Sexual selection, mate choice and parental investment · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Mating success and parental investment

Science · Ecology & Conservation · ages 20-21
Name ______________________   Date ____________

  1. A heritable long tail lowers survival but is preferred by mates. Under what condition can sexual selection favour it overall?

    • When mate preference raises mating success, with survival left out of the comparison
    • When mating benefits exceed survival costs in expected reproductive contribution
    • When reduced survival is offset by greater energy invested in growing the tail

  2. In the parental-investment argument, what tendency is predicted when greater investment makes one sex less available for mating?

    • More choice by the less-available sex and more competition by the other
    • More choice by females and more competition by males, based on gamete size
    • More competition by the less-available sex and more choice by the other

  3. Males fight for mating opportunities, and females choose among males. How are these two processes classified?

    • Fights: intersexual choice; female choices: intersexual choice
    • Fights: intrasexual contests; female choices: intrasexual contests
    • Fights: intrasexual contests; female choices: intersexual choice

  4. A male spends hours displaying instead of feeding his chicks. Which opportunity cost is established by this description?

    • The chick-feeding effort forgone while he uses those hours to display
    • The reduction in chick survival caused by those missed feeds
    • The energy spent on chick feeding before those hours

  5. In a fish population, males invest more overall. Brooding delays their next mating, so ready males are scarce relative to females. Which tendency does the investment argument predict?

    • Greater male competition for ready females and greater female choosiness
    • Greater female competition for ready males and greater male choosiness
    • Less female competition and less male choice as brooding limits mating

  6. A study finds greater male investment, fewer ready males, female competition and male choice. What does this role-reversed case show about the investment argument?

    • The observations support the prediction under the measured investment and readiness conditions
    • The observations establish investment as the explanation for mating roles across species
    • The observations challenge the prediction because the competing individuals are females

  7. Sexual selection acts only through survival, never through differences in mating success.

    Circle one:   True   False

  8. A loud song attracts mates and raises predation risk. A student calls it an honest signal of condition. No relationship between song and condition has been measured. Which conclusion is supported?

    • Predation cost establishes honesty because producing the song is risky
    • Mate preference establishes honesty because listeners favour the song
    • The song's honesty remains untested without evidence linking it to condition
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Mating success and parental investment W1-mt_6oTPGFw_p5-s1

  1. When mating benefits exceed survival costs in expected reproductive contribution · Mate preference alone is insufficient. Its benefits must more than compensate for survival costs in expected reproductive contribution.
  2. More choice by the less-available sex and more competition by the other · Less-available partners can limit mating opportunities, favouring their choosiness and competition for access. This is a conditional tendency.
  3. Fights: intrasexual contests; female choices: intersexual choice · The male-male contests are intrasexual selection. Female choice among males is intersexual selection. Both concern mating success.
  4. The chick-feeding effort forgone while he uses those hours to display · The description identifies an alternative use of time and energy forgone. It does not specify how many offspring are lost.
  5. Greater female competition for ready males and greater male choosiness · The stated conditions make ready males the scarcer partners. The argument predicts more female competition and male choice.
  6. The observations support the prediction under the measured investment and readiness conditions · The observed pattern matches the prediction under the measured conditions. One matching case does not prove a universal explanation.
  7. False · Sexual selection concerns differences in mating success. Survival costs can affect the overall reproductive outcome.
  8. The song's honesty remains untested without evidence linking it to condition · Cost and attractiveness do not establish that a signal reliably reflects condition. That relationship needs evidence.
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