BIOL 3500: Ecology

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Lecture 10

• BIOL 3500 Ecology
• Chapter 12 Life History Patterns

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Learning Objectives

• Contrast
• Monoecious vs. dioecious plants
• Monogamy vs. Polygamy
• Polygyny vs. polyandry
• Semelparity vs. iteroparity
• R vs. K selected species
• Define
• Clutch

3
Moneocious Plants

• Greek for one house
• Both male and female reproductive parts on one
  plant
• Botany Question
• Which of these has a
• perfect flower?
• Imperfect?

4
Dioecious Plants

• Greek for two houses
• Male and female parts are on different plants

5
Pine Trees

• Which reproductive pattern would pine trees fall
  into?

6
Mating Systems

• Involve the number of mates, nature of bond,
  pattern of parental care
• Monogamy
• Polygamy
• Polygyny
• Polyandry

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Monogamy

• Unique pair bond formed by one female and one
  male
• Good mating system if raising offspring requires
  cooperation, or if male and female equally able
  to contribute
• Common among birds (90 of species)
• Rare among mammals (but some exist, like foxes,
  wolves, mustelids)
• Both parents can bring meat

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A Variation

• Monogamy w/ extra-pair copulations
• Advantage extra genetic variability among
  offspring
• Can still maintain strong partnership to rear
  offspring

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Polygamy

• Acquiring two or more mates
• Polyandry one female, many males
• Polygyny one male, many females

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Sexual Selection

• Process of choosing a mate (generally females
  choose males)
• Idea is to pick mate w/ best genes
• Bowerbirds are a great example
• PBS website (check NOVA News Minute)
• Bird Families of the World website

11
Runaway Selection

• Females look at trait for judging male fitness
• Males evolve to enhance that trait
• Survival of males decreases because of trait
• Irish elk
• UC Berkeley website
• Discovery Channel website
• BBC website

12
Handicap Hypothesis

• Put forward by A. Zahavi (1975, 1977)
• Still very controversial
• 3 elements
• A handicap which decreases males survival
• Bright plumage
• Viability trait which affects males ability to
  survive
• Escape from predators
• Female mating preference for handicap
• Peacocks?

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Different Kinds of Sexual Selection

• Intrasexual selection
• Occurs when competing/fighting against ones own
  sex is important
• Male-male combat in bighorn sheep
• Combat among male sea elephants
• Intersexual selection
• When convincing a mate is more important
• Competing male bowerbirds building big houses

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7th Inning Stretch
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Iteroparous Organisms

• Can potentially breed repeatedly over lifetime
• Examples
• Humans
• Rats
• Oak trees
• Sequoias

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Semelparous Organisms

• Reproduce once, then die
• Pacific salmon
• Overlapping generations Reproduce _at_ 2, 3, 4, or
  5 years old
• Some bamboos
• Reproduce asexually most of time
• Produce flowers once every 100 years!

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Adjusting Reproduction

• Organisms have a variety of ways to adjust
  reproduction for maximum fitness
• Options exist for
• Kinds of offspring (babies either altricial vs.
  precocial)
• Size of offspring (seeds in plants)
• Number of offspring

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Altricial offspring

• Small, helpless
• Rodents born blind
• Robins need food from parents
• Parental investment is generally smaller
• Shorter gestation time
• Smaller eggs (although parents must feed later)

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Precocial offspring

• Young can care for themselves
• Whales can swim
• Baby elephants can walk
• Chickens, quail feed themselves
• Parental investment is generally large
• Long, long gestation times!

20
Trade-offs and Environment

• Some species (like goldenrod) have phenotypic
  plasticity
• In competitive environment, large seeds favored
• In uncolonized (or disturbed) environment, many
  seeds are favored

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Body Size and Fecundity

• Among many mammals, number offspring depends upon
  body size
• European red squirrelss fecundity depends upon
  body weight at first winter as adults
• Irrespective of habitat type

22
Clutch Size and Environment

• Clutch bunch of eggs
• Clutch size ( of eggs) is variable among similar
  bird species
• Icteriadae blackbirds, orioles, meadowlarks
• Oxyura ruddy ducks and masked ducks
• More food available for babies (temperate vs.
  tropical) more eggs. Why is more available?

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R vs. K selected Species

• MacArthur Wilson (1967)
• Emphasized trade-off between many life history
  traits
• Number of offspring
• Lifespan
• Survivorship
• Parental investment

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r selected species

• Species which reproduce quickly
• Many offspring
• Short-lived
• Low parental investment
• Have Type III survivorship curve
• Ex rats, oysters, dandelions

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K selected species

• Species which reproduce slowly
• Few offspring
• Longer-lived
• High parental investment
• Have Type I survivorship curve
• Ex polar bears, trees

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Grimes Triangle

• 3-strategy alternative to Mac Ws paradigm
• C competition
• S stress
• R ruderal (disturbance)