The State Superintendent for Public Instruction in Arizona is up for re-election soon, and that means updating state standards to support voters and lobbyists. In a recent draft of updated science standards, the word "evolution" was removed, as well as the big bang theory. Naturally, science teachers are pretty upset. As I read comments online from supporters that think evolution is a made up theory, it becomes clear that people simply don't understand the term. The first thing we need to clarify is the word theory. Out of the scientific context, the word theory might imply just a guess or an idea. In science, we don't use the word lightly. A theory is a highly tested explanation of a scientific phenomena. If something is just a guess or prediction, we call it a hypothesis. To become a a theory, a hypothesis must have mounds of evidence. Can a theory be proven wrong? Yes. But I'd love for you to find me scientific evidence that disproves the theory of evolution.
When you think of the term evolution, what comes to your mind? Is it the idea of monkeys turning into humans? If so, you need to erase that image. The term evolution means change in genes in a population over time. Based on this definition, I guarantee you've seen evolution occur in your life repeatedly. (I'll give you examples in a minute). To be completely transparent to all my readers out there: yes, I wholeheartedly believe in God. And yes, I support the theory of evolution. The two are not mutually exclusive. I don't like saying I "believe" in evolution, because I think the word believe implies faith. We don't have to have faith that evolution is occurring, because we can see it happening! Let's dive in.
Scientists break evolution into two categories: microevolution, and macroevolution. Since you probably know the prefix "micro" means small, microevolution refers to small changes in DNA in an organism's genome. These could be caused by a variety of reasons such as random mutations or selective breeding. If these changes are beneficial to the survival of a species, they will become more common. If they aren't beneficial, the organism likely dies and that variation disappears. Ready for a few examples?
1. The Flu Virus- Ever wonder why you get the flu even though you got the vaccine last year? It's because this year's flu is a different strain than last year's flu. As the flu virus makes copies of itself, mutations (changes in the DNA sequence) occur. These changes are often resistant to the vaccine, reproduce quickly, and spread to new victims. This leads to the evolution of new strains, which is likely the cause of next year's flu season. Did we see changes in genes in a population over time? Check.
2. The Rock Pocket Mouse- Let's look at an example from my native area- the Sonoran Desert. There is a species of mouse that typically has tan fur. This is great camouflage on the desert floor. Every once in a while, a random mutation (changes in a few amino acid sequences) causes the mouse to have black fur. Living in the desert with visual predators like owls and snakes, this is no bueno. These mice get eaten pretty quickly because that gene is not beneficial.
BUT.... in the Sonoran desert there are areas that are volcanic. In these volcanic areas, the ground is covered in black lava. Now who survives well? Obviously, the mouse with the black fur. Over many generations we see that there are almost no mice with tan fur living in the volcanic areas, only mice with black fur. Did changes in genes in a population over time occur? You bet. Mutations aren't necessarily always good or always bad- it depends on your environment. If you want to see more about this cute little mouse, watch the first 5 minutes of this video:
Other examples of microevolution explain the reason we have so many dog breeds (selective breeding) and why farmers only save seed from the best crops.
Macroevolution (big changes) refers to the formation of new species, which in biology we call speciation. This form of evolution takes much longer- generally tens of thousands of years. To be considered a species, you must be able to reproduce and produce viable offspring. So this means that dog breeds are the same species, because a Labrador and a German Shepard can breed and produce puppies which can also reproduce. But if you tried to breed a dog and a cat, it wouldn't happen. Different species.
Darwin first saw variations among related species when he visited the Galapagos Islands in 1835. Among Darwin's famous finches, he noticed that finches that had large beaks ate large seeds, and finches that had small beaks ate small seeds. But were they the same species? He wasn't sure at the time, but we now know based on DNA evidence that there are 13 different species of finches living on the islands. Darwin wondered if God made each species, or if one species flew over from the mainland and evolved out on the islands. Based on DNA evidence we can see that the birds living on the islands are more closely related to each other than any one is to a species on the mainland. This implies one species flew over and evolved from there. (This is the same as your DNA being more similar to your family members than other humans on Earth). Now, do we have to rule out the theory that God could have a hand in this process? Of course not. But we know new species form, regardless of who you believe their creator to be.
Below is one of my favorite videos to show my students on Darwin's finches. Peter and Rosemary Grant from Princeton University set out to test Darwin's theory of evolution among finches on the Galapagos Islands. Their results were pretty spectacular- they saw the birds evolve twice within a short period of time.
