2-21-08 - Psyc-131 February 21, 2008 After midterm #1....

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Psyc-131 February 21, 2008 After midterm #1… - Individuals will compete with one another for the chance to reproduce - Natural selection involves competition and structured relationship between males and females o Intersection of parental investment and mating systems - Sexual reproduction entails the formation of sex cells and the formation of gametes - Asymmetry in parental investment between male and females: o Before fertilization: asymmetry in size and number of gametes and in the rate that gametes are released Males small gametes, large numbers, energetically cheap Can produce gametes more often than females Females large gametes, small numbers, energetically costly Long time passes between time she can make one egg and then the next o After fertilization: asymmetry in incubation (some birds asymmetry in the care of the eggs), in gestation (mammals), and in care and feeding of young (mammals and some birds) Asymmetry between feeding and care has major implications Most pronounced in animals that have long life-spans Female is almost entirely responsible in the feeding of the young bc of lactation asymmetry in parental investment that starts with gametes has repercussions all along the timeline - Elephant – tremendous difference in the reproductive potential of males and females female elephant mates with male, gets pregnant for approx 2 years and then must wein offspring for 9 years that’s an 11 year investment whereas the male is free to mate with more females during that time and then each female must care for the offspring - Because the fastest rate that a female can reproduce is very much slower than the fastest rate that a male can reproduce (especially in birds and mammals) females are a scarce resource for males o Female RS is limited by food, physical condition (ability to acquire food and maintain good health/shape) o Male RS is limited primarily by his access to females Simply by the virtue of physiology, females reproduce more slowly than males which leads them to be a limiting source for males The reproductive potential of males is huge; that of females is much more constrained Can see this… 1
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Psyc-131 February 21, 2008 - Maximum number of offspring produced during lifetime: o Elephant seal – m100 – f8 Male fight for mating opportunities with each female – and large aggressive male elephant seals can monopolize mating with a huge number of females, whereas females produce one offspring per year females do well if they produce 8 offspring, male can produce up to 100 o Red deer – m24 – f14 Females moving through territory held by males o Human m>2000 – f30 The reproductive potential of males is huge! -
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This note was uploaded on 04/17/2008 for the course PSYC 131 taught by Professor Seyfarth/cheney during the Spring '08 term at UPenn.

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2-21-08 - Psyc-131 February 21, 2008 After midterm #1....

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