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Bet hedging (biology)

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**1. Bet Hedging Overview and Evolution:**
– Bet hedging involves organisms lowering expected fitness in typical conditions for increased fitness in stressful conditions.
– Three categories of bet hedging are conservative, diversified, and adaptive coin flipping.
– Bet hedging alleles must be compared for long-term fitness using the geometric mean in variable environments.
– Persistence of bet hedging alleles through genetic drift is crucial for their spread.
– Bet hedging allows survival in fluctuating conditions, providing an evolutionary advantage.
– Bet hedging traits may not be optimal for specific environments but offer benefits across various conditions.
– Bet hedging alleles are favored in variable environments due to higher fitness across different conditions.

**2. Prokaryotic Bet Hedging:**
– Prokaryotic model organisms provide simplified views of bet hedging evolution.
– Prokaryotes display bet hedging through stochastic switching between phenotypes.
– Experimental evolution models in prokarya help deduce the evolutionary origins of bet hedging.
– Sinorhizobium meliloti and Mycobacterium tuberculosis are examples of prokaryotes displaying bet hedging.
– Prokaryotic bet hedging is crucial in medicine due to bacterial persistence.

**3. Eukaryotic Bet Hedging Models:**
– Eukaryotic models study complex evolutionary processes in Animalia, Plantae, and Fungi.
– Vertebrates like West Atlantic salmon and marsupials like Sminthopsis macrour demonstrate bet hedging strategies.
– Invertebrates like Diaptomus sanguineus and fungi also employ bet hedging mechanisms.
– MHC diversity is crucial for the reproductive success of Atlantic salmon.
– Bet hedging in eukaryotes is influenced by environmental factors.

**4. Bet Hedging Examples in Various Organisms:**
– Examples of bet hedging in fungi, viruses (Herpes and Varicella Zoster Virus), and plants (delayed seed germination, seed banks).
– Bet hedging in yeast aids survival under harsh conditions and makes pathogenic yeast strains harder to treat.
– Neurospora crassa produces ascospores with variation in dormancy to ensure survival under changing conditions.

**5. Bet Hedging in Animal Behavior and Plant Adaptation:**
– Bet hedging observed in yeast survival strategies and age-correlated expression of stress protectant.
Plant examples include optimal germination strategies in desert winter annual plants and adaptive bet hedging in seed germination of desert annuals.
– Studies on bet hedging in seed germination of desert annuals and experimental evolution of bet hedging under environmental uncertainty.

Biological bet hedging occurs when organisms suffer decreased fitness in their typical conditions in exchange for increased fitness in stressful conditions. Biological bet hedging was originally proposed to explain the observation of a seed bank, or a reservoir of ungerminated seeds in the soil. For example, an annual plant's fitness is maximized for that year if all of its seeds germinate. However, if a drought occurs that kills germinated plants, but not ungerminated seeds, plants with seeds remaining in the seed bank will have a fitness advantage. Therefore, it can be advantageous for plants to "hedge their bets" in case of a drought by producing some seeds that germinate immediately and other seeds that lie dormant. Other examples of biological bet hedging include female multiple mating, foraging behavior in bumble bees, nutrient storage in rhizobia, and bacterial persistence in the presence of antibiotics.

Variance in egg size is an example of bet-hedging. Fitness may be maximized by producing many, small eggs and thus many offspring. However, larger eggs may help offspring survive stressful conditions. Producing a range of egg sizes can both ensure that some offspring survive stressful conditions, and that many offspring are produced in good conditions.
The evolution of an allele that is deleterious in a normal environment (white) but advantageous in an alternate environment (grey). The bet-hedging allele arises twice due to mutation. The first occurrence is lost before the environment changes, but the second mutant reaches fixation due to the presence of the alternate environment.
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