1 / 13

A Recap Regarding Senescence

This overview delves into the complexities of sexual reproduction and senescence, exploring how selection pressures shape reproductive strategies up to peak reproductive value. It discusses the impact of pleiotropic genes on longevity and the advantages of sexual reproduction, including genetic "proofreading" and parasite resistance. The analysis also highlights the dynamics of sexual dimorphism, the 1:1 sex ratio, and the differing investment from males and females in offspring production. Ultimately, it emphasizes the significance of sex in evolutionary biology and its implications for future mating strategies.

knox-mccarthy
Télécharger la présentation

A Recap Regarding Senescence

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A Recap Regarding Senescence • Selection is more powerful in the stages up to the age of peak reproductive value • If a pleiotropic gene is introduced that gives an benefit early in life, at the expense of a cost much later on, than it will be selected • Senescence is the outcome of such negative effects later in life

  2. The Evolution of Sex The Mathematics Urge Sublimated

  3. What Use is Sex? • The Problem: • Asexual: 100% copy in offspring • Sexual: 50% (usually) copy in offspring • So why do some species have sex? • Some answers: • Genetic “proofreading” • Certainty of environment • Parasite resistance

  4. The Genetic Manuscript • “We are no4 ready for winter” • What is the correct letter? • A second copy from another organism of the same species may help • After “proofreading,” some recombination takes place • New genotypes are produced

  5. The Certainty of the Environment • Offspring produced in environments similar to parents: • Asexual reproduction • Offspring reproduced in environments dissimilar to parents: • Sexual reproduction • Gambling theories are not well supported by the data

  6. Parasite Resistance • Parasites are responsible for far more deaths than physical threats • Correlation between high parasite infestation and amount of recombination • Sex allows for new genetic “locks” to keep out old parasite “keys”

  7. Hermaphroditism • Simultaneous hermaphroditism • When sexual functions serve both sexes • Sequential hermaphroditism • Generally due to maturation and size-advantage • Separate sexes • When sexual functions do not serve both sexes

  8. Eggs & Sperm • “Cheating” organisms may produce a greater number of smaller gametes • Disruptive selection: • organisms producing many small gametes or fewer large gametes vs. producing average gametes

  9. Minimum Investment • Females in most species have a greater minimum investment in offspring than males • Ova • Gestation • Lactation… • Male & female “needs” differ due to minimum investment

  10. The Sex Ratio • If males can inseminate several females, why do we have 1:1 ratio? • Reproductive efficiency? • Island with 90 men & 10 women vs. 10 men & 90 women • Frequency dependent selection

  11. Sexual Dimorphism • Intrasexual contests • Lead to dimorphism of competing sex relative to other sex • No intrasexual contests leads to females typically being larger • Ova production

  12. The Wrap-Up • Evolution of sex • Proofreading • Gambling • Parasite resistance • Sex ratio • Minimum investment • Sexual dimorphism

  13. Things to Come • Long-term mating strategies • Female • Male • Short-term mating strategies

More Related