J Flashcards
What is sperm competition?
Sperm competition occurs when a female mates with multiple males during a single fertile period, leading to competition among sperm to fertilize the egg.
In which species does sperm competition occur?
It occurs in externally fertilizing species (ex, fish, clams, frogs) and internally fertilizing species (ex, birds, mammals, reptiles, insects).
What are the main factors influencing sperm competition?
Sperm quantity, sperm quality, mating order, cryptic female choice, and re-mating interval.
How does sperm quantity affect competition?
Males who deposit more sperm generally have a higher chance of fertilization (“Scramble sperm competition”).
What is Adaptive Soerm loading?
Males increase sperm per ejaculate when competition is high.
What is sperm quality?
It refers to the fertilizing efficiency of sperm, including size, longevity, viability, motility, and velocity.
How does sperm size vary across species?
Some species, like Drosophila Bifurcation, produce sperm 20x the length of the males body.
How long can a human sperm survive in the female reproductive tract?
A few hours in the vaginea, but up to 3-5 days in the cervix.
What are the affects of sperm viability/
morphological defects, environmental stress, and overall sperm health.
What are the two types of sperm motility?
Progressive 9forward movement) and non-linear (winding path).
How does sperm velocity affect fertilization success?
faster sperm have better success, as seen in the three-spined stickleback fish and zebrafish.
How does mating order influence sperm competition?
In many species, the last male to mate has precedence in fertilization.
How do some species remove previous males’ sperm?
Some males have specialized penises that scoop out rival sperm (ex: dragonflies, damselflies).
What is cryptic female choice?
A female’s ability to select which sperm successfully fertilizes her egg through physical or chemical means.
How do some females control paternity?
Some species, like Japanese quail, eject sperm following copulation to favour certain males.
How does re-mating interval affect sperm competition?
The time between matings determines if the first or last male has fertilization precedence.
How does sperm precedence work in silkworms?
If a female mates immediately after a previous mating, the last male’s sperm blocks the first; if she waits, the first male’s sperm has precedence.
What is the Kamikaze Sperm hypothesis?
The controversial idea that sperm from different males attack and kill each other inside the female reproductive tract.
How do nuptial gifts influence sperm competition?
In nursery web spiders, males who present food gifts have their sperm stored preferentially by females.
How might human males be adapted for sperm competition?
Some researchers suggest the shape of the human penis may aid in sperm displacement
