Chapter 5: Evolutionary Ecology

what is evolution

the grand unified theory of biology that is the change in the inherited characteristics of biological populations over successive generations

dna

the molecule of inheritance

allele

different forms of a particular gene

genes

regions of DNA that code for particular proteins

gene pool

alleles from all of the genes of every individual in a population

polygenic

when a single trait is affected by several genes

what are the sources of genetic variation

random assortment, recombination, and mutation

random assortment

during sexual reproduction parental chromosomes are randomly assorted into the gamete’s chromosomes

recombination

genetic material recombined during meiosis

mutation

a random change in DNA that can silent with no detectable effect or alter the physical appearance of an organism or have lethal effects

genetic drift

random change in allele frequencies within a population

why can genetic drift occur

process can occur due to random variation in mating, mortality, fecundity, and inheritance

where is genetic drift more common

in small population because random events can have a disproportionately large effect on the frequencies of genes

bottleneck effect

a reduction of genetic diversity in a population due to a large reduction in population size (e.g. from loss of food)

founder effects

a type of bottleneck that occurs with colonization

bottleneck example

prairie chicken, in Illinois there were 12,000,000 birds in 1860 then there was habitat loss through agricultural intensification and 72 birds remained in 1990, bottleneck caused reduction in genetic diversity

microevolution

the evolution of populations; affected by random processes and selection within species variation and occurring faster than macroevolution

what are the two types of selection that can occur in microevolution

artificial or natural

artificial selection

individuals chosen to reproduce based on desired traits, can be a conscious process with goals in mind like agriculture and conservation

unintentional artificial selection

mycobacterium tuberculosis can be cured with antibiotics but this also creates a strong selective force for drug resistance, in large bacterial populations a few mutated bacteria survive then thrive then pass on their resistance leading to a multidrug resistant tb

natural selection

favors traits that provide higher fitness (ability to survive and reproduce)

what kind of process is natural selection

an ecological process; individuals interact with their environment and traits that lead to greater fitness in an environment are passed on

what are forms of selection

the type of relationship between the trait value and fitness, can be stabilizing selection, directional selection, and disruptive selection

stabilizing selection

favors intermediate phenotypes and progeny have more narrow distribution of phenotypes

characteristics of stabilizing selection

expected when the environment is relatively unchanging and generates little evolutionary change

what does stabilizing selection remove

harmful genetic variation (outliers)

directional selection

there is a direct linear relationship between a trait value and fitness

disruptive selection

outliers are favors, individuals with extreme phenotypes experience higher fitness than those with an intermediate phenotype, and genetic and phenotypic variation increases

macroevolution

evolution at the species level and higher

speciation

the evolution of new species

phylogenetic trees

hypothesized patters of relatedness among different groups such as populations, species, or genera

what do species that are closely related share

a recent common ancestor

what is allopatric speciation

the evolution of new species by geographic isolation

how does allopatric speciation occur

one population is separated and the isolated populations experiences genetic drift and founder effects and populations evolve separately, over time the populations become so different that they cannot interbreed and they evolve into new species

what is sympatric speciation

the evolution of new species without geographic isolation

polyploidy

a type of sympatric speciation in which a species contains three or more sets of chromosomes

example of polyploidy

triploid salamander, a distinct species of Tremblay’s salamander

what is the relationship between genes and alleles

alleles are different forms of a particular gene

what is not one of the primary courses of genetic variation

genetic drift

selection that favors more than one phenotype in future generations is called

disruptive selection

the difference between the processes involve in allopatric speciation and sympatric speciation is that

allopatric speciation require geographic isolation

what is a species phylogenetic tree

a hypothesized patterns of relatedness of species based on their morphological or DNA similarities