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Life History

Life History. Photo of size variation in seeds from Panama from http://www.tc.umn.edu/~hmuller/. Life History. Major events related to an organism’s growth , development , reproduction & survival. Timing , duration , phenology , rate , allocation , allometry , etc .

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Life History

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  1. Life History Photo of size variation in seeds from Panama from http://www.tc.umn.edu/~hmuller/

  2. Life History Major events related to an organism’s growth, development, reproduction & survival Timing, duration, phenology, rate, allocation, allometry, etc. shaped by natural selection Life-history traits vary among individuals & populations Mallard w/ 11 Wood duck w/ 5 Wood duck w/ 7 Life-history strategy is a population-level representation Photos from: http://westboroughlandtrust.org/nn/nn54.php; http://portlandbirds.blogspot.com/2010_05_01_archive.html; http://www.rampantscotland.com/colour/supplement070519.htm

  3. Asexual vs. sexual reproduction Binary fission produces genetically identical clones Paramecium Image from http://biodidac.bio.uottawa.ca/thumbnails/filedet.htm?File_name=OLIH023P&File_type=GIF

  4. Asexual vs. sexual reproduction Asexual vs. sexual reproduction Sexual reproduction produces genetically variable offspring Isogamous gametes Chlamydomonas Anisogamous gametes Homo sapiens Cain, Bowman & Hacker (2014), Fig. 7.7 Cain, Bowman & Hacker (2014), Fig. 7.7

  5. Asexual vs. sexual reproduction A “cost of sex” / “cost of males” Assume each adult female in a population produces 4 offspring, either asexually or sexually Cain, Bowman & Hacker (2014), Fig. 7.8

  6. Asexual vs. sexual reproduction Benefit of sex: Genetic variation E.g., Red Queen Hypothesis (coping with ever-evolving enemies) From a statement the Red Queen makes to Alice in Lewis Carroll’s “Through the Looking Glass” (“Alice in Wonderland”): “Now, here, you see, it takes all the running you can do, to keep in the same place” Photo of harvestman with parasitic mites from Wikimedia Commons

  7. Simple vs. complex life cycles Complex life cycle – 2 or more distinct stages that differ in habitat, physiology, or morphology E.g., Alternation of Generations in plants Larval, pupal & adult wasps E.g.,Holometabolousinsects Anadromous salmon adults live at sea, but spawn in freshwater E.g.,Anadromous&catadromousfishes Herbivorous, aquatic tadpole will become carnivorous, terrestrial adult E.g., Metamorphic amphibians Photos from Wikimedia Commons

  8. The Life Cycle of Animals – Illustrated for Humans Generation 1 Generation 2 Gen. 3 Specialized cells undergo meiosis to produce gametes Gametes fuse during fertilization to become a zygote AA XX A X Aa XX AA XY a X A Y Aa XY Aa XY a X From the single-celled zygote stage onward, cells undergo mitosis to increase the number of cells in the maturing individual. Aa XX Unicellular zygote; Diploid (2n) cell Unicellular gametes; Haploid (1n) cells Multicellular individuals; Diploid (2n) cells Muticellular individuals; Diploid (2n) cells

  9. The Life Cycle of Fungi – Illustrated for Bread Mold Brief inter- generational zygote stage Several generations Several generations Multiple rounds of asexual reproduction possible; all cell divisions occur by mitosis. Multiple rounds of asexual reproduction possible; all cell divisions occur by mitosis. Zygotic meiosis Aa +- a - A + a - Fusion of compatible hyphae (plasmogamy and karyogamy) to form a zygote-like structure Multiple rounds of asexual reproduction possible; all cell divisions occur by mitosis. Multiple rounds of asexual reproduction possible; all cell divisions occur by mitosis. a - a + Haploid (1n) cells of hyphae Haploid (1n) cells of hyphae Diploid (2n) zygote Haploid (1n) spore

  10. The Life Cycle of Plants (Alternation of Generations) – Illustrated for a Dioecious Flower Gen. 4 Generation 3 Generation 1 Generation 2 Specialized cells undergo meiosis to produce spores Gametes fuse during fertilization to become a zygote a B aa BB Pollen grain A b A b AA bb Aa Bb A b a B a B Aa Bb Embryo sac Single-celled spores undergo mitosis to increase the number of cells in the maturing gametophyte. Mature gametophyte produces gametes by mitosis Specialized cells undergo meiosis to produce spores Aa Bb Multicellular gametophyte Unicellular zygote Unicellular spores of gametophyte Unicellular spores Unicellular gametes Multicellular sporophyte Multicellular sporophyte Haploid (1n) cells Haploid (1n) cells Diploid (2n) cells Diploid (2n) cells

  11. Allocation Trade-offs, Costs & Benefits, Constraints Resources vs. Photos from Wikimedia Commons

  12. Allocation Trade-offs, Costs & Benefits, Constraints There is no free lunch A jack of all trades is master of none E.g., offspring or propagule size-number tradeoff Number Size Each dot represents the life-history strategy of a given species in a given clade

  13. Allocation Trade-offs, Costs & Benefits, Constraints Constraint lines and wedge-shaped distributions Number Size Each dot represents the life-history strategy of a given species in a given clade

  14. Design Trade-offs, Costs & Benefits, Constraints Design: shape, function, etc. vs. Photos from Wikimedia Commons

  15. Design Trade-offs, Costs & Benefits, Constraints A jack of all trades is master of none E.g., consider pond-breeding salamander species in ephemeral pools vs. stable ponds What life-history strategy would perform best in each habitat? Is there a “one size fits all” solution?

  16. Semelparous vs. Iteroparous (Monocarpic vs. Polycarpic) Often entails a reproduction – survival tradeoff Monocarpic talipot palm Polycarpic coconut palm Photo of monocarpic talipot palm from http://www.etawau.com/Agriculture/IndexTrees.htm; photo of polycarpic coconut palm from http://www.hawaii.edu/cpis/MI/plants/ni.html

  17. r-selected vs. K-selected General environmental or population-level correlates Disturbance Population growth rate Stability K-selected r-selected Correlated organismal traits Body size Life span Parental investment in offspring Developmental rate Rate of maturation Reproductive rate The concepts of r-selection & K-selection originated with MacArthur & Wilson (1967)

  18. Grime’s Triangular Model Competitive Ruderal (“weedy”) Stress-tolerant Competition = “tendency of neighboring plants to utilize the same quantum of light, ion of a mineral nutrient, molecule of water, or volume of space” Disturbance = “process that destroys plant biomass” Stress = “abiotic factor that limits vegetative growth” Image from http://hosho.ees.hokudai.ac.jp/~tsuyu/top/dct/lc.html; original concept from Grime (1977) American Naturalist

  19. Competition – Colonization Tradeoff Colonization Ability Competitive Ability The concept was elaborated by Rees & Westoby (1997) Oikos

  20. Tolerance – Fecundity Tradeoff Fecundity Stress Tolerance Original concept from Muller-Landau (2010) Proceedings of the National Academy of Sciences

  21. Ontogenetic niche shifts Occur routinely in organisms with complex life cycles, but occur in other organisms as well Aquatic larva Winged adult Photo of hellgrammite (larva) and adult Dobson flies (Order Megaloptera) from Wikimedia Commons

  22. A Classic Example: Clutch Size David Lack “Lack Clutch Size” = clutch size that maximizes the number of offspring that a parent can rear to maturity, given the tradeoff between investment per offspring vs. number of offspring Experimental evidence through clutch-size manipulation experiments Original concept from Lack (1947) Ibis

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