Evolution (Bz 220)

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Life history

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life time patterns of energy allocation to growth maintenance and reproduction

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Life history trait

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Those directly associated with growth, maintenance and reproduction

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Life history trade-off

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-Ideally, an organism would maximize all fitness components across entire life history, but limited by time and resources.
-Investment in one aspect of fitness takes away from another
-Invest in growth vs. early reproduct
-Invest in current offspring vs. future offspring
-Invest in many/small vs few/big offspring

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Senescence

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-late-life decline in fertility and probability of survival

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What is the evolutionary theory of aging?

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- failure to repair damage caused by
1) accumulation of deleterious mutations (Mutation accumulation hypothesis)
2) trade-offs between repair and reproduction (antagonistic pleiotropy hypothesis)

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Mutation Accumulation Hypothesis

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-Natural selection is weak late in life: alleles expressed late in life (after reproduction has already occured) have little impact on fitness
-If they are mildly deleterious: may persist in mutation selectin balance
-Nutral: may rise to high frequency by genetic drift

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Antagonistic Pleiotropy Hypothesis

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- Pleiotropy: single gene effect multiple traits
- Alleles that increase early reproduction also cause early senescence
- Trade-off between early reproductive success and late life reproductive success
-If they are beneficial: may rise to high frequency by selection; benefits of early reproduction must outweigh costs of early death

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What is Lack’s hypothesis?

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- Selection would favor clutch size that produces most SURVIVING offspring ---> intermediate optimal clutch size

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What are some possible reasons that bird clutches are often smaller than predicted by Lack’s hypothesis?

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- Trade-off between parent's current and future reproduction: smaller clutch may allow for greater reproduction by parent in next year
- Trade-off between quantity and quality of surviving offspring: smaller clutch size may allow each offspring to have higher reproductive success when they are adults

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What 2 other factors (besides number of surviving offspring in one breeding season) would scientists also have to measure to understand why these clutch sizes are smaller?

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1) resources
2)

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Why are some life-history traits not perfectly optimized?

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- not enough time or genetic variation to evolve toward new optimum
- constraints impede evolution

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Are life history traits predicted to have low levels of heritability or high levels of heritability? Why?

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- Life history traits are closely related to fitness, so have lower heritability than other traits
- but they often still have genetic variation

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Evolutionary Species Concept

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- Independent evolutionary lineage with own evolutionary tendencies and historical fate
- evolutionary independence: mutation. selection, migration, and drift operate on populations seperately

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Biological species concept

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- a group of actually or potentially interbreeding organisms that are reproductively isolated from all other such groups
- Interbreeding: successfully producing fertile offspring

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Phylogenetic species concept

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- Smallest monophyletic group of ordanisms diagnosable by FIXED, UNIQUE combination of character state
- fixed, unique character states: can range from single nucleotide substitution to a major morphological change

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Morphospecies concept

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- subset of phylogenetic species concept
- distinct morphological differences (in comparable individuals)
-historical, older concept

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Allopatric

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- geographic isolation

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Sympatric

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- something other than geographic isolation

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Dispersal

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- individuals cross barier

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Vicariance

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-barrier divides population (effects many species)

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Hybridization

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- the tow once isolated populations interbreed creating hybrids

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Reinforcement

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- diverging populations come back into secondary contact
-return to sympatry or are no longer isolated

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Prezygotic isolation

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- selection favors mechanisms to prevent hybridization

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Ring species

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- a circular distrabution of adjacent populations that interbredd, except where the two ends of the ring come together

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What are the differences between the species concepts?

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- biological species concept: reproductive isolation
- phylogenetic species concept: unique character states
- morphospecies concept: morphological differences

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What are 3 problems with the biological species concept?

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1) extinct populations in fossil record
2) asexual organisms (there is no interbreeding)
3) Lateral gene transfer ( some distantly related organisms can transfer genetic material, is this interbreeding?

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Organic molecules

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-produced from inorganic molecules in Erath's atmosphere
OR
-arrived in meteroites