Explore the Spanish Series

Logo with the text Biology Crash Course in collaboration with HHMI BiointeractiveHHMI BioInteractive is a proud collaborator on Crash Course Biology and Biología, a new project that reimagines the original Crash Course Biology series that was released in 2012 and makes engaging biology videos available to a wider audience. This new project will consist of two 50-episode series — one in English (Crash Course Biology), and one in Spanish (Crash Course Biología) — covering fundamental topics for general high school and AP-level biology courses...

Through this collaboration, Crash Course Biology and Biología will reflect current priorities in science education while maintaining the levity, humor, and energy that are hallmarks of Crash Course videos. The series will also highlight new scientific advances; emphasize the process of science, including social aspects; and increase access and relevance for all students. 

As part of our commitment to creating more accessible content, the English and Spanish series will be released simultaneously. More than just a direct translation, the Spanish series is adapted from the English series and includes culturally relevant stories and examples presented by a Spanish-speaking scientist. 

What You Can Expect

This page will be the home for Crash Course Biology on BioInteractive. Here, you will find links to all the episodes, which will be released weekly. Most episodes will include links to relevant BioInteractive resources and activities. As always, we look forward to your feedback and ideas for additional resources. 

Image of a man
English Host

Sammy Ramsey

Dr. Sammy Ramsey is an insect researcher, science communicator, and an endowed professor of entomology at the University of Colorado Boulder. His past research has focused on predatory and parasitic insect relationships. As a science communicator, Dr. Sammy uses social media to inspire the next generation of curious minds to fall in love with STEM.
Graphic of a man with biology imagery and the text CC Biology Preview

Preview: Crash Course Biology #00

Welcome to Crash Course Biology! Over the next 50 episodes, we’ll find out how you are connected to every bug, bat, and bacteria that has ever lived. From itty-bitty cells to vast global systems, we’ll see how biology can help us understand ourselves better—and our relationships with the living (and non-living) things all around us. Now I know some of you might be thinking: “Didn’t you already do a Biology series?” Yes, we did. But we’re using everything that we’ve learned over the past decade of Crash Course to make you an even better series. Biology 2.0, if you will. Extra-shiny!

Graphic that has the text 'What is Life?'

Introduction to Biology: Crash Course Biology #01

Biology is the study of life—a four-letter word that connects you to 4 billion years’ worth of family tree. The word “life” can be tricky to define, but a shared set of characteristics helps biologists identify living things. In this episode of Crash Course Biology,  you’ll learn how all of life is connected, and why studying biology can help us better understand ourselves and our relationship to all living things.

Graphic with the text 'The Scientific Method'

The Scientific Method: Crash Course Biology #02

Science offers a way of discovering and understanding the world around us, driven by questions and tested with evidence. And it’s a twisty-turny team effort— you won’t find many lone geniuses out there, or straight lines from hypothesis to conclusion. In this episode of Crash Course Biology, we’ll talk about the big picture of how scientific progress is made, from peer review to mathematical models, with some exploding eggs along the way.

Graphic of two scientists holding a fish with the text "Best job ever"

What Biologists Do: Crash Course Biology #03

A biologist’s natural habitat is anywhere questions about life are being asked—whether the subject is a nematode or a narwhal, a single cell, or a whole ecosystem. In this episode of Crash Course Biology, we’re flipping the microscope around to show how biologists’ work goes down. Along the way, we’ll learn why zebrafish and fruitflies are some of biology’s next top models.

Life's Layers

How Life is Organized: Crash Course Biology #04

Here on Earth, life is dizzyingly diverse—but it’s also surprisingly organized. A sense of order structures life and its processes, from the tiniest cell to the total sum of every living thing. In this episode of Crash Course Biology, we’ll uncover the levels of biological organization, discover soil’s superpowers, and find out why the biosphere is kind of like a really, really long train.

Graphic displaying the text 'Solving the mystery'

Why Did All These Elephants Die? (Intro to Ecology): Crash Course Biology #05

Ecology is the study of the interactions of living things with each other and their environment. It’s a field that not only lets us explore the interconnections between living things, but also how our environment affects us, and how we influence it in turn. In this episode of Crash Course Biology, we’ll get an overview of the field of ecology, see how matter and energy are conserved and transferred through ecosystems, and follow an ecological mystery surrounding the deaths of hundreds of elephants in Botswana, Africa.

Graphic displaying text 'Animal friendships'

Community Ecology: Crash Course Biology #06

Community ecology is the study of interactions between different species of living things, and lets ecologists examine the effects of predator-prey relationships, parasites, and mutually beneficial interactions. In this episode of Crash Course Biology, we’ll examine the myriad interspecies interactions with examples, see how keystone species impact their environment and explore how communities rebuild when they are disrupted, through the lens of the 1980 eruption of Mount St. Helens.

