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Discover natural selection as a mechanism of evolution with the Amoeba Sisters. This video also uncovers the relationship of natural selection and antibiotic resistance in bacteria.

Although Hardy-Weinberg equilibrium is a fundamental part of introductory biology classes, students often have difficulty understanding its implications. This interrupted case study places students in the role of small teams who are conducting preliminary research into the impact of roads on the population structure of timber rattlesnakes in order to apply for a grant for further research. Research groups consisting of 3-4 students work through a series of questions allowing them to use HWE principles to discover for themselves how deviations from HWE can have implications for conservation biology. Periodic interruptions with help sheets (see Supplemental Materials) allow teachers to maintain an active role in the students' progress, while also demonstrating the collaborative nature of scientific research. Ultimately students formulate formal emails summarizing and interpreting their findings in order to "apply" for the grant. The case is designed for undergraduate students in introductory biology or in lower-level population genetics/conservation courses where connecting basic genetic principles to ecology and sustainability is key.

A deadly disease known as African sleeping sickness has puzzled doctors for decades. It would disappear from villages without a trace, only to re-emerge weeks or months later with no known cause. Frustrated health officials wondered how sleeping sickness could persist when not a single villager or animal-the disease's only carriers-tested positive for the insect-borne parasite that causes it. Now, scientists may have an answer at last: They've discovered the disease was hiding in plain sight this whole time, living in and even transmitting via human skin.

Sometimes, a genetic tweak can make a really big difference in an animal's appearance. That's what likely happened when the predecessors of modern snakes lost their legs, a process that started some 150 million years ago, two separate groups of scientists have discovered. Although the teams took very different approaches to solve the mystery of how those limbs vanished, both came up with similar results: Mutations in DNA located near a gene key to limb formation keep that gene from ever turning on, they report today.

A soft brush that feels like prickly thorns. A vibrating tuning fork that produces no vibration. Not being able to tell which direction body joints are moving without looking at them. Those are some of the bizarre sensations reported by a 9-year-old girl and 19-year-old woman in a new study. The duo, researchers say, shares an extremely rare genetic mutation that may shed light on a so-called "sixth sense" in humans: proprioception, or the body's awareness of where it is in space. The new work may even explain why some of us are klutzier than others.

Researchers led by Terra D. Barnes of Washington University discovered that their genetically-engineered mice stutter due to DNA defects in a humdrum "housekeeping" gene. This gene codes for a protein that simply places a "routing tag" on certain enzymes that shred cellular trash. The tag ensures that the shredding enzymes end up in chambers called lysosomes, basically the cell's garbage disposal. It's a mundane cellular activity, yet mutations in the same process in humans have also been linked to stuttering-a bizarrely specific condition for such a general gene. And, so far, scientists have no idea why the two are linked.

The short film opens with two questions: "So what determines how many species live in a given place? Or how many individuals of the species can live somewhere?" The research that provided answers to these questions was set in motion by key experiments by ecologists Robert Paine and James Estes. Robert Paine's starfish exclusion experiments on the coast of Washington state showed that removing starfish from this marine ecosystem has a big impact on the population sizes of other species, establishing the starfish as a keystone species. James Estes and colleague John Palmisano discovered that the kelp forest ecosystems of the North Pacific are regulated by the presence or absence of sea otters, which feed on sea urchins that consume kelp. These direct and indirect effects of sea otters on other species describe a trophic cascade. These early studies were the inspiration for hundreds of investigations on other keystone species and trophic cascades, as well as ongoing studies into the regulation of population sizes and species numbers.

In recent years, Claverie and his colleagues have discovered a host of giant viruses, which are as big as bacteria but lack characteristic cellular machinery and metabolism of those microorganisms. At least one family of these viruses likely evolved from single-celled parasites after losing essential genes, although the origins of other giant viruses remain a mystery, Claverie said.

Reporting on a small preliminary study, Johns Hopkins researchers say a simple blood test based on detection of tiny epigenetic alterations may reveal the earliest signs of pancreatic cancer, a disease that is nearly always fatal because it isn't usually discovered until it has spread to other parts of the body.

