ClassX Video Lessons Youtube Channel MinuteEarth We don’t know what a tree is (and this video won’t tell you)
Hey there! I’m David from MinuteEarth. We love talking about trees, but recently, we stumbled upon something surprising: there’s no clear-cut way to define what a tree actually is.
Most of us picture a tree as a tall plant with a single, wooden trunk. But if we use that definition, some plants we call trees might not fit. Take palm trees, for example. They’re tall and have trunks, but their trunks aren’t made of the hard, woody material we usually think of as “wood.” Instead, they’re made of softer, fibrous stuff. The same goes for banana trees. So, are they not trees?
Then there are trees like dwarf cypress and bonsai. They have single, wooden trunks but are shorter than many shrubs, which also have woody trunks. Does that mean these small trees aren’t real trees? And what about aspens? They’re tall and woody but have multiple trunks. Are they trees?
Maybe we shouldn’t define a “tree” just by how it looks. There’s a science called taxonomy that organizes living things. It groups organisms based on their genetic relationships. For example, all primates are more closely related to each other than to non-primates. Could we do the same with trees?
Let’s look at an oak tree and a pine tree. Surprisingly, they’re not that closely related. An oak tree is more closely related to an orchid—definitely not a tree—than to a pine tree. Similarly, a maple tree is more closely related to a cabbage—again, not a tree—than to a cedar tree. It seems like “tree-ness” has evolved in different ways in different places, so the tree of life doesn’t really help us define what a tree is.
Scientists have tried, but there’s no universal way to define a tree. Taxonomy doesn’t help, and physical traits aren’t enough. This can be frustrating for researchers who want to organize and understand the world, and for anyone trying to explain what seems like a simple concept. But nature and language can be complex, so maybe it’s okay to accept a bit of uncertainty.
Take a walk around your neighborhood or schoolyard and try to identify different types of trees. Use a tree identification app or guidebook to help you. Pay attention to the characteristics like trunk type, height, and leaf shape. Discuss with your classmates whether each plant fits the traditional definition of a tree and why.
Create a “family tree” for trees using taxonomy. Research the genetic relationships between different trees and plants, like oaks, pines, orchids, and cabbages. Draw a diagram showing these relationships and present your findings to the class. Discuss how these relationships challenge the traditional concept of what a tree is.
Organize a debate in class about what should be considered a tree. Divide into groups and argue for or against including certain plants like palm trees, banana trees, and bonsai as trees. Use evidence from the article and your own research to support your arguments.
Create an art project that represents the diversity of trees. Use different materials to show the variety in trunk types, leaf shapes, and sizes. Display your artwork in the classroom and explain how each piece challenges or supports the traditional definition of a tree.
Research the evolution of trees and create a timeline showing how different types of trees have evolved over time. Include major evolutionary milestones and how these changes have affected the definition of a tree. Present your timeline to the class and discuss the implications for understanding tree diversity.
Sure! Here’s a sanitized version of the transcript:
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Hi, this is David from MinuteEarth. Here at MinuteEarth, we talk about trees a lot. In doing research for another tree video, I came across something that our team had never quite realized before: there’s no definitive way to tell what’s a tree and what isn’t.
We all have a general idea of what a tree is – it’s a tall plant with a single trunk made of wood, right? But it turns out that when you use that definition, some plants that we think of as trees actually aren’t. For example, a palm tree is tall and has a trunk, but that trunk isn’t made of the hard, structured cells we commonly refer to as “wood.” Instead, its trunk is made of less dense, fibrous material. The same goes for a banana tree. So, are they not trees?
Then you have trees like the dwarf cypress and various bonsai. They all have single trunks made of wood, but they’re short—shorter than many shrubs, some of which also have woody trunks. So, are those small trees not actual trees either? And what about aspens, which are tall and woody but have multiple trunks—are they trees?
Maybe defining a “tree” based on physical characteristics isn’t the best approach. Luckily, there’s a whole branch of science dedicated to organizing living things—taxonomy. Surely, it can help us figure out what a tree is. After all, we can classify most groups of organisms by their genetic relationships. For example, all primates are more closely related to each other than they are to non-primates. Maybe we can do the same with trees.
Let’s take an oak tree and a pine tree. It turns out they aren’t actually that closely related. Interestingly, an oak tree is more closely related to an orchid—definitely not a tree—than it is to a pine tree. Similarly, a maple tree is more closely related to a cabbage—again, definitely not a tree—than it is to a cedar tree. What we think of as “tree-ness” seems to have evolved multiple times in different places, so the tree of life doesn’t help us narrow down what a tree is.
Researchers have tried, but there is no universal, agreed-upon way to define a tree. Taxonomy isn’t helpful, and physical characteristics aren’t enough. That’s frustrating—not just for researchers who need to organize and categorize the world to better understand it, but also for those of us who just want to clearly explain what seem like simple concepts. But nature and language can be quite complex, so maybe it’s good for us to tolerate a bit of uncertainty.
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Let me know if you need any further modifications!
Tree – A large plant with a trunk, branches, and leaves, often living for many years. – The tree in our backyard provides shade and is home to many birds.
Plants – Living organisms that typically grow in soil, have stems, leaves, and roots, and produce their own food through photosynthesis. – Plants are essential for life on Earth because they produce oxygen and food.
Trunks – The main woody stem of a tree that supports the branches and leaves. – The trunks of old trees can be very thick and provide a habitat for various animals.
Taxonomy – The science of classifying organisms into groups based on similarities and differences. – In biology class, we learned about taxonomy and how scientists classify living things.
Organisms – Any living thing, from the smallest bacteria to the largest animals and plants. – All organisms need energy to survive, which they obtain in different ways.
Primates – A group of mammals that includes humans, apes, monkeys, and others, known for their large brains and complex behaviors. – Primates are often studied to understand more about human evolution.
Oak – A type of tree known for its strong wood and acorns, often found in forests and parks. – The oak tree in the park is over a hundred years old and provides a habitat for squirrels.
Pine – A type of evergreen tree with needle-like leaves, often found in colder climates. – Pine trees are commonly used as Christmas trees because they stay green all year round.
Maple – A type of tree known for its distinctive leaves and sweet sap, which can be made into syrup. – In the fall, maple trees turn beautiful shades of red and orange.
Nature – The natural world, including plants, animals, landscapes, and other features and products of the earth. – We went on a hike to enjoy the beauty of nature and observe wildlife.
