Important words and concepts from Chapter 52, Campbell & Reece, 2002 (3/25/2005):

by Stephen T. Abedon ( for Biology 113 at the Ohio State University



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Vocabulary words are found below



Consider putting in an annotated sigmoid growth curve somewhere in this lecture (e.g., like the overhead I use)

Consider breaking up discussion of fecundity into a number of offspring component and a generation time component


(1) Chapter title: Population Ecology

(a)                    [population ecology (Google Search)] [index]

(2) Population ecology

(a)                    Population ecology studies organisms from the point of view of the size and structure of their populations

(b)                    A population ecologist studies the interaction of organisms with their environments by measuring properties of populations rather than the behavior of individual organisms

(c)                    Properties of populations include

(i)                      Population size (size)

(ii)                    Population density (density)

(iii)                   Patterns of dispersion (dispersion)

(iv)                  Demographics (demographics)

(v)                    Population growth (growth)

(vi)                  Limits on population growth (limits)

(d)                    Note that all of these properties are not those of individual organisms but instead are properties which exist only if one considers more than one organism at any given time, or over a period of time (i.e., they are emergent properties)

(e)                    "The characteristics of a population are shaped by the interactions between individuals and their environments on both ecological and evolutionary time scales, and natural selection can modify these characteristics in a population."

(f)                      Thus, population ecology also goes beyond consideration of just population parameters and additionally considers how the characteristics of individual organisms impact on population parameters

(g)                    [population ecology (Google Search)] [index]




(3) Population

(a)                    A population in an ecological sense is a group of organisms, of the same species, which roughly occupy the same geographical area at the same time

(b)                    Individual members of the same population can either interact directly, or may interact with the dispersing progeny of other members of the same population (e.g., pollen)

(c)                    Population members interact with a similar environment and experience similar environmental limitations

(d)                    [population (Google Search)] [index]

(4) Population size

(a)                    A population's size depends on how the population is defined

(b)                    If a population is defined in terms of some degree of reproductive isolation, then that population's size is the size of its gene pool

(c)                    If a population is defined in terms of some geographical range, then that population's size is the number of individuals living in the defined area

(d)                    Ecologists typically are more concerned with the latter means of defining a population since this is both easier to do and is a more practical measure if one is interested in determining the impact of a given population on a given ecosystem, or vice versa

(e)                    “Although we can determine an average population size for many species, the average is often of less interest than the year-to-year or place-to-place trend in numbers.” (p. 1166, Campbell & Reece, 2002)

(f)                      [population size, "population size" and "population ecology" (Google Search)] [index]

(5) Population density

(a)                    Given that a population is defined in terms of some natural or arbitrarily defined geographical range, then population density may be defined as simply the number of individual organisms per unit area

(b)                    Different species, of course, exist at different densities in their environments, and the same species may be able to achieve one density in one environment and another in a different environment

(c)                    Population densities may additionally be determined in terms of some measure other than population size per unit area such as population mass per unit area

(d)                    [population density, "population density" and "population ecology" (Google Search)] [index]

(6) Patterns of dispersion

(a)                    Individual members of populations may be distributed over a geographical area in a number of different ways including

(i)                      Clumped distribution (attraction)

(ii)                    Uniform distribution (repulsion)

(iii)                   Random distribution (minimal interaction/influence)

(b)                    See Figure 52.2, Patterns of dispersion within a population’s geographical range

(c)                    Clumping may result either from individual organisms being attracted to each other, or individual organisms being attracted more to some patches within a range than they are to other patches; the net effect is that some parts of the range will have a large number of individuals whereas others will contain few or none

(d)                    A uniform distribution means that approximately the same distance may be found between individual organisms; uniform distributions result from individual organisms actively repelling each other

(e)                    A random distribution means that where individual organisms are found is only minimally influenced by interactions with other members of the same population, and random distributions are uncommon; "Random spacing occurs in the absence of strong attractions or repulsions among individuals of a population."

