Evolution is a cornerstone of middle and high school biology curricula, but it is sometimes hard to find clear and well-designed research examples that students can easily understand. This collection of adapted research articles provides students with approachable, empirical evidence of evolution at work in our world. Engage students with standards-matched adaptations, introductory video content, comprehension questions, and vocabulary to further your lesson outcomes. Each adapted article also comes with additional suggestions for activities to enhance student understanding and make class more exciting.
Abstract: It is not easy being small. Especially when nature seems to favor larger individuals. But why don’t all animals evolve to be bigger? We studied a wild population of snow voles (a small rodent species) in their alpine habitat. Genetic analysis indicated a hidden evolutionary change: voles evolved to become smaller but the average body size of the population stayed the same. To understand the underlying causes, we separated genetic and environmental influences on vole body size. We found that young voles with genes for small bodies developed faster. This allowed them to survive better when environmental conditions changed (earlier arrival of winter). As a result, the population evolved towards a smaller body size. Our study shows that populations can evolve rapidly. But without a genetic perspective and understanding the underlying causes, we may not be able to detect these changes.
This article is suitable for high school students.
- Key terms: climate change, natural selection
- Scientific figures: bar graph, line graph
- Scientific methods: experiment, scientific modeling
Abstract: The Earth is getting warmer, and we can see the effects of it – destructive floods, severe droughts, and intense storms. Just as we must look for ways to adjust to our changing environment, animals and plants must also adapt if they want to survive. We wanted to know how animals’ reproductive traits change to help them survive in warmer climates. We looked at dragonflies because the males use dark coloring on their wings to attract mates and intimidate rivals. We created a database to compare dragonflies living in warm climates to those living in cooler climates. We found that male dragonflies living in warmer climates have less wing coloring than those living in cooler climates. We also found wing ornamentation in warmer areas to be lighter in color. This is because the darker coloring can overheat the dragonfly and they become unable to reproduce. Lighter or reduced ornamentation is naturally selected when climates are warmer.
This article is available in both UPPER and LOWER reading levels, and is suitable for middle school and high school students. It includes an extensive Lesson Plan.
- Key terms: adaptation, climate change
- Scientific figures: line graph
- Scientific methods: climate scenarios, observation
Abstract: What can we learn from fossils? We can estimate the shape and size of an extinct animal. Anything else? Well, if soft tissues (like the brain or muscles) fossilize, it could tell us how the animal functioned or behaved. Unfortunately, soft tissue decomposes quickly after an animal dies. They aren’t preserved as fossils very often. That’s why we felt really lucky when we came across a fossil of an extinct horseshoe crab with a preserved central nervous system (CNS). We discovered that the organization of the CNS in our fossil is the same as in horseshoe crabs living today. It hasn’t changed in over 300 million years! We also figured out how our unique fossil might have formed. This could help others discover similar fossils in the future.
- Key terms: fossils, neuroscience, paleontology
- Scientific figures: pictograph
- Scientific methods: microscopy, observation
Abstract: Have you heard of flying dinosaurs named pterodactyls [terr-oh-dak-tlz]? Well, you may be surprised to hear that they are not technically dinosaurs. Pterodactyls, part of the group pterosaurs [terr-oh-sorz], were reptiles. They were related to dinosaurs, which are also reptiles, but do not belong to that group. Pterosaurs were the first vertebrates that were able to fly by flapping their wings. This makes them all the more interesting. Have you ever thought about how it is possible that some animals started to fly? How did they get their wings? The general answer is: evolution. But here the mystery deepens. For a long time it seemed like there was a huge evolutionary gap between pterosaurs and most other animals. How did they come about? By looking at fossils, we found out that lagerpetids [la-jer-pe-tids] (a small group of non-flying reptiles) are close relatives of pterosaurs. Finding out about lagerpetids told us a bit about how pterosaurs started to fly.
- Key terms: fossils, dinosaurs, reptiles, paleontology
- Scientific figures: pictograph
- Scientific methods: experiment, tomography scans, X-ray scanner
Abstract: Geladas are an unusual primate. They eat mostly grass instead of fruit or meat. They are known as “bleeding heart monkeys” for the bright red patch of skin on their chests. They also live high in the mountains instead of in the jungle or the savanna. The air is thinner high in the mountains, so it is harder to get enough oxygen. How can geladas thrive in that environment? That’s what we wanted to find out. We studied the DNA of wild geladas. We found a surprising difference in how DNA is packaged between geladas from two different regions of Ethiopia. Also, we know that some animals react to low oxygen by increasing the amount of hemoglobin in their blood. But we learned that geladas don’t do that. Instead, they might have evolved to have larger lungs to help them get more oxygen with each breath.
This article is suitable for high school students. It includes a Lesson Idea video.
- Key terms: genetics, species distribution
- Scientific figures: map, scatter plot
- Scientific methods: DNA sequencing, experiment
Abstract: Clownfish are one of the most well-known tropical fish. But even though we see them on our TV screens, what do you know about them in real life? They live in social groups in which individuals are ranked by size (size-based dominance hierarchy). The two biggest dominant individuals breed (have babies), but the smaller individuals do not. So why do some clownfish forgo their own reproduction? We decided to investigate the smaller clownfish. We looked at the risks and rewards of moving to a different home to breed or of contesting to breed in their current home. We found that it’s too risky for these clownfish to move to a new home. Furthermore, they aren’t likely to contest by getting bigger and potentially fight the dominants since they risk being evicted from the group. So, they choose to stay put and wait in the hope that they will one day be able to breed.
This article is suitable for middle school students. It includes an Ask-A-Scientist interview with the original researcher.
- Key terms: animal behavior, genetics
- Scientific figures: pictograph
- Scientific methods: experiment, field study, observation
Abstract: We all know what it feels like when we have not had enough sleep. You might feel tired, have trouble concentrating, or even be grumpy and irritable. Despite it being such an important part of our daily lives, sleep still remains a bit of a mystery! To help answer the question of why we sleep, scientists have started researching sleep in other animals. This can help us understand how and why sleep evolved. Sharks are hundreds of millions of years old. In fact, they are the oldest living group of jawed vertebrates! Because of this, we think they could help unlock important information about the evolution of sleep. We studied the metabolic rate and behavior of draughtsboard sharks (Cephaloscyllium isabellum) over a 24-hour period. Our results show that when sharks sleep, they typically have a flat body posture and a reduced metabolic rate. Our study supports the hypothesis that the conservation of energy is a core function of sleep. It also provides insight into its evolution.
This article is available in both UPPER and LOWER reading levels, and is suitable for elementary school, middle school and lower high school students. It includes a Lesson Idea video.
- Key terms: animal behavior, metabolism
- Scientific figures: bar graph, pictograph
- Scientific methods: experiment, observation
That’s Not All!
Check out all of our articles on the topics:
Or look at these excellent resources on teaching evolution:
- Understanding Evolution Teaching Guide, University of California, Berkeley
- “15 Evolutionary Gems,” Nature Education
The featured image, “Timeline of the evolution of life,” was created by user LadyofHats and added to the Wikimedia Commons with Public Domain Dedication in 2012.