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Join the Amoeba Sisters as they explore biomagnification! Discover why toxins are especially bad news for high level consumers.

The PBL Clearinghouse contains problems from a wide variety of disciplines. As the problems and supporting materials are covered by the Creative Commons Attribution-NonCommercial 4.0 International License, you are welcome to borrow and adapt these problems for your classroom. Because these files are open sourced, your students may search and discover the teaching notes and solutions. We encourage you to make changes, adapt the problems to your specific goals and classroom contexts and thereby discourage your students from "borrowing" solutions or otherwise circumventing your instructional goals.

"Thus far, the lineages of wolves that likely gave rise to dogs have not yet been discovered and it's possible that these puppies could be on that lineage, which would be very exciting," said evolutionary biologist Greger Larson, of the University of Oxford, one of the scientists behind a collaborative project aimed at finding out when and where dogs became the first domesticated animals.

In this tutorial you will be learning about the Linnaean system of classification used in the biological sciences to describe and categorize all living things.  The focus is on finding out how humans fit within this system.  In addition, you will discover part of the great diversity of life forms and come to understand why some animals are considered to be close to us in their evolutionary history.

A year since launching the international partnership, the Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator, CARB-X ,announced its second round of antibiotic research and development funding, awarding seven projects in six countries - two in the United States, and one each in France, India, Switzerland, Ireland and the United Kingdom.

Discover what happens when random events meet allele frequencies: genetic drift! This Amoeba Sisters video also discusses the bottleneck and founder effect as well as contrasts genetic drift with natural selection.

This flipped case was designed to introduce students in a general introductory biology course to basic protein structure. The two videos and interrupted case use keratins in hair as model proteins. From the videos students learn how amino acids regulate protein structure, and how small changes in amino acid sequence have large impacts on overall protein organization and function. The case story focuses on a puppy whose hair changes from straight to curly when it sheds its coat. The protagonist tests the adult versus puppy hair, and discovers that the amino acid composition is different in the curly versus straight hair samples. Students apply basic principles of protein structure to hypothesize why the dog's coat switched from straight to curly. The case intentionally stops short of providing a complete answer to the mystery, so students think through the molecular processes logically rather than having a final "correct" answer. An optional activity is provided that makes the case more appropriate for an introductory cell biology class.

Behold the microscopic jungle in and around you: tiny organisms living on your cheeks, under your sofa and in the soil in your backyard. We have an adversarial relationship with these microbes -- we sanitize, exterminate and disinfect them -- but according to microbiologist Anne Madden, they're sources of new technologies and medicines waiting to be discovered. These microscopic alchemists aren't gross, Madden says -- they're the future.

In this article, we'll examine scientific ideas about the origin of life on Earth. The when of life's origins (3.53.53, point, 5 billion years ago or more) is well-supported by fossils and radiometric dating. But the how is much less understood. In comparison to the central dogma or the theory of evolution, hypotheses about life's origins are much more...hypothetical. No one is sure which hypothesis is correct - or if the correct hypothesis is still out there, waiting to be discovered.

Scientists have discovered that the newly found Tapanuli orangutan of Sumatra is more closely related to its cousins in Borneo than it is to its fellow Sumatran apes. The Tapanuli population numbers only around 800 individuals.

Scientists have discovered a previously unrecognized genus of extinct horses that roamed North America during the last ice age. The new findings are based on an analysis of ancient DNA from fossils of the enigmatic 'New World stilt-legged horse'

This case study centers on symbiotic relationships between insects and bacteria using Drosophila melanogaster, the common fruit fly, and the recently discovered bacterial species Sodalis praecaptivus. Until recently, the only known Sodalis species of bacteria were symbiotically associated with several different species of insects. However, free-living non-symbiont Sodalis species are being tested in several different insect species to determine if they can transition into symbiotic relationships. A pre-class assignment (see Supplemental Materials) directs students to read an open access research journal article providing a comprehensive review of S. praecaptivus and describing an experimental weevil model that parallels that of the fruit fly. A PowerPoint presentation shown in class (see Supplemental Materials) provides further background before students work in small groups to complete the case study focusing on results from D. melanogaster and S. praecaptivus model experiments.  Although developed for a genetics course, this interrupted case is appropriate for an upper-level biology course. It can be completed within a 75-minute class meeting, or adapted for shorter time periods.

This "clicker case" tells the story of "Hannah," a baby girl adopted by two loving parents who grows up with an uncontrolled appetite and develops severe early-onset obesity. Students follow Hannah's story as she develops excessive eating early in life, which her health care team is unable to explain. A visit to obesity specialists finally reveals the underlying cause of Hannah's obsession with food: extremely low levels of circulating leptin, a hormone that regulates appetite and body weight. It is further discovered that Hannah's leptin deficiency is due to a mutation in the LEP gene. As the story unfolds, students first work on unit conversions and BMI calculations to practice quantitative skills as well as graph and data interpretation skills. Students then apply their knowledge of DNA transcription, translation, and protein structure to answer questions based on figures from a 2019 study on LEP mutations. The case is best suited for high school and lower-level undergraduate biology courses.

As a renter, there are few things more unsettling than discovering that your home has bed bugs. These pesky insects are notoriously difficult to get rid of and can quickly turn a comfortable living situation into a nightmare. If you find yourself dealing with bed bugs in a rental property, it's important to act quickly and follow the proper protocol to ensure that the problem is resolved as soon as possible.

article on key scientists

Summary of agouti mouse research into epigenetics as well as epigenetics and cancer summary.

Summary of mouse study looking at neurogenerative differences in mice.

Liver buds and brain organoids are among this year's life-saving advances in growing spare human parts.

A single genetic mutation causes resistance to DDT and pyrethroids (an insecticide class used in mosquito nets), new research concludes. With the continuing rise of resistance, the research is key as scientists say that this knowledge could help improve malaria control strategies. The researchers used a wide range of methods to narrow down how the resistance works, finding a single mutation in the GSTe2 gene, which makes insects break down DDT so it's no longer toxic. They have also shown that this gene makes insects resistant to pyrethroids raising the concern that GSTe2 gene could protect mosquitoes against the major insecticides used in public health.

The discovery of this genetic disorder, reported in two papers in the journal Cell, demonstrates the growing power of new tools to uncover the causes of diseases that previously stumped doctors.