Revision Flashcards
Gradient of straight line
Y=mx+c
Eco ecology definitions
Several answers, lecturer says a branch of eco bio concerned with contemporary natural populations and emphasis on the study of process and mech as well as pattern and outcome
Teleology
Doctrine that everything happens for a reason. Natural selection is not this.
Inheritance
Heritability- similarity between offspring and parent
What contributes the most to phenotype
Genetics then environment
What contributes the most to genotype
Genetics then environment
Populations definitions
If a population has:
a. variation among individuals in some attrbute or trait: variation;
b. a consistent relationship between that trait and mating ability, fertilising ability. fertility, fecundity, and, or survivorship: fitness differences;
c. a consistent relationship, for that trait, between parents and their offspring. which is at least partially independent of common environmental effects:
inheritance.
Then:
1. the trait frequency distribution will differ among age classes or life-history stages, beyond that expected from ontogeny:
2. if the population is not at equibrium, then the trait distribution of all offspring in the population will be predictably different from that of all parents, beyond that expected from a and c alone.
Fitness difference
Consistent relationship between trait and fitness
Selection differential
Difference in trait means (z) before and after selection
S=Zafter-Zbefore
Intensity of selection
I=s/O
Intensity= selection differential/standard deviation
Selection gradient
This is relative change of direness with change in phenotype. Gradient of graph with number of animal on y and feature observed on X (e.g. number of chicks fledged and weight)
The modes of selection
Directional- there is a association between trait and fitness (changes mean)
Stabilising- non-linear selection against extreme phenotypes
Disruptive- non-linear selection against intermediate phenotypes
Correlational- non-linear selection on combinations of traits (effects covariance between traits)
Breeders equation
This is response to selection. Comes from selective breeding
R=h^2S
R- response (transmission of within generation changes)
h^2-heritability (0 if none)
S-selection differential (0 if none)
Polymorphism
Same as phenotypes
Frequently controlled by a small number of genes. Not always genetic.
Sometimes controlled by many genes eg height
Quantitive genetics
Vp=Va+Vg+Ve
Vp- phenotypic variance among individuals
Va-additive genetic variance (variance due to simple genetic effects)
Vg-Non-additive genetic variance (Doninave and epistasis)
Ve-Environmental and genetic variance
Coefficient of variation
CV= standard deviation/mean
Heterosis
Heterozygote advantage
Antagonistic Pleiotrophy
Phenotype is good for one thing but damaging to another. To do with aging (evolution stops acting after reproduction age is passed)
Genotype x Environment action
Trait value depends on genetic composition as well as environment
Covariance
How related the variances are to eachother
Vector of responses equations
R= Va X directional selection gradient
Correlated characters problems
Experimental manipulation- may be. Different within vs. Between populations
Missing relationships- focus on one thing and miss another relationship (do multiple regression)
Estimating phenotype
Animal model phenotype= population mean+additive genetic component(breeding value) +fixed effects + error
Vp= Va+Vg+Ve
Game theory
Developed to Analyse economic behaviour
Stratergy
Plan of how to behave in different situations (no teleology)
ESS
Evolutionarily stable strategy
A strategy that if all members adopted it no mutants could invade through natural selection
Frequency dependence
Central to ESS
Fitness depends on own phenotype as well as others and their frequencies
Group selection
Generally not a thing!
Individuals act selfishly/to increase own fitness
Alternative strategy examples
Genetic polymorphism
Equal fitness
Generally uncommon
Mixed stratergies
Probabilistic
Equal fitness
Rare!!
Conditional strategies
Best-of-a-bad-job- theory
Unequal fitness here
Most common
Sex ratio theory
Most have a 50:50 ratio- genetics passed through both sons and daughters. All have one mother and father and have equal genetic contribution- natural selection favours ‘strategy’ where parental investment is equal.
If not 50:50 rarest sex contributes more
Reader will obtain more matings and leave more offspring
Overproducing rarer sex has benefits until 50:50- frequency dependent selection
This is an ESs
Caveats of 50:50 sex ratio
Only expected when:
Diploid species
Nucleus has control of sex determination
Costs and benefits of both sexes are equal
r&K selection
R-growth
K-carrying capacity
Grow quickly reproduce many or grow slow reproduce few
Life history trait definition
A trait that if all else is equal still has a Corellarion between it and fitness
Traits that govern reproduction, fitness etc
Life history trait examples
Size at birth
Age at maturity
Adult size
Age specific fecundity
Number and size of offspring
Mortality rate and aging
Reproductive value
The number of offspring an individual expects to have over the rest of life.
-depends on fecundity and survival at different ages
-depends on rate of population growth/decline
-in stable/growing pop. Early offspring are more valued
Life history contraints
Phylogenetic- you only have the genes you have. Mammals don’t become fish
Biomechanics- your body needs to work
Developmental- an ear in the foetus does not become an eye in adulthood
Physiological- principals of allocation(limited resources exist)
Principals of allocation framework
Start with recourses R. Q goes to cell maintenance and protection. 1-Q goes to reproductive cells
Q must be split between A(defence of somatic cells) B (defence of reproductive cells) and 1-(a+b) (cell maintainence)
House and car problem
The amount of energy an organism has is as important as how the allocate that
Variation in allotment will see little variation in condition
Variation in condition will see little variation in allotment
Semelparity
Reproduce once then die
Iteroparity
Survive and repeatedly breed
Disposable soma
Theory that there is a time where repair is worth doing and a point at which it takes too much energy- not a well supported idea
Effect of extrinsic mortality
Senescence is greatest when extrinsic mortality is high as few individuals survive long so there is little selection against deleterious mutations at old age. Why invest in repair if going to die young?
