Deck 12: Population Growth and Regulation

Question 1

Describe how the geometric growth model is different from the exponential growth model. For each growth model, give an example of an organism that fits the growth pattern it describes. Explain why the organism fits the model.

Answer 1

not answered

Question 2

Which reflects density-independent population regulation?
I) a winter storm that kills birds with equal probability regardless of bird abundance
II) a drought that kills a higher proportion of plants when there are many plants and a smaller proportion when there are fewer plants
III) a lethal disease that is more easily transmitted when animals are found in high abundance than in low abundance

A) I only
B) II only
C) III only
D) I and III
E) II and III

Answer 2

A

Question 3

Which illustrates a negative relationship between population density and the average size of individuals over time?

A) an exponential growth curve
B) a J-shaped curve
C) a survivorship curve
D) a self-thinning curve

Answer 3

D

Question 4

Which is likely to follow an exponential increase in population size?
I) a population of mice that has consumed most of the food in its habitat
II) a small population of rats recently introduced to an island with many resources
III) bacteria recently placed on a new petri dish with suitable growth medium

A) I only
B) II only
C) III only
D) I and II only
E) II and III only

Question 5

The Allee effect describes

A) density-independent population regulation.
B) negative density-dependent population regulation.
C) positive density-dependent population regulation.
D) logistic population growth.

Question 6

Under positive density dependence, population growth rate

A) increases as populations become larger.
B) remains the same as populations become larger.
C) decreases as populations become larger.
D) is highest at intermediate population size and lowest when population is large or small.

Question 7

Define population doubling time. Starting with the model for exponential population growth, explain how to derive the formula for population doubling time.

Question 8

Consider a biologist studying a population of deer. At the beginning of the year, there are 100 adult deer in the population. Over the course of the year, 15 adult deer die, and an additional 25 deer are born. What can we conclude about $\lambda$ for this year?

A) $\lambda$ < 0
B) $\lambda$ = 0
C) $\lambda$ > 0
D) $\lambda$ = 1
E) $\lambda$ > 1

Question 9

Which reflects positive density-dependent population regulation?
I) Small populations of flowers produce fewer seeds per individual than large populations of flowers.
II) Large groups of birds are better able to detect and avoid predators than small groups of birds.
III) The probability that a forest predator will kill a squirrel does not depend on the size of the squirrel population.

A) I only
B) II only
C) III only
D) I and II
E) I and III

Question 10

According to an exponential growth population model, when the number of births is less than the number of deaths,

A) r < 0.
B) r = 0.
C) 0 $\le$ r $\le$ 1.
D) r > 1.

Question 11

In the exponential growth model, which term indicates the intrinsic rate of increase?

A) N₀
B) e
C) r
D) t

Question 12

In a population growing according to the exponential growth model, population size is

A) limited by density-dependent factors.
B) limited by density-independent factors.
C) limited by both density-dependent and density-independent factors.
D) not limited.

Question 13

Which plot is consistent with a geometric growth model in which $\lambda$ = 1?

A) a
B) b
C) c
D) d

Question 14

Which reflects negative density dependence?
I) A fungus infects and kills plants at a higher rate when they are abundant than when they are rare.
II) A group of birds has a higher per capita survival rate when it is large than when it is small.
III) A large population of deer exhausts local food supplies and has a high risk of death; a small population has plentiful food and low risk of death.

A) I only
B) II only
C) III only
D) I and II
E) I and III

Question 15

In what way is the geometric growth model different from the exponential growth model?

A) The geometric growth model uses continuous time.
B) The geometric growth model uses regular time intervals.
C) The geometric growth model includes carrying capacity (K).
D) The exponential growth model includes carrying capacity (K).

Question 16

Negative density dependence occurs when the

A) per capita population growth rate increases as population becomes larger.
B) per capita population growth rate remains constant as population becomes larger.
C) per capita population growth rate decreases as population becomes larger.
D) population increases without limit.
E) population decreases until it becomes extinct.

Question 17

According to the exponential growth model, which would reduce a population's doubling time?

A) an increase in the initial population size
B) a decrease in the initial population size
C) an increase in the intrinsic growth rate
D) a decrease in the intrinsic growth rate

Question 18

The intrinsic growth rate, r, is the

A) number of new individuals produced minus the number that die.
B) highest possible per capita increase in population size under ideal conditions.
C) time it takes for a population to double in size.
D) maximum population size that can be supported by the environment.

