BIO 331 Exam 4
Primary sexual characteristics – answer genitalia and organs of reproduction
Secondary sexual characteristics - answer morphological differences between the
sexes that are not directly involved in reproduction
sexual selection - answer selection for traits that enhance mating success even if they
have negative effects on survival (benefits in mating outweigh costs in survival)
intersexual selection - answer mate competition; selection in which one sex competes
with other members of the same sex for access to the other sex for reproduction
-study: male dung beetles with large horns won more fights and mated with females; the
maintenance of long horns can be explained by sexual selection driven by male-male
competition
Intersexual selection - answer mate choice; selection by one sex ('choosier sex") for
members of the other sex for reproduction
-study: in peafowls, males (peacocks) performing the most displays and with the
greatest number of ocelli obtained the most copulations; peacock tails are used as an
ornament in mate choice and females choose males with more ocelli
What hypotheses explain who should be "choosey" in a relationship? - answer(1)
Bateman's hypothesis
(2) Parental investment hypothesis
Bateman's hypothesis - answer the sex that has the highest reproductive limitation will
choose the mate (typically females); male reproductive success is limited by number of
mates he has while the female reproductive success is mostly limited by the number
and success of eggs that she can produce
parental investment hypothesis - answerthe sex that has the greater investment of
offspring production and care should be choosier when it comes to mates
What are three reasons why females notice/respond to displays? - answer(1) Sensory-
bias hypothesis
(2) Direct material benefits
(3) Indirect benefits
sensory-bias hypothesis - answerfemales have a pre-existing bias toward noticing
certain traits and are thus more likely to notice males with those traits
-study: female guppies were attracted to the orange disc; female mating preference
could be linked to preexisting preference for orange food objects
, direct material benefits - answermaterial resources obtained by a female from mating
with a particular male (may get territories with abundant resources, nuptial gifts, and
enhanced parental care)
-study 1: firefly males with longer flash duration had larger spermatophores; females
responded more to longer flashes; females prefer to mate with males with the longest
flash duration and thus the largest spermatophores which should increase fitness
-study 2: female side-blocked lizards preferred improved territories (more rocks) and
laid eggs sooner/produced larger egg masses; females select males based on territory
quality (high quality = more rocks) and derive a significant fitness gain by doing so
nuptial gift - answera physical resource such as a food item that a male provides to a
female to enhance his mating success
-ex: fireflies produce spermatophore (a protein rich sperm package that provide females
with sperm and food)
indirect benefits - answergenetic benefits female can obtain for their offspring by mating
with males that have high genetic quality
-ex: runaway selection, handicap hypothesis, good genes
runaway selection - answera male trait co-evolves with a female preference for it and
becomes increasingly exaggerated (may select for trait that is detrimental to male
survival --> handicap principle)
-ex: peacock's long tail
handicap hypothesis (handicap principle) - answerwell-developed secondary sexual
characteristic are costly because it handicap's a male's survival
good genes - answercertain traits indicate high genetic quality of mate; may associate
with enhanced immune system, greater fighting ability, increased viability; reliable
indicators of male genetic quality because these traits are costly to produce or maintain
-study 1: female european tree frog females select males for genetic benefits (females
attracted to vocalizations --> indicate good genes); males that mated more sired more
offspring and produced tadpoles with higher growth rates
-study 2: some red jungle fowl were infected with intestinal nematode; parasitized males
had smaller duller combs than control; females preferred control males
alternative reproductive strategies - answerstrategies displayed by low-quality or low-
ranked males with low resource holding potential
-types: satellite males and sneaker males
-evolution: because it is the evolutionary stable strategy or conditional strategy
What are the two types of alternative reproductive strategies? - answer(1) satellite
males
(2) sneaker males
Primary sexual characteristics – answer genitalia and organs of reproduction
Secondary sexual characteristics - answer morphological differences between the
sexes that are not directly involved in reproduction
sexual selection - answer selection for traits that enhance mating success even if they
have negative effects on survival (benefits in mating outweigh costs in survival)
intersexual selection - answer mate competition; selection in which one sex competes
with other members of the same sex for access to the other sex for reproduction
-study: male dung beetles with large horns won more fights and mated with females; the
maintenance of long horns can be explained by sexual selection driven by male-male
competition
Intersexual selection - answer mate choice; selection by one sex ('choosier sex") for
members of the other sex for reproduction
-study: in peafowls, males (peacocks) performing the most displays and with the
greatest number of ocelli obtained the most copulations; peacock tails are used as an
ornament in mate choice and females choose males with more ocelli
What hypotheses explain who should be "choosey" in a relationship? - answer(1)
Bateman's hypothesis
(2) Parental investment hypothesis
Bateman's hypothesis - answer the sex that has the highest reproductive limitation will
choose the mate (typically females); male reproductive success is limited by number of
mates he has while the female reproductive success is mostly limited by the number
and success of eggs that she can produce
parental investment hypothesis - answerthe sex that has the greater investment of
offspring production and care should be choosier when it comes to mates
What are three reasons why females notice/respond to displays? - answer(1) Sensory-
bias hypothesis
(2) Direct material benefits
(3) Indirect benefits
sensory-bias hypothesis - answerfemales have a pre-existing bias toward noticing
certain traits and are thus more likely to notice males with those traits
-study: female guppies were attracted to the orange disc; female mating preference
could be linked to preexisting preference for orange food objects
, direct material benefits - answermaterial resources obtained by a female from mating
with a particular male (may get territories with abundant resources, nuptial gifts, and
enhanced parental care)
-study 1: firefly males with longer flash duration had larger spermatophores; females
responded more to longer flashes; females prefer to mate with males with the longest
flash duration and thus the largest spermatophores which should increase fitness
-study 2: female side-blocked lizards preferred improved territories (more rocks) and
laid eggs sooner/produced larger egg masses; females select males based on territory
quality (high quality = more rocks) and derive a significant fitness gain by doing so
nuptial gift - answera physical resource such as a food item that a male provides to a
female to enhance his mating success
-ex: fireflies produce spermatophore (a protein rich sperm package that provide females
with sperm and food)
indirect benefits - answergenetic benefits female can obtain for their offspring by mating
with males that have high genetic quality
-ex: runaway selection, handicap hypothesis, good genes
runaway selection - answera male trait co-evolves with a female preference for it and
becomes increasingly exaggerated (may select for trait that is detrimental to male
survival --> handicap principle)
-ex: peacock's long tail
handicap hypothesis (handicap principle) - answerwell-developed secondary sexual
characteristic are costly because it handicap's a male's survival
good genes - answercertain traits indicate high genetic quality of mate; may associate
with enhanced immune system, greater fighting ability, increased viability; reliable
indicators of male genetic quality because these traits are costly to produce or maintain
-study 1: female european tree frog females select males for genetic benefits (females
attracted to vocalizations --> indicate good genes); males that mated more sired more
offspring and produced tadpoles with higher growth rates
-study 2: some red jungle fowl were infected with intestinal nematode; parasitized males
had smaller duller combs than control; females preferred control males
alternative reproductive strategies - answerstrategies displayed by low-quality or low-
ranked males with low resource holding potential
-types: satellite males and sneaker males
-evolution: because it is the evolutionary stable strategy or conditional strategy
What are the two types of alternative reproductive strategies? - answer(1) satellite
males
(2) sneaker males
