2-28-08 - Psyc-131 February 28, 2008 Why is there so much...

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Psyc-131 February 28, 2008 - Why is there so much variation in mating systems and parental care? o Solitary species – don’t maintain any bonds except between parent and offspring for a sort period of time o Monogamous species many birds, fish, mammals o Polygamous species with 1 male, more than 1 female o Polygamous species with more than 1 male, more than 1 female o No parental care many turtles o Bi-parental care Both parents contribute in rearing of offspring o Male parental care only o Female parental care only Why?? Why is there so much variety? - Questions that arise as a result of these imbalances: o Why are males more brightly colored and ornamented than females in some species but not others? o Why are males larger than females in most mammals but fewer birds? o Why is sexual dimorphism usually greater in polygamous species than in monogamous species? In some species, it is hard to tell which is the male/female - Most mammals are polygamous o Males contribute comparatively little parental care o Males are typically larger than females (but not always) o Males typically have more “weapons” than females (ex: antlers and canines which enhance fighting ability) - Most birds are monogamous o Males and females contribute relatively equally to parental care o Males and females are the same size and color - But, in polygamous bird species, males (like male mammals) contribute relatively little parental care; and their usually more brightly colored and ornamented than females o And the question is WHY?? - Pheasant – females are relatively more drab than the males (in color) o Males have red eppilets on their shoulders - Red-winged blackbird – males are more brightly colored - Peacock – males have elaborate tails that they can put up in displays – these appear to be maladaptive o Hard to recognize that the males and females are members of the same species o An extreme case - Elephants – males are a lot larger in size than females (weigh nearly double) - Antelope – males have elaborate horns, females don’t 1
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Psyc-131 February 28, 2008 o This seems odd because the females are defending against offspring where as the males aren’t, so it would seem that the females should have horns (if they were selected for to defend against predators) but they aren’t for defending against predators bc males shed their antlers after the breading season (seems to make no sense) - Aragatangs – males are double the size of females - Why is sexual dimorphism usually greater in polygamous species than in monogamous species? o Hedge sparrows – in many monogamous species, they are monomorphic (can’t tell the difference between the male and female) o Egyptian geese – hard to tell the difference between the males and the females - Chart: o Physiological differences between males and females in reproduction o Males have greater reproductive potential than females; they give less parental care typically He can father more offspring than a female can produce
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2-28-08 - Psyc-131 February 28, 2008 Why is there so much...

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