It is estimated that there are over 8 million species on Earth, and there are many not yet discovered. There are currently new species being created, and species going extinct. Ready for some food for thought? If you are a religious person, you are no doubt familiar with the story of Noah's ark. In the story, God tells Noah he is going to flood the Earth, so Noah builds a huge ark, takes his family and two animals of each kind (male and female), and they live on the ark for about a year while everything else on Earth got wiped out. Do you think it is possible Noah had 8 million species on the ark? Of course not. If that bible story is true, the plants and animals Noah saved had to have evolved into the millions of species we have today. There is not a ton of evidence proving that a world-wide flood occurred... but if you are a faith based person and believe God had his hand in a catastrophic flood, then why couldn't He have also had a hand in the evolution of new species following the flood?
Up to this point, I'm hoping that most of you are thinking "okay, that makes sense." Most people can see that changes in genes in populations occurs all the time. But once we get to human evolution people freak. The bible states that God created man in his own image. If this is true, then how can we have evolved from other hominid species that don't look like we do today? I'm not here to tell you what to think or believe (remember, I believe in God too). But I want to clear up a few misconceptions that I frequently hear.
Misconception #1: There is no evidence of human evolution.
There is quite a bit of evidence showing that hominids have evolved over time. By looking at the fossil record, we are able to date fossils back in time and look at their characteristics. Over 6,000 hominid fossils have been found and analyzed. By using these fossils we can figure out how old they are, what areas of earth they inhabited, if they walked upright, and their ability to live in different environments. We can also learn about their behaviors if the fossils are found with tools or other artifacts.
As a biologist, DNA is always strong evidence that we like to lean on. When you analyze DNA of primates, humans and chimpanzees share more DNA than chimpanzees share with apes or any other primates. This tells us that chimpanzees are our closest primate ancestor. To clarify: does this mean that chimpanzees turned into humans? No. It means that we share a common ancestor. It is estimated that we branched out from this common ancestor between 6 and 8 million years ago. A great visual timeline can be seen HERE.
Misconception #2: If evolution is still occurring, then why aren't humans still evolving?
We haven't seen macroevolution in humans in a long time, but we have definitely seen small changes in the human genome in recent times. Take lactose intolerance for example. In the majority of species, only babies drink milk, and after infancy the gene for producing lactase enzyme (which allows you to digest lactose) is turned off. Several thousand years ago, being able to drink milk as an adult without getting sick became an advantage (possibly because farming became more common). In our species, the majority of adults can drink milk with no problems.
The average human height has also increased over time. 10,000 years ago, the average human height for a European male was 5 feet 4 inches. Currently, that average has increased to 5 feet 9 inches. This could be from access to better nutrition, or simply because females select taller males.
Misconception #3: If apes evolved into humans, we should not have apes around today.
This is a misconception stemming from the idea that if one species evolves into a new species, than the former one should no longer exist. This is like saying "if dogs evolved from wolves, we should not have wolves around today." This is not how evolution works. When species evolve, they generally branch out into multiple species, not one species simply evolving into a new one (see image). So as our ape ancestors evolved, there are several lineages that resulted. A great visual of the hominid/ape family tree can be seen HERE.
(If you are a biology teacher and would like more homonid evolution teaching resources, check out this blog post).
I realize this can be a sensitive subject for many. I will always have faith in a higher power, but also will not let that faith discredit scientific discoveries. The more we discover, the more we figure out how the two can go hand in hand.
Teaching human evolution can be a topic many teachers shy away from. Depending on the type of school you teach at and your student demographic, you might come across a few obstacles. In my 10 years of teaching I haven't had any push back or complaints from parents, but I know this isn't the case for everyone reading this post. I think it is 100% necessary for you to teach evolution (most importantly because it is in the standards) but you should decide how far to delve into hominid evolution based on your student population.
I personally teach general biology to sophomores, and college biology to seniors through a duel enrollment program. I hammer evolution pretty hard with the sophomores, but don't dive into hominid evolution with them. By senior year I have them learning about our hominid ancestors by analyzing skulls, comparative anatomy, looking at fossil maps, and watching videos to help them learn about the hominid family tree. I've put together a list of resources that will hopefully help you as you plan for your unit.
1. PBS Learning Media: To help students visualize the migration patterns of early hominids, I use this map activity from PBS lerning media. Students map out where fossils have been found of Australopithecus, Neanderthals, Homo Erectus, and early Homo sapiens. PBS also has a wealth of resources that can be found here.
