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1

What is competition?

Negative interaction between individuals due to limited resources.

2

A resource is any substance or factor which can lead to ________ _______ _______ ________ as its availability in the environment is increased, and which is consumed by an organism. -Tilman 1982

increased population growth rates

3

Resources are entities which __________ ________ __ _________ ________ and are consumed in the process.

contribute positively to population growth

4

Resources can be classified as either ________ or ________.

Abiotic or biotic

5

Abiotic factors are ___-_______. These include? (4)

non-living. These include minerals, nutrients, light, space.

6

Biotic factors are ______ or _____-_________.
These include? (3)

living or self producing.
prey for predators, plants for herbivores, seeds for granivores

7

_________ competition is between individuals of the same species.

Intraspecific

8

__________ competition is between individuals of a different species.

Interspecific

9

If an individual encounters increasing density of other individuals, it will:
- _________ its growth rate
- be _______ when it matures
- leave _______ offspring
- the offspring will be of _______ quality
- mortality will __________.
This is __________ competition.

1) decrease
2) smaller
3) fewer
4) lower
5) increase
6) Intraspecific

10

______________ competition is likely the major factor influencing community structure.

interspecific

11

Interspecific competition between 2 species occurs where individuals of 1 species suffer a ________ ___ _______ ____ from a second species due to:
1) ________ competition (resource competition)
2) _________ competition (contest competition)

1) reduction in growth rate
2) Exploitative
3) Interference

12

Exploitative competition is also called __________ competition.

resource

13

Interference competition is also called _______ competition.

contest

14

Exploitative competition occurs when two or more species share a limited resource, ________ ______ _________ ________ for the other species.

less resource available

15

Interference competition occurs when one species limits the ______ __ ______ _______ to a ________ __________.
Often involves __________ or occupying a _______ to the exclusion of the other.

1) access of another species
2) limiting resource
3) aggression
4) space

16

________ effects are linked to interference competition.

interference

17

For logistic growth of two species grown _______, there is an exponential growth until one reaches the carrying capacity, K.

alone

18

______-________ competition model.

Lotka-volterra

19

If two species are competing. The per capita effect of species 2 on species 1 is given by _____. The per capita effect of species 1 on species 2 is given by ____.

1) aN(2) (alpha*N of species 2)
2) BN(1) (beta*N of species 1)

20

If the coefficient of competition is zero, then competition is _______.

absent

21

The stronger the competition, the ______ the values of alpha and beta.

larger

22

Suppose that K1 = 100, N2 = 100, alpha = 0.2.
How many individuals is removed from species 1 by species 2?

aN2 = 0.2*100
=20
So, species 2 removes 20 individuals from species 1.

23

aN2 is the total ________ effect of species _ on species _.

competive;2;1

24

For the graphical analogy for interspecific competition, the frame represents the _______ _______ (_) for species 1.

carrying capacity (K)

25

In the graphical analogy for interspecific competition, each individual _______ __ _______ __ ___ ______ _______ ___ __ __________ __ _ ____.

consumes a portion of the limited resource and is represented by a tile.

26

For the graphical analogy of interspecific competition, assume that individuals of species 2 reduce the carrying capacity 4 times as much as species 1. This means that the tiles of species 2 are ___ times the size of species 1. Thus, alpha = __.

4; 0.4

27

Assumptions of the Lotka-Voltera competition model:
1) the effect of one species on the other is ______
2) Carrying capacities are ________
3) The environment is ________

1) linear
2) constant
3) stable

28

A species will stop growing when either __ = 0 or __ = 0.

r = 0 or N = 0

29

Zero percent growth is given by a species _______.

isocline

30

To plot the isocline, what values are used?

Recall, N1 = K1 - aN2
Set N1 = 0
aN2 = K1
N2 = K1/a

Set N2 = 0
N1 = K1
slope is dN1/dT = 0
N2 on y, N1 on X, when zero, reach fixation.

