Crash Course Biology

40 videos
Hank Green teaches you biology! Learn, study and understand the science of life. Topics covered range from: taxonomy, systems, biological molecules, photosynthesis, evolution, animals, plants, anatomy, and ecology.

Why carbon is a tramp

VIDEO 9:38 minutes
Hank discusses the properties of carbon and the bonding behavior of atoms.

Water - Liquid awesome

VIDEO 10:54 minutes
Hank teaches us why water is one of the most fascinating and important substances in the universe.

Biological molecules - You are what you eat

VIDEO 13:46 minutes
Hank talks about the molecules that make up every living thing - carbohydrates, lipids, and proteins - and how we find them in our environment and in the food that we eat.

Eukaryopolis - The city of animal cells

VIDEO 11:11 minutes
Hank tells us about the city of Eukaryopolis - the animal cell that is responsible for all the cool things that happen in our bodies.

In da club - Membranes & transport

VIDEO 11:19 minutes
Hank describes how cells regulate their contents and communicate with one another via mechanisms within the cell membrane.

Plant cells

VIDEO 10:00 minutes
Hank describes why plants are so freaking amazing - discussing their evolution, and how their cells are both similar to & different from animal cells.

ATP & respiration

VIDEO 12:59 minutes
In which Hank does some push ups for science and describes the "economy" of cellular respiration and the various processes whereby our bodies create energy in the form of ATP.


VIDEO 12:47 minutes
Hank explains the extremely complex series of reactions whereby plants feed themselves on sunlight, carbon dioxide and water, and also create some by products we're pretty fond of as well.


VIDEO 9:57 minutes
Hank and his brother John discuss heredity via the gross example of relative ear wax moistness.

DNA structure and replication

VIDEO 12:38 minutes
Hank introduces us to that wondrous molecule deoxyribonucleic acid - also known as DNA - and explains how it replicates itself in our cells.

DNA, hot pockets, & the longest word ever

VIDEO 13:36 minutes
Hank imagines himself breaking into the Hot Pockets factory to steal their secret recipes and instruction manuals in order to help us understand how the processes known as DNA transcription and translation allow our cells to build proteins.

Mitosis: Splitting up is complicated

VIDEO 10:24 minutes
Hank describes mitosis and cytokinesis - the series of processes our cells go through to divide into two identical copies.

Meiosis: Where the sex starts

VIDEO 11:12 minutes
Hank gets down to the nitty gritty about meiosis, the special type of cell division that is necessary for sexual reproduction in eukaryotic organisms.

Natural Selection

VIDEO 12:24 minutes
Hank guides us through the process of natural selection, the key mechanism of evolution.

Speciation: Of ligers & men

VIDEO 10:01 minutes
Hank explains speciation - the evolutionary process by which new biological species arise - in terms of finches, ligers, mules, and dogs.

Animal development: We're just tubes

VIDEO 11:04 minutes
Hank discusses the process by which organisms grow and develop, maintaining that, in the end, we're all just tubes.

Evolutionary development: Chicken teeth

VIDEO 10:18 minutes
Hank introduces us to the relatively new field of evolutionary developmental biology, which compares the developmental processes of different organisms to determine their ancestral relationship, and to discover how those processes evolved. ...

Population genetics: When Darwin met Mendel

VIDEO 10:40 minutes
Hank talks about population genetics, which helps to explain the evolution of populations over time by combing the principles of Mendel and Darwin, and by means of the Hardy-Weinberg equation.

Taxonomy: Life's filing system

VIDEO 11:52 minutes
Hank tells us the background story and explains the importance of the science of classifying living things, also known as taxonomy.

Evolution: It's a Thing

VIDEO 11:11 minutes
Hank gets real with us in a discussion of evolution - it's a thing, not a debate. Gene distribution changes over time, across successive generations, to give rise to diversity at every level of biological organization.

Comparative anatomy: What makes us animals

VIDEO 8:23 minutes
Hank introduces us to comparative anatomy, which studies the similarities and differences in animal anatomy to support the theory of evolution and the shared ancestry of living things.

