Second Exam: Thursday 29 October 2015Covers Chapters 5, 8, 9,10, and 11Lectures 10 to 19 plus Agriculture Global Warming The Vanishing Book of Life on Earth Plastics Intelligent Design?The Weakest Link TechnologyEconomics

Lecture # 1620 October 2015

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”

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 individualsClumped, random, or dispersed (variance/mean ratio)mobility = motility = vagility (sedentary sessile organisms)

Use of SpacePhilopatryFluid versus Viscous Populations

Individual Distance, Daily MovementsHome RangeTerritoriality (economic defendability)Resource in short supply

Feeding TerritoriesNesting TerritoriesMating Territories

V

V

NetBenefit

Sexual Reproduction

Monoecious versus DieciousEvolution of Sex —> AnisogamyDiploidy as a “fail-safe” mechanismCosts 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 competitionheterozygositybiparental origin of many unisexual species

Male

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 MalesPrimary, Secondary, Tertiary, QuaternaryWhy 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 Males Number of Females__________________________________________________________________Initial population 100 100

Family A 4 0Family C 2 2

Subsequent population (sum) 106 102CA = 4/106 = 0.03773CC = 2/106 + 2/102 = 0.03846 (family C has a higher reproductive success)

__________________________________________________________________

Note: The contribution of family x is designated Cx.

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios__________________________________________________________________Case a Number of Males Number of Females

__________________________________________________________________

Initial population 100 100Family E 0 4Family C 2 2

Subsequent population (sum) 102 106

CE = 4/106 = 0.03773CC = 2/106 + 2/102 = 0.03846 (family C has a higher reproductive success)

__________________________________________________________________

Note: The contribution of family x is designated Cx.

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios__________________________________________________________________Case a Number of Males Number of Females

__________________________________________________________________

Initial population 100 100Family A 4 0Family C 2 2Family E 0 4

Subsequent population (sum) 106 106

CA = 4/106 = 0.03773CC = 2/106 + 2/106 = 0.03773 All three families have equal successCE = 4/106 = 0.03773

__________________________________________________________________

Note: The contribution of family x is designated Cx.

___________________________________________________________________________Case b Number of Males Number of Females____________________________________________________________________________Initial population 100 100

Family A 2 0Family B 1 2

Subsequent population (sum) 103 102CA = 2/103 = 0.01942CB = 1/103 + 2/102 = 0.02932 (family B is more successful)

Initial population 100 100Family B 1 2Family C 0 4

Subsequent population (sum) 101 106CB = 1/101 + 2/106 = 0.02877CC = 4/106 = 0.03773 (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 100 200

Family B 1 2Family C 0 4

Subsequent population (sum) 101 206CB = 1/101 + 2/206 = 0.001971CC = 4/206 = 0.01942 (family B now has the advantage)

_____________________________________________________________________________Note: The contribution of family x is designated Cx.

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

Differential Mortality of the sexes during the period of parental care

Sexual Selection

Mating Preferences

Certainty of Maternity, uncertainty of paternity Competition for the best mates of the opposite sex Sex that invests the most is the most choosy about mates Jealousy, Desertion, Cuckoldry

Epigamic selection (intersexual, between the sexes)“Battle of the sexes”

Natural selection produces a correlation between male genetic quality and female preference

“Sexy son” phenomenon (females cannot afford to matewith males that are not attractive to other females)

Sexual Selection Mating Preferences

Drosophila subobscura

Inbred versus outbred male flies differed in viable sperm counts.Females mated to inbred males laid an average of only 264 eggs,whereas females mated to outbred males laid 1134 fertile eggs.

Within an hour, virgin females exposed to outbred males mated 90%of the time but only 50% of those exposed to inbred males matedduring the first hour. Female side-step dance courtship display.

Sexual SelectionMating Preferences Mate Choice Experiments

Nancy Burley Nancy Moran

BlueCheck

Blue Bar

Ash Red

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Columba livia

Sexual Selection

Mating PreferencesSex that invests the most is the most choosy about matesCompetition for the best mates of the opposite sexJealousy, Desertion, CuckoldryCertainty of Maternity, Uncertainty of PaternityEpigamic selection (intersexual, between the sexes)“Battle of the sexes”Natural selection produces a correlation between male genetic quality and female preference“Sexy son” phenomenon (females cannot afford to mate with males that are not attractive to other females)

Sexual Selection

Mating PreferencesSex that invests the most is the most choosy about matesCompetition for the best mates of the opposite sexJealousy, Desertion, CuckoldryCertainty of Maternity, Uncertainty of PaternityEpigamic selection (intersexual, between the sexes)“Battle of the sexes”Natural selection produces a correlation between male genetic quality and female preference“Sexy son” phenomenon (females cannot afford to mate with males that are not attractive to other females)

Mating Systems Promiscuity

Monogamy

Polygamy

Polygyny

Polyandry

Polygyny threshold: minimal difference in male territory quality that

is sufficient to favor bigamous matings by females

Long-billed Marsh Wren

Jared Verner

b = Polygyny threshold

etzelputed to bemorphic

Male Peacock, a victim of female mating preference

Leks

Runaway Sexual Selection (Fisher)

Handicap Hypothesis (Zahavi)

Sensory Exploitation Hypothesis (Ryan)

Alternative mating tactics

Internal versus External Fertilization

Satellite males

Ecological Sexual Dimorphisms

Bower birds

Ratites

Bushland tinamou

Dinosaur fossils suggest that male parental care could be ancestral in birds

If so, ratites could have retained the ancestral state

And, if so, then female care and biparental care would be derived conditions

A male of the medium-sized predatory dinosaur Troodon (North America late Cretaceous) brooding a large clutch of eggs. Female archosaurs extract substantial amounts of calcium and phosphorus from their skeletal tissues during egg formation. Histologic examination of cross sections of bones (femur, tibia, and a metatarsal bone) from an adult Troodon found in direct contact with an egg clutch revealed little evidence of bone remodeling or bone resorption,

suggesting that the bones were those of a male. Fossilized remains of Troodon and two other types of dinosaurs found with large clutches of eggs suggest that males, and not females, protected and incubated eggs laid by perhaps several females (Credit: Bill Parsons)

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Red-eyed Vireo