Biology connects all of life—all of YOUR life. In the final episode of Crash Course Biology, Dr. Sammy is taking your questions. No matter how big, small, or personal, biology is in them all! He’ll show us how biology can help us solve...

Why do animals do what they do? It’s a huge question, and in this episode, we’ll learn how scientists break it down. We’ll talk about the proximate and ultimate studies they use to understand animal behavior, and some of what they’ve...

When it comes to animal reproduction, there’s no one-size-fits-all strategy. Some animals need a mate, others don’t, and for some, it depends! In this episode, we’ll learn about sexual and asexual reproduction, internal and external...

The world is full of microbes and viruses that can get us sick, but we’ve got an Avengers-style defense system ready to take them on. In this episode of Crash Course Biology, we’ll learn about an animal’s immune system, from their skin...

When you think about the body’s infrastructure, you probably think of bones. But what about the heart, the blood vessels, and the lymphatic system? In this episode of Crash Course Biology, we’ll tour the cardiovascular, lymphatic, and...

Yep, this is the poop episode. Getting resources and getting rid of waste is so important, we have three whole systems dedicated to it! In this episode, we’ll learn how the respiratory system, digestive system, and urinary system work,...

There are countless types of plants and animals on Earth, but how do they work? In this episode of Crash Course Biology, we’ll take a bird’s eye view of how multicellular life functions, including how it’s organized, how it regulates...

On its own, a huge DNA sequence is a meaningless pile of data — so, how do biologists figure out what it means? They turn to the power of bioinformatics! In this episode, we’ll learn what bioinformatics is, how it works, and how...

From the flu to COVID-19, viruses are a major threat in our everyday lives. In today’s episode of Crash Course Biology, we’ll learn why viruses are like genes in a box, and how they invade and spread between cells. We’ll also discover...

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...

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...

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...

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...

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...

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.”

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.

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...

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...

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...

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...

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...

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...

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...

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.