Competition Tutorial

Do not start this tutorial until the gekcos start eating the flies.

(1) When a number of organisms utilize a common resource that is in short supply this is known as

You answered "(a) interfence competition".
No, while this is a form of competition it describes a situation where organisms prevent others from obtain a resource regardless of if it is in short supply.
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Question 1

You answered "(b) resource competition".
Yes! When organisms are competing for a resource which is in short supply this is known as resrouce competition.
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Question 1

You answered "(c) a competition".
No. There is no such thing as a competition. Your are probably thinking of a selection
. a selection does involve competition, but it describes the evolutionary traits which allow individuals to better compete in interferance competition.
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Question 1

You answered "(d) r competition".
No. There is no such thing as r competition. You are probably thinking of r selection. This involves the evolution of traits which allow individuals to be better colonists of new habitats. These individuals tend to be poor competitors.
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Question 2

(2) Which below best describes what it means when a = 0.35 for species A and B?

(a) There is a 65% niche overlap between species A and B.

(b) Each individual of species B uses as many resources as 35% of an individual of species A.

(d) There is a 35% probability one species will go extinct because of competition.

Question 2

You answered "(a) There is a 65% niche overlap between species A and B.".
No. Remember that the a terms refer to the strength of interspecific competition. It would be more likely to suggest that there is a 35% niche overlap between the two species. However that would be true if we were describing their niches only with respect to what they eat.
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Question 2

You answered "(b) Each individual of species B uses as many resources as 35% of an individual of species A.".
Yes! The a terms refer to the strength of interspecific competition. This describes the percentage of the resources, that are in limited supply, are used by an individual of species B
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Question 2

You answered "(c) Interspecific competition is 35% stronger than intraspecific competition.".
No. The a term does refer to the strength of interspecific competition, but it indicates that interspecific competition is only 35% as strong as intraspecific competition. Remember that the strength of intraspecific competition is always 1.0 (because they compete for 100% of the same resources). This is saying that 1 individual of species B uses 35% of the limiting resources that an individual of species A uses.
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Question 2

You answered "(d) There is a 35% probability one species will go extinct because of competition.".
No. The a term does refer to the strength of interspecific competition, but it indicates that interspecific competition is only 35% as strong as intraspecific competition. Remember that the strength of intraspecific competition is always 1.0 (because they compete for 100% of the same resources). This is saying that 1 individual of species B uses 35% of the limiting resources that an individual of species A uses.
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Question 3

(3) In the equation that describes population dynamics in the presence of competition the terms a and b refer to what?

(a) the slope of the coefficient of reproduction

(b) the strength of intraspecific competition

Question 3

You answered "(a) the slope of the coefficient of reproduction".
No. The slope of the coefficient of reproduction describes how the population changes in the descrete generation population equation.
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Question 3

You answered "(b) the strength of intraspecific competition".
No. We don't have specific terms to represent the strenght of intraspecific competition because it is always 1.0 because each individual of the same species uses exactly the same set of resources in the same manner. We do account of intraspecific competition though when we use K (carrying capacity) in equations for population growth.
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Question 3

You answered "(c) the strength of interspecific competition".
Yes! These two terms describe the strength of interspecific competition of species 2 on species 1, and the strength of interspecific competition of species 1 on species 2 respectively.
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Question 4

(4) When R₀ = 1.2 which of the following is true?

(a) the population is decreasing

(b) the population size is not changing

(d) none of the above

Question 4

You answered "(a) the population is decreasing".
No. The term R₀ refers to the net finite reproductive rate, or how many daughters a female will have over her life. If each female is on average having 1.2 daughters the population would be getting larger.
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Question 4

You answered "(d) none of the above".
No. One of the answeres is correct.
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Question 5

(5) Which equation below describes interspecific competition?

