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Flashcards in Adaptation Deck (17):

Evolution Definition

-Evolution: Changes in the heritable properties of populations of organisms over the course of generations
-result in a a change in the frequency of alleles with in a gene pool over generations (doesn't have to be an adaptation)


Evidence for evolution (5)

-Fossils: shows transitional forms and new (but similar species that arise)
-Genetic variation w/in existing species
-Relationships between existing species (morphology, beh., genes)
-Imperfections (e.g. whales having small bones for hind legs)
-Can experiment and observe natural selection


Common features of Darwin's Natural Selection (3)

1. Variation in traits (is what selection can act upon)
2. Heredity
3. Differential reproduction (trait survives better in those that can reproduce better)
-aka Darwinian fitness


Types of traits and advantage they give

-Unfavourable traits: compromise reproduction (are therefore eliminated)
-Beneficial traits: are spread
-Neutral traits: can reside within population as neither help nor harm an organism


Principles of natural selection (4)

-More offspring produced than what can survive
-Variation in particular trait
-Genetic basis of trait means it is inherited
-Differential reproductive fitness (beneficial trait = more offspring produced)


Biological species

-Biological species: Groups of interbreeding natural populations that are reproductively isolated from other such groups
-explain why members of species resemble each other (form phenetic clusters)
-Genotype: The set of genes carried by an organism
-Phenotype: The actual expression of the genotype (only a subset of genes are actually expressed)


2 Modes of Speciation

1. Allopatric Speciation: "Other country"
-Geographical separation of the diverging populations - is some barrier b/w populations
2. Sympatric Speciation: "Same country"
-Without geographic speciation


Mechanisms of Speciation (how does it occur)

-Pre-mating isolation (3 types)

-Post-mating isolation (2 types)

1. Pre-mating isolation: Prevents cross breeding before occurs
-Seasonal/habitat isolation: Mates do not meet
-Behavioral isolation: Meet but do not mate
-Mechanical isolation: Attempt to mate but cannot
2. Post-mating isolation: Prevents fertilisation or further development
-Hybrid mortality: egg fertilised but hybrid dies
-Hybrid viable but partially or completely sterile (e.g. mules)




Adaptive traits

-Adaptation: The process, through evolution, that allows organisms (or sets of genes) to better survive in their environment
-Adaptive traits are any physiological or behavioural feature that allows or enhances survival and reproduction
*Can have evolution without adaptations (but adaptation very strong driver for evolution



-Adaptive Radiation

-Adaptive Niche and e.g.

-Adaptive Radiation: a process of adaptive evolution in which variations of a single species fill different niches and eventually become a new species
-Adaptive Niche: The role of an organism in its community; what and where it eats, and what eats it
-is a finite number and hard to occupy new niche
-e.g. horses; as niches became available, began to fill them = 25 general of horses


Divergent Evolution in the Galapagos island

-Repeated colonisation from S america by plants and animals
-Founder effect: small no. of organisms go onto island and then speciate
-many population crashes = reshuffling of gene proportions
-Different islands also had organisms with different morphologies due to differences in environment
-is less competition if animals exploit a range of environmental niches


Divergent Finches - Example of Divergent Evolution

-Land on the backs of other birds, open a wound and drink blood
-Probably arose from feeing on external parasites such as ticks
-also roll eggs from nests to break them and feed on contents



-what it is and when likely to occur
-e.g. in wild

-Where similar animals come back together and mate, can lead to new species forming
-esp occur after unusal or catastrophic conditions
-many wild geese and ducks hybridise


Parallel evolution

Convergent Evolution

Divergent Evolution

Parallel Evolution: Occurs when species with a similar ancestor develop similar traits over time - due to shared environment or pressures

Convergent Evolution: Species that are not related, independently develop similar traits

Divergent Evolution: Where a species evolves into two or more different forms (have a common ancestor)


Artificial Selection

-Where humans cause evolution by selecting for some traits
e.g. Trophy hunters for Alberta rams means horn size fell


Assortive differences - e.g. of can toads

-Cane toads at front of pack are faster - breed with each other to pass on fitter genes
-means that cane toads in W.A are smaller and fitter than the fat ones in Queensland
*is an example of evolution across space


Assortative Selection

-Is a mating pattern and form of sexual selection whereby organisms choose to mate with organisms with similar genotypes or phenotypes more frequently than if they mate randomly
-may increase genetic relatedness w/in a family