BIO120 Lecture 6: Sex, Reproductive Systems, and Evolution

Vocabulary flashcards covering the evolution of sex, reproductive modes, inbreeding versus outbreeding, and the genetic consequences of different mating systems based on BIO120 Lecture 6.

Biidaasige Park

A brand-new natural park in Toronto where one can observe migrating songbirds, ducks, wildflowers, and insects.

Inbreeding

Self-fertilization or a mating system where mates are more closely related than random.

Outbreeding

Cross-fertilization or a mating system where mates are less closely related than random.

Dioecious

A sexual system where an individual organism has either male or female reproductive organs, but not both.

Hermaphrodite

An organism that possesses both male and female reproductive organs.

Daphnia reproductive plasticity

Water fleas exhibit sexual reproduction in warmer, turbulent water and asexual reproduction in cooler, calm water.

Costs of sex

Includes the time/energy to find mates, increased energetic costs, risk of predation/infection, cost of producing males, $50\,\%$ less genetic transmission, and the break up of adaptive gene combinations.

The Paradox of Sex

The big question of why sexual reproduction evolved and persists despite its high biological costs compared to asexuality.

Two-fold cost of producing males

A transmission bias favoring asexuals because an asexual population can increase at twice the rate of a sexual population.

Tangled Bank hypothesis

The theory that sex is advantageous in spatially-variable environments.

Lottery model

The hypothesis that genetic variation provides benefits in temporally-variable environments.

Brachionus calyciflorus

A facultatively sexual rotifer used to show that heterogeneous environments favor higher percentages of sexual reproduction.

Bdelloid rotifers

A rare example of ancient asexuality where males are unknown, yet the group has diversified into over 300 species over millions of years.

Genetic consequences of inbreeding

Alters genotypic frequencies and reduces heterozygosity by up to $50\,\%$ per generation, while leaving allelic frequencies unchanged.

Inbreeding depression

The reduction in fitness (viability and fertility) of inbred offspring compared with outcrossed offspring, often due to the accumulation of deleterious recessive alleles.

Automatic selection of a selfing gene

A theory by R.A. Fisher stating a selfing variant has a transmission advantage because it contributes 3 copies of its genes to the next generation (2 via seed, 1 via pollen) compared to an outcrosser's 2 copies.

Capsella grandiflora

A large-flowered, self-incompatible outcrosser with high DNA sequence diversity.

Capsella rubella

A small-flowered selfer that spread through Europe and has a higher burden of deleterious mutations and reduced DNA diversity.

Oenothera (Evening Primrose)

A plant genus where asexual populations show higher rates of protein evolution and more stop codons, suggesting the accumulation of deleterious mutations.

Parthenogenesis

A process mentioned by Darwin where new beings are produced without the union of two sexual elements.