Question 19

A species of louse (an external parasite) infests salmon. Researchers have found that the lice have difficulty finding a mate when there are only a few lice on an individual fish. The lice find mates more easily and produce more offspring when there are many lice on an individual fish. This is an example of

A) the geometric growth model.
B) positive density-dependent population regulation.
C) negative density-dependent population regulation.
D) density-independent population regulation.

Question 20

Which plot is consistent with an exponential growth model when r > 0?

A) a
B) b
C) c
D) d

Question 21

Consider a biologist who is studying a fish. The biologist conducts an experiment with four treatments in artificial ponds of the same size. In the first treatment he adds 10 fish to each pond. In the second treatment he adds 100 fish to each pond. In the third treatment he adds 10 fish and additional food. In the fourth treatment he adds 100 fish and additional food. At the end of the experiment he finds that female fish in ponds with only 10 fish produce many more eggs than female fish in ponds with 100 fish. However, adding food did not alter the number of eggs each female fish produced. Explain what this experiment tells us about how these fish are affected by density-independent, positive density-dependent, or negative density-dependent factors.

Question 22

The logistic growth model describes a maximum population size that is

A) limited by density-dependent factors.
B) limited by density-independent factors.
C) limited by both density-dependent and density-independent factors.
D) not limited by any factors.

Question 23

In the logistic growth model, which term determines how quickly a population will initially grow from low density?

A) r
B) N
C) K
D) dN/dt

Question 24

Which form of population growth results in an S-shaped curve?

A) exponential growth
B) geometric growth
C) logistic growth
D) density-independent growth

Question 25

The figure shows the change in population size of Paramecium from Gause's experiment, raised in either high-food or low-food conditions. Based on this figure, how was the logistic growth model for Paramecium changed by adding food?

A) High food increased r.
B) High food decreased r.
C) High food increased K.
D) High food decreased K.

Question 26

In the logistic growth model, which term determines the maximum number of individuals a population can sustain?

A) r
B) N
C) K
D) dN/dt

Question 27

Which of the following statements about the logistic growth model is accurate?
I) The per capita rate of population increase declines as population size increases.
II) The overall rate of population increase is highest at K/2.
III) The overall rate of population growth is negative when N is greater than K/2.

A) I only
B) II only
C) III only
D) I and II only
E) I and III only

Question 28

A biologist grew 10 groups of flowers in 1-square-meter plots of soil. In five plots, the biologist planted 20 flowers, and in the other five plots, the biologist planted 100 flowers. At the end of the summer, the biologist counted the seeds that each flower produced and found 100 seeds per plant in the plot with 20 plants and 500 seeds per plant in the plot with 100 plants. This is an example of

A) density-independent population regulation.
B) positive density-dependent population regulation.
C) negative density-dependent population regulation.
D) a self-thinning curve.

Question 29

In the logistic growth model, under which condition is the per capita rate of increase the highest?

A) N = K
B) N = $\frac { K } { 2 }$
C) N = $\frac { K } { 4 }$
D) N = K + r

Question 30

Which factors could limit a species' carrying capacity?
I) the amount of food available
II) the number of eggs a female can produce
III) the number of nesting sites present

A) I only
B) II only
C) III only
D) I and II
E) I and III

Question 31

The larvae of a carnivorous species of salamander inhabit ponds. When the pond contains few larvae, they mostly eat small invertebrates and have a high survival rate. When there are many salamander larvae in a pond, the larvae will also cannibalize each other and have a low survival rate. This is an example of

A) geometric growth.
B) positive density-dependent population regulation.
C) negative density-dependent population regulation.
D) density-independent population regulation.

Question 32

Which accurately describes the inflection point in the logistic growth model?
I) Population growth slows after the inflection point.
II) The inflection point is equal to the carrying capacity.
III) The highest growth rate occurs at the inflection point.

A) I only
B) II only
C) III only
D) I and II
E) I and III

Question 33

Alpine ibex are a type of wild goat that lives high in the mountains. During winters with heavy snow, Alpine ibex have high mortality rates regardless of the population size. This is an example of

A) geometric growth.
B) positive density-dependent population regulation.
C) negative density-dependent population regulation.
D) density-independent population regulation.

Question 34

A park biologist is planting saplings (young trees) in an old field that has recently been turned into a park. Draw a hypothetical self-thinning curve for these trees over 5 years. Be sure to label the axes. Describe a practical use of this curve.

Question 35

In the logistic growth model, in which of the following conditions is the overall rate of increase the highest?

A) N = K
B) N = $\frac { K } { 2 }$
C) N = $\frac { K } { 4 }$
D) N = K + r

Question 36

The age structure of a population is often represented by a pyramid. What does an age structure pyramid with a broad base and a narrow top indicate about a population?

