BIOL 336 Final: 336 FINAL
L14: Conflict Cooperation Interacting Linages
Interaction species co-evolve
- Adaptation and counter-adaptation
o Bat vs. moth, moths developed tympanal organs – thought to have evolved at
least 7x independently in response to bat. Hear the bat -> avoidance or escape
o Tiger moths emit ultrasound clicks that jam the bat’s sonar (sonar detects insects
in complete darkless)
- Escaping old enemies: invasive species
o Success of a species can be limited by its predators or prey having evolved
adaptations against it.
o Species that disperse to a new area can be “freed” from these interactors and
thus become invasive species
Interactions among species are important
- Competition is an important evolutionary force: a large fraction of an individual’s
resources may be dedicated to it. Tree competing for sunlight
- Mutualism
- Parasitism
- Commensalism: one benefits the other is neither benefit nor harm
- Predation
The choice: conflict vs. cooperation
- Animals pollinating plants: a mutualism
- Pollinator gets reward (nectar, pollen), flower gets pollen transferred to the next flower
- BUT animals CHEAT
o Nectar robbing
- Plants can CHEAT too
o Orchid, yellow areas look like pollen but aren’t
o Insects that visit get pollen stuck on body and pollen gets transferred to the next
orchid, unpaid delivery service
o Orchid looks and smells like a female wasp, male tries to copulate but gets pollen
bundle instead
The evolution of cooperation
- Mutual benefit
- Entangled fates
o Mechanism that inhibits cheating
o Aphid and bacteria
▪ Bacterial is transmitted vertically (aphid mother to offspring)
▪ Vertical transmission -> co-speciation
▪ Parallel divergence, parallel phylogenies!
▪ Vertical transmission -> selection for cooperation, if bacterium takes too
many resources from its aphid host, the aphid might not have many
babies and so the bacterium won’t have so many vehicles for its own
babies
▪ Mitochondria and eukaryotes
- Entangled fates lead to co-speciation
Interactions:
- Among species
- Among individuals within species
- Among cells within individuals
- Among genes within cells
Conflict and cooperation among individuals
- Colonies, sociality, and cheating
- Competition, density dependence, cooperation in colonial organisms
- Why don’t spiders cheat??
o Cooperation helps the colonies to grow and produce more daughter colonies
o A selfish “lazy” mutation might spread but its colony won’t survive and wont
reproduce daughter colonies so well
o Colony-mates build the “vehicle” for all of their offspring to thrive
o If you harm your colony mates, you are also harming your own offspring because
their FATES ARE LINKED in future generation
o If individuals could jump between/among colonies then selfishness could win but
they can’t.
- Entangled fates: selection for cooperation between linages whether within species
(spider) or between species (aphid and bacteria)
Conflict and cooperation among cells
- Selfish cells could take over (cancer) but wont succeed over evolutionary time because
the fates of all cells of an individual are shared. Entangled.
Conflict and cooperation among genes
- Intragenomic conflict
- Genes can cheat and get EXTRA COPIES into the next generation
o 1. Bias meiosis
▪ SD+ sperm killed by SD allele
o 2. Duplicate: when a gene duplicates, a second copy of a locus is made, and so
now there are two loci where there had been one (eyes)
- A gene can’t completely take over the genome without killing itself. But some levels of
cheating persist
- Big genomes are big because they have lots of transposable elements (DNA sequence
that can change its position within a genome)
o LINE elements: long interspersed sequences (scatter among or between things)
o SINE: short interspersed sequences
o They are called selfish because they do not normally perform useful functions,
they exist because they are succeeded in replicating themselves.
o Isn’t intrinsically good or bad. It simply is.
- What is good for TEs is often bad for the “host”
Two extra stories:
1. Sequestration of the germ line
2. Conflict among mom, dad, and baby, and among different genes
o Dad: greedy gene that increase fetus’s demands
o Mom: generous gene that decreases fetus’s demands
L15: Life History Evolution
If selection could have improved longevity, why didn’t it?
- Extrinsic mortality (bad luck)
- Intrinsic mortality (your own genes fault)
- Intrinsic mortality evolves to match extrinsic mortality
o If extrinsic mortality tended to kill your ancestors by the time they were age X,
then intrinsic mortality will have evolved to kill you at about age X also, even if
you are protected from extrinsic mortality
Why do we have genes that make us Senescene: deterioration with age
- Mutation accumulation theory: late-acting mutations accumulated because they are not
selected against because individuals rarely live that long and therefore almost no loss of
reproduction. This reduces intrinsic longevity.
o Mutation are late ACTING not late occurring
o Affects germ-line cells
- Antagonistic pleiotropy theory:
o Pleiotropy: a gene has more than one effect
o Antagonistic: the different effects oppose each other – early effect is good, late
effect is bad
o Pleiotropic genes that increase early fertility at the expense of late health – trade
off (spending your resources early may damage late health)
▪ Such genes are selected for because extrinsic mortality and the
advantage of early reproductive
▪ Extrinsic mortality: high extrinsic mortality means early selection is much
stronger than late selection, as individuals mostly die before old age
anyways. Thus the early good effect would have more power than the
late bad effect
Document Summary
Adaptation and counter-adaptation: bat vs. moth, moths developed tympanal organs thought to have evolved at least 7x independently in response to bat. Hear the bat -> avoidance or escape: tiger moths emit ultrasound clicks that jam the bat"s sonar (sonar detects insects in complete darkless) Competition is an important evolutionary force: a large fraction of an individual"s resources may be dedicated to it. Commensalism: one benefits the other is neither benefit nor harm. Pollinator gets reward (nectar, pollen), flower gets pollen transferred to the next flower. Plants can cheat too: orchid, yellow areas look like pollen but aren"t. Insects that visit get pollen stuck on body and pollen gets transferred to the next orchid, unpaid delivery service: orchid looks and smells like a female wasp, male tries to copulate but gets pollen bundle instead. Competition, density dependence, cooperation in colonial organisms.
