Evolutionary Biology
Population Genetics
Sexual Selection
Allele Fixation
Selection
Harvey Weinberg
Mullers Ratchet
Sexual Reproduction
Costs of Sex
Requires finding appropriate mate
parents are less related to their offspring
risk of contracting sexually transmitted disease
Red Queen Effect= Evolutionary Arms Race Between Parasites and Hosts
Sex allows for faster adaptation because of reshuffling of genetic diversity (alleles)
Sexual Dimorphism= Phenotypic difference between males and females of a population
Morphology
Behavior
Types of Reproduction
Physiology
Sexual Lineages=Recombination allow unfavorable mutations to be purged by natural selection
Asexual Lineages=entire genome is passed along so deleterious mutations accumulate
Asexual Reproduction= offspring derive from a single parent
Sexual Reproduction= two parents contribute genetic information to offspring
Reproductive Trade-Offs
What to Invest in?
Produce as many offspring as possible
Produce the best offspring as possible
Females and Investing
Anisogamy= gametes are dissimilar (eggs are much larger--> more energy and effort
Internal Fertilization
Evolved multiple times Independently
Sex Differences in Parentage --> one with internal knows they are parent
females often have specialized care for offspring
Extra-pair paternity
Operational Sex Ratio
Male-Biased
More males than females can mate
Sexual Selection acts stronger on males
Males invest in attracting femates
Female-Biased
Females invest in attracting males
More females than males
Sexual Selection acts stronger on females
As males mate, their reproductive success increases while females may get a bump but also have costs
As females mate, their reproductive success increases while males may get a bump but also have costs
Member under sexual selection will have to compete with
Mating Competition
Intrasexual Selection
Mate Choice
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Direct Benefits
Territories/Nesting
Help with raising young
Food
Protection from other males
Reduced disease/parasite risk
Indirect Benefits
'Good Genes'
Arbitrary Choice (Fisher's Runaway)= post-copulary mate choice
Females of many species can store sperm
Female chooses her sperm
Combination Models
More variance in reproductive success for males
More reproductive success for females
Hermaphrodies
Hypodermic Insemination
costly potentially to be on the receiving end
fight over who plays which role
Penis Fencing to inseminate the other
Whoever is mother has to stay with baby and take care of it
Sexual Conflict
Antagonistic Coevolution
Males try to force copulation on females
Expolosion Eversion
Females have opposite spirals to prevent insemination
Sexual Cannabilism= males offer themselves up to the females for sex and then get eat them
Species and Speciation
Species get revised all the time
Definitions: No one definition has satisfied everyone
Phonetic Species Concept: species are defined using morphological traits
Advantages
Disadvantages:
Members of the same species can be morphologically difference
Cryptic Species: morphologically similar, genetically different
concept relies on human interpretatoin
Phylogenetic Species Concept= Species are the smallest possible groups whose members are descended from a common ancestor and possess characteristics that distinguish them from other groups
Fossil Record
Uses of fossil record
Intermediates as evidence of descent with modification
Reconstructing Evolutionary History
calibration of molecular evolution, minimum divergence dates
Reconstructing Climate, ancient environments
Infer the tempo and mode of evolution through time
Time x Morphology Plots
Diversity_T2= Diversity_T1 +Originations -Extinctions
Turnover= originations + extinctions
Adaptive Radiation= Rapid Diversification into many forms over short periods of time
Mass Extinction= huge number of species go extinct over short period of time
General Lineage Species= Species= metapopulation of organisms that exchange alleles frequently enough that they comprise the same gene pool
Biological Species= Species= a group of actually or potentially interbreeding populations that are reproductively from other groups
Reinforcement= increase in reproductive isolation between hybridizing populations through selection against hybrid offspring
Fusion= Results in divergence in allopatry results in no prezygotic or postzygotic isolation, and the geographical barrier is removed
Sepkoski's Diversity Curve = Biological Diversity over time
5 mass extinctions
Permeo-Triassic
Largest Volcanic Eruption Ever: Releases CO2 and methane
CO2 and methane warm planet
Increase in temperature decreases O2 in oceans
Increases in CO2 acidifies oceans
84% of marine genera go extinct
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Three Modes of Evolutionary Change
Cladogenesis= splitting of lineages (Disruptive Selection)
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Anagenesis= gradual change within a lineage (Directional Selection)
Morphological Stasis= "Living Fossils" (Stabilizing Selection)
Plants
Fungi
Assumptions
no selection
no mutation
no migration
infinite population size (no genetic drift)
Random mating
(diploid, sexually reproducing organism)
Directional Selection
Directional Selection- shifts to one side
Dominance doesn't become fixed
Recessive becomes fixed
Co-Dominant (Additive)
Dominant Heterozygote has most fitness (directional selection) so A1 will reach fixation
Over Dominance
Homozygous have equal fitness and heterozygote has increased fitness
Reaches equilibrium at 50%
A1A1 worse than A1A2 but also doesn't rise until there are enough A1A2 so it is in between the co-dominant and dominant curves
Heterozygote Advantage= heterozygote has higher fitness than either homozygote
Purifying Selection (Stabilizing Selection)- Removes extreme phenotypes
Disruptive Selection-disfavors phenotypic intermediates (ignores mean)- goes to both ends
Ex: Sickle Cell and Malaria
AA die from malaria
SS suffer from sickle cell
AS have lower oxygen carrying capacity but are less likely to die from malaria
Population Bottleneck= individual's are killed reducing population
Random Genetic Drift
Habitat Fragmentation
Loss of Variation
Large population becomes multiple small populations
genetic drift high
Fixation of Deleterious Alleles?