(f)                      Note that both clumping and uniform distributions suggest that individual organisms are either interacting with one another (actively seeking each other out or actively avoiding each other), or are all competing with one another for the same limited resources, regardless of the overall population density (as in the case of clumping which results from geographical patchiness)

(g)                    [patterns of disperson (Google Search)] [index]




(7) Demographics

(a)                    A population's demographics are its vital statistics, particularly those statistics which can impact on present and future population size

(b)                    Two statistics that are of particular import are a population's age structure and a population's sex ratio

(c)                    Additional considerations (in human populations and for example) are considered to the right à

(d)                    [demographics (Google Search)] [Center for Demography and Ecology] [index]

(8) Age structure

(a)                    Age structure refers to the size of cohorts within a population

(b)                    Parameters related to age structure include

(i)                      Fecundity (birth rate)

(ii)                    Generation time

(iii)                   Death rate

(c)                    See Figure 52.22, Age structure pyramids for the human population of Kenya (growing at 2.1% per year), the United States (growing at 0.6% per year), and Italy (zero growth) for 1995

(d)                    Below is the actual and predicted age structure the Dutch civil service in 2000, 2005, 2010, and 2015:


(f)                      [age structure (Google Search)] [index]

(9) Cohort

(a)                    A cohort is a group of individuals all of whom have the same age

(b)                    In a typical population, the size of cohorts will vary with age

(c)                    For example, in a typical population, younger cohorts will be larger (i.e., more individuals per cohort) than older cohorts, all else being equal

(10) Fecundity [birth rate]

(a)                    Fecundity refers to the average birth rate associated with a population

(b)                    The greater a population's fecundity, all else held constant, the faster a population will increase in size

(c)                    Note that fecundity typically varies with the age of individuals

(d)                    [fecundity, birth rate (Google Search)] [index]

(11) Generation time

(a)                    Generation time is simply the average span between the birth of individuals and the birth of their offspring

(b)                    "Other factors being equal, a shorter generation time will result in faster population growth."

(c)                    Note that species which are capable of reproducing more than once will display an overlapping of generations which basically means that parental cohorts and progeny cohorts can be alive (and potentially competing with one another) at the same time

(d)                    Note that another way of saying this is that when life expectancies exceed the minimum time between generations, generations will overlap

(e)                    [generation time (Google Search)] [index]

(12) Death rate

(a)                    Death rate is the rate at which individuals of a certain age die

(b)                    Note that death rates often vary with age with either the very young or the very old displaying the greatest death rates

(c)                    Note additionally that population growth occurs when overall birth rates exceed overall death rates

(d)                    [death rate, "death rate" and "population ecology" (Google Search)] [index]

(13) Sex ratio

(a)                    More often than not the rate at which a population may grow is dependent on the sex ratio in the population; the fewer females, the slower the rate of population growth

(b)                    This, of course, is because uteruses are limiting and males often can inseminate more than one female

(c)                    This generalization falls apart, however, when males are limited in their ability to inseminate more than one female, or when males contribute significantly to the raising of offspring

(d)                    Below are sex ratios (New South Wales) as they vary with age (units on y axis are in living males per 100 females):


(f)                      [sex ratios, "sex ratios" and "population ecology" (Google Search)] [index]




(14) Survivorship curves

(a)                    Observing age structure graphically can provide insights into a species' (or a population's) ecology

(b)                    Survivorship curves graph cohort size against relative age

(c)                    See Figure 52.3, Idealized survivorship curves

(d)                    The typical survivorship curve shows cohort size declining with age

(e)                    There exist three general types of survivorship curves

(i)                      Type I

(ii)                    Type II

(iii)                   Type III

(f)                       Note in the following survivorship curves that the y axis is logarithmic!!!


