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ASU / OTHER / BIO / What is the Evolution of Sex?

What is the Evolution of Sex?

What is the Evolution of Sex?


School: Arizona State University
Department: OTHER
Course: Evolution
Term: Fall 2018
Tags: evolution, sex, LifeHistory, Genome, cooperation, and development
Cost: 50
Name: Evolution Exam 2 Study Guide
Description: This study guide reviews these topics that will be on the exam - evolution of sex - genome evolution - evolution of development - evolution of cooperation - life history theory
Uploaded: 10/06/2018
5 Pages 4 Views 13 Unlocks

diana martinez (Rating: )

provides a good reference to the material in class

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Evolution Study Guide Exam 2  

What is the Evolution of Sex?


 -This study guide will go over the terminology and topics talked about in lecture and that  would appear in the online readings.  

Main ideas : Evolution of Sex, Genome Evolution, Evolution of Development, Evolution of  Cooperation, Life History Theory  

Evolution of Sex  

- Biological sex is defined by relative size of gamete contributed to zygote   • Male: small gamete  

 • Female: large gamete  

Common misconceptions  

 An individual can’t change sex  

 Females nurture eggs, males only contribute gametes  

 Males are bigger than females on average  

-Costs of sexual reproduction  

Twofold cost of sex- For each asexual individual that produces X offspring, sexual reproduction  must generate 2X offspring to stay equal.  

Cost of mating - Sexual reproduction also depends on the chancy event of finding a mate each  generation.  

What is Twofold cost of sex?

Parsimony - All else being equal, the simplest hypothesis is more likely to be true, this is applied  to phylogenetic trees and how to infer ancestral trait values.  

Genome Evolution

Selective sweeps- As natural selection drives a trait to fixation, near by genomic variation in a  population is eliminated.  

Things that affect selective sweeps  

● Mutations because they appear and recreate patterns of variation  

● Recombination limits the size of the selective sweep in the genome  We also discuss several other topics like What is Kc?

Recombination Rates - Symbolized by r, is the probability of a recombination event occurring  between the two locations shown during reproduction.

Linkage disequilibrium- Describes the observed deviation from random association between  pairs of alleles.  

Formula: D = PAB – (PA*PB)  

 DN/DS Ratio  

DN- number of non-synonymous mutations in an alignment of coding  

What is Parsimony?

If you want to learn more check out

DS- number of synonymous mutations in an alignment of coding  

DN/DS <<1 = Negative Selection  

DN/DS ~1 = Neutral Selection  

DN/DS >>1 = Positive Selection  

● Which DN/DS ratio is most common?  

Answer: DN/DS <<1 , because messing with protein structure will usually result in a  negative effect.  

● The majority of non-synonymous mutations are strongly deleterious  ● Synonymous mutations generally have small to zero fitness effects  

Meanings of biological functions  

Evolutionary Function Role Function  -A trait has an evolutionary function -A part in a system has a role function if  If it is an adaptation it casually contributes to a system capacity  

Evolution of Development

Breeder’s Equation : Δz = h2*S  

 Δz = change in parent offspring means  

 h2 = heritability  

 S = selection differential  

● Can estimate h2 by observing Δz and S  If you want to learn more check out what is the social science concerned with how Individuals, institutions and society make optimal choices under conditions of Scarcity?
If you want to learn more check out Who is dorothea dix?

● Fitness differences can’t change trait mean without heritability Don't forget about the age old question of What is Essential Nutrient?

Reaction Norms - These are phenotype value(s) produced by a genotype as a function of  environmental condition.  

Zero Slope: Means that there are no environmental  




Non-zero Slope: Means the organism has  environmental plasticity  

Evolution of Cooperation  

● Interactions affect fitness  


● four types of interaction by  

yWe also discuss several other topics like How to Calculate components of the income statement?







E1 E2

Effect on actor

how they affect individual’s  fitnesses  

● Cooperation can evolve  through both mutualistic and  altruistic interactions  

t Mutualistic Altruistic













Selfish Spiteful







Inclusive Fitness- There are two types of inclusive fitness, two ways to increase the  probability of allele X being passed to the next generation. The sum of direct and indirect  fitness.  

 Direct fitness: Expected number of allele X copies in the individual’s offspring.   Indirect fitness: Expected gain/loss of allele X copies in relatives as a result of  individual’s actions.  

Relatedness - The probability that an allele carried by the actor is also carried by the recipient  of the altruistic behavior, r is the proportion of alleles the actor shares with recipient.  

• r = Proportion(mom)*Pr(shared) + Proportion(dad)*Pr(shared)  

Hamilton’s Rule - An allele that causes an altruistic behavior will spread if the following  conditions are met.  


r: altruist’s relatedness to recipient  

B: amount of benefit for recipient  

C: cost to altruist’s direct benefit  

Evolutionary Stable Strategies (ESS) - A behavior (strategy) with fitness at least equal to that of  any other possible behavior if individuals in the population behave that way. If a mutation  causing a different behavior appears in a population that is at an ESS, it will not have a fitness  advantage and thus not spread.  

Coevolution - Reciprocal genetic change in interacting species, owing to natural selection  imposed by each on the other, interacting means the species exist at the same place at the  same time.  

Life History Theory  

Life history of a species- The age- size-, and stage- specific patterns of development, growth,  reproduction, survival, and lifespan.  

Life history strategy- An individual’s allocation of resources to the components of its life history.  - High external morality selects for fast life history- selection for quick reproduction  - Low external morality leads to selection on competition for limited resources  Examples:  

High predation means -----> high growth investment (need to reach sexual maturity fast), low  somatic maintenance investment, and low investment in raising individual offspring  

Low or no predation ------> can get 2 species, low and high growth investment and small and  large sizes  

A weed adapted to a region with high forest fires-------> High growth investment, low somatic  maintenance investment, and low reproductive investment (not caring for each individual  offspring)  

Peto’s Paradox - The more cells an organism has the better chance it has to fight off cancer.

Conclusion: Make sure you understand how to apply these concepts to scenarios. Look at the  cooperation lecture slides to see how the equation works with relatedness between parent in  offspring. Review the worksheets and the cogbook quizzes to get extra practice applying these  terms and concepts.

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