Chapter 10 - Evolutionary Genetics Flashcards
central concept in biology
evolution
one of the foundations of evolution
genetics
group of individuals of the same species
population
- series of partial or complete and irreversible transformations of the genetic structure of a population based principally on altered interaction with the environment
- chance processes, interacting with a changing environment, generated complex structures and organs that now have purposes which were not planned or designed
organic evolution
Requirements for Evolution
- heritable variation
- limited environmental opportunities
- changing environments
genetic mechanism that is not perfect but produces offspring that are sometimes slightly different from their parent/s
heritable variation
insufficient resources for all individuals to survive and reproduce, leading to competition for necessary resources
limited environmental opportunities
as conditions change, different individuals are best able to survive and reproduce
changing environments
Forces that modify gene frequencies in populations
- mutation
- migration
- natural selection
- genetic drift
- gene recombination
increases variability within a population
mutation
adds genetic variability to a population
migration
- decreases genetic variability through elimation of unfavorable mutations
- results in the perpetuation of those life forms having favorable characteristics that enable them to adapt to a specific environment
natural selection
results in the chance elimination of genotypes due to small population size
genetic drift
causes reshuffling of genes to produce new gene combinations for acceptance or rejection by selective forces of evolution
gene recombination
identification by humans of desirable traits in plants and animals, and the steps taken to enhance and perpetuate those traits in future generations
Artificial selection
genetic base in artificial selection
narrow
genetic base in natural selection
broad
- change in population’s gene pool over a succession of generations
- occurs over relatively brief period of time
microevolution
- total collection of genes in a population at any given time
- reservoir from which members of next generation derive their genes
gene pool
genetic drift that results from event that drastically reduces population size
bottleneck effect
refers to the reduction in genomic variability that occurs when a small group of individuals becomes separated from a larger population
founder effect
Three Evolutionary Patterns
- divergent evolution
- convergent evolution
- parallel evolution
- occurs when members of a species are placed in different environmental conditions
- members of population may gradually develop into different species with no particular point in time for their separation
divergent evolution
- refers to the development of superficial resemblances between organisms of different ancestries
- these groups, which are unrelated by descent, but living under similar environmental conditions can exhibit similarities in habits and general appearances
convergent evolution
herbaceous plant or shrub with milky latex and very small, typically greenish, flowers
spurge
- two organisms acquire similar characteristics independently of one another
- have stemmed from related ancestries
- akin, yet distinguishable from convergence
parallel evolution
Modes of Selection
- directional selection
- stabilizing selection
- disruptive selection
ex. of directional selection
english peppered moths
ex. of stabilizing selection
horseshoe crab
ex. of disruptive selection
African swallowtail
process of splitting a genetically homogenous population into two or more populations that undergo genetic differentation and reproductive isolation
speciation
The Rate of Speciation
- phyletic gradualism
- quantum speciation
speciation is a microevolutionary event resulting from the accumulation of many small gene differences over time under the influence of natural selection
phyletic gradualism
- stochastic or catastrophic speciation
- evolutionary events occur suddenly and intermittently
quantum speciation
Models of Quantum Speciation
- Punctuated Equilibrium
- Founder-Flush Theory
- idea that evolution occurs in spurts instead of following the slow, but steady path that Darwin suggested
- Long periods of stasis with little activity in terms of extinctions or emergence of new species are interrupted by intermittent bursts of activity
Punctuated equilibrium
genetic evolution is in some way different in a population that is founded by a small number of individuals and that subsequently grows rapidly
Founder-flush theory
Models of Speciation (Recent, most developed)
- allopatric speciation
- sympatric speciation
- stasipatric speciation
- geographic features such as lakes, rivers, or mountains act as barriers to gene flow between population
- physical isolation is the first step in the process of evolution
allopatric speciation
formation of species from populations that live in the same geographic range and do not become geographically isolated
sympatric speciation
- rapid speciation that may occur among small breeding populations that are not completely isolated genetically or spatially.
- formation of new species as a result of chromosomal rearrangements
stasipatric speciation
Human Evolution
- loss of alleles
- increasing allele frequencies
branch of systematics that attempts to construct phylogenetic trees based on the presence of shared derived characters
cladistics
Two types of Isolation
- Geographical Isolation
- Reproductive Isolation
Two types of Reproductive Isolation
- Prezygotic Isolation
- Postzygotic Isolation
Prezygotic Isolation
- ecological
- seasonal
- ethological
- physiological
- mechanical
- gametic mortality
Postzygotic Isolation
- cytological
- zygotic mortality
- hybrid inviability
- hybrid sterility
- hybrid breakdown
