2.3a - costs and benefits of reproduction

• sexual and asexual reproduction have both costs and benefits
• disadvantages of sexual reproduction include the fact that males cannot produce offspring, and there can be disruption of successful parental genomes and only half of a parents genome passes to their offspring
• the benefits of sexual reproduction outweigh the disadvantages
• the benefits of sexual reproduction include the increase in genetic variation in the population due to the mixing of parental genomes
• the genetic variation provides the raw material required for adaptation, giving sexually reproducing organisms a better chance of survival under changing selection pressures
• the red queen hypothesis can be used to explain the persistence of sexual reproduction
• co-evolutionary interactions between parasites and hosts may select for sexually reproducing hosts
• host better able to resist and tolerate parasitism have greater fitness; parasites better able to feed, reproduce and find new hosts have greater fitness
• if hosts reproduce sexually, the genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasites
• asexual reproduction can be a successful reproductive strategy as whole genomes are passed on from parent to offspring
• in asexual reproduction, just one parent can produce offspring and establish a colony of virtually unlimited size over time
• maintaining the genome of the parent is an advantage, particularly in very narrow, stable niches or when recolonising disturbed habitats
• offspring can be reproduced more often and in larger numbers with asexual reproduction
• vegetative cloning in plants and parthenogenesis in lower plants and animals that lack fertilisation are examples of asexual reproduction in eukaryotes
• parthenogenesis is more common in cooler climates with low parasite density and diversity
• parthenogenesis

  development of an offspring from a female gamete without fertilisation
• both sexual and asexual reproduction are examples of vertical gene transfer in which parent individuals of one generation pass copies of their genes on to offspring that form the next generation
• asexually reproducing populations are not able to adapt easily to changes in their environment, but mutations can occur that provide some degree of variation and enable some natural selection and evolution to occur
• organisms that reproduce principally by asexual reproduction often have mechanisms for horizontal gene transfer between individuals to increase variation, for example the plasmids of bacteria and yeast
• prokaryotes can exchange genetic material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer