Mutation and sexual reproduction

Mutations

Changes of the genetic sequence, often as errors during DNA replication

• Chromosomal duplications, deletions, and translocations

• Errors during meiosis

Hardy weinberg equilibrium

Genetic variation in population will remain constant from one generation to the next in the absence of evolutionary mechanisms

Mutation (as an evolutionary mechanism)

• Mutations from one allele can change proportions of alleles in a population

• Mutation rates are generally low → little to no effect on Hardy-Weinberg equilibrium frequencies

  • Other evolutionary processes are more freuent

Why is mutation vital for evolution

• Ultimate source for new genetic variation (new alleles among individuals)

• Rare and random event

• Many mutations are neutral or lethal. Very few are beneficial

• They do not occur more frequently in situations in which they would be favored by natural selection

What is the significance of Mutation opposing natural selection?

• It explains why many genetic diseases with negative fitness have not been eradicated from the population

• Even if one allele is consistently favored, a different allele with disease causing products will be produced more by the mutation

Sources of genetic/phenotypic variation among individuals

• Mutation

• Sexual reproduction

• Migration

• Hybridization, introgression, and lateral gene transfer

Genetic recombination

Most immediate and influential source of variation in sexually reproducing species and involves:

• Meiosis

• Recombination by crossing over

• Gamete fusion

Meiosis

Process of randomly assigning one of two chromosomes to each gamete

Recombination by crossing over

Homologous chromosomes trade parts

• Occurs during meiosis after chromosomes have been duplicated

Gamete fusion

Combining the gamete egg with gamete sperm to make a zygote

Random mating

• Hardy weinberg assumes that all individuals choose their mates randomly (with respect to their own genotypes)

Sexual selection

Selection for traits and behaviors that maximize reproductive (mating) success

• sexes have different reproductive strategies

Sexual dimorphism

When selection acts on males and females differently in the same population, leading to differences in how the same trait manifests in males versus females

Parental investment

contributions each sex makes in producing and rearing offspring

• Females usually have higher investment

• Eggs larger than sperm

• Females are usually more responsible for gestation and lactation or yolk production

Consequences of disparities in reproductive investment (sexes face differing selective pressures

Females are specific BECAUSE it is costly for them to reproduce

INTERsexual selection

When individuals of one sex select among individuals of the other sex

• BENEFITS:

  • Choosing males that provide them with resources and help raise offspring

  • Choose males that provide territories, nesting sites, food, etc

  • Choose male that is healthiest/oldest

INTRAsexual selection

Members of one sex COMPETE with each other for mating access to the other sex

• FORMS

  • Fighting between males for females

  • Fighting between males for territory

Good genes

A suite of genes that code for favorable traits

• Passed to offspring, increasing their survival and/or fecundity

• Males must indicate their quality in some way

  • Evolution of honest signals that accurately demonstrate that an individual has favorable genes