2. Nat Geo Talk: Check out this Nat Geo Live video clip of Dr. Spencer Wells, the geneticist behind the Genographic project. Prior to Ancestry.com and 23 and Me DNA kits, the Genographic Project was working to sample DNA across all continents and create a migration map. If you would like a worksheet to accompany the video, CLICK HERE.
3. ADI Lab: If you've used ADI labs before, then your students will be skilled at the CER (claim, evidence, and reasoning) process. In this ADI lab students compare hominid skulls and make inferences based on their observations. You will need access to skulls to complete this lab. The lab itself is available online for free, but to acces the teacher guide and answer key it must be purchased through NSTA or other online vendors.
4. Becoming Human: Is a website with multiple activities on human evolution. Check out "building bodies" and "the chromosome connection" lesson plans by clicking HERE.
5. Human Migration Patterns: Use this close reading article to have students learn about how our DNA is a written document that gives us clues to the past. In this article students will learn about how we can test for ancestry and how we can even trace our ancestors back to the earliest humans in Africa. CLICK HERE to download.
6. Hominid Family Tree: This website from the Smithsonian includes an interactive hominid family tree. You can click on each species and it will give students information about where, when, and how they lived. They also provide free teaching resources which you can find HERE.
I hope you found these resources helpful! My tip for dealing with students that are resistant to evolution is this: stick with the basics. Reiterate the idea of change in genes over time. We see evolution all around us- the flu virus is a great example. Once you get students on your side understanding that genes can change, then you can begin to delve a little deeper. If you would like to check out a blog post on tips for teaching natural selection, click here.
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Cladograms are my favorite part of the classification and taxonomy unit. They are relatively simple for students to grasp and are great for visual learners. While they can be easy to read, sometimes students struggle once you ask them to make their own.
Enter: the ultimate teacher engagement tool. Candy.
In this activity, students will be given a ziplock baggie with 4 types of candy inside. On the front of the worksheet students will be given the traits to analyze and then are asked to complete the cladogram. On the back of the worksheet students need to use the same candies but analyze them using different traits. Once they finish their cladograms they are free to eat!
TIP: As I've used this activity over the past few years, I've found students sometimes struggle with the back side of the worksheet where they have to make their own cladogram. One line of questioning that really helps them organize their thoughts is this:
"What is a trait all 4 candies have in common? What is a trait only 3 of them have in common? What is a trait that 2 of those 3 remaining candies have in common? What is a trait that only 1 of the remaining candies has?" Once they think of it that way it is much easier to fill out the chart and complete the cladogram.
I've made this lab worksheet completely editable so you are free to change the candy types based on what you can find on sale at the store. Don't feel forced to use the candies I have listed! Keep in mind, if you change the candy types you will likely have to change the traits students are looking for on the front side of the worksheet.
I hope you enjoy this activity! Want another classification lab activity? Check out this blog post where students use preserved specimen jars to classify organisms.
Natural selection is one of my favorite topics to teach. Students enter the classroom with prior misconceptions and it's fun to have students figure out what natural selection and evolution really mean. Here is a list of my favorite natural selection and evolution activities:
1. Battle of the Beaks- This lab is always a hit! Students get to simulate Darwin's finches by having different "beaks" (tweezers, clothespins, etc) and feeding on different foods. Check it out here FREE in my TpT store!
2. Rock Pocket Mouse- In this activity students examine how fur color in pocket mice determines their fitness. Students learn that mutations aren't good or bad, but instead are beneficial or harmful based on their environment. Check it out here for free on biointeractive's website. Note: there are multiple versions of this activity based on your grade level.
3. Who Wants To Live A Million Years?- In this online game, students get to choose traits of a fictional species and see if their species can survive a million years.
4. Analyzing Darwin's Finches- This activity looks at the research of Peter and Rosemary Grant. This couple studied Darwin's finches on the Galapagos Islands and saw evolution occur twice within a short number of years. This activity incorporates graphing skills which is always great to throw in! Check it out here.
5. Speciation Video- When you talk about how all of today's species evolved from a common ancestor, naturally many questions will arise. How do new species form? I love how clearly this video explains the process of speciation.
6. Speciation Lab- This lab is simple to do and is a winner because it uses skittles! I created this lab because I couldn't find any activities that reinforced the types of isolation that lead to speciation. CLICK HERE to download it.
If you feel like your students are ready to delve into hominid evolution, check out this blog post that includes some resources.
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