LEC.245 Evolution

Evolution

Variation forms within pool of individuals within a species.
Accumulation of specific adaptations.

Good of the Species Fallacy

George Williams - - Selection acts on individuals not groups or species.
Richard Dawkins - - Selection acts at gene level.

Genotype

Information stored in genes of an individual.

Alleles

Alternative genes which occupy locus within genome.

Polygenic

Traits controlled by many genes.

Pleiotropic

Single gene impacts many features.

Epistasis

One allele may influence expression of another.

Phenotype

Observable properties of an organism.

Variation in Phenotype

= Variation in genes + Variation in environment.

Variation in genes

= Additive genetic variation + Variance in gene dominance + Variance in gene interactions.

Heritability

= Additive genetic variance / Variance in gene dominance.
Proportion of variation in phenotype thats due to heritability from parents.

Fishers Fundamental Theorem

Traits which influence reproductive success are under great selection pressure to maximise it.

Adaptation

The selection over generations of heritable characteristics
(metabolism, physiology, morphology, behaviour, etc.) that optimise
performance ("fitness") in a particular environment.

Phenotypic Plasticity (Acclimation)

The adjustment of an individual's phenotype that optimizes that
individual's performance ("fitness") in a particular environment.
Adaptations are variable and fluctuate based on what the environment is doing.

Mutation

Random changes in DNA sequence.

Qualitative Characteristics

Mutations to a single gene that results in qualitative differences in a character.
Character is present or absent.

Quantitative Characteristics

Show continuous variation across a population.
3 kinds: Stabilising, directional and disruptive.

Stabilising Selection

Both extremes are at selective disadvantage.
Variation is reduced as whole distribution becomes concentrated around the mean.
Pushes population to express one particular type of gene.

Directional Selection

One extreme is at selective disadvantage.
Whole distribution is shifted towards one extreme of range.

Disruptive Selection

'Average' individuals are at selective disadvantage.
Distribution is 'split' towards two extremes.
Leads to speciation.

Exaptation

...any organ (or function) not evolved under natural selection for its
current use - either because it performed a different function in
ancestors or because it represented a non-functional element
available for the action of subsequent selection.

Asexual Reproduction

Mutation rates extremely low.

Sexual Reproduction

Meiosis.
Recombination of genes at chromosome level.
High levels of mutation.

Red Queen Hypothesis

Dynamic between host and parasite evolution occurs under similar
timeframes - - Although selection is constantly happening, appears as though
we are at equilibrium between the two - - Both should be adapting at the same speed.

Evolutionary Arms Race

Natural selection increases efficiency with which predators detect and
capture prey.

Crypsis

Ability of an animal to avoid observation or detection by other animals.
May be predation strategy or anti predator adaptation.

Mimicry

Unpalatable objects - - Close external resemblance of an organism, the
mimic, to some different organisms, the model.
Mimic benefits from the mistaken identity,
as seeming to be unpalatable or harmful.
Other animals - - Close external resemblance of an organism,
the mimic, to some different organism, the
model. Mimic benefits from the mistake
identity as being seem as harmful.

Prey Profitability

= Energy / (Recognition time + Handling time)

Aposematism

Distasteful or dangerous animals usually have
gaudy and contrasting colours.
Visually apparent colouration so predator notices
you but pairing it with dangerous internal toxin so
predator knows colour is a warning system so
doesn't predate.

Batesian Mimicry

Mimics evolve colouration similar to models.
Models need to outpopulate mimics.

Mullerian Mimicry

All species are 'unprofitable'.
All work together to reinforce signal is dangerous.

Symbiosis

Any long-term intimate relationship between two or more species.

Resistance

Ability to reduce severity of infection by pathogen or herbivory.

Tolerance

Ability to endure effects of infection by pathogen or herbivory.

Commensalism and Host Tolerance

Parasitic (symbiotic) relationship could evolve into commensalism (symbiotic) relationship via increased host tolerance.

Mutualism

Relationship where organisms of different species interact to their mutual benefit.

Obligate Mutualism

One or both species cannot survive without the other.

Facultative Mutualism

Both species directly benefit from each other but are capable of surviving independently of each other.

Ideal Free Distributions (Fretwell 1972)

Explains how animals are dispersed in environments.
Assumes: animals have ideal information, free to go wherever rewards are best.
Model predicts that individuals should distribute themselves in
relation to pay-offs they receive rather than direct patch
quality.

Animal Dispersion

Territorial when economically viable and group together when economically variable.

Benefits of Foraging in Groups

Avoidance of predation.
Increased foraging capabilities.

Costs of Foraging in Groups

Have to share resources.
Interference with foraging method.
May attract predators.

Avoiding Predation

Increased vigilance against predators.
The dilution effect - - As group size increases, attacks per individual decreases.
The confusion effect - - Predators cannot pick individuals out as easily when they're in larger groups.
Group defence.

Increasing Foraging Success

Animals that group together have an increased ability of finding food.
Information Centre Hypothesis - - Individuals gather together to exchange information about where food is.
Larger prey can be caught.

Competition

Resource may not be divisible by group.

The Food Problem

Natural selection should favour individuals whose behaviour increases probability of surviving to breed.

Diminishing Returns

As time spent feeding at patch increases, food eaten increases and then food eaten levels off due to food availability decreasing.

Marginal Value Theorem

Used to understand time spent at different things.
Best 'leave time' will depend on travel time.

Parental (Sexual) Conflict

Conflict over agreement about whats best for individual.
Conflict over maternity.

Parent-Offspring Conflict (POC)

Conflict over resource allocation - - How resources are allocated to individuals offspring from parents.

Sibling Rivalry

Competition for resources between individuals in same nursery.
Occurs due to: Genetic differences between siblings or parents over-produce offspring.

Genetic Relatedness

Individuals are expected to behave to maximise their own fitness - - Fitness is a measure of how well a particular type of organism can contribute to future gene pools.

Inclusive Fitness Theory (Hamilton)

Relatives share some genes by descent.
Hamiltonian rule defines thresholds for evolution of selfishness and altruism.

Altruism

One individual gives another individual a resource at a cost to itself.
Evolves when

Inclusive Fitness

= Direct + Indirect fitness

Cooperative Breeding

Individuals maximise their inclusive fitness by helping close relatives rear offspring.

Reasons for Increased Success with Helpers

Reduce predation by modding and alarm call.
Reed nestlings.

Resource Tracking

Interaction between environmental quality and reproductive success.

Brood Reduction Hypothesis

David Lack
Predicts brood reduction is adaptive when food is scarce.

Polygyny

One male is breeding with more than one female.

Extra-Pair Paternity

Greater variation in reproductive success than appears.