asexual reproduction - creates genetically identical offspring
- all chromosomes from a single parent
- animal asexual reproduction involves budding off of a mass of cells
- parthenogenesis - development of an adult from an unfertilized egg
- common form of reproduction in arthropods
- diploid female bees, haploid male bees
- more advantageous than sexual reproduction (recombination does more harm than good in evolution)
sexual reproduction - multiple theories on its origin
- no other process makes diversity more quickly, speeds up evolution
- asexually reproducing organisms tend to live in isolated, demanding habitats where natural selection doesn’t favor change
- sexually reproducing organisms tend to favor versatility, best supported by genetic recombination
DNA repair hypothesis - diploid cells can repair chromosome damage
- protists only use sexual reproduction in times of stress
- synaptonemal complex may have evolved as a way to fix double-stranded DNA damage
- undamaged homologous chromosome used as template to fix damaged DNA
contagion hypothesis - mobile genetic elements infected eukaryotes
- elements w/ genes for fusion w/ uninfected cells and synapsis can quickly copy itself onto homologous chromosomes
- idiomorph - genes in homologous positions on chromosomes but are so different that they can’t be of homologous origin
- explains the mating type “alleles” in fungi
red queen hypothesis - saves recessive alleles useful in the future
- keeping alleles allow organism to keep up w/ changing environment
- sexual species can’t get completely rid of recessive traits in heterozygotes
Muller’s ratchet - can keep mutation level down
- asexual populations can’t get rid of mutations
- sexual populations get rid of mutations through natural selection
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