(h)                    [survivorship curves (Google Search)] [index]

(15) Type II survivorship curves

(a)                    The simplest type of decline is exponential, i.e., the death rate for every cohort is the same

(b)                    These survivorship curves graph as a straight line on semi-logarithmic graph paper (i.e., as presented in a typical survivorship curve)

(c)                    The individuals in populations that display a type II curve are those that both do not age and are born as fully fit as adults, e.g., hydra

(d)                    Individuals are lost in these populations mostly to accidents and predation

(e)                    [(Google Search)] [index]

(16) Type I survivorship curves

(a)                    Because individuals tend to die exponentially due to accidents or predation, it often is a good strategy to reproduce relatively early in a life span rather than relatively late

(i)                      That way individuals achieve reproduction while they still have a reasonable likelihood of being alive

(ii)                    This is assuming, of course, that the goal is a Darwinian one, i.e., maximizing one's reproductive output

(iii)                   Note that how such a strategy works is complicated if individual fecundity increases with age

(b)                    Very often for a given species there will be some age at which individuals are maximally fecund

(c)                    Species that combine maximum fecundity with early ages typically do so at the expense of their ability to survive long periods (i.e., this is an example of the principle of allocation)

(d)                    A survivorship curve of such individuals may display a relatively shallow slope while individuals are younger (i.e., maximally robust and maximally reproductive) but then show an abrupt increase in death rate at ages that are coincident to declines in fecundity

(e)                    Humans, of course, have a type I survivorship curve; evolution makes us get married young and have lots of babies before a saber toothed tiger comes along and picks us off, i.e., à

(f)                      [(Google Search)] [index]

(17) Type III survivorship curves

(a)                    The other side of the survivorship coin is the degree of investment in individual progeny

(b)                    Some organisms invest a great deal in each offspring and those organisms are (ideally at least) rewarded with relatively high survivorship at early ages

(c)                    Other organisms invest little in individual offspring, and display very low early-age survivorship (which they make up for by producing buckets of offspring)

(d)                    Organisms that produce large numbers of cheap progeny and which display minimal declines in fecundity with age, if they survive their youth, display type III survivorship curves

(e)                    Examples include sea turtles and trees

(f)                      That is, type III survivorship species have a very large rate of mortality when young, but should they survive their youth, they put significant energy into continued survival since the longer they survive, the more progeny they will produce

(g)                    [(Google Search)] [index]




(18) Life history

(a)                    “The traits that affect an organism’s schedule of reproduction and survival (from birth through reproduction to death) make up its life history.” (p. 1156, Campbell & Reece, 2002)

(b)                    The study of life history characteristics is the detailed study of those ecological and evolutionary parameters that impact on survivorship curves

(c)                    "In many cases there are trade-offs between survival and traits such as clutch size (number of offspring per reproductive episode), frequency of reproduction, and investment in parental care. The traits that affect an organism's schedule of reproduction and death make up its life history. Of course, a particular life history pattern, like most characteristics of an organism, is the result of natural selection operating over evolutionary time."

(d)                    In other words, the Darwinian goal is to maximize lifetime reproductive output, and this can be achieved by having babies more rapidly or living longer, or some combination of the two, as well as by varying many additional details having to do with survival and reproduction

(e)                    However, different combinations of these life history parameters will result in organisms producing different numbers of surviving offspring—evolution will tend to maximize the representation in a population of those individuals who display those combinations of life history traits that maximize the number of surviving progeny they produce

(f)                      [life history (Google Search)] [index]

(19) Allocation of limited resources

(a)                    "Darwinian fitness is measured not by how many offspring are produced but by how many survive to produce their own offspring: Heritable characteristics of life history that result in the most reproductively successful descendants will become more common within the population. If we were to construct a hypothetical life history that would yield the greatest lifetime reproductive output, we might imagine a population of individuals that begin reproducing at an early age, have large clutch sizes, and reproduce many times in a lifetime. However, natural selection cannot maximize all these variables simultaneously, because organisms have a finite energy budget that mandates trade-offs. For example, the production of many offspring with little chance of survival may result in fewer offspring that can compete vigorously for limited resources in an already dense population."

(b)                    “The life history we observe in organisms represent a resolution of several conflicting demands. An important part of the study of life histories has been understanding the relationship between limited resources and competing functions: Time, energy, and nutrients that are used for one thing cannot be used for something else."

(c)                    "These issues can be phrased in terms of three basic questions:

(i)                      How often should an organism breed?

(ii)                    When should it begin to reproduce?

