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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.

People who are attracted to others of the same sex develop their orientation before they are born. This is not a choice. And scientific evidence shows their parents cannot be blamed. Research proving that there is biological evidence for sexual orientation has been available since the 1980s. The links have been emphasised by new scientific research.

Biologists have long puzzled about how evolutionary selection, known for its ruthless requirement for efficiency, allows the existence of males - when in so many species their only contribution to reproduction are spermatozoa. But research published today in Nature shows that sexual selection - when males compete and females choose over reproduction - improves population health and protects against extinction, even in the face of genetic stress from high levels of inbreeding.

HPV is considered one of the most common sexually transmitted infections, and it affects both men and women! Is it dangerous, and can it be prevented? Get your official DNews t-shirt here: http://www.forhumanpeoples.com/collec... Read More: Genital HPV Infection - Fact Sheet http://www.cdc.gov/std/hpv/stdfact-hp... "Human papillomavirus (HPV) is the most common sexually transmitted infection in the United States. Some health effects caused by HPV can be prevented with vaccines." Time To Rethink 'Girls-Only' Approach To HPV Vaccine? http://www.futurity.org/hpv-vaccines-... "Encouraging parents to have their sons get the human papillomavirus (HPV) vaccine-rather than just trying to get more girls vaccinated-could ultimately protect more people for the same price, according to a study by a mathematician."

Deep-sea mystery solved: astonishing larval transformation and extreme sexual dimorphism unite three fish families by Johnson, et al. (2009)* published in Biology Letters, Royal Society. The deep sea fishes at the heart of the investigation and this activity were historically classified into three families or clades based on the obvious morphological differences between the members of each group. 

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.

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

4:00 video 93% of Americans agree that sex education should be taught in schools, but what's the best approach to get teens to practice safe sex? Read More: Sex Education Delays Teens' Sexual Activity http://www.huffingtonpost.com/2012/03... "Teens who receive formal sex education wait longer to have sex, a new study finds - and when they do get around to doing the deed, they're more likely than teens who haven't had sex ed to use contraception." Sex Education in the U.S. is Screwing Our Kids http://www.salon.com/2014/12/01/why_s... "Government-funded abstinence programs and a lack of instructor training are failing the country's teens." Teaching Good Sex http://www.nytimes.com/2011/11/20/mag... "Across the country, the approach ranges from abstinence until marriage is the only acceptable choice, contraceptives don't work and premarital sex is physically and emotionally harmful, to abstinence is usually best, but if you must have sex, here are some ways to protect yourself from pregnancy and disease."

Bozeman video 10:26 Paul Andersen explains how life has evolved and continues to evolve today. A brief discussion of artificial, natural and sexual selection is included. The beak of the finch is used to explain how directional selection is achieved.

The Y chromosome is only one-third the size of the X. Although the Y has a partner in X, only the tips of these chromosomes are able to recombine. Thus, most of the Y chromosome is inherited from father to son in a pattern resembling asexual, not sexual, reproduction. No recombination means no reassortment, so deleterious mutations have no opportunity to be independently selected against. The Y chromosome therefore tends to accumulate changes and deletions faster than the X. Degradation doesn't occur in X chromosomes because during female meiosis, the X has the other X as a full partner in recombination.

HIV is a disease of the gut, a concept that's easy to lose sight of with all the attention paid to sexual transmission and blood measurements of the virus and the CD4+ T cells it infects and kills. But the bottom line is that about two thirds of all T cells reside in the lymphoid tissue of the gut, where the virus spreads after exposure, even before it shows up in blood.

4:13 Bowerbirds with David Attenborough

Video segments describing evolution in engaging cartoon format

The Birds-of-Paradise Project reveals the astounding beauty of 39 of the most exquisitely specialized animals on earth. After 8 years and 18 expeditions to New Guinea, Australia, and nearby islands, Cornell Lab scientist Ed Scholes and National Geographic photojournalist Tim Laman succeeded in capturing images of all 39 species in the bird-of-paradise family for the first time ever. This trailer gives a sense of their monumental undertaking and the spectacular footage that resulted.

From peacocks to birds-of-paradise, many male birds have evolved extreme forms of fanciness. Here you'll explore some of the most impressive displays on the planet and learn about the evolutionary processes that drive these cases of excess. Begin by using exaggerated plumage patterns as a clue to identify the males in a series of colorful bird pair photos.

The dewlaps of Anolis lizards provide a classic example of a complex signaling system whose function and evolution is poorly understood. Dewlaps are flaps of skin beneath the chin that are extended and combined with head and body movements for visual signals and displays. They exhibit extensive morphological variation and are one of two cladistic features uniting anoles, yet little is known regarding their function and evolution.