Evolution of Sex Flashcards
What percentage of flowering plants are hermaphroditic, and how do they exhibit male and female functions?
94% of flowering plants are hermaphroditic, with male and female functions either within the same flower or within the same plant.
What is dioecy, and what proportion of flowering plants exhibit this reproductive strategy?
Dioecy refers to the presence of separate male and female individuals within a species. Approximately 6% of flowering plants exhibit this reproductive strategy.
What is trioecy, and how does it differ from dioecy?
Trioecy is a reproductive system where male, female, and hermaphroditic individuals coexist within the same species, unlike dioecy which only includes separate male and female individuals.
Among animals, how common is hermaphroditism compared to separate sexes?
Most animals have separate sexes, but around 5% are hermaphroditic. Hermaphroditism is more common among fish and invertebrates.
Why might some hermaphroditic animals switch genders?
Gender switching in hermaphroditic animals often occurs due to benefits related to size or social stature, optimizing reproductive success.
What are the advantages and drawbacks of hermaphroditism over dioecy in plants and animals?
Sequential hermaphroditism ensures both sexes can exist in small populations.
Reproductive assurance increases the likelihood of finding a mate or self-fertilizing.
Greater efficiency in seed dispersal as all individuals can reproduce.
Flexibility to reproduce via eggs or sperm.
Drawbacks: Potentially higher susceptibility to sexually transmitted diseases and developmental errors in producing both egg and sperm.
What are the advantages of dioecy compared to hermaphroditism?
Avoids inbreeding and selfing.
Allows for parental role specialization.
Reduces energy costs associated with maintaining both reproductive structures.
Promotes stronger sexual selection.
Avoids chromosomal errors associated with complex sex determination
How does sexual reproduction differ from asexual reproduction?
Sexual Reproduction: Involves mating between individuals, leading to genetically mixed offspring.
Asexual Reproduction: Offspring are produced without mating or genetic mixing, as seen in methods like budding, fission, and apomixis.
What percentage of animals and angiosperms reproduce exclusively asexually?
Less than 0.1% of animals and around 1% of angiosperms reproduce exclusively asexually.
When did sexual reproduction arise among eukaryotes?
Sexual reproduction arose approximately 1-1.6 billion years ago, with all living eukaryotes descending from an ancestor possessing the genetic toolkit for meiosis.
What are the evolutionary advantages of asexual reproduction?
Lower costs, as time and energy are saved by not needing a mate.
Rapid reproduction and exponential growth when resources are abundant.
Preservation of advantageous genotypes.
What are the evolutionary advantages of sexual reproduction
Greater genetic variation and faster evolutionary responses.
Diversified offspring reduce the risk of all dying from the same disease.
Better adaptability to fluctuating environments.
What are the key costs of sexual reproduction?
Producing males reduces direct reproductive output.
Destruction of favorable gene combinations.
Time and energy spent finding a mate.
Risk of not finding a mate or disease transmission during mating.
How does sexual reproduction generate variation, and why is this important?
Sexual reproduction generates variation through recombination and segregation, allowing for greater adaptability and evolutionary resilience in fluctuating environments.
What is the “evolutionary enigma of sex,” and what hypotheses address it?
The enigma lies in why sexual reproduction persists despite its costs.
Hypotheses suggest that sex reduces selective interference among loci, untying alleles from specific genetic backgrounds and enabling effective selection.
