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.

Chapters:
A Changing Climate
Ecosystem Effects
Ecosystem Responses
Increased Carbon Dioxide
Effects on Society
Review & Credits
Credits

This week Craig is going to give you a broad overview of elections in the United States. So as you may have noticed, there are kind of a lot of people in the U.S, and holding individual issues up to a public vote doesn't seem particularly plausible. So to deal with this complexity, we vote for people, not policies, that represent our best interests. But as you'll see, this process was not thoroughly addressed in the Constitution, so there have been a number of amendments and laws at the state level implemented to create the election system we all know and (maybe) love today.

In which John Green teaches you about the election of 1860. As you may remember from last week, things were not great at this time in US history. The tensions between the North and South were rising, ultimately due to the single issue of slavery. The North wanted to abolish slavery, and the South wanted to continue with it. It seemed like a war was inevitable, and it turns out that it was. But first, the nation had to get through this election. You'll learn how the bloodshed in Kansas and the truly awful Kansas-Nebraska Act led directly to the decrease in popularity of Stephen Douglas, the splitting of the Democratic party, and the unlikely victory of a relatively inexperienced politician from Illinois, Abraham Lincoln. Lincoln's election would lead directly to the secession of several southern states, and thus to the Civil War. John will teach you about all this, plus Dred Scott, Roger Taney, and John Brown.

Chapters:
Introduction: The Civil War
The Fugitive Slave Law
Railroads
The Kansas-Nebraska Act
How the Republican Party Formed
Public Opinion on Free vs. Slave States
The New Republican Party Gains Traction
How Kansas Became a State
The Dred Scott Decision
Mystery Document
John Brown & Harpers Ferry
The Election of 1860
The Start of the Civil War
Credits

Moving on to our unit on the Physics of Electricity, it's time to talk about charge. What is charge? Is there a positive and negative charge? What do those things mean? In this episode, Shini talks about electrostatic forces, electrical charge, Coulomb's law, and the force between charged particles.

So, electric current works like a river... kinda... Instead of flowing based on elevation, electric current works a little differently. But it's a good metaphor. In this episode of Crash Course Physics, Shini talks to us about electric current, voltaic cells, and how we get electric charge.

As we learn more about electricity, we have to talk about fields. Electric fields may seem complicated, but they're really fascinating and a crucial part of physics. In this episode of Crash Course Physics, Shini chats about capacitors, conductors, electric field lines, and how objects with net charge generate electric fields.

Today, we'll explore the materials electrical engineers work with. We'll look at high-conductors, insulators, and how low-conductivity conductors can be used to generate light and heat.

The study of electricity goes all the way back to antiquity. But, by the time electricity started to become more well known, a few familiar names started to appear. Edison, Galvani, and a few others really changed the way the world worked.

Chemistry raised to the power of AWESOME! That's what Hank is talking about today with Electrochemistry. Contained within, Hank discusses electrochemical reactions, half-reactions, how batteries work, galvanic cells, voltage, standard reduction potential, cell potential, electrolysis, electroplating, and the things that go into making it possible for you to watch this episode of Crash Course Chemistry!

So we ended last episode at the start of the 20th century with special purpose computing devices such as Herman Hollerith’s tabulating machines. But as the scale of human civilization continued to grow as did the demand for more sophisticated and powerful devices. Soon these cabinet-sized electro-mechanical computers would grow into room-sized behemoths that were prone to errors. But is was these computers that would help usher in a new era of computation - electronic computing.

The legal system can seem like a complicated tangle of arcane rules and loopholes, and it can sometimes seem like it is designed to confuse. But it is possible, with the right application, for the legal system to rectify injustices. Today we're going to tell you about one instance of this, the story of Elizabeth Key, who in 1665 won her freedom in a court in Virginia.

In 1955, a 14-year-old boy named Emmett Till was brutally murdered in Money, Mississippi. The white men who murdered him killed him for being Black. Emmett Till's mother chose to have an open casket funeral, and show the world what had been done to her son. Despite the killers being acquitted in court, the story of Emmett Till and the jarring images of his funeral shocked the nation and were a vital catalyst in turning the civil rights movement into a nationwide phenomenon.

So, it turns out we have an easy time reading emotions in facial expressions, but emotions can straight up kill us! In this episode of Crash Course Psychology, Hank discusses stress, emotions, and their overall impact on our health.

Chapters:
Introduction: How Emotions Work
Facial Expressions
Expressing Emotions
How Many Emotions Are There?
Two-Dimensional Model of Emotional Experience
Defining Stress
Chronic Stress & the Autonomic Nervous System
Stress & Heart Disease
Pessimism & Depression
Review & Credits
Credits

Hank begins teaching you about your endocrine system by explaining how it uses glands to produce hormones. These hormones are either amino-acid based and water soluble, or steroidal and lipid-soluble, and may target many types of cells or just turn on specific ones. He will also touch on hormone cascades, and how the HPA axis affects your stress response.

Chapters:
Introduction: What are Hormones?
Endocrine System
Glands & Organs of the Endocrine System
Hormones Trigger Reactions in Target Cells
Water Soluble vs Lipid Soluble Hormones
How the Pancreas Regulates Blood Sugar
Hormone Cascades
Hypothalamic-Pituitary-Adrenal (HPA) Axis
Review
Credits

In the second half of our look at the endocrine system, Hank discusses chemical homeostasis and hormone cascades. Specifically, he looks at the hypothalamus-pituitary-thyroid axis, or HPT axis, and all the ways your body can suffer when that system, or your hormones in general, get out of whack.

Chapters:
Introduction: Graves Disease & Hyperthyroidism
Hormone Cascades
Hypothalamus-Pituitary-Thyroid (HPT) Axis
Thyroid Disorders & Autoimmune Dysfunction
Review
Credits

In which John Green teaches you about the Bronze Age civilization in what we today call the middle east, and how the vast, interconnected civilization that encompassed Egypt, The Levant, and Mesopotamia came to an end. What's that you say? There was no such civilization? Your word against ours. John will argue that through a complex network of trade and alliances, there was a loosely confederated and relatively continuous civilization in the region. Why it all fell apart was a mystery. Was it the invasion of the Sea People? An earthquake storm? Or just a general collapse, to which complex systems are prone? We'll look into a few of these possibilities. As usual with Crash Course, we may not come up with a definitive answer, but it sure is a lot of fun to think about.

Grumpy Professor Hank admits to being wrong about how everything is chemicals. But he now wants you to listen as he blows your mind with a new sweeping statement: everything (yes, really everything this time) is energy. What?!

This week, Hank takes us on a quick tour of how thermodynamics is applied in chemistry using his toy trebuchet as an example because he is a proud nerd.

Chapters:
Everything Is Energy
Forms of Energy
Potential Energy
Chemical Energy
Energy Is Constant & Law of Thermodynamics
System & Surroundings
Energy Transfer
Work
Heat
Trebuchets

This week we are looking at renewable energy sources and why we need them. We’ll explore hydropower, wind, geothermal, and solar power, as well as some of the challenges, and how engineers are working to make their use more widespread.

We’ve talked about many important concepts for engineers, but today we’re going to discuss a hugely important one that you might not even realize is an engineering concept: ethics. We’ll talk about what a Code of Ethics is. We’ll explore engineering ethics and the ethical theories of utilitarianism, rights ethics, and duty ethics. We’ll also take a look at a few different real life examples of ethical problems in engineering.

One of the greatest inventions is the steam engine. But why? What makes it so useful? And how does it work? In this episode of Crash Course Physics, Shini talks to us about how engines work, what makes them efficient, and why they're pretty cool.