Sexual Selection Flashcards
What are hidden conflicts between males and females in animals?
Gamete investment
Number of mating partners/offspring each can have
Parenting efforts of each
Describe conflict of differences in number of mating partners of offspring
Mammals often polygynous
Males often mate with as many females as possible, low resource utilization
Females: less benefit from mating with multiple males, limited number of eggs and pregnant during specific times of year, unable to get pregnant while lactating
Describe differences in parenting efforts between
Polygyny
Females: provide most or all of parental care(major source of taking energy)
Males invest little to no resources
Overall, male offspring have higher number of offspring than females
Overall, female provide more valuable resources than male for offspring
How can offspring tell you about the maternal conditions in deer?
male - good maternal conditions, means can handle larger offspring
female - maternal conditions poor, only handle smaller offspring
Driving what sex SHOULD be; males best under conditions with plentiful resources and healthy maternal conditions; females best under conditions with less positive and more limited resources
Intra-sexual compeition
more active fighting, competition for limited resources
Inter-sexual competition
all about being chosen, animals picky
Dimorphisms
Physical characteristics between males and females
such as being best chosen or better male competitor for resources
Describe examples of influences of sex ratio on offspring
Examples:
Bees, wasps: female can control whether egg is fertilized or not; fertilized can make males and females while unfertilized can make males
Reptiles: temperature of egg incubation determines sex ratio, females can control this by the depth at which she buries her eggs
Describe examples of influences of sex ratio in mammal offspring
Resources associated with food availability
Resources associated with female maternal condition
good = male, not so good = female
Describe the ant mandible in sexual selection
the ant mandibles are only there to take out other ants/competition
Factors of Intrasexual competition
Fighting
Strength competitions
Visual or auditory displays
Repellant odors
Mate guarding
Increase number of sperm delivered
Sperm plug (why)
Sperm competition
Give an example of intrasexual competition of mate guarding
orb weaving spider
Males and females different size (dimorphism, so either competition or pickiness)
Female bigger than male
Male will insert pedipalps for sperm transfer into female
Peidpalps swell and male locked into place
Does not allow for other mates to come along
Male will die and female consumes them
Describe sperm plug (r u kidding)
a literal block; temporary block to prevent other sperm from entering canal
Describe Sperm competition
males and females both use this, use of spermatheca important
males can clean out spermatheca to increase chance offspring are his
What do females choose in Inter-sexual competition
Females:
Choose who
choose how much time to mate with males
Choose material resources males provide
Choose gifts received from male
Choose genetic benefits received from male
Describe 2 example2 of sperm competition
Dunnock bird/Intra-sexual competiton
Males peck cloaca, so female releases sperm from spermatotheca
Birds then put cloacas together to reproduce
Pirate bug:
Stronger male injects weaker male with their sperm, so when weaker male mates it will actually inject stronger male’s sperm into female
Describe an example of sperm plugs
Use sperm plugs on each other
Males use sperm plugs on other males to prevent competition….okay I guess
Moniliformes dubius
Describe sperm competition in salamanders
Males lay down spermatophore for female to walk over and pick up
Competitor male will lay their spermatophore on top of another one in order to be the one picked up by the female
Describe how frogs use inter-sexual competition
Lots of female choices
Depth of water (material); shallow water is warmer while deep water is colder which affects when eggs hatch
Amount of vegetation(material); needs right amount to allow appropriate development
Quality of habitat important to female
Describe how Satin Bowerbird will attempt to get chosen by females
Male wants to be chosen by females
Males attracted to anything blue, so will create a bower to attract females with lots of blue objects
Blue objects can be anything (trash, caps, etc.)
Males will sabotage other males
Female does not always choose the first male
Describe inter-sexual relationship of scorpion fly
male provides female nuptial gift (food)
In other cases, Males approach with action without approaching only first; forced copulation
- Some do this due to not having the best quality traits based from other males
Describe intersexual relationship of Common Tern (bird)
Females will choose male depending on how they are provided for (food, etc.) through reproduction stages
This means male can provide well for family
How do male guppies become desirable for females in intersexual competition?
Copying mate choice theory
- Males hanging out with older females let the younger females know they have good traits that the younger females want
Good genes theory
Females looking for the best traits they can get from males
Males may fall under too much pressure to give those traits, and it leads to traits with negative impacts
Give an example and experiment of the good genes theory
Long-tailed Widowbird
- Polygynous
Male tails about 50cm in length
Female tails about 7cm in length
Males said to have long tail in order to be desirable to females
Experiment:
Group with untouched tail, Group with cut tail feathers to 14cm, Group with cut tail feathers and glued back on, Group with elongated tails (85cm)
Experiment favored 85cm tail, BUT not favorable to live like this; Handicap theory tail too long and too much to handle
Describe how male Moorhen (bird) are chosen
¾ of time related to incubation
- Males chosen based on how chunky they are; more plump, more desirable
For what reason(s) might forced copulations exist?
happens when organism does not have the most valuable traits
What factors can influence the sex ratio of offspring?
In the context of sexual selection, why are males with a handicap perceived to have a benefit?
- it could be taken as a sign they are healthy and can provide resources the female needs, when in reality it creates difficulty for the male to go about daily activities
