Lecture 19 Flashcards
how does the species interactions of compeition, predation and mutualism effect both species
compeition hurts both species
predation benefits the predators and hurts the prey
mutualism benefits both
Intraspecific compeition
competition with individuals of the same species = conspecifics for food, space, mates, resources
- mostly represented by the logisitc model
interspecific competition
compeition of individuals that involve different species = heterospecifics for food, space, resources
- shows more in the Lotka-Volterra competition
Exploitative competition = scramble
depletion of a shared resource
if one species eats all the food that another species also feeds on = none left for the others
- they species don’t need to directly interact at the same time to = contest
- can be same or different species
EX: squirrel eats all the bird seeds before the bird arrives
interference competiton = contest
direct interactions - physical fight - over food, territory, battles
- invasive ants fight a harvester ant in california
what does the lotka volterra equation add
the logistic growth already has an exponential and a braking term for the intraspecific compeition
- it adds another braking term for the interspecific compeition
- combines both species - bc interspecific = 2 different species - need to see the effect that species 2 has on 1 or 1 has on 2
T/F alpha (21) is the impact of species 1 on species 2
yes, read them backwards
whatever subscript is on the carrying capacity is the one being impacted, and the other one is doing the interspecific compeition damage
T/F alpha is not a constant
false
it is a constant
what does alpha measure
constant
converts individuals of both species to be equivalent
- a squirrel can eat a lot more seeds than a bird can
- alpha measures how many sparrows worth of seeds a single squirrel eats
- for the amount of that the squirrel eats, how many sparrows would be equivalent to the same amount of food
what are the 4 possible outcomes for lotka volterra compeition
- the 2 species stay consistently stable = coexistence
- the intra comp > inter comp to coexist
- compeition between its own members must be stronger than comp with other members - may drive out of existence - species 1 always wins
- species 2 always wins
- the identity of the winner may be dependant on the starting size of the pop
what do the 4 outcomes of the lotka volterra compeition depend on
depends on the values of K = carrying capacity and alpha = compeition coefficient
what does equilibrium mean
pop size to not change over time
- the derivative (equations) = 0
in a community, the community needs to not change overtime - all populations in a community = equilibrium
what does stability mean in a species
the ability of a system to return to equilibrium following a disturbance
coexistence
when 2 or more species = thriving = not zero population sizes at equilibrium
what is the principle of competitive exclusion
lotka volterra predicts that for 2 species to coexist, the compeition between different species needs to be weaker than competition within a species to ensure the 2 different species do not drive the other to extinction
- 2 species usually have different niches
what is character displacement
2 similar species that compete for the same resources in overlapping geographical areas (sympatry) evolve different traits to reduce the competition
Galapagos finches that had 3 similar finches in the same area developed different beak shapes, small, medium, large so that they can eat different sized seeds and avoid
- when 1 type of finch occupied a land alone, they showed lots of variation in their beaks to reduce intraspecific compeition within their own members
what is the paradox of the plankton
- the principle of competitve exclusion is not true all the time and shows bc of plankton
- alot of plankton coexist in an aquatic ecosystem despite compeiting for a limited amoutn of resources - light, nutrients, space, carbon dioxde, N, P
- contradicts the competitve exclusion principle because 2 species cannot coexist together in equilibrium if they are competing for the same resources
what is the paradox of the tropical rainforest
so many species of trees that are condensly living in one area
- how do they not compete for resources and have one species win while the others = 0?
- either all species have evolved different niches or resources needed to live
- or something else prevents driving species to extinction
- not fully understood in science
how does the lotka volterra model relate to the real world
Gause studied compeition among protozoa (paramecium) = he saw both stable coexistence and competitve exclusion occuring at the same time
- when P. caudatum and P, aurelia grew tg = competitive exclusion
- when P. caudatum and P. busaria grew tg = stable coexistence = non zero pop sizes
explain the field experiment with 2 barnacle species in the marine intertidal zone
upper intertidal zone = chthamalus
lower intertidal zone = balanus
when u remove the chthamalus the balanus under does not extend its territory upwards - because it doesnt have the right living conditions to tolerate
when you remove the balanus underneath, the chthamalus move to the territory below suggesting that there was competition
what is wrong with the lotka volterra model
- too simple
- most real communities are not at a competitve equilibrium
real populations can not reach the carrying capcity because predation, natural disaster - real conditions = flucuation, favouring different species at different times/places
competition composition
the identity and the abundance of different species that make up a biological community in a specific area
- competition can affect which and how many species occur in an ecological community
species richness
the number of different species present in the community
T/F competition is expected to increase species diversity
false
it decreases specieis diversity
- if one superior competitor drives others to extinction