(a) dN₁/dt = r₁N₁ ((K₁ - N₁)/K₁)

(b) dN₁/dt = r₁N₁ ((K₁ - N₁ - aN₂)/K₁)

(d) N_t = N₀ e^rt

Question 5

You answered "(a) dN₁/dt = r₁N₁ ((K₁ - N₁)/K₁)".
No. This equation only describes intraspecific competition (you know this because K is included). For it to describe interspecific competition there would have to be a set of terms accounting for the second species.
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Question 5

You answered "(b) dN₁/dt = r₁N₁ ((K₁ - N₁ - aN₂)/K₁)".
Yes! This equation has two sets of terms. The term between the "=" sign and the "-" acount for population growth with intraspecific competition. The second set of terms, to the left of the "-" sign, accounts for interspecific competition. The alpha term converts individuals of species 2 (the total number of these individuals is represented by the term N₂) into individuals of species 1. The alpha term represents how much of the limiting resource for species 1 is used by an individual of species 2.
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Question 5

You answered "(c) N_t+1 = (1.0 - Bz_t)N_t - CN_tP_t".
No. This equation represents population growth in a prey speciecs in the presence of a predator.
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Question 5

You answered "(d) N_t = N₀ e^rt".
No. This equation describes population growth in a species with no intraspecific or interspecific competition.
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Question 6

(6) When r = 0.0 which of the following is true?

(a) the population is decreasing

(b) the population size is not changing

Question 6

You answered "(a) the population is decreasing".
No. r is the intrinsic rate of increse, that is how quickly the population is changing at that point in time. For the population to be decreasing the value of r would have to be less than 0.0.
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Question 6

You answered "(b) the population size is not changing".
Yes! r is the intrinsic rate of increse, that is how quickly the population is changing at that point in time. When r = 0.0 it means that the population size is not changing.
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Question 6

You answered "(c) the population is increasing".
No. r is the intrinsic rate of increse, that is how quickly the population is changing at that point in time. For the population to be increasing the value of r would have to be greater than 0.0.
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Question 7

(7) Based on the above graph, which value is closest to R₀?

You answered "(a) - 1.0".
No. If R₀ were negative it would mean that for every one female in the population they were having the number -1 of daughters. This is imposible, so R₀ must always be greater than or equal to zero.
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Question 7

You answered "(b) 0.0".
No. When R₀ = 0.0 it means that on average each female is having 0.0 daughters. In this case the population would rapidly be crashing and end up going extinct.
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Question 7

You answered "(c) 1.0".
No. When R₀ = 1.0 it means that each female is producing one daughter on average. If this is happening the population would stay at a constant size.
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Question 7

You answered "(d) 2.0".
Yes! When R₀ = 2.0 it means that each female is producing 2.0 daughters on average. That means that the population will be doubling each generation and thus experiencing exponential growth.
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Question 8

(8) Based on the graph above, what conclusion can you make? The graph is from two different populations in identical habitats.

(a) no competition occurs between red fox and coyotes

(b) competition occurs between red fox and coyotes

(d) resource competiton is occuring

Question 8

You answered "(a) no competition occurs between red fox and coyotes.
No. We know that some form of competition is occuring becuase the maximum population size that the red fox reach is lower in the presence of coyotes compared to foxes by themselves.
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Question 8

You answered "(b) competition occurs between red fox and coyotes.
Yes! Because the maximum population size (or carrying capacity) of foxes is different in identical habitats except for the presence of coyotes we know competition must be occuring. However, we don't know what form this competition is taking on (resource or interferance) so all we can conclude is that competition does occur.
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Question 8

You answered "(c) interference competition occurs by coyotes killing foxes.
No. We do know that some form of competiton is occuring because the maximum population size (or carrying capacity) of foxes is different in identical habitats except for the presence of coyotes. However, we don't know what type of competition is occuring.
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Question 8

You answered "(d) resource competiton is occuring.
No. We do know that some form of competiton is occuring because the maximum population size (or carrying capacity) of foxes is different in identical habitats except for the presence of coyotes. However, we don't know what type of competition is occuring.

