Christopher X J. Jensen
Associate Professor, Pratt Institute

Common Student Misconceptions

Having taught for many years, I find that there are some scientific misconceptions that students commonly bring with them into my classroom. Below I collect these misunderstandings, explaining why they should be considered misconceptions.

Climate change is caused by ozone depletion

Image provided by Vincent Tedeschi; source unknown

This is probably the most common misconception that I have encountered. Obviously climate change is a big topic in my Ecology and Ecology for Architects classes, where we mostly talk about the effects — rather than the causes — of global warming. But I do make sure that my students have a basic understanding of the causes of climate change, because you cannot do anything about climate change if you don’t pretty precisely understand its causes.

So climate change is not caused by the hole in the ozone layer, which — as suggested by the cartoon above — is most serious above the poles. It’s not clear to me whether the author of this cartoon is being ironic or also shares the misconception that climate change — including the melting of polar ice — is caused by a hole in the ozone layer. But consistently students bring this misconception to my courses!

Ozone depletion is a serious issue because loss of ozone high in the earth’s atmosphere exposes us to more harmful UV radiation from the sun. Increased exposure to UV radiation has been identified as a threat to some species, including amphibians (Blaustein et al. 2003). It also represents a potential health threat to us, as increased UV exposure can increase skin cancer risk. However, ozone depletion is not the cause of climate change, and it represents a far smaller threat to ecosystems than climate change.

I am not exactly sure where the idea that the hole in the ozone layer relates to climate change comes from. Ozone depletion seems like a 1980’s or 1990’s problem to us because — while it still remains a potential threat — it has been rather effectively dealt with by United Nations treaties adopted under the so-called Montreal Protocol. The cartoon above correctly identifies refrigerant chemicals as a major source of ozone depletion, and thanks to an international agreement the global use of ozone-depleting chemicals has dramatically decreased. In fact, the hole in the ozone layer is already showing signs of recovery (Mäder et al. 2010). Many point to the way we have dealt with ozone depletion as a model for dealing with climate change, but the analogy between the problems may be weak. Ozone depletion was halted by replacing a few chemicals with rather particular functions with comparable alternatives; reversing climate change will require the wide-spread replacement of fossil fuels with energy sources that have not yet been made economically viable.

Perhaps students still have a vivid image of this hole in the atmosphere, presumably letting in too much light, from some old kids’ cartoon they watched when they were very young. Such an idea would represent a serious misunderstanding about climate change, which is caused by an increase in the amount of the sun’s energy being trapped by the atmosphere rather than by an increase in the amount of the sun’s energy reaching the earth’s surface. In a nutshell, climate change is caused by an increase in atmospheric greenhouse gases, which prevent more infrared energy (produced by light absorption at the earth’s surface) from escaping into space. This can be confusing to students because some of the chemicals that cause ozone depletion are also greenhouse gases… just not the most prominent ones.

Diversity is a property of individuals

“We can use an understanding of common ancestry to help us find medicinal treatments that are applicable to all humans no matter how diverse the individual may be.”

The quote above is an actual answer from a student who did very well in my class overall. It reflects what I find is a common misconception among students: that we can think of “diversity” in individual terms.

Obviously the term “diversity” has a lot of different cultural meanings. But it has a pretty precise meaning in biology, and students should be aware of this meaning. In biology, “diversity” is a measure of how much variation there is in a population (group). Diversity is a property of populations, not individuals. And — critically — diversity is always relative: whether an individual increases or decreases the diversity of a group depends on the current composition of that group. If an individual has characteristics that are different from most members of the group, that individual may add to the diversity of the group.

Diversity also depends on what you measure. A given group or population may be extremely diverse based on one characteristic and show no diversity — no variation — in another characteristic. This is particularly evident at the genetic level, where most populations of particular species show no diversity at most gene loci.

I think that the student who provided the answer above was trying to suggest that we can find effective medical treatments for a diversity of human individuals by considering their ancestry. That is to say, by understanding our differences that have emerged due to differences in how far back we share a common ancestor, we may be able to provide medical treatments that can be fined tuned to any individual in our diverse societies. But the need for customized medical treatment is not due to some individuals being “more diverse” than others: we need to maintain a diversity of medical treatments because we live in a society that is diverse, including a substantial amount of genetic diversity, the result of our divergent ancestry.