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Unformatted text preview: Lab 5 - Sexual Selection: Why does sex matter? Before the lab- Read the background information provided in this lab and Chapter 25 (Sexual Selection) Be VERY quiet when you come into lab so you do not disturb the cricketsthe lights will be turned off and only special red lights will be on to minimize the stress on the crickets. Bring your lab coat! Objectives By the end of this lab session students should be able to 1. Define intersexual and intrasexual competition in terms of differential success of individuals obtaining mates. 2. Explain why intersexual and intrasexual competition affects the asymmetry in morphology and behavior between sexes. 3. Evaluate the direct and indirect benefits for females when choosing a mate through female choice. 4. Design a simple experiment to test an appropriate hypothesis about male-male competition in crickets and female choice. Time Schedule 2:10 2:25 Introduction 2:25 4:00 Cricket experiments (both intrasexual and intersexual selection experiments) 4:00 4:20 Widowbird case study discussion 4:20 5:00 Discussion of results of Lab 4 (Bacteria and Evolution) Introduction Most individuals have one main goal in life, survive in order to breed and sire offspring (Sparks, 1999). The fitness of an individual is an important concept to grasp when trying to understand both natural and sexual selection. The fittest individual is not necessarily the strongest, fastest, or biggest. An individuals fitness includes its ability to survive, find a mate, produce offspringand ultimately pass its genes onto the next generation. Bright colours, enlarged fins, feather plumes, songs, horns, antlers, and tusks are often exaggerated conspicuous displays that are seen on certain animals. In addition to recognizing natural selection as a mechanism for evolutionary change, Charles Darwin had questioned the morphological extravagance of certain species and genders. Why have males in many species evolved more conspicuous ornaments, signals, and weapons than females? How can such traits evolve when they may reduce male survival? Such questions prompted Darwin to propose perhaps his most scientifically controversial ideathe theory of sexual selection. Male Competition and Female Choice Due to different resource allocation to have and rear young and often the biased operational sex ratio, males and females have different strategies for maximizing their fitness. Intrasexual selection - Same Sex Competition Often there are many more males than receptive females; therefore, males compete against each other for access to females. Individuals that show greater strength, size, agility, confidence, or cunningness are usually more successful during fights....
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This note was uploaded on 11/30/2010 for the course BIO BIO152 taught by Professor Cordon during the Fall '09 term at University of Toronto- Toronto.
- Fall '09