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Lecture

1&2 Population structure.docx

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Department
Biology (Biological Sciences)
Course
BIOL208
Professor
James Cahill
Semester
Winter

Description
February 10, 2014 Population structure : sex, age, survival = Chapter 11 - Sex ratio - Age structure - Life tables and survivorship curves - Dispersal ***MATH****Very close to the book so use the text - Open populations are harder to estimate than closed populations - Be able to do sex determination, but very difficult in many populations (our data is worse for sex distribution than our population data) Sex ratios: o If sexes don’t equally contribute to repro then it is good to know the importance of whichever the limiting gender is o 1:1 is typical for most species o Fisher’s theorem – frequency dependent selection  Ex: Sex type can be genetically or environmental determined. Assume males and females for the next generation is equal (100 to 100). They should all be able to mate, but in one situation males become rare (biased sex ratio and males are limited) some females may not have mating opportunities if there is a monogamy going on  ^better off making male or female babies?  Male (= directional selection because they are the limiting resource). Overtime, abundance of males should increase and females will decrease. Then selection favours daughters o Depends on frequency (in this ex: rarity is selected for) o But if it costs different energy to have a son (maybe cost less energy), it should be less common in a population o Ex: Heavy biased for females at undergraduate and at U of A o Global births - more males than females, why? More embryos are male than female  XY sperm may be faster (weigh less) Age: - Relative/absolute abundance of different age classes (could be days/months/years) - Growing (If there are more young organisms than old – growing is still occurring in the population) vs. non-growing population (Even between young and old- non-growing pop) - Why do we never report statistics of males? Get info from females easily, males are much more difficult to get info for - Fig 1.5 pop crash because reproductive individuals taken out, fishery gets closed, fish are coming back (intervening shift structure) - Human wildlife conflict tends to occur in younger polar bears Survivorship Curves/ Patterns of Mortality: - *********Survivorship curve (fig 11.4) – on exams usually: age vs. number of survivors - Cohort study (study every individual in a cohort until they are not alive) - Need to know shapes of survivorship and reproduction curves Ex: drawing a graph: Y axis (# of survivor), X axis (age) Probability of mortality - % of death before it enters next age mark Ex: 50% of dying before age one
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