A) The population is declining.
B) The population is growing.
C) The population is stable.
D) The shape of the pyramid does not provide information on population growth.

Question 37

Which is the most accurate statement about the conservation biology of species with positive density-dependent population regulation?

A) If the population is small, it may not be able to increase.
B) The population will quickly exhaust all resources.
C) Species with positive density dependence are not at risk for extinction.
D) Population growth rate is highest when N > K.

Question 38

A biologist studies a population of birds for 25 years. Each year the biologist records the amount of rainfall and the density of birds (number of birds per 100 square meters). In addition, the biologist determines the survival rate for eggs laid that year. The biologist then plots egg survival rate against both rainfall (graph a) and density (graph b). In each plot the individual points represent the data for one year of the study. Based on these data, does this population of birds appear to be subject to positive density-dependent population regulation, negative density-dependent population regulation, or density-independent population regulation? As part of your answer, list the prediction for each type of population regulation and explain whether the data meet that prediction. (a) (b)

Question 39

Which describes the figure of logistic population growth shown in the graph?

A) r > 0; K > 300
B) r < 0; K > 300
C) r > 0; K < 300
D) r < 0; K < 300

Question 40

Using the logistic growth model, draw a line that shows the relationship between per capita growth rate (y axis) and population size (x axis) for a hypothetical population with a carrying capacity of 500 individuals. Explain how the slope relates to changes in population size over time and give an example of an environmental factor that could cause a population to follow a logistic model of population growth.

Question 41

Explain the difference between positive density dependence and negative density dependence.

Question 42

What is true about the life table data and resulting survivorship curve for Dall sheep as published by O. Murie in 1944?

A) The survivorship curve showed a definitive type II curve.
B) Age class 0-1 had higher survivorship then any of the next three ages classes.
C) When the population size for a particular age class was small, survivorship rates were unreliable.
D) The real-world survivorship curve based on the collection of 608 Dall sheep skeletons did not differ from the expected, generalized curve for similar species.

Question 43

Consider a perennial plant with four life stages: seed, seedling, small adult, and large adult. Seeds survive to seedlings with a probability of 50 percent; seedlings survive to be small adults with a probability of 20 percent; small adults survive to be large adults with a probability of 20 percent. Both small adults and large adults produce an average of 10 seeds. Use this information to fill in the life table that follows; then calculate the R0 and explain whether the population is increasing, stable, or decreasing.
Age Class (x)
Survival Rate (s_x)
Survivorship (l_x)
Fecundity (b_x)
Seed
Seedling
Small adult
Large adult
R₀: _____________________

Question 44

Applying life tables to sea turtle conservation demonstrated that the most effective way to increase sea turtle populations is to

A) raise large numbers of hatchlings and release them into the ocean.
B) protect nests from human poaching and other predators.
C) protect adults from being captured in fishing nets.
D) harvest small numbers of adults for human consumption each year.

Question 45

Describe the difference in appearance of the type I and type III survivorship curves. What do the shapes of the curves tell us about the species that have these curves? In addition, how do these curves instruct us as to the comparative reproductive strategies of type I versus type III species?

Question 46

The following table shows the survival and fecundity of a flowering plant.
$$\begin{array} { | c | c | c | c | } \hline \begin{array} { c } \text { Age in } \\\text { Years } ( x )\end{array} & \begin{array} { c } \text { Survival Rate } \\\left( \mathrm { s } _ { \mathrm { x } } \right)\end{array} & \begin{array} { c } \text { Survivorship } \\\left( \mathrm { l } _ { \mathrm { x } } \right)\end{array} & \begin{array} { c } \text { Fecundity } \\\left( \mathrm { b } _ { \mathrm { x } } \right)\end{array} \\\hline 1 & 0.1 & 1.0000 & \\\hline 2 & 0.8 & 0.1000 & \\\hline 3 & 0.8 & 0.0800 & \\\hline 4 & 0.8 & 0.0640 & 10 \\\hline 5 & & 0.0512 & 20 \\\hline\end{array}$$

A) 30
B) 24
C) 1.664
D) 0.1152

Question 47

When a population has a stable age distribution,

A) the total number of individuals stays constant over time.
B) the proportion of individuals in each age class remains constant.
C) the net reproductive rate is less than one.
D) it is at its carrying capacity.

Question 48

When looking at plants, what would be considered a plant's generation time?