Graphic displaying the text 'Saving the bald eagle'

Population Ecology: Crash Course Biology #07

When the Bald Eagle population started to decline in the mid-20th century, scientists began to ask why. Population ecology, the study of organisms of the same species, played a big role in answering that question. In this episode of Crash Course Biology, we’ll take a look at the methods population ecologists use to study a population and the types of data they collect. We’ll also find out how scientists helped bring the Bald Eagle back from the brink.

Graphic displaying text 'And how we know it's happening

What is Climate Change? : Crash Course Biology #08

Life on Earth has weathered boiling-hot oceans and volcanic-ash-darkened skies—but that’s nothing like the climate change we’re experiencing now. In this episode of Crash Course Biology, we’ll talk about the greenhouse effect, learn why our climate is like a tangled pair of headphones, and discover that we’ve understood the science behind climate change for much longer than you might think.

Graphic displaying text 'More than polar bears'

The Effects of Climate Change: Crash Course Biology #09

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.

Graphic displaying text 'Our biosphere'

Conservation Biology: Crash Course Biology #10

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 damage impacts human communities, and learn about wolves’ return to Yellowstone National Park.

Graphic display text 'too long?'

What a weirdly long giraffe nerve can teach us about evolution.: Crash Course Biology #11

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 its diversity. Along the way, we’ll explore the fishy origins of a giraffe’s neck, and find out what a cat’s paw and your own arm have in common.

Graphic displaying the text 'Why some black bears are...white?'

Microevolution: What's An Allele Got to Do With It?: Crash Course Biology #12

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 you, and how some tigers changed their stripes.

Graphic displaying text 'Survival of the..stickiest?'

Natural Selection: Life's way of Stayin' Alive: Crash Course Biology #13

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 survive hurricanes.

Graphic displaying text '99.9% the same'

Why do we have different skin colors? (Population Genetics) : Crash Course Biology #14

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 to be, and learn there’s much more in our DNA that we share than that sets us apart.

Graphic displaying text 'horse+zebra=???'

Where Do Species Come From? (Speciation): Crash Course Biology #15

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 New Zealand continues to stump scientists.

Grapic displaying text '4.6 billion years ago'

How Did Life Begin?: Evolutionary History: Crash Course Biology #16

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.

Graphic displaying text 'More related?'

How We're All Related (Phylogeny): Crash Course Biology #17

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 in.

Graphic displaying text "The biggest family tree ever'

The Tree of Life: Crash Course Biology #18

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, great Tree of Life, and we learn what that tree can tell us about our own place among the planet’s biodiversity.

Graphic displaying text "Nope"

Humans Didn't Evolve From Chimps (Human Evolution): Crash Course Biology #19

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.

Graphic displaying text 'Building blocks of life'

The Tiny Stuff that Makes Big Life: Carbon & Biological Molecules: Crash Course Biology #20

Despite the diverse appearance and characteristics of organisms on Earth, the chemicals that makeup 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 team of six atoms forms the vast majority of living matter.


A Love Letter to H2O: Water & pH: Crash Course Biology #21

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 helps it sustain life on a larger scale. We’ll see how some water-based solutions can be acidic or basic, and examine how our bodies maintain the narrow pH range necessary for life.

Graphic displaying text 'How do microscopes work?'

How Do Microscopes Work? : Crash Course Biology #22

There’s an immense world of tiny stuff within us and around us—but how do we know about it? In this episode of Crash Course Biology, we’ll discover how we see what we can’t see, thanks to the help of centuries-old tools and more recent technology. Along the way, we’ll learn about the major types of microscopes and how to use a typical light microscope.

Graphic displaying text 'Welcome to the cell'

A Tour of the Cell: Crash Course Biology #23

The cell is the basic unit of life, and our understanding of it has advanced as science, and the tools available to scientists, has advanced. In this episode of Crash Course Biology, we’ll take a look at the difference between prokaryotic and eukaryotic cells, take a guided tour of the eukaryotic cell, and learn why most cells are small. We’ll explore the eukaryotic cell’s surprising beginnings through an endosymbiosis that occurred about 1.5 billion years ago.

Graphic displaying text 'It's like a castle gate'

How Does Stuff Get Into Your Cells? (Cell Membranes): Crash Course Biology #24

The cell membrane is a protein-studded phospholipid bilayer that not only protects our cells, but also regulates what goes in and out. In this episode of Crash Course Biology, we’ll look at the structure of the bilayer, learn about its discovery, and explore the many ways substances can be transported into and out of cells.

Graphic displaying text 'How do cells communicate'

How Do Cells Communicate? : Crash Course Biology #25

Even though it might seem like our bodies are on autopilot, there is a whole lot happening inside us to keep things moving. In this episode of Crash Course Biology, we’ll learn that our cells are in constant communication, reminding each other—and themselves—to perform important functions like breathing, walking, or even sleeping.

Graphic displaying text 'How do we get our energy?'

