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Ecology > LIFE HISTORIES: multiple solutions to multiple challenges > Flashcards

LIFE HISTORIES: multiple solutions to multiple challenges Flashcards

1
Q

Life History:

A
  • those traits that help individuals achieve fitness (genetic contribution by an individual’s descendants to future generations).
  • Ultimately an organism’s life history patterns are geared towards increasing survival and reproduction to maximize fitness.
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2
Q

The adaptation – driven by natural selection

A

that is manifested by this genetic potential for survival and reproduction includes a wide variety of attributes pertaining to:

  • Morphology
  • Physiology
  • Behavior
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3
Q

Life Histories pt 2

A
  • description of typical patterns of development, reproduction, survival
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4
Q

Life-history Traits

A
  • Characteristics that directly affect development, reproduction, lifespan
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5
Q

Life history strategies

A

suites of life history traits common to groups of species

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6
Q

Life- History Traits pt 2

A
  • Developmental rate
  • Body size
  • Age at maturity
  • Mode of reproduction (asexual vs. sexual)
  • N offspring per litter
  • N reproductive episodes
    • – Semelparous – one reproductive episode, then die
    • – Iteroparous – multiple reproductive episodes
  • Degree of parental care
  • Lifespan
    *
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7
Q

Life history traits pt 3

A
  • When trying to understand variation in life-history traits, it helps to consider two things:
    • Allocation trade-offs
    • Mortality schedules
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8
Q

Allocation Trade-offs

A
  • Allocation = distribution of a limited quantity of resources across multiple operations
  • Energy and nutrients are limiting
  • With those resources, organisms must grow, maintain themselves, and reproduce
  • Trade-offs are ubiquitous; the phenotype represents a compromise to meet multiple requirements for the individual to live.
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9
Q

How many times to reproduce? 2 basic strategies- Semelparity

A
  1. Semelparity (semelparous): one major reproductive effort in a lifetime
    semel: “once”

Concept applies to both animals and plants

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10
Q

Reasons to be semelparous

A
  • Adults are more likely to be healthy at time of reproduction because they have invested more energy into growth, development, and energy storage
  • Adults (plants as well) can time reproduction to favorable year. “Carpe diem”
  • Long intervals between good years
  • For animals rearing of young can be exhausting
  • Examples: most insects and many plants (annuals and short-lived perennials)
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11
Q

How many times to reproduce? 2 basic strategies - Iteroparity

A
  • repeat reproduction (and production of fewer young per event) in a lifetime
  • itero: “to repeat”
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12
Q

Reasons to be iteroparous

A
  • Increases chances of offspring success at least once because conditions should be favorable in at least one year.
  • A good strategy if the chances of adult survival are high → adults will live long enough to have reproductive events over several years. (If adults have very low survival chances, it doesn’t make sense for them to be iteroparous).
  • Examples of iteroparous organisms: most vertebrates, many invertebrates, most perennial plants, including trees
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13
Q

Allocation Trade- Offs graph

A
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14
Q

Allocation Trade-offs and litter size example

A
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15
Q

Mortality and Age of Female Deer

A
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16
Q

Mortality schedules affect patterns of natural selection

A
  • After thousands of generations with these patterns of mortality, what sorts of life history traits would selection favor?
17
Q

Mortality schedules affect patterns of natural selection pt 2

A
  • Early reproduction
  • Fast development
  • Small body size
  • Many offspring per reproductive episode
  • Extended reproduction
  • Slower development
  • Larger body size
  • Fewer offspring per reproductive episode
18
Q

Age at Senescence

A
  • Evidence - Higher extrinsic mortality rates correlate with faster senescence and shorter potential life spans
19
Q

Classification of Life History

A
  • Life history traits tend to cluster
    • “Life history strategies”
  • Several classifications exist
    • r and K selection
    • Grime’s triangular model of plant life history
20
Q

Life History - r and K-selection

A
  • r-selection and K-selection describe two ends of a reproductive strategy continuum.
  • r is the intrinsic rate of increase of a population.
  • r-selection: Selection for high population growth rates; an advantage in newly disturbed habitats and uncrowded condition.
21
Q

Life History - K

A
  • K is the carrying capacity for a population.
  • K-selection: Selection for lower growth rates in populations that are at or near K; an advantage in crowded conditions; efficient reproduction is favored.
22
Q

Life History - r

A
  • r-selected (“live fast, die young”):
    • Short life spans, rapid development, early maturation, low parental investment, high reproduction rates
    • Most insects, small vertebrates such as mice, weedy plant species
23
Q

Life History - K pt 2

A
  • K-selected (“slow and steady”):
    • Long-lived, develop slowly, late maturation, invest heavily in each offspring, low reproduction rates
    • Large mammals, reptiles such as tortoises and crocodiles, and long-lived plants such as oak and maple trees
24
Q

K - Selected Species

A
  • Evolution in populations close to K
  • Around K, expect intraspecific competition
  • Organisms selected to compete well in stable environments
    • Large body size
    • Slow development
    • Long lifespan
    • Late maturity
    • Few offspring per reproductive episode
    • High parental investment
25
Q

K - Selected Species pt 2

A
  • Examples of K-selected species
    • Elephant
    • Albatross
    • Chestnut, mangosteen
26
Q

r - Selected Species

A
  • Evolution in populations that can rarely reach K
  • Unstable environments, high probability of early death
  • Selection for weedy, short-lived species with high reproductive output
    • Small body size
    • Fast development
    • Short lifespan
    • Early maturity
    • Many offspring per reproductive episode
    • Little parental investment
27
Q

r vs K Selection

A
  • Examples of “r-selected” species:
    • Dandelions, many annual grasses
    • Many insects & spiders
    • Mice & rabbits
  • Heuristic tool
  • r and K classification identifies extremes of a continuum
  • More useful in relative (e.g. within genera or families) than absolute terms
28
Q

Grime’s triangular model of plant life histories

A
  • Reasoned two factors limit success of plant
    • Stress – external abiotic factors that affect reduce performance (temperature, water, nutrients, shading)
    • Disturbance – any process that destroys plant biomass (herbivory, fire, mowing, construction)
29
Q

Grime’s triangular model of plant life histories pt 2

A

Three habitat types characterized:

  • Low stress, low disturbance = Competitive plants
  • High stress, low disturbance = Stress tolerant plants
  • Low stress, high disturbance = Ruderals (weedy)
  • (High stress, high disturbance deemed unsuitable for any species)
  • BOLD = life history type
30
Q

Life History Triangle

A
31
Q

Life Equation ( a concept )

A
  • (The conundrum of wrapping up genetic material in a package that can survive and reproduce)
  • S = f (G x (a + b + c + ………i))
    • S = Species of a certain fitness
    • G = genetic makeup of species S
    • a, b, c, …i = environmental challenges
32
Q

Many Solutions to Life Equation

A
  • The “life equation” has many solutions (S).
  • Each species (or ecotype), by virtue of their unique life history, represents a solution to the “life equation”:
    • white-crowned sparrows, blue whales, >400,000 species of beetles (!)
  • Each solution (S) represents an aggregate of the interaction of genetics and environment in an attempt to compromise amongst the multiple challenges of in the environment –
    • To live long enough to pass on your genetic material to the next generation

Ecology (5 decks)

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