assortative mating

Examples of assortative mating in the following topics:

• Nonrandom Mating and Environmental Variance

  • Population structure can be altered by nonrandom mating (the preference of certain individuals for mates) as well as the environment.
  • If individuals nonrandomly mate with other individuals in the population, i.e. they choose their mate, choices can drive evolution within a population.
  • There are many reasons nonrandom mating occurs.
  • One common form of mate choice, called positive assortative mating, is an individual's preference to mate with partners that are phenotypically similar to themselves.
  • The American Robin may practice assortative mating on plumage color, a melanin based trait, and mate with other robins who have the most similar shade of color.

• Conditional probability exercises

  • Assortative mating is a nonrandom mating pattern where individuals with similar genotypes and/or phenotypes mate with one another more frequently than what would be expected under a random mating pattern.

• Mating Systems and Sexual Selection

  • In mating, there are two types of selection (intersexual, intrasexual) and three mating systems (monogamous, polygynous, polyandrous).
  • Intrasexual selection involves mating displays and aggressive mating rituals such as rams butting heads; the winner of these battles is the one that is able to mate.
  • Polygynous mating refers to one male mating with multiple females.
  • In polyandrous mating systems, one female mates with many males.
  • Seahorses are a good example of a polyandrous mating system, in which one female mates with several males.

• Life Cycles of Sexually Reproducing Organisms

  • During sexual reproduction, specialized haploid cells from two individuals, designated the (+) and (−) mating types, join to form a diploid zygote.
  • The mechanisms of variation (crossover, random assortment of homologous chromosomes, and random fertilization) are present in all versions of sexual reproduction.

• Epistasis

  • The recessive yellow genotype is epistatic to the B gene: mating two heterozygotes (BbEe) results in a 9:3:4 ratio of black (B_E_) to brown (bbE_) to yellow (__ee) offspring.
  • Note that we are assuming the interacting genes are not linked; they are still assorting independently into gametes.

• Mendel's Law of Independent Assortment

  • Independent assortment allows the calculation of genotypic and phenotypic ratios based on the probability of individual gene combinations.
  • Mendel's law of independent assortment states that genes do not influence each other with regard to the sorting of alleles into gametes: every possible combination of alleles for every gene is equally likely to occur.
  • The independent assortment of genes can be illustrated by the dihybrid cross: a cross between two true-breeding parents that express different traits for two characteristics.
  • The law of independent assortment states that a gamete into which an r allele sorted would be equally likely to contain either a Y allele or a y allele.
  • The values along each forked pathway can be multiplied because each gene assorts independently.

• Signaling in Yeast

  • Yeasts utilize cell-surface receptors, mating factors, and signaling cascades in order to communicate.
  • In order to find another haploid yeast cell that is prepared to mate, budding yeasts secrete a signaling molecule called mating factor.
  • When mating factor binds to cell-surface receptors in other yeast cells that are nearby, they stop their normal growth cycles and initiate a cell signaling cascade that includes protein kinases and GTP-binding proteins that are similar to G-proteins.
  • Budding Saccharomyces cerevisiae yeast cells can communicate by releasing a signaling molecule called mating factor.

• Sexual Selection

  • Sexual selection, the selection pressure on males and females to obtain matings, can result in traits designed to maximize sexual success.
  • The selection pressures on males and females to obtain matings is known as sexual selection.
  • Females almost always mate, while mating is not guaranteed for males.
  • The bigger, stronger, or more decorated males usually obtain the vast majority of the total matings, while other males receive none.
  • In either case, this variation in reproductive success generates a strong selection pressure among males to obtain those matings, resulting in the evolution of bigger body size and elaborate ornaments in order to increase their chances of mating.

• Animal Communication and Living in Groups

  • Mating usually involves one animal signaling another so as to communicate the desire to mate.
  • There are several types of energy-intensive behaviors or displays associated with mating called mating rituals.
  • Male crickets make chirping sounds using a specialized organ to attract a mate, repel other males, and to announce a successful mating.
  • If at any point the display is performed incorrectly or a proper response is not given, the mating ritual is abandoned and the mating attempt will be unsuccessful.
  • A male peacock's extravagant, eye-spotted tail is used in courtship displays to attract a mate.

• Store Retailers

  • Store retailers vary in size, in the kinds of services, the assortment of merchandise they carry, and many other respects.
  • Store retailers vary in size, in the kinds of services that are provided, in the assortment of merchandise they carry, and in many other respects.
  • Their entire approach to the distribution of food and household cleaning and maintenance products was to make available to the public large assortments of a variety of such goods at each store at a minimal price.
  • Merchandise assortments are generally broad, including both hard and soft goods, but assortments are typically limited to the most popular items, colors, and sizes.
  • Such regional shopping centers are successful because they provide customers with a wide assortment of products.