31

______ the isocline we will see an increase in growth rate until the stable state is reached.
_______ the isocline, the opposite occurs.

Below; above

32

The isocline (for species 1) represents all combinations of numbers at which ______ _ _____ _____ _______.

Species 1 will stop growing

33

If there is a mixture of species 1 and 2 above the species 1 isocline, then N1 must ________ = _______ _______ _____

decrease; negative growth rate

34

Similarly, if there is a mix of species 1 and 2 below the species 1 isocline, then N1 must _____ = _____ ______ _____.

increase; positive growth rate

35

Being above or below the species 1 isocline will result in movement that is _______ to the x-axis.

parallel

36

Being above or below the species 2 isocline will result in movement that is ________ to the x-axis.

perpendicular

37

What values and variables are important for the species 2 ZPG isocline?

Recall, N2 = K2 - BN1
Set N1 = 0
N2 = K2

Set N2 = 0
K2 = BN1
N1 = K2/B

38

Now, combine the ZPG isoclines for both species. Identify the regions where _____ ______ ______ and _______.

both species increase and decrease

39

The regions where both species increase or decrease are?

Below both ZPG isoclines or above both.

40

The L-V model makes _ mutually exclusive predictions:
___ cases of competitive _______ and ___ cases of competitive __________.

4; 2-exclusion; 2-coexistence

41

The four mututally exclusive predictions are?

Exclusion:
1) species 1 wins and species 2 is excluded
2) Species 2 wins and species 1 is excluded
Coexistence:
3) Stable, equilibrium coexistence. Both species persist.
4) Unstable non-eqb coexistence. Persistence is short lived.

42

For the competitive exclusion, the distance that the isoclines are apart ______ affect the outcome.

doesn't

43

Draw prediction 1: Species 1 wins. Also note the direction the growth rate is going in each area between, above or below ZPG isoclines.

Refer to notes (27)

44

Draw prediction 2: Species 2 wins. Also note the direction the growth rate is going in each area between, above or below ZPG isoclines

Refer to notes (28)

45

Draw Prediction 3: Stable equilibrium. Also note the direction within each zone delimited by the ZPG isoclines, along with the intercepts. Also note the stable equilibrium point and indicate the densities of both species exist beneath their own K.

Refer to notes (29) (30)

46

Since coexistence occurs, it doesn't matter at what density you begin the population; all ________ on the stable equilibrium point.

converge

47

Draw prediction 4: unstable non-equilibrium exists. Indicate the direction between the ZPG isoclines and the final equilibrium points. Also write the intercepts and which species density belongs to what axis.

Refer to notes (32)

48

There are two types of equilibrium predicted by the L-V model. These are _______ and __________. Equilibrium is only reached when the diagonals ________ each other.

1) stable and unstable
2) Cross

49

Stable coexistence - both _______ __-_________.

competitors co-exist

50

Unstable coexistence - both competitors can coexist, but __ __ _______.

it is unlikely

51

The coexistence afforded by unstable equilibrium is only __________ and typically ends in the _________ __________ of one of the species.

1) Temporary
2) Competitive exclusion

52

What are the criticisms of the L-V model? (4)

1) Assumes density independent competition
2) Deals only with competition between 2 species
3) Assumes that we can ignore other ecological processes
4) Assumes constant environmental conditions and logistic growth in the absence of competition

53

Problem:
You are studying competition between red and black desert scorpions.
For the red scorpion, K = 100 and a = 2
For the black scorpion, K = 150 and B = 3
Suppose the initial population sizes are 25 red scorpions and 50 black scorpions.
What is the competitive outcome?

1) Graph the isoclines for each species
Note: N1 = K1 - BN2
-make N1 and N2 = zero
N2 = K2 - aN1
- make N1 and N2 = zero

2) Plot the initial population sizes

3) Predict the short term dynamics of each population.
- unstable coexistence

4) What is the final outcome of the interspecific competition?
- black scorpion wins