View
21
Download
1
Category
Tags:
Preview:
DESCRIPTION
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 . - PowerPoint PPT Presentation
Citation preview
Life History
Photo of size variation in seeds from Panama from http://www.tc.umn.edu/~hmuller/
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
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
Asexual vs. sexual reproduction
Cain, Bowman & Hacker (2014), Fig. 7.7
Isogamous gametes
Asexual vs. sexual reproduction
Cain, Bowman & Hacker (2014), Fig. 7.7
Anisogamousgametes
Sexual reproduction produces genetically variable offspring
Chlamydomonas
Homo sapiens
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
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
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
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
AY
aX
AaXY
From the single-celled zygote stage onward, cells undergo mitosis to increase
the number of cells in the maturing individual.
Unicellularzygote;
Diploid (2n)cell
Muticellular individuals;Diploid (2n) cells
AX
aX
AAXY
AaXX
AAXX
AaXY
Gen. 3
AaXX
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-generationalzygote stage
Haploid (1n) cells of hyphae
Zygotic meiosis
Multiple rounds of asexual reproduction
possible; all cell divisions occur by
mitosis.
Multiple rounds of asexual reproduction
possible; all cell divisions occur by
mitosis.
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
-
Haploid (1n) spore
A+
a-
a-
a+
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
aB
AaBb
Single-celled spores undergo mitosis to increase the number of cells in the
maturing gametophyte. Mature gametophyte produces gametes
by mitosis
Multicellular gametophyte
Ab
Haploid (1n) cells
Ab
aB
Unicellulargametes
Generation 3
Diploid (2n) cells
Multicellular sporophyte
Diploid (2n) cells
Unicellular spores of
gametophyte
Haploid (1n) cells
Pollengrain
Embryo sac
Gen. 4
AAbb
AaBb
AaBb
Unicellularzygote
aaBB
Specialized cells undergo meiosis to produce spores
Ab
aB
Allocation Trade-offs, Costs & Benefits, Constraints
Photos from Wikimedia Commons
vs.
Resources
There is no free lunchA 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
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
Design Trade-offs, Costs & Benefits, Constraints
Photos from Wikimedia Commons
vs.
Design: shape, function, etc.
A jack of all trades is master of none
Design Trade-offs, Costs & Benefits, Constraints
E.g., consider pond-breeding salamander speciesin ephemeral pools vs. stable ponds
What life-history strategy would perform best in each habitat?
Is there a “one size fits all” solution?
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
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
DisturbancePopulation growth rate
K-selected r-selected
Body sizeLife spanParental investment in offspring
Developmental rateRate of maturationReproductive rate
Stability
CompetitiveRuderal (“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”
Competition – Colonization Tradeoff
The concept was elaborated by Rees & Westoby (1997) Oikos
Competitive Ability
Colonization Ability
Tolerance – Fecundity Tradeoff
Original concept from Muller-Landau (2010) Proceedings of the National Academy of Sciences
Stress Tolerance
Fecundity
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 larva Winged adult
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
Recommended