Transcript 投影片1
雄性美麗的廢物：生存無益 Sexual dimorphism • a) Male, with mane b) Female Sexual dimorphism • The large, male California sea lion, is distinctive from the surrounding, smaller females. Secondary sexual characteristics 生殖表現有利 • This male kudu, a resident of Africa, sports spiraled horns which are part of its social display during the reproductive season. Red winged blackbird • This male red winged blackbird illustrates the colorful shoulder feathers, which are displayed during courtship and territorial defense. Peacock • The peacock has a luxuriant tail and bright body used to attract the attentions of the female, the peahen. For what? Sexual Selection 性擇 • 性的二態性的形成由於動物物種內部的繁殖競爭 引起的，競爭越激烈，二態性越明顯 配偶制不同與 子代數之差異 雄性與交配對象的數量有關 Male-Male competition 雄性競爭內涵 - Female’s reproductive potential - Sperm Competition 雄性位階的確立是需名副其實 人類為例：具吸引的女人 →生殖潛能高 強暴：不正常的交配行為 一夫多妻的精子型態較長 代表意味？ 雄性暴力演化意義？ Why? 精神異常‧偶發事件 Hypothesis (a) Density – dependence （X） (b) Food （X） (c) Quality for offspring （X） (d) Fitness for male （O） Question? For female: why do not defend? Female Reproductive Strategy • Females produce large, energetically expensive eggs • Females often provide parental care • Females increase reproductive success by increasing the quality of their mates Female Choice • Good man or Good gene? Choosy Females • Female choice can dictate rules of male competition and shape male behavior • Selects for males that appeal to females • Male sage grouse display in leks • Male hangingflies offer nuptial gifts 有無好禮物的重要性 數字代表生殖成功對數 Longer is better? 子代數也較多 Handicap Principle “Look me! I am special! I have good genes and I am strong!” Sexy Sons Hypothesis “Like mother like daughter.” 長尾巴偶然機會有較佳的存活 他的子代也較強 女兒學媽媽喜歡長尾巴 兒子則為性感小生人見人愛 有選擇才知好 僅一隻公的交配成功次數9/41 多隻公的交配成功次數30/41 Male female Male Contests • Females of some species cluster in groups • Males of such species may fight one another for access to harems • Selects for large males that can defeat other males in contests 高階的母猴喜歡生女兒；低階的則多生兒子 WHY？Fitness of Female Why we need parental care? Parental Care • (a) The female parent defends and saves her three offspring, but she dies in the effort. Nevertheless, because half of her genotype is carried in the offspring (F1), a total of 1and1/2 of her genotype survives. (b) No parental defense and the female survives, but all offspring (F1) perish, leaving a total of only one (1) of her genotype surviving (the same applies to males). 有媽媽照顧的好處 Parenting Behavior • Enhancing the survival of offspring can increase parents’ reproductive success • Parental behavior comes at a cost; drains time and effort that could be spent producing additional offspring 親子矛盾演化意義 小孩的天真可愛 其演化的意義 Human Nature Sociobiology 社會生物學 http://www.ylib.com/author/wilson/books.htm