From Crash Course. This is a love letter to water, life’s solvent, and one of the most wonderful molecules around. In this episode of Crash Course Biology, we’ll learn about how water’s polarity and hydrogen bonding help it sustain life on a larger scale. We’ll see how some water-based solutions can be acidic or basic,…

From Crash Course. Despite the diverse appearance and characteristics of organisms on Earth, the chemicals that make up living things are remarkably similar, often identical. In this episode of Crash Course Biology, we’ll look at the building blocks of the four major classes of biomolecules, how those join up to form macromolecules, and how a…

From Crash Course. What’s a human? And how did we become humans, anyway? In this episode of Crash Course Biology, we’ll meet some of our closest relatives and trace how we evolved into the brainy, inventive, complex species we are today. Chapters: The First Humans 00:00 What is a Human? 1:18 Hominins 2:31 Dr. Xinzhi…

From Crash Course. Everywhere you look on Earth, you’ll find wonderful and diverse living things, from tiny tardigrades to soaring sequoias. And incredibly, everything alive today, and everything that’s ever lived, is related. In this episode of Crash Course Biology, we reveal how the evolutionary relationships between living things define their place on a single,…

From Crash Course. Crocodiles, and birds, and dinosaurs—oh my! While classifying organisms is nothing new, phylogeny— or, grouping organisms by their evolutionary relationships—is helping us see life in a whole new light. In this episode of Crash Course Biology, we’ll learn why this kingdom-phylum stuff is going out of style and why phylogenetic trees are…

From Crash Course. Humans may have been around for a long time, but life has existed for way longer. In this episode of Crash Course Biology, we’ll journey through deep time to uncover the history of life on Earth. We’ll explore the big, game-changing leaps where life diversified, changed, and just plain persisted. Introduction: How…

From Crash Course. How can you tell two species apart? It’s not always simple. In this episode of Crash Course Biology, we’ll learn about speciation—a process that can happen over millions of years, or within a single generation. Along the way, we’ll discover how a single species can split into two and how a reptile…

From Crash Course. In this episode of Crash Course Biology, we’ll learn about the ways population genetics reveals how groups of living things evolve—by comparing genetic similarities and differences. We’ll discover the most genetically diverse species of all (hint: it’s not us), find out why “race” isn’t the biologically valid category we’ve made it out…

From Crash Course. There are lots of ways that evolution happens, and natural selection is just one of them. In this episode of Crash Course Biology, we’ll find out how this process works and shapes traits in all living things —from ginkgo trees to howler monkeys. We’ll also learn how extra-grippy toes help some lizards…

From Crash Course. Whether we’re talking about tigers, trees, or tarantulas, evolution happens at the level of the population. In this episode of Crash Course Biology, we’ll find out how natural selection, gene flow, genetic drift, and other processes drive changes in populations. We’ll learn about the Hardy-Weinberg equation, how your alleles make you uniquely…

From Crash Course. We’ve learned a lot about plants throughout this series, but there’s much more to discover. In this episode of Crash Course Botany, we’ll peek into the future of botany. We’ll consider current plant mysteries, bridges between Western science and traditional knowledge, and what it might take to garden on the moon. Chapters:…

From Crash Course. From a single-celled common ancestor, evolution has brought us all of Life’s Greatest Hits — including butterflies, beetles, bacteria, and human beings. In this episode of Crash Course Biology, we’ll learn how evolution explains life’s unity and diversity. Along the way, we’ll explore the fishy origins of a giraffe’s neck, and find…

From Crash Course. Whether in a desert, the savanna, or a tropical rainforest, plants have an important role in the ecological processes of Earth’s biomes. In this episode of Crash Course Botany, we’ll explore these different living locales, the effects of climate change on them, and how our photosynthetic friends make the world go ‘round.…

From Crash Course. Some scientists believe we are in the middle of Earth’s sixth mass extinction: a big, precarious game of Jenga that involves every ecosystem on the planet. In this episode of Crash Course Biology, we’ll see how conservation biology aims to restore habitat and preserve biodiversity. Along the way, we’ll see how environmental…

From Crash Course. From the driest deserts to the lushest forests, ecosystems are networks of life where organisms and the environment interact. In this episode of Crash Course Botany, we’ll explore how plants function as the foundations of these systems, without which no other life on Earth would be possible. Chapters: The Foundations of Ecosystems…

From Crash Course. Climate change shakes up all of Earth’s systems, including the living ones. In this episode of Crash Course Biology, we’ll see how climate change’s effects rattle the entire chain of life. Changes felt in one population ripple out to affect entire communities and ecosystems—whether they’re composed of pine trees, puffins, or people.…

From Crash Course. The social dynamics of plants are as complex as those at any high school. By studying how plants interact — one-on-one, as a population, and in their communities — ecologists can figure out how to conserve our photosynthetic friends. In this episode of Crash Course Botany, we’ll explore these complex relationships—and eavesdrop…