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BIOL 208 (February 10, 2014) - Population Structure: Sex, Age, Survival

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University of Alberta
Biology (Biological Sciences)
James Cahill

BIOL 208 (February 10, 2014) Population structure: Sex, age, survival • Our BIOL 208 class is known as a closed population so we know how many people are in this class • Sex ratios o Estimating: # of individuals, and sex determination (is sometimes hard to determine) o Important to know sex ratio because:  If the sexes don’t equally contribute to reproduction, it is important to know the numbers of each so you can predict the population health of next generation o *1:1 ratio is found in most species o *In monogamic situations, rarity is favoured  *Only exception: if one sex costs more to reproduce than the other… more expensive gender will be selected against o *Don’t expect a 1:1 ratio in small populations o Sex ratios change in different age ranges:  *At birth the ratio of males to females is 1.07 but at ages of >65, the ratio drops to 0.79 • *At conception, it is more likely for XY zygotes to be created vs. XX zygotes because X-chromosome-carrying sperm are heavier. • Age structure o Males generally excluded from these types of graphs because males could potentially mate with multiple women; also, it’s harder to find out who
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