provides a good reference to the material in class
Evolution Study Guide Exam 2
-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
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.
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.
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- number of non-synonymous mutations in an alignment of coding
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?
Effect on actor
how they affect individual’s fitnesses
● Cooperation can evolve through both mutualistic and altruistic interactions
t Mutualistic Altruistic
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.