Simple animals: Sponges, jellies, & octopuses

VIDEO 11:00 minutes
Hank introduces us to the "simplest" of the animals, complexity-wise: beginning with sponges (whose very inclusion in the list as "animals" has been called into question because they are so simple) and finishing with the most complex ...

Complex animals: Annelids & arthropods

VIDEO 12:37 minutes
Hank continues our exploration of animal phyla with the more complexly organized annelida and arthropoda, and a biolography on insects.


VIDEO 11:39 minutes
Hank introduces us to ourselves by taking us on a journey through the fascinatingly diverse phyla known as chordata. And the next time someone asks you who you are, you can give them the facts: you're a mammalian amniotic tetrapodal ...

Animal behavior

VIDEO 10:23 minutes
Hank and his cat Cameo help teach us about animal behavior and how we can discover why animals do the things they do.

The nervous system

VIDEO 11:37 minutes
Hank begins a series of videos on organ systems with a look at the nervous system and all of the things that it is responsible for in the body.

Circulatory & respiratory systems

VIDEO 11:10 minutes
Hank takes us on a trip around the body - we follow the circulatory and respiratory systems as they deliver oxygen and remove carbon dioxide from cells, and help make it possible for our bodies to function.

The digestive system

VIDEO 11:24 minutes
Hank takes us through the bowels of the human digestive system and explains why it's all about surface area.

The excretory system: From your heart to the toilet

VIDEO 11:45 minutes
Hank takes us on the fascinating journey through our excretory system to learn how our kidneys make pee.

The skeletal system: It's ALIVE!

VIDEO 12:41 minutes
Hank introduces us to the framework of our bodies, our skeleton, which apart from being the support and protection for all our fleshy parts, is involved in many other vital processes that help our bodies to function properly.

Big Guns: The Muscular System

VIDEO 12:10 minutes
Hank tells us the story of the complicated chemical dance that allows our skeletal muscles to contract and relax.

Your immune system: Natural born killer

VIDEO 14:41 minutes
Hank tells us about the team of deadly ninja assassins that is tasked with protecting our bodies from all the bad guys that want to kill us - also known as our immune system.

Great glands - Your endocrine system

VIDEO 10:56 minutes
Hank fills us in on the endocrine system - the system of glands which produce and secrete different types of hormones directly into the bloodstream to regulate the body's growth, metabolism, and sexual development & function.

The reproductive system: How gonads go

VIDEO 11:30 minutes
Hank lets us in on the meaning of life, at least from a biological perspective - it's reproduction, which answers the essential question of all organisms: how do I make more of myself? So, sex, how does it work?

Old & Odd: Archaea, Bacteria & Protists

VIDEO 11:49 minutes
Hank veers away from human anatomy to teach us about the (mostly) single-celled organisms that make up two of the three taxonomic domains of life, and one of the four kingdoms: Archaea, Bacteria, and Protists. They are by far the most ...

The sex lives of nonvascular plants

VIDEO 9:16 minutes
Hank introduces us to nonvascular plants - liverworts, hornworts & mosses - which have bizarre features, kooky habits, and strange sex lives. Nonvascular plants inherited their reproductive cycle from algae, but have perfected it to the ...

Vascular plants = Winning!

VIDEO 11:23 minutes
Hank introduces us to one of the most diverse and important families in the tree of life - the vascular plants. These plants have found tremendous success and the their secret is also their defining trait: conductive tissues that can take ...

The plants & the bees: Plant reproduction

VIDEO 9:46 minutes
Hank gets into the dirty details about vascular plant reproduction: they use the basic alternation of generations developed by nonvascular plants 470 million years ago, but they've tricked it out so that it works a whole lot differently ...

Fungi: Death Becomes Them

VIDEO 11:19 minutes
Death is what fungi are all about. By feasting on the deceased remains of almost all organisms on the planet, converting the organic matter back into soil from which new life will spring, they perform perhaps the most vital function in the ...

Ecology - Rules for living on earth

VIDEO 9:47 minutes
Hank introduces us to ecology - the study of the rules of engagement for all of us earthlings - which seeks to explain why the world looks and acts the way it does. The world is crammed with things, both animate and not, that have been ...