How Do We Get Energy? (Chemical Reactions) : Crash Course Biology #26

Cells need energy to power the chemical reactions that keep their microscopic cities running, and most of that energy comes from a chemical called ATP. In this episode of Crash Course Biology, we’ll learn how our cells use energy, what an enzyme’s role is in chemical reactions, and what makes a reaction exergonic or endergonic.

Graphic displaying text 'Cellular respiration'

How do cells get their energy? (Electron Transport Chain): Crash Course Biology #27

You know ‘em, you love ‘em. They’re the powerhouse of the cell: mitochondria. They produce the ATP molecules that we use to do everything from talk to our friends to run a marathon. In this episode of Crash Course Biology, we’re taking a deep dive into cellular respiration, the process that produces the ATP inside of our mitochondria.

Photo displaying text 'photosynthesis: the original solar power"

Photosynthesis: The Original Solar Power: Crash Course Biology #28

Photosynthesis is a powerful process that is responsible for some of life’s most vital functions. In fact, consumers like us rely on photosynthetic producers to harness energy from the sun so that we can survive and thrive. In this episode of Crash Course Biology, we’ll explore photosynthesis in two acts, and learn how the process works inside and out.

Graphic displaying text 'Mitosis'

Mitosis and the Cell Cycle: Crash Course Biology #29

What’s the life of a cell like?  In this episode of Crash Course Biology, we’ll follow a cell’s life cycle, from its beginning as a shiny new cell all the way to division via mitosis. We’ll learn how our cells control this process, and what happens when things go wrong.

Graphic displaying text 'Meiosis'

Why Are All Humans Unique?: Meiosis: Crash Course Biology #30

Ever wonder why we aren’t exact clones of our parents, or why siblings aren’t exactly alike? The reason traces back to meiosis. In this episode of Crash Course Biology, we’ll discover how egg and sperm cells get made and learn why you’re a totally unique remix of your parents’ DNA.

Graphic displaying text 'Why your cats look like that'

Why Your Cat Looks Like That: Genetics: Crash Course Biology #31

How do traits get passed down in our DNA? And what do genes have to do with cat fur? In this episode of Crash Course Biology, we’ll untangle the simplest patterns of inheritance, and reassure our redheaded friends—you’re not going anywhere.

Graphic displaying text 'it's both'

Nature? Nurture? Not so simple: Genetic Traits: Crash Course Biology #32

It’s not nature versus nurture—it’s both! In this episode of Crash Course Biology, we’ll explore how complex interactions between genes and the environment shape all sorts of traits, from human skin color to honeybees’ “royal jelly.”

Graphic displaying text 'DNA'

Our Instruction Manual for Existing: DNA Structure & Replication: Crash Course Biology #33

Your DNA contains all the instructions your body needs to function. In this episode of Crash Course Biology, we’ll figure out what this giant instruction manual looks like and how this three-billion-letter code gets copied into your trillions of cells through DNA replication.

Graphic displaying text 'RNA and Transcription'

How mRNA helped save lives: DNA Transcription: Crash Course Biology #34

You’ve probably heard of mRNA, thanks to the COVID-19 vaccine. But what is mRNA exactly? In this episode of Crash Course Biology, we learn about the role of messenger RNA in living things and how it decodes our DNA instruction manual through transcription.

Graphic displaying text 'translation'

How RNA gets translated into protein power: Crash Course Biology #35

How does the information from mRNA turn into a protein? It all comes down to translation, where nucleotides are translated into a chain of amino acids. In this episode of Crash Course Biology, we’ll cover codon-reading ribosomes, tRNA delivery trucks, and scientists who are using what they know about translation to save lives.

Graphic displaying text 'Gene Expression'

How Genes Express Themselves: Crash Course Biology #36

If nearly all your cells have the same DNA, why are muscle cells so different from skin cells? In this episode, we’ll learn how gene expression is regulated in eukaryotes, and how methylating DNA, modifying histones, and messing with translation not only leads to different types of cells, but allows cells to adapt to the world around them.

Image of a person drinking milk with the text "Got Mutations?"

Is drinking milk a Superpower? Genetic Mutations: Crash Course Biology #37

Science fiction is full of superpowered mutants, but in reality, mutations are much more diverse and complex. Sometimes, they can change someone’s entire body, and other times, we don’t notice them at all! In this episode, we’ll unpack what mutations are, how they work (including substitutions and frameshift mutations), and how scientists are learning to control mutations using tools like CRISPR/Cas9 and gene therapy.

Graphic displaying text 'You, your bacteria'

We’re full of bacteria!: Crash Course Biology #38

Bacteria often get a bad rap, but they’re some of our best partners in science and medicine! In this episode, we’ll explore what bacteria are doing with their DNA — including how they can trade it around. We’ll learn about chromosomes and plasmids, gene expression and recombinant DNA, and how E. coli are used to make insulin.