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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.

In the end, Darwin came up with an entirely new theory to explain the extraordinary lengths many animals will go to in order to woo a potential mate. He called it sexual selection. Simply put, sexual selection is the evolutionary process that favors adaptations that increase an animal's chances of mating. Darwin identified two kinds. In the first, males compete fiercely with each other for access to females. This kind favors the evolution of secondary sexual characters, such as large size and armaments like horns, that enhance a male's ability to fight. In the second, males compete to win over a female.

In the deep, dark ocean, many sea creatures make their own light for hunting, mating and self-defense. Bioluminescence expert Edith Widder was one of the first to film this glimmering world. At TED2011, she brings some of her glowing friends onstage, and shows more astonishing footage of glowing undersea life.

This interrupted case study introduces the topic of bacterial sporulation and cannibalism in Bacillus subtilis. The storyline follows Susan and her lab mates who are presenting research at a lab meeting when Susan falls asleep and dreams they are stranded on a deserted island. She makes connections between their fight for survival in the dream and the survival mechanisms of the bacteria they study in the lab. The benefits of sporulation under conditions of sustained stress are fairly obvious, but Susan's dream is used to examine the idea that sporulation may not always be beneficial and that bacteria would not want to commit to entering such a state in response to temporary stresses. Through the analysis of actual data from the scientific literature, students uncover a mechanism by which B. subtilis delays its commitment to sporulation by killing members of its own species to release nutrients (i.e., cannibalism). Originally developed for a general undergraduate microbiology course when discussing the structure and growth of prokaryotic cells, the case could also be used in an introductory biology course that emphasizes bacteria and data literacy.

Malaria has long been a problem in Mali. But in 2006, the situation got worse: a malaria-carrying mosquito species named Anopheles coluzzii became increasingly resistant to common insecticides. Scientists searched for an explanation in its genes. Somehow, the species had acquired mutations that were previously only found in another species, Anopheles gambiae - despite the fact that these two species didn't usually mate with each other, and that their hybrids tended to die without producing offspring of their own, the mutations were identical.

When you leave the house, does your dog or cat even remember you? Read More: A Rat's Tenacious Memory http://www.indiana.edu/~rcapub/v17n1/... "In the wild, rats scramble over the network of pathways they have created, combing their surroundings for food, water, mates, and shelter. Their movements may seem automatic to the untrained eye, simply a reflexive pattern. Decades ago, however, researchers established that rats know where they are going and remember where they have been."

Focusing on this species of fruit fly, he and the other researchers in the lab of molecular biologist Sean B. Carroll, had made a prolonged assault on one of the key questions in evolutionary biology: how nature endows creatures with their colorful patterns, from a leopard's dark spots to a butterfly's bold swirls. In different species the patterns serve to attract mates, provide camouflage or provide other advantages in the struggle to survive. But what causes the colors to fall so precisely into place?

In most animals, the drive to breed and produce offspring is strong. However, most males live their whole lives without having the chance to breed. The events leading up to mating can be very dangerous and also very costly to an individual. Some males have evolved elaborate structures, or weapons, as a result. The structures do help males in both combative situations and with attracting females, but ironically, the structures themselves come with certain costs. This flipped case study provides students with the opportunity to not only see how animal structures and functions are linked, but also to see how certain animal structures are needed and costly. There are videos that students are expected to view before the case. The case was initially designed for a second semester college general biology class for majors. However, it can also be used in non-major biology classes. Students should have some background knowledge of natural selection, specifically sexual selection as well as energetic demands of certain structures.

If the lab technique works in the field, it could offer a new way of stopping the biting insects from spreading malaria to humans, they say. The scientists put a new "resistance" gene into the mosquito's own DNA, using a gene editing method called Crispr. And when the GM mosquitoes mated - their offspring inherited the same resistance, PNAS journal reports. In theory, if these mosquitoes bite people, they should not be able to pass on the parasite that causes malaria.

4:13 Bowerbirds with David Attenborough

Our first exception today concerns the hermit crab and the animal that determines whether hermit crabs live or die. Hermits don't eat snails, but snails are the most important things in the life of a hermit crab. And it all relates to our ongoing to tale of bilateral asymmetry. Biology concepts - bilateral asymmetry, directional asymmetry, antiasymmetry, crabs, evolution, mate choice, sexual selection, sexual dimorphism

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