random sampling

Examples of random sampling in the following topics:

• Genetic Drift

  • Genetic drift is the change in allele frequencies of a population due to random chance events, such as natural disasters.
  • Through random sampling, or the survival or and reproduction of a random sample of individuals within a population, allele frequencies within a population may change.
  • Genetic drift is the shift of alleles within a population due to chance events that cause random samples of the population to reproduce or not.
  • Because the random sampling can remove, but not replace, an allele, and because random declines or increases in allele frequency influence expected allele distributions for the next generation, genetic drift drives a population towards genetic uniformity over time.
  • Thus even while genetic drift is a random, directionless process, it acts to eliminate genetic variation over time.

• Gene Duplications and Divergence

  • Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling.
  • The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces.

• Misconceptions of Evolution

  • Genetic drift occurs when allelic frequency is altered due to random sampling.
  • It is evolution by chance, and the smaller the population, the more significant the effects on genetic distribution due to sampling error.

• Population Size and Density

  • Scientists study population size and density using a variety of field sampling methods, including quadrats and mark-recapture.
  • A variety of methods can be used to sample populations.
  • A field study usually includes several quadrat samples at random locations or along a transect in representative habitat.
  • For sampling daffodils, a 1 m2 quadrat could be appropriate.
  • Choose the appropriate method to sample a population, given features of the organisms in that population

• Rules of Probability for Mendelian Inheritance

  • In other words, in a large population of F2 offspring chosen at random, 75 percent were expected to have round seeds, whereas 25 percent were expected to have wrinkled seeds.
  • To use probability laws in practice, it is necessary to work with large sample sizes because small sample sizes are prone to deviations caused by chance.

• Population Genetics

  • For example, in a sample population of humans, the frequency of the IA allele might be 0.26, which would mean that 26% of the chromosomes in that population carry the IA allele.
  • Random events that alter allele frequencies will have a much larger effect when the gene pool is small.

• Biotechnology in Medicine

  • A scientist scans a patient's DNA sample for mutated sequences.
  • In its simplest form, it involves the introduction of a good gene at a random location in the genome to aid the cure of a disease that is caused by a mutated gene.

• The Punnett Square Approach for a Monohybrid Cross

  • Because fertilization is a random event, we expect each combination to be equally likely and for the offspring to exhibit a ratio of YY:Yy:yy genotypes of 1:2:1.
  • Indeed, working with large sample sizes, Mendel observed approximately this ratio in every F2 generation resulting from crosses for individual traits.

• Species Distribution

  • Individuals of a population can be distributed in one of three basic patterns: they can be more or less equally spaced apart (uniform dispersion), dispersed randomly with no predictable pattern (random dispersion), or clustered in groups (clumped dispersion) .
  • Random dispersion occurs with dandelion and other plants that have wind-dispersed seeds that germinate wherever they happen to fall in a favorable environment.
  • Just as lower density species might have more difficulty finding a mate, solitary species with a random distribution might have a similar difficulty when compared to social species clumped together in groups.
  • A population may have a uniform, random, or clumped distribution.

• The Second Law of Thermodynamics

  • An important concept in physical systems is disorder (also known as randomness).
  • The more energy that is lost by a system to its surroundings, the less ordered and more random the system is.
  • Scientists define the measure of randomness or disorder within a system as entropy.
  • When the ice cube melts and becomes water, its molecules are more disordered, in a random arrangement as opposed to a structure.
  • Entropy is a measure of randomness or disorder in a system.