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Life History Photo of size variation in seeds from Panama from

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Presentation on theme: "Life History Photo of size variation in seeds from Panama from"— Presentation transcript:

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

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

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

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

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

6 Benefit of sex: Genetic variation E.g., Red Queen Hypothesis (coping with ever-evolving enemies) Asexual vs. sexual reproduction 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 Complex life cycle – 2 or more distinct stages that differ in habitat, physiology, or morphology Simple vs. complex life cycles E.g., Alternation of Generations in plants E.g., Holometabolous insects E.g., Anadromous & catadromous fishes E.g., Metamorphic amphibians Larval, pupal & adult wasps Anadromous salmon adults live at sea, but spawn in freshwater Herbivorous, aquatic tadpole will become carnivorous, terrestrial adult Photos from Wikimedia Commons

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

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

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

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

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

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

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

15 A jack of all trades is master of none Design Trade-offs, Costs & Benefits, Constraints 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 Often entails a reproduction – survival tradeoff Semelparous vs. Iteroparous (Monocarpic vs. Polycarpic) 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 Monocarpic talipot palm Polycarpic coconut palm

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

18 Competitive Ruderal (“weedy”) Stress-tolerant Grime’s Triangular Model Image from http://hosho.ees.hokudai.ac.jp/~tsuyu/top/dct/lc.html; original concept from Grime (1977) American Naturalist 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”

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

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

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

22 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 A Classic Example: Clutch Size Original concept from Lack (1947) Ibis Experimental evidence through clutch-size manipulation experiments


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