(iii)                   How many offspring should it produce during each reproductive episode?

(d)                    The way each population resolves these questions results in the integrated life history patterns we see in nature." (all one quote starting with (c) but broken up for clarity)

(e)                    “Many life history issues involve balancing the profit of immediate investment in offspring against the cost to future prospects of survival and reproduction. These issues can be summarized by three basic “decisions”: when to begin reproducing, how often to breed, and how many offspring to produce during each reproductive episode. The various “choices” are integrated into the life history patterns we see in nature.” (p. 1157, Campbell & Reece, 2002)

(f)                      ”It is important to clarify our use of the word choice. Organisms do not choose consciously when to breen and how many offspring to have… Life history traits are evolutionary outcomes reflected in the development, physiology, and behavior of an organism. Age at maturity and the number of offspring produced during a given reproductive episode are usually maintained within narrow ranges by stabilizing selection.” (pp. 1157-1158, Campbell & Reece, 2002)

(g)                    [allocation of limited resources (mostly not biology but fun nonetheless) (Google Search)] [index]

(20) Semelparity

(a)                    Organisms that produce one clutch of offspring (progeny) per life time are said to be semelparous (i.e., to display semelparity)

(b)                    The advantage of semelparity is that at the point of reproduction few if any resources need be devoted to survival past reproduction

(c)                    (your text also employs the phrase “Big-bang reproduction” to describe semelparity)

(b)                    [semelparity, semelparous (Google Search)]

(21) Iteroparity

(a)                    Organisms that produce more than one clutch of offspring (progeny) per life time are said to be iteroparous (i.e., to display iteroparity)

(b)                    The advantage of iteroparity is that it allows organisms to display more than one statistical “shot” at producing a successful litter

(c)                    (your text also employs the phrase “repeated reproduction” to describe iteroparity)

(d)                    “The critical factor in the evolutionary dilemma of big-bang versus repeated reproduction is the survival rate of the offspring. If their chance of survival is poor or inconsistent, repeated reproduction will be favored.” (p. 1156, Campbell & Reece, 2002)

(c)                    [iteroparity, iteroparous (Google Search)]




(22) Population growth

(a)                    The simplest case of population growth is that which occurs when there exist no limitations on growth within the environment

(b)                    In such situations two things occur

(i)                      The population displays its intrinsic rate of increase

(ii)                    The population experiences exponential growth

(c)                    [population growth, "population growth" and "population ecology"  (Google Search)] [index]

(23) Intrinsic rate of population increase (rmax) biotic potential

(a)                    The intrinsic rate of population increase is the rate of growth of a population when that population is growing under ideal conditions and without limits, i.e., as fast as it possibly can

(b)                    This rate of growth implies that the difference between the birth rate and death rate experienced by a population is maximized

(c)                    Note that the intrinsic rate of population increase is a characteristic of a population and not of its environment

(d)                    Indeed, in most environments a population is not able to achieve this maximum rate of growth

(e)                    However, a population that is not growing maximally can still experience exponential growth

(f)                      "A population with a higher intrinsic rate of increase will grow faster than one with a lower rate of increase. The value of rmax for a population is influenced by life history features, such as age at the beginning of reproduction, the number of young produced, and how well the young survive."

(g)                    [intrinsic rate of population increase, intrinsic rate of population growth, biotic potential (Google Search)] [index]

(24) Exponential growth

(a)                    Exponential growth simply means that a population's size at a given time is equal to the population's size at an earlier time, times some greater-than-one number

(b)                    For example, if a population increased in size per unit time in the following manner: 1, 2, 4, 8, 16, 32, 64, 128, etc. (or, e.g., 1, 3, 9, 27…, or 1, 5, 25, 125, …, etc.) then the population is displaying exponential growth, each unit time the population is increasing by a factor of 2 (or 3 or 5 in the other examples; note that exponential growth is occurring so long as the rate of increase per unit time is greater than a factor of 1, e.g., 2 or 4 or 10 or 1.2, etc.)

