Lecture 20 Flashcards
Predation/carnivory
prey is killed and eaten
- predator is usually larger than the prey
- a predator can seek multiple prey
grazing/herbivory
plant eaters = predator
eats plant but it usually survives if the roots is still intact
parasitism/disease
host sometimes survives and sometimes doesnt
host = larger than parasite
there can be multiple parasites per singular host
Brood parasites
organisms that rely on others to raise their offspring
- some birds lay egges in the nests of other birds to avoid spending time and resourses on parental care
- brood mimicry
- usually birds do this if their eggs resemble the host eggs - look similar to the point where the mother cant tell
why do lotka volterra models for predator and prey interactions form a lagged population cycle?
as more predators eat more prey it drives the prey population close to zero which drives the predator pop down as well
- the predator population lags behind the prey because the predator growth depends on prey availability
- lynx and snowshoe hare
briefly explain the cycles of the lynx and hare interaction curves
as there is a decline in the lynx (predator) there is an increase in the hares (prey)
as the lynx population started to increase, the hares started to decrease
why are the lynx and the hare models unusual in nature
there can be additional factor that make the curves non cyclic
- social stresses to overcrowding - stress hormones may impact reproduction level and cause a decline in the pop not bc they were eaten
- when the hare populations grow rapidly with the absence of lynxes - it may not be because of there is an endless food supply
- in reality, the food supply is not constant and can deplete like plants when lots of hares consume them
How did the disease cycles change due to different factors?
measles was driven by the number of susceptible humans and before the vaccine is fluctuated in waves until it declined rapidly due to vaccination doses
COVID = increases and decreases in waves and cycles due to the fact that most people were quarantining and not quarantining
what is antagonistic coevolution
evolutionary arms race between 2 species that have opposing interactions
predator-prey, host-parasite, herbivore-plant
- prey evolve better defence mechanisms –> Predators evolve better hunting strategies
red queen hypothesis
how a species must continuously adapt and evolve just to maintain its relative fitness in an ever-changing environment
- at the end of the day neither species win, they keep cycling
- continuous selection pressure of coevolving
rough-skinned newt = poison of TTX and garter snake has evolved resistance to TTX
- more toxic the newt is the more resistant the snakes have to be = antagonist evolution
T/F Prey have a stronger selection for adaption
true
prey are fighting for survival
predators are only fighting for food - they have a wider selection of prey to eat
what inducible defences do victims like plants overcome when under attack
phenotypic plasticity
morphology
behaviour
secondary chemicals
- induced = turned on or off when under attack
what does competition do to biodiversity
decreases biodiversity
- the bigger and stronger competitors out rule the smaller competitors - they die
what does predation do to biodiversity
it can increase or decrease
but Robert Paines - sea star maintains biodiversity
explain robert paines sea star example
when sea stars are in the ocean, they eat mussels and remove them from areas so algae and barnacles can grow
when the sea stars are reduced, the mussels act as an out competitor/superior competitor and doesn’t allow algae/barnacles to grow
- this shows that sea stars maintain and increase biodiversity by preventing competitive exclusion from occurring (species 1 takes over while species 2 = zero)
