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