A) Plants do not have generation times; only animals have generation times.
B) the time it takes for a seed to grow into a mature plant and produce seeds of its own
C) the time it takes for a seed to germinate
D) the time it takes for a seed to flower

Question 49

If a population has relatively few individuals in the young classes but many in the medium-aged and old classes, what can we conclude about population growth?

A) The population is declining.
B) The population is growing.
C) The population is stable.
D) The population is below carrying capacity.

Question 50

A disadvantage of static life tables is that

A) they require following individuals for their entire life span.
B) environmental conditions in any given year may confound survival data for a specific age group.
C) environmental conditions at the time of data collection may confound survival data across all age classes.
D) they cannot be used for long-lived organisms.

Question 51

Plants are more likely to show which type of survivorship curve?

A) type I
B) type II
C) type III
D) All three survivorship curves are found equally among plant species.

Question 52

The exponential growth model and the logistic growth model both initially look the same. Explain the difference between the two models. What causes the logistic model to change trajectory?

Question 53

For 5 years, a biologist studied a population of mice living in a field. The mice have three age classes: 1 year old, 2 years old, and 3 years old. The number of individuals in each age class over the course of the study is shown in the table.
$$\begin{array} { | c | c | c | c | } \hline \begin{array} { c } \text { Age in } \\\text { Years } ( \mathrm { x } )\end{array} & \begin{array} { c } \text { Survival Rate } \\\left( \mathrm { s } _ { \mathrm { x } } \right)\end{array} & \begin{array} { c } \text { Survivorship } \\\left( \mathrm { l } _ { \mathrm { x } } \right)\end{array} & \begin{array} { c } \text { Fecundity } \\\left( \mathrm { b } _ { \mathrm { x } } \right)\end{array} \\\hline 1 & 0.1 & 1.0000 & \\\hline 2 & 0.8 & 0.1000 & \\\hline 3 & 0.8 & 0.0800 & \\\hline 4 & 0.8 & 0.0640 & 10 \\\hline 5 & & 0.0512 & 20 \\\hline\end{array}$$

A) 4 years
B) 4.6 years
C) 5 years
D) 7.7 years

Question 54

An age structure graph that appears rectangular in overall shape would likely see what in the future?

A) an increase in population size
B) a decrease in population size
C) an increase, followed by a decrease in population size
D) no change in population size

Question 55

All cohort life tables

A) follow individuals born at the same time from birth to death.
B) quantify the survival and fecundity of all individuals at a single time interval.
C) have a stable age distribution.
D) describe a population at its carrying capacity.

Question 56

What type of survivorship curve describes a species that has a high rate of juvenile mortality but low adult mortality?

A) type I curve
B) type II curve
C) type III curve
D) type I and type III curve

Question 57

The net reproductive rate refers to

A) the total number of offspring that a population produces per year (or breeding cycle).
B) the total number of female offspring a population produces per year (or breeding cycle).
C) the largest number of offspring a female can produce under ideal conditions.
D) the total number of female offspring an average female can produce over its lifetime.

Question 58

Describe the similarities and differences between a cohort life table and a static life table. Give an actual example of each.

Question 59

You are a biologist studying deer populations in four parks: Chagrin, Bedford, Bradley, and Brookside. These four parks are all the same size, and they have similar weather. You estimate deer population size in October 2011, before winter comes. Then you estimate the size of the herd the next year, in October 2012. The data are listed in the table:
Park
October 2011 Population
October 2012 Population
Chagrin
125
90
Bedford
50
77
Bradley
150
68
Brookside
75
96
Explain whether each of the following statements is supported by the data and why or why not.
I. These populations have exponential growth.
II. The changes in population size are density dependent.
III. All of these populations are below their carrying capacity.

Question 60

The following table for a species of plant that has four life stages was constructed from research done in the 1960s.
Age Class (x)
Survival Rate (s_x)
Survivorship (l_x)
Fecundity (b_x)
Seed

Question 61

When working with life tables, we work with many variables and make many calculations. One such variable of importance is bx or fecundity. An important calculation we make as we determine the net reproductive rate is lxbx. This calculation is often referred to as "realized fecundity." Why might that be the case?

A) because we are looking at fecundity rate for females as well as considering how many females survive (survivorship rate) to each reproductive age class
B) because we are looking at both male and female survivorship at each age class
C) because we are looking at survivorship only at prereproductive age classes
D) because we are looking at survivorship only at postreproductive age classes

Question 62

That individuals are more likely to find mates and reproduce when populations are larger as compared to when populations are smaller might be termed

A) the Allee effect.
B) negative density dependence.
C) a density-independent variable.
D) self-thinning