Competitive exclusion
Ecological
Superior competitor excludes inferior from some parts of niche
Character displacement
Evolutionary
One species influences the evolution of resource use in another due to interspecific competition
Sympatry
Two closely related species/populations which exist in the same geographic area
Allopatry
Isolated species
Criteria for character displacement
Chance is ruled out as an explanation
Phenotypic differences between populations in sym/allopatry have genetic basis
Differences between simpatico species should be due to evolutionary shifts NOT inability of similar sized species to coexist
Morphological differences reflect resource use differences
Sites of sym/allo should not differ greatly in food/climate/generally effect phenotype.
Evidence should be gained that similar phenotypes compete for food
Evolutionary outcomes of predator/prey interactions
Camouflage/increased visual accuracy
Speed for escape/pursuit
Flocking and herding/counterstrategies
Predator avoidance
Trickery
Coevolution predation
Between species not within
Technology limited approach to coevolution
No cost to adaptation but mutation/selection rates are the limit. Steady state, cylicity or extinction
Trade-off approach to co-evolution
Adaptation reflects a cost/benefit balance. Cycles or reaches a steady state
Abram’s approach to predator prey coevolution
Investments by either side reduce the other aspects to own fitness
General predictions of predator/prey coevolution
If predator invests prey will increase avoidance.
If prey invests predator may not respond due to prey density increase
Geographic mosaic of coevolution
Can’t look at modern species through time. Instead look at differences in different populations to understand the past
TTX
Toxin found in some crabs, frogs and jellyfish. Causes paralysis and stops breathing. Variation of snakes resistance formed several genes- faster snakes generally crawled slower than other snakes when they had the toxin. The slower snakes where the southern variant, though northern had no trade off.
Adaptations of bats and moths
We don’t know the sequence of evolution
Bats: sonar, changed frequency, wide beam sonar, stealth sonar
Moths:ears, stealth scales, evasion of sonar, sound production(aposematism, mimicry, jamming), sensory illusion
Definition of parasite
Organisms that have an obligate relationship with and negative effect on another organism.
They don’t kill the host, or reproduce before killing it. They live on or in the host for a part of the life cycle.)
Optimal parasite virulence
Virulence- damage done to host.
Many commensalisms start as predator/prey interactions. (Mitochondria and chloroplasts, bacteria’s plasmids, lichens and fungi)
Modern view is virulence is optimised between benefit to parasite and cost (reducing the hosts survival)
Parasite intrinsic reproductive rate
R0= (transmission rateXhost pop density)/(deaths due to disease+disease free deaths+recovery)
R0 is the number of new cases from every existing case in an unexposed population on average. R0>1 = epidemic.
Vertical vs horizontal parasite transmission
Vertical- parent to offspring. Favours reduced virulence
Horizontal- between host individuals in a generation. Favours increased virulence
Tolerance vs resistance
Tolerance- cost of being infected
Resistance- avoiding being infected
Speciation allopatry vs sympatry
Allopatry- by-product mechanism
Sympatry- reinforcement
Genetic drift/bottleneck speciation
Genetic drift causes divergence. Reduced hybrid fitness from genetic or sexual incompatibility.
Polyploid speciation
Divergence from polyploidy(having more than two paired sets of homologous
chromosomes) and hybridisation. This causes genetic incompatibility and is a reinforcement mechanism.
Uniform selection
Different advantages in different populations. Can be pre or post zygotic. Causes generic or sexual incompatibility. Drives fixation of incompatible mutations then reinforces.
Ecological speciation
Divergent natural selection. Pre/post zygotic. Ecological selection, causes genetic or sexual incompatibility. Drives divergence in phenotype traits and reinforces. Amplifies divergence of mate preferences
Environment vs genotype speciation
Diff E diff G - divergent selection
Same E diff G- uniform selection
Same E same G- parallel evolution
Criteria for character displacement
Chance ruled out
The phenotypic differences between populations in Sympatry and Allopatry should have genetic basis
Enhanced differences between sympatric species should be due to evolutionary shifts NOT inability for co-existence
Phenotypic differences should reflect differences in resource use
Sites of sym/Allopatry should not vary in environmental features which effect phenotype
Independent evidence should be gained that similar phenotypes compete for food- most important but least usually met
This is more common in carnivores- study bias
Genome wide association study
Research approach to identify genomic variants which are linked to risk of a trait. Survey genomes of many and look for the variants which appear linked to the trait.
Manhattan plots
indicators of selective sweep
Reduced variation
Increase linkage disequilibrium
Increased genetic differentiation compared to other populations
Soft vs hard generic sweep
Hard sees one pair of genes reach near fixation while soft has the beneefital gene sweeped with a variety of other genes
Fixation index
Measure of population differentiation due to genetic structure
Fixation index= (mean heterozygosity total population-sub population)/mean heterozygosity total population
Recombination
Recombination shapes the extent of effect of selection and gene flow
Parapatry
Populations are separated with a small degree of gene flow. The usual real life case.
Stages of divergence
One of few loci under disruptive selection
Divergence hitchhiking due to linkage
Genome hitchhiking (restriction in gene flow now)
Genome wide isolation