Leads to genetic drift and population bottleneck
Founder's Effect- certain individuals move from one place to an isolated area where they only mate with each other
Genetic Drift vs Natural Selection
Small population--> genetic drift is strong
large population--> NS is strong
Gene Flow= movement and incorporation of genes from one population into another population
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Divergence of Subpopulations
F_ST = variance in allele frequency among subpopulations
Alleles:
Fixed for different alleles= 1
Identical frequencies= 0
Partially isolated is between 0 and 1
F_ST= 1/ (4Nm +1)
N= size of population
m = migration rate
migration makes more similar
A single event gave rise to chloroplasts of glaucophytes, red algae and green plants
Glaucophytes- retained peptidoglycan in chloroplast membrane
Unknown Ancestor
Red Algae- can live at deeper depth because of its red pigment
Green Plants- has chrloryphyll A and B, allowing for the transition to land plants which make a ton of energy, allowing them to store it as a starch.
Land Plants
Green Algae
Vascular Plants
Challenges:
dessication
Increased UV Radiation
Movement of Fluids/Nutrients
Physical Support
Protection of Gametes/Embryos
Alternation of Generation (Two different stages of plant development
Multicellular diploid parent structure- Sporophytes (2n) produce spores using meiotic (asexual) reproduction, which turn into gametophytes
Gametophyte (1n) give rise to the haploid gametes. Sperm fertilizes egg and sporophyte grows out of it
Liverworts- release spores
increase genetic diversity
produced by sporophytes to form gametophytes
Sporophyte most of the time
Three Key Aspects
Stomata- pores
Pholem-carries food
Xylem- provides transport and support
Lycophyte
small photosynthetic gametophyte
Independent branching sporophytes
True roots, microphylls, vascular system
Megaspore--> female gametophyte
Microspore--> male gametophyte
Unnamed Taxon
Ferns
diverse forms and habitats
sporophytes branched
Megaphylls- huge variety of leaf morphologies
spores produced on underside of leaves
Seed Plants
Gymnosperm-naked seed plants
Angiosperm- Vestled seed plants
Gametophytes
Pollen- cells inside spore wall
Ovules contain the female gametophyte which is at least multi-nucleate
Fertilization and Double Fertilization
Fertlization- sperm nucleus fuses with egg nucleus
Double Fertilization- one sperm fertilizes the egg, one sperm fertilizes the central nuclei to form triploid (3n) endosperm
Two Properties!!
Four Types of Fugni
*Absorptive Heterotrophy = can aboorb food
Chitin in the cell walls
Saprobic Fungi- "Decomposers"- take up nutrients from non-living orgnaic matter
Predatory Fungi- active predators, tapping and killing prey
Use Adhesives and Constricting Ring
Parasitic Fungi- absorbs nutrients from parasitic interactions, with varying dependence on their host; sometimes helpful
Mutualistic Fungi- symbiotic mutualism- when two species are in close association and both parties benefit
Lichens= fungus+ agreen algae and/ or cyanobacterium (+yeast)
pioneers and extreme survivor
Microspordia (reduced mitochondria, polar tube)- small, unicellular parasites, infect via a polar tube
"cytrids- has a flagella which it uses to swim. unicellular/multicellular, asexual/sexual reproduction. More sapbrobic but few are parasitic
Unnamed Taxon
Arbuscular Mycorrhizal Fungi- form important symbioses with vascular plants; obtain photosynthate from plants; assist plant with nutrient absorption from the soil
Dikarya- sexual reproductive structure of sac fungi (ascomycota) is the ascus, which is a sac that encases the spores. Sexual reproductive structure of club fungi (basidomycota) are pedestals called basidia, the spores are not the surface of the basidia