Lying dormant in our genomes are millions of jumping genes. Originally discovered by Barbara McClintock, transposons are DNA sequences that can move from one location to another in our DNA. Transposons cause mutations when they jump to new locations, so keeping them from jumping is important. 

The structure of DNA, discovered by James Watson and Francis Crick, suggests a mechanism of replication. The double helix unwinds, and each strand acts as a template for the construction of the new DNA molecule.

2:25 video  Scientists have recently discovered that the limbs of some sea stars have been turning into goo, and populations are dying off! Why is this happening, and will this hurt their ecosystem? Join Laci as discusses how this disease is spreading, and why it have some negative consequences.

We, and the West Turkana Archaeological Project which we co-lead, had discovered the earliest stone artifacts yet found, dating to 3.3 million years ago. The discovery of the site, named Lomekwi 3, instantly pushed back the beginning of the archaeological record by 700,000 years. That's over a quarter of humanity's previously known material cultural history.

Explore the human body like never before! With hundreds of interactive anatomy pictures and descriptions of thousands of objects in the body, InnerBody.com will help you discover what you want to know about human anatomy, right here at your fingertips. Join the millions of students, patients and inquisitive visitors - start your anatomy exploration by clicking on any of the systems above.

Origins of Life Abiogenesis article in Wikipedia. The Origin of Life - Abiogenesis, a youtube video produced by Chuck Kopec.  A Simpler Origin for Life, an article by Robert Shapiro in Scientific American. The Miller-Urey Experiment article in Wikipedia. RNA and the RNA World Exploring the New RNA World, an essay by Thomas Cech published on the Nobel Prize website. RNA Video Clips from the HHMI website that include demonstrations of catalysis and interviews with Thomas Cech. A World Apart, an HHMI article about RNA World reseearch and the role of RNAs in medicine.  RNA World article in Wikipedia. Protocells The Emergence of Cells During the Origin of Life, an essay by Irene Chen published in Science.  What Came Before DNA? an article published in Discover featuring Jack Szostak and Steven Benner.  The Szostak Lab Astrobiology The National Astrobiology Institute, established by NASA to study life in the universe.  The SETI Institute, studying the origins, nature and prevalence of life in the universe.  Astrobiology: The Search for Life, a website hosted by the Exploratorium.

Japanese knotweed (Fallopia japonica) is an invasive plant that can be very hard to eliminate. This PowerPoint-driven case study briefly describes this plant and asks students to identify possible solutions for its control when a homeowner discovers it growing next to his house. The case was designed for an introductory college course, either a general biology course or a plant biology course, and while it can be used as a regular case, it was actually written to assess the students' ability to solve a problem and write an analysis. If you teach with cases, shouldn't you test with cases as well?

Like many newborn mammals, baby mice cry to get their mother's attention. But the mother doesn't instinctively recognize these calls; she must learn the sounds of her offspring-just as human parents must learn the cries of their infants. Now, a team of researchers has discovered that the hormone oxytocin, which has been tied to trust and maternal bonding, holds the key to how this learning occurs. Only after oxytocin  tweaks the brain of a female mouse does she respond with a mother's concern and attentiveness to crying pups.

Scientists are now one step closer to understanding how genetic mutations contribute to autism. In a study released Thursday in the journal Cell, experts from UNC School of Medicine discovered how one specific autism-linked gene mutation actually works

Discover more types of non-Mendelian inheritance such as incomplete dominance and codominance with the Amoeba Sisters! This video uses vocabulary that was previously defined in the Amoeba Sisters Monohybrid Crosses video.

3:49 video, Alzheimer's disease is the most common cause of dementia, affecting over 40 million people worldwide. And though it was discovered over a century ago, scientists are still grappling for a cure. Ivan Seah Yu Jun describes how Alzheimer's affects the brain, shedding light on the different stages of this complicated, destructive disease.