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Question 9

Volume of check

pouches (mm³)

allopatric

sympatric

ord’s kangaroo rat

18.5

15

merriam’s kangaroo rat

19.5

22

(9) Given the data shown above what best describes the ecological process is occurring? Checkpouch volume directly relates to the size, number and types of seeds (the only food source of kangaroo rats) that a kangaroo rat can carry.

(a) character displacement

(b) competition

(d) speciation

Question 9

You answered "(a) character displacement".
Yes! We see that the morphological structure of the two kangaroo rats changes depending on if they are sympatric or allopatric. We would also need to know that the samples came from multiple populations, that checkpouch volume is heritable, and that the change in values is not predicatble based on observed variation. We know that the trait influences competiton because they are all competeting for the same seeds. See page 256 for more information.
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Question 9

You answered "(b) competition".
Well, yes and no. Competition is occuring, but we can be more precise about what process this data illustrates. Go back and try again.
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Question 10

You answered "(c) predation".
No. This data shows no information about predation.
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Question 9

You answered "(d) speciation".
Well maybe. If these sympatric populations remain isolated from other populations of conspecifics speciation may occur. However, this is not very likely and the process that is occuring rarely results in speciation. Go back and try again.

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Question 10

(10) A species which produces many offspring with good dispersal ability and a rapid rate of reproduction is describe by what type of selective competitive ability?

You answered "(a) r selection".
Yes! r-selected species typically have lots of offspring with good dispersal abilities. They are usually good colonists of disturbed habitat and poor competitors. See the chart I gave you on the handout to see more of their traits..
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Question 10

You answered "(b) K selection".
No. K-selected species typically have few offspring and don't disperse as well as r-selected species. They typically enter a habitat after it has been colonized by other species and are very good competitors for resources.
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Question 10

You answered "(c) a selection".
No. a-selected species typically have few offspring and don't disperse as well as r-selected species. They typically enter a habitat after it has been colonized by other species and are very good competitors. However they compete through interferance competition rather than resource competition.
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Question 10

You answered "(b) b selection".
No. There is no such thing as a b-selected species.

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Question 11

(11) When an organism seeking a resource harms another individual or prevents that individual from obtaining the resource even if it is not in short supply, this is known as,

(a) interference competition

(b) resource competition

(d) r competition

Question 11

You answered "(a) interfence competition".
Yes! Interference competition occurs when organisms prevent others from obtain a resource regardless of if it is in short supply.
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Question 11

You answered "(b) resource competition".
No. When organisms are competing for a resource which is in short supply this is known as resrouce competition.
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Question 11

Question 13

(12) This equation describes which of the following?

(a) intraspecific competition

(b) interspecific competition

(d) predation

Question 12

You answered "(a) intraspecific competition".
Yes! Intraspecific competion occurs when individuals of the same species are competiting for limited resources. This competition results in either increased death rates or decreased birth rates (or both) as population density increases. When birth and/or death rates are density dependent population growth slows the closer the species gets to carrying capacity. This is achieved in the equation by the terms within the parantheses.

You have reached the end of the tutorial. I hope it helped.

Question 12

You answered "(b) interspecific competition".
No. Intersepecific competition does include all of this equation, but there must also be another term which converts individuals of the competiting species in to individuals of the species with which we are concerned. This value must then be subtracted from the carrying capacity of our species of concern.
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Question 12

You answered "(c) mutualism".
No. Mutualism occurs when two species benefit each other. If we wanted to incorporate mutualism we would need to put an additional term into the equation that allowed carrying capacity to increase when the other species is present.
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Question 12

You answered "(d) predation".
No. Predation removes individuals from the population so we would need a term incorporating how many predators are present and how efficient they are at catching prey.
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	Volume of check	pouches (mm³)
	allopatric	sympatric
ord’s kangaroo rat	18.5	15
merriam’s kangaroo rat	19.5	22