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NESC 3180 (6)

November 26th, 2012.docx

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NESC 3180
Shelly Adamo

November 26th, 2012 November-26-12 12:46 PM Immunology and Serial selection  Huge range in some species in male mating success o Because of male-male competition, most never mate, then some select few produce hundreds of offspring o Like in caribou  But in females o There will be a few that are too weak to never have offspring o Large number that will manage to have one every year o Range of number of offspring much tighter in females  Because of theses skews, females will have much more selection for longer lives, because the longer they live, the more offspring they have because they only have 1 a year o But males have shorter lifespan, because excellent one time reproduction skills an asset because they can have hundreds in one season  So trade-off more weighted towards sexual selection (antlers, ect.) than towards immune function, because it is more beneficial for the males to do it that way Highly polygynous species  Where only a few males do the majority of mating with females  Males usually less immunocompetent o Males more susceptible to disease and infection Sex differences in disease resistance  Seoul virus in rats  Wild rats a very much winner take all situation (few males)  Males show much greater signs of infections than females do o Both infected at same rate o But has more replication in males, and lasts for longer  If ovaries and testes removed, these differences disappear o So hormones clearly play some roles in this Mechanisms of sex differences - not just steroids  Other reasons besides steroids  TLRs o Gene for one type resides on x chromosome o So females produce more of this gene than males do  Most genes on one x chromosome inactivated in females, but this is one of the few exceptions o So there is heightened immune response in some females because of increased expression of immune cells like this example, where gene expressed on x chromosome and not inactivated in females  Women have increased production of immune gene and cells o Double the dendritic cells (present pathogens) o Double the macrophages (circulating cells on patrol) o Start out with more t-cells and B-cells to begin with in bone marrow o During clonal expansion, tend to clone more of these cells  So women usually have antibody immune response Indirect benefits  Hamilton Zuk Hypothesis o Idea that males have to advertise disease resistance to females o Because females want very fit offspring Early exposure to disease also reduces sexually selected traits  Such as singing o Requires a lot of neural investment to make complex songs o When birds infected wi
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