Evolution of Sex and Reproductive Strategies

Vocabulary practice flashcards covering natural selection trade-offs, the twofold cost of sex, Mueller's ratchet, bacterial recombination, the Red Queen hypothesis, and anisogamy based on the lecture.

Behavioral Ecology

The study of evolutionary trade-offs in organisms, focusing on how life balances the constraints of survival and reproduction within its ecological context.

Evolutionary Trade-off

The biological principle that an organism has a finite energy budget and cannot be good at everything, requiring sacrifices in one trait or function to invest in another.

John Maynard Smith

The twentieth-century evolutionary theorist who formulated the concept of the twofold cost of sexual reproduction.

Twofold Cost of Reproduction

The evolutionary disadvantage of sexual reproduction where males do not directly produce young, making females the sole rate-limiting step and halving the population growth rate compared to asexual clones, while also reducing genetic relatedness to offspring to $50\%$.

Mueller's Ratchet

The unidirectional evolutionary process in asexual lineages where deleterious, negative mutations inevitably accumulate over generations without a mechanism to purge them without wiping out the lineage.

Conjugation

A bacterial process of transferring genetic material, such as plasmids, directly between cells, enabling the exchange and spread of beneficial alleles without formal sexual reproduction.

Transformation

The mechanism by which bacteria acquire new genetic alleles by taking up foreign DNA fragments directly from dead organisms in their environment, originally highlighted by the Griffith experiment.

Plasmid

A small, extrachromosomal DNA molecule in bacteria that can carry advantageous alleles and be transferred between cells to circumvent the limits of strictly clonal reproduction.

Red Queen Hypothesis

An evolutionary theory—inspired by the scene in Alice in Wonderland where everyone must run constantly to stay in place—proposing that sexual reproduction is necessary for organisms to continuously generate genetic variation to keep up with rapidly evolving parasites and microbes.

Rhine Hook's Fish Experiment

A field experiment on pool-dwelling fish showing that when sexual fish lost genetic variation through inbreeding after a drought, they were heavily targeted by parasites; introducing genetically diverse sexual fish restored variability and dropped parasite loads back down below those of asexual clones.

Isogamy

A reproductive system where the mating gametes produced by different sexes or mating types are equal or similar in morphology and size.

Anisogamy

A reproductive system characterized by gametes of unequal size and resource investment, specifically small, mobile male gametes (sperm or pollen) and large, nutrient-rich female gametes (ova or eggs).

Female Reproductive Strategy

A strategy characterized by putting significant energetic investment into producing fewer, larger gametes (ova) and committing extended resources to gestation, nourishment, and parental care.

Male Reproductive Strategy

A high-risk, high-reward strategy that prioritizes the production of vast quantities of tiny, low-cost gametes (such as millions of sperm or pollen grains) to maximize mating opportunities and offspring numbers.