Jessi and Squeaks are making special valentines for all of their friends! And while they’re working they’re watching older videos to help them remember how they can make the best gifts!

How much is one living blue whale worth in the fight against climate change? A lot more than you may think, says financial economist Ralph Chami. He explains the value of bringing the language of dollars and cents to conservation -- and...

Paul Andersen details the first 7 of 13 labs in the AP Biology Curriculum. The following topics are all covered: Artificial Selection, Hardy-Weinberg Equilibrium, Comparing DNA using BLAST, Diffusion and Osmosis, Photosynthesis,...

In this video Paul Andersen explains how the greenhouse effect and greenhouse gases keep our planet warm enough to be habitable. He explains how greenhouse gases keep heat closer to the surface. He finally shows how increases in...

In this video Paul Andersen explains how atoms are conserved in a chemical reaction. This can be seen in a chemical equation where the subscripts represent the atoms in the molecule and the coefficients represent the molecules. The...

Paul Andersen introduces the concept of bioenergetics. He explains how living organisms utilize free energy in the Universe. He begins with a brief discussion of thermodynamics and Gibbs free energy. He then explains how reactions can...

Paul Andersen explains how living organisms exchange matter with the environment. The importance of the surface area to volume ratio is emphasized using a simple mathematical model. The essential chemicals for life; water, carbon,...

The final AP Biology Review.

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The lower half of Mr. Andersen's head explains why cells are small. This video begins with a simple geometry problem and ends with a discussion of Allen's Rule and reasoning for the microscopic nature of cells.

Paul Andersen answers over 500 questions from 39 states and 20 countries. Good luck on the AP Biology exam.

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In this video Paul Andersen shows how increasing ocean temperatures causes coral polyps to release their symbiotic algae. This process of coral bleaching decreases the availability of energy for the coral and may eventually lead to coral...

Photosynthesis plays a huge role in regulating the earth's CO2. But what happens when the temperature gets high enough that photosynthesis slows down?

Hank brings us another simple experiment that demonstrates the important biochemical process of osmosis by turning a chicken egg into a frightening alien-looking thing.

In 1990, an experiment conceived by Carl Sagan was performed using using the Galileo spacecraft. The purpose? To detect life on a planet based on measurements by a space probe. The experiment was successful, and abundant life was...

Why do shell building living creatures live near the surface of the ocean? Learn how chemistry creates a dissolving depth for calcium and determines where shell builders can live.

So, the stars made the elements, we're all made of star stuff, etc. But what does all this mean? This week Emily Graslie teaches you how the formation of chemical elements in the bellies of the earliest stars made life as we know it...

Since 1850, global average temperatures have risen by 1 degree Celsius. That may not sound like a lot, but it is. Why? 1 degree is an average. Many places have already gotten much warmer and if average temperatures increase one more...

Natural selection can lead to some pretty amazing adaptations, but sometimes the resulting traits aren’t the most efficient solutions to the problems at hand. With the bar set to “good enough,” here are some features that arose from...

As we construct more complex organic molecules, it can start to feel like decrypting a complex code. Organic synthesis takes simple starting materials, and turns them into complex structures, and reverse engineering can help us figure...

Alternative energy is great, but our infrastructure isn't exactly equipped to handle it. So scientists are coming up with other ways to use it, including turning it into food.

Over the years, scientists have made a lot of predictions about how Earth's climate is changing, but they don't just pull those predictions from thin air.

There are a lot of weird places here on Earth, but here are a few of our favorite strange spots!

Our planet is full of beautiful places, but it’s also full of wonderfully weird places. We've put together some of our favorite episodes about our planet’s weirdest lakes!

In 1986, a prospecting crew in southern Romania was looking for a good place to build a geothermal power plant, when they accidentally discovered one of the oddest caves of all...