Lecture 19

Question 1

how does the species interactions of compeition, predation and mutualism effect both species

Answer 1

compeition hurts both species
predation benefits the predators and hurts the prey
mutualism benefits both

Question 2

Intraspecific compeition

Answer 2

competition with individuals of the same species = conspecifics for food, space, mates, resources
- mostly represented by the logisitc model

Question 3

interspecific competition

Answer 3

compeition of individuals that involve different species = heterospecifics for food, space, resources
- shows more in the Lotka-Volterra competition

Question 4

Exploitative competition = scramble

Answer 4

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

Question 5

interference competiton = contest

Answer 5

direct interactions - physical fight - over food, territory, battles
- invasive ants fight a harvester ant in california

Question 6

what does the lotka volterra equation add

Answer 6

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

Question 7

T/F alpha (21) is the impact of species 1 on species 2

Answer 7

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

Question 8

T/F alpha is not a constant

Answer 8

false
it is a constant

Question 9

what does alpha measure

Answer 9

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

Question 10

what are the 4 possible outcomes for lotka volterra compeition

Answer 10

1. 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
2. species 1 always wins
3. species 2 always wins
4. the identity of the winner may be dependant on the starting size of the pop

Question 11

what do the 4 outcomes of the lotka volterra compeition depend on

Answer 11

depends on the values of K = carrying capacity and alpha = compeition coefficient

Question 12

what does equilibrium mean

Answer 12

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

Question 13

what does stability mean in a species

Answer 13

the ability of a system to return to equilibrium following a disturbance

Question 14

coexistence

Answer 14

when 2 or more species = thriving = not zero population sizes at equilibrium

Question 15

what is the principle of competitive exclusion

Answer 15

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

Question 16

what is character displacement

Answer 16

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

Question 17

what is the paradox of the plankton

Answer 17

• 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

Question 18

what is the paradox of the tropical rainforest

Answer 18

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

Question 19

how does the lotka volterra model relate to the real world

Answer 19

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

Question 20

explain the field experiment with 2 barnacle species in the marine intertidal zone

Answer 20

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

Question 21

what is wrong with the lotka volterra model

Answer 21

• 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

Question 22

competition composition

Answer 22

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

Question 23

species richness

Answer 23

the number of different species present in the community

Question 24

T/F competition is expected to increase species diversity

Answer 24

false
it decreases specieis diversity
- if one superior competitor drives others to extinction