta: something is evolving for a particular purpose, individuals are evolving, and acquired characteristics are being inherited.
Based on the few of you that dared to put their answers in the comments section, I’m thinking that you all did pretty well! Think you can get the next six, too? I’ll post them on Monday.