Second Exam: Thursday 2 April 2015 Covers Chapters 5, 8, 9, and 10 Lectures 10 to 19 plus Agriculture Global Warming The Vanishing Book of Life on Earth Plastics Intelligent Design? The Weakest Link Technology Economics

Population Growth and Regulation S - shaped sigmoidal population growth Verhulst-Pearl Logistic Equation: dN/dt = rN [(K – N)/K] Assumptions, Derivation Density Dependence versus Density Independence Equilibrium, Opportunistic, and Fugitive species r-selection versus K-selection (r-K selection Continuum) Correlates of r and K-selection, Bet Hedging Winemiller ’ s 3-dimensional fish life history surface Population Change versus Population Density Plots Microtine Rodent Population Fluctuations Hudson Bay Fur Company: Snowshoe Hare and Lynx “ Cycles ”

Notice apparent 10-year periodicity

Population “ Cycles ” Sunspot Hypothesis Time Lags Stress Phenomena Hypothesis Predator-Prey Oscillations Epidemiology-Parasite Load Hypothesis Food Quantity Hypothesis Nutrient Recovery Other Food Quality Hypotheses Genetic Control Hypothesis

Sunspot Hypothesis (Sinclair et al Am. Nat.) 10 year cycle embedded within year periods Maunder minimum: Three periods of high sunspot maxima: Canadian Government survey Hare cycle synchronized across North America Yukon: 5km strip, tree growth rings (N = 368 trees) One tree germinated in 1675 (>300+ years old) Hares prefer palatable shrubs, but will eat spruce leaving dark tree ring marks

Other Food Quality Hypotheses: Microtus (Freeland 1974) palatability toxic Snowshoe hares: Plant chemical defenses against herbivory (Bryant 1980)

Chitty ’ s “ Genetic Control ” Hypothesis Could optimal reproductive tactics be involved in driving population cycles?

Population “ Cycles ” Sunspot Hypothesis Time Lags Stress Phenomena Hypothesis Predator-Prey Oscillations Epidemiology-Parasite Load Hypothesis Food Quantity Hypothesis Nutrient Recovery Other Food Quality Hypotheses Genetic Control Hypothesis

Social Behavior Hermits must have lower fitness than social individuals Clumped, random, or dispersed (variance/mean ratio) mobility = motility = vagility (sedentary sessile organisms) Use of Space Philopatry Fluid versus Viscous Populations Individual Distance, Daily Movements Home Range Territoriality (economic defendability) Resource in short supply Feeding Territories Nesting Territories Mating Territories

V V Net Benefit

Sexual Reproduction Monoecious versus Diecious Evolution of Sex —> Anisogamy Diploidy as a “fail-safe” mechanism Costs of Sexual Reproduction (halves heritability!) Facultative Sexuality (Ursula LeGuin -- Left Hand of Darkness) Protandry Protogyny (Social control) Parthenogenesis (unisexual species) Possible advantages of sexual reproduction include: two parents can raise twice as many progeny mix genes with desirable genes (enhances fitness) reduced sibling competition heterozygosity biparental origin of many unisexual species

Male Female Female = Male Female No Sex Change Protogyny Protandry Robert Warner

Why have males? “The biological advantage of a sex ratio that is unbalanced in favor of females is readily apparent in a species with a promiscuous mating system. Since one male could fertilize several females under such a system, survival of a number of males equal to the number of females would be wasteful of food, home sites, and other requirements for existence. The contribution of some of the surplus males to feeding the predators on the population would be economically advantageous. In other words, the eating of the less valuable (to the population) males by predators would tend to reduce the predator pressure on the more valuable females.” — Blair (1960) The Rusty Lizard W. Frank Blair Sceloporus olivaceus

Sex Ratio Proportion of Males Primary, Secondary, Tertiary, Quaternary Why have males? Fisher ’ s theory: equal investment in the two sexes Ronald A. Fisher

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios __________________________________________________________________ Case a Number of MalesNumber of Females __________________________________________________________________ Initial population Family A 4 0 Family C 2 2 Subsequent population (sum) C A = 4/106 = C C = 2/ /102 = (family C has a higher reproductive success) __________________________________________________________________ Note: The contribution of family x is designated C x.

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios __________________________________________________________________ Case a Number of MalesNumber of Females __________________________________________________________________ Initial population Family E 0 4 Family C 2 2 Subsequent population (sum) C E = 4/106 = C C = 2/ /102 = (family C has a higher reproductive success) __________________________________________________________________ Note: The contribution of family x is designated C x.

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios __________________________________________________________________ Case a Number of MalesNumber of Females __________________________________________________________________ Initial population Family A 4 0 Family C 2 2 Family E 0 4 Subsequent population (sum) C A = 4/106 = C C = 2/ /106 = All three families have equal success C E = 4/106 = __________________________________________________________________ Note: The contribution of family x is designated C x.

___________________________________________________________________________ Case bNumber of MalesNumber of Females ____________________________________________________________________________ Initial population Family A 2 0 Family B 1 2 Subsequent population (sum) C A = 2/103 = C B = 1/ /102 = (family B is more successful) Initial population Family B 1 2 Family C 0 4 Subsequent population (sum) C B = 1/ /106 = C C = 4/106 = (family C is more successful than family B) Natural selection will favor families with an excess of females until the population reaches its equilibrium sex ratio (below). Initial population Family B 1 2 Family C 0 4 Subsequent population (sum) C B = 1/ /206 = C C = 4/206 = (family B now has the advantage) _____________________________________________________________________________ Note: The contribution of family x is designated C x.

Differential Mortality of the sexes during the period of parental care.

Differential Mortality of the sexes during the period of parental care