RE: Aviary (birds birds)
02-22-2013, 08:47 PM
A+ post, would perch upon again
Sexual dimorphism is actually really interesting! It stems from the fact that to be biologically successful, an animal has to survive, but more importantly it has to reproduce. Living to a respectable twenty-five years or whatever won't help a passerine shit if a weird quirk of his assorted glands means he constantly smells like cats.
The other force at play is the uneven effort put in by males and females to produce offspring, which even starts at the sperm-and-egg level (eggs are basically a pre-packaged somatic cell with all the apparatus necessary (mitochondria, endoplasmic reticula, nuclear envelope, probably some other junk), other than missing half the DNA. Sperm, by comparison, are a torpedo with a data packet strapped to the front rather than explosives, which is why males can constantly produce new sperm and a female enters adulthood with all the eggs she's ever gonna have packed away in her ovaries.
At a higher level, females have to gather food and nourish the offspring while they develop, and in many cases will continue to do so after the offspring are born. (You could always have better-developed babies so they can fend for their own damn selves, but a female will have to invest more resources in the gestational stage to do so). Males might be evolutionarily predisposed to help, but that's not a given across the animal kingdom. The net result of all this is that in most (vertebrate) cases (but also in a lot of other ones), females are the choosier sex.
If females make the ultimate decision about whose sperm (and constituent genetic code) they pass on into the next generation, then clearly they're looking for good genes, because why waste your time raising substandard stock, right? Seeing as there is no easy pee-and-see test for "good genes" or "bad genes", raunchy redpolls will have to use other cues to figure out who is the damn finest of them all. Visual cues are used as an index of both "good traits that help you survive", but also "a good appearance that'll give the kids similar reproductive success".
This interplay between choosing for survivability and baby-making capacity is what causes things like male peafowl tails! The tail has no bloody use to help the peacock camouflage or not get caught in nasty places, but if his kids look as good as he does he's perceived to produce more offspring over his lifespan (the live fast, die young strategy). The alternative hypothesis is that a big stupid tail or conspicuous colouring demonstrates your good genes that help you survive despite the extra pressure. The above reason is why symmetry is sexy - asymmetry is caused by external forces (parasites, injury, disease) and maintaining your symmetry in the face of all this indicates strong genes to fight parasites/disease.
Sexual dimorphism is actually really interesting! It stems from the fact that to be biologically successful, an animal has to survive, but more importantly it has to reproduce. Living to a respectable twenty-five years or whatever won't help a passerine shit if a weird quirk of his assorted glands means he constantly smells like cats.
The other force at play is the uneven effort put in by males and females to produce offspring, which even starts at the sperm-and-egg level (eggs are basically a pre-packaged somatic cell with all the apparatus necessary (mitochondria, endoplasmic reticula, nuclear envelope, probably some other junk), other than missing half the DNA. Sperm, by comparison, are a torpedo with a data packet strapped to the front rather than explosives, which is why males can constantly produce new sperm and a female enters adulthood with all the eggs she's ever gonna have packed away in her ovaries.
At a higher level, females have to gather food and nourish the offspring while they develop, and in many cases will continue to do so after the offspring are born. (You could always have better-developed babies so they can fend for their own damn selves, but a female will have to invest more resources in the gestational stage to do so). Males might be evolutionarily predisposed to help, but that's not a given across the animal kingdom. The net result of all this is that in most (vertebrate) cases (but also in a lot of other ones), females are the choosier sex.
If females make the ultimate decision about whose sperm (and constituent genetic code) they pass on into the next generation, then clearly they're looking for good genes, because why waste your time raising substandard stock, right? Seeing as there is no easy pee-and-see test for "good genes" or "bad genes", raunchy redpolls will have to use other cues to figure out who is the damn finest of them all. Visual cues are used as an index of both "good traits that help you survive", but also "a good appearance that'll give the kids similar reproductive success".
This interplay between choosing for survivability and baby-making capacity is what causes things like male peafowl tails! The tail has no bloody use to help the peacock camouflage or not get caught in nasty places, but if his kids look as good as he does he's perceived to produce more offspring over his lifespan (the live fast, die young strategy). The alternative hypothesis is that a big stupid tail or conspicuous colouring demonstrates your good genes that help you survive despite the extra pressure. The above reason is why symmetry is sexy - asymmetry is caused by external forces (parasites, injury, disease) and maintaining your symmetry in the face of all this indicates strong genes to fight parasites/disease.
peace to the unsung peace to the martyrs | i'm johnny rotten appleseed
clouds is shaky love | broke as hell but i got a bunch of ringtones
eyes blood red bruise aubergine | Sue took something now Sue doesn't sleep | saint average, day in the life of
woke up in the noon smelling doom and death | out the house, great outdoors
staying warm in arctic blizzard | that's my battle 'til I get inanimate | still up in the same clothes living like a gameshow
clouds is shaky love | broke as hell but i got a bunch of ringtones
eyes blood red bruise aubergine | Sue took something now Sue doesn't sleep | saint average, day in the life of
woke up in the noon smelling doom and death | out the house, great outdoors
staying warm in arctic blizzard | that's my battle 'til I get inanimate | still up in the same clothes living like a gameshow