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Their nervous systems have changed over time to fight off the powerful chemicals-an extraordinary example of evolution in action, according to a new study. "I've been wanting to understand how organisms could acquire neurotoxins, [which] requires an animal to reorganize their nervous system," says study coauthor Rebecca Tarvin, a biologist at the University of Texas at Austin and National Geographic Society grantee.

This case study was written for an introductory course for biology majors who are first learning about embryonic development. The case is composed of several parts and involves a storyline about a team of researchers who find frogs and eggs in bamboo plants during a field study. Students consider what these observations mean, learn basics about the stages of animal embryonic development, and make connections to phylogeny and natural selection. Students then apply their understanding of animal embryonic stage development to the chemical atrazine in the environment by examining data from several experiments. As a concluding activity students write a letter to an agency or newspaper of their choosing stating their opinion surrounding the use of atrazine in the environment. The case proceeds in a progressive disclosure format and involves a combination of class discussion, small group work, and homework. Because the case focuses on very basic animal embryonic development, it would also be a great start to a developmental biology course or an embryology course.

Evolutionary biologists have developed many techniques to analyze how male and female mating preferences have co-evolved. These studies combine animal behavior, sensory biology, phylogenetics, and neurobiology to observe the effects of male trait biases based on female receiver systems; that is, the "attractiveness" of the male trait to potential female mating partners.

Would you rather be bitten by a venomous rattlesnake or touch a poisonous dart frog? While both of these animals are capable of doing some serious damage to the human body, they deliver their dangerous toxins in different ways. Rose Eveleth sheds light on the distinction between poison and venom (and why you shouldn't treat either one like you've seen in the movies).

Interactive to build food chains.