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9:16 Biological Evolution

Costslessmatingsuccess

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Unformatted text preview: ected to be more reproductively successful thus continually increase in frequency across generations until they eventually replace the old ancestral types. (rare) (due to the relative nature of the female mating preference). ancestral type (common) Costs: worse flier (so worse at negotiating all aspects of the reproductive obstacle course entailing flight). As long as the benefits of greater mating success are greater than the costs associated with encumbered flight, the even-longer-tailed males could increase in frequency across generations and eventually replace the better flying ancestral type. ancestral type (common) ancestral type ancestral type 6-5 3. longer-tailed males: shorter-tailed males: worse fliers, worse at surving (worse genes) Long-tailed widowbirds better fliers, better at surviving (better genes) ancestral type modified type Wow! shorter tail!! Wow! longer tail!! modified type ancestral type How will the composition of the population change across generations? Focus on male offspring: Benefits: greater mating success Benefits: better flier Costs: worse flier Costs: less mating success (because they are preferred by the most common type of female in the population). (so worse at negotiating all aspects of the reproductive obstacle course entailing flight). (so better at negotiating all aspects of the reproductive obstacle course entailing flight). (because they are preferred by the least common type of female in the population). Conclusion: Which combination is expected to produce the most successful male offspring depends on which case the benefits exceeds the costs. That the females preferring the longer-tailed worse-flying males could potentially produce the most reproductively successful male offspring illustrates that once a certain form of mating preference becomes common it becomes self-reinforcing. Altruism (helping behavior): One individual helps another at a cost to itself. 1. Problem with altruismIf you help out your competitors as much as you help out yourself, you will lose in a reproductive race. 2. Kin selectionFamily first in any sort of altruistic behaviors. Idea that altruistic behaviors are disproportionately given out to kin. Will help if benefits are greater than the costs. rB - C > 0 Speciation: 1 species becoming two or more - If you have some form of isolation, you can have individuals that used to be of the same breeding population become two different species. Check your understanding: 1. Come up with your own examples of ancestral type vs. modified type comparisons and apply the concepts of reproductive obstacle course to determine which one would be expected to persist. 2. How do concepts from previous chapters (eg. the concept of two loops and one sun, predator/ prey relationships, relationships between competitors, etc.) apply to the reproductive obstacle course and selection thinking? 6-6...
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