(c)                    When population size is graphed against time (e.g., generations) a population growing exponentially displays a J-shaped curve

(d)                    See Figure 52.8, Population growth predicted by the exponential model

(e)                    Note differences in intrinsic rates of growth, in this J-shaped curves, that result in differences in rates of exponential growth  (declining intrinsic growth rates are seen going from left to right in this graph):


(g)                    See Figure 52.20, Human population growth

(h)                    [In a rich culture medium bacteria, grown under aerobic conditions, achieve a final concentration of 2-5 x 109 cells per ml in about 12-18 hours. Although plotted on a different time scale the human growth curve looks the same; the human population at similar points on the growth curve are shown in red.

(i)                      ]

(j)                      When population size is graphed against time (e.g., generations) a population growing exponentially displays a straight line curve when graphed on semi-logarithmic graph paper (for example, below is a graph of the exponential increase in the computer processing power available per dollar—note that on log-linear graph paper this curve is approximately a straight line):


(l)                      "The J-shaped curve of exponential growth is characteristic of populations that are introduced into a new or unfilled environment, or whose numbers have been drastically reduced by a catastrophic event and are rebounding."

(m)                  In other words, a population that is in an environment lacking limits will grow exponentially (indeed, a population that is capable of growing will tend to grow exponentially), and the rate at which growth will occur will be a function of rmax and the degree to which the environment matches the ideal environment in which an organism is capable of achieving rmax.

(n)                    [exponential growth (Google Search)] [index]

(25) Limits on population growth

(a)                    Exponential growth cannot go on forever; sooner or later any population will run into limits in their environment

(b)                    [limits on population growth (Google Search)] [index]

(26) Carrying capacity (K)

(a)                    "Populations subsist on a finite amount of available resources, and as the population becomes more crowded, each individual has access to an increasingly smaller share. Ultimately, there is a limit to the number of individuals that can occupy a habitat. Ecologists define carrying capacity as the maximum stable population size that a particular environment can support over a relatively long period of time. Carrying capacity, symbolized as K, is a property of the environment, and it varies over space and time with the abundance of limiting resources."

(b)                    In other words, for any given organism, there will be a maximum number of individuals that the environment can support without the environment being consequently degraded to the point where it can no longer support that number of individuals

(c)                    Generally, as population size approaches carrying capacity, the amount of some key resource declines per capita to the point where individuals experience either a higher death rate or a lower fecundity; thus, as population size approaches carrying capacity, the rate of population growth declines towards zero

(d)                    See Figure 52.10, Reduction of population growth rate with increasing population size (N)

(e)                    [carrying capacity (Google Search)] [index]

(27) Logistic growth

(a)                    Logistic growth is a mathematical description of population growth that employs two parameters, rmax and K, and two variables, N and t

(b)                    The logistic growth curve is S-shaped

(c)                    See Figure 52.11, Population growth predicted by the logistic model


(e)                    That is, the population grows exponentially at a rate which is determined by rmax and the suitability of a given environment to an organism’s needs until population size is sufficient that the limitations associated with the carrying capacity of the environment are approached

(f)                      This slows the rate of population growth in a way such that the larger the population becomes, the slower its rate of growth; this slowing of the growth transforms the curve from a J-shaped one to an S-shaped one

(g)                    Ultimately the rate of growth of the population reaches zero at the carrying capacity

(h)                    See Figure 52.10, Reduction of population growth rate with increasing population size (N)

(i)                      "Because the rate at which a population grows changes with the density of organisms that are currently in the population, the logistic model is said to be density dependent." That is, population growth grows as population density approaches that dictated by an environment’s carry capacity for that population

(j)                      Note that populations do not typically display the idealized logistic growth seen with the model

(k)                    One deviation from idealized logistic growth is delayed feedback; this can cause population size overshooting and, in fact, what is typically observed in real populations is not just effects of random events but also populations sizes which vary up and down around the carrying capacity rather than remaining invariant exactly at the carrying capacity

(l)                      [logistic growth (Google Search)] [index]

(28) K-selected populations (equilibrial populations)

(a)                    Idealized populations may be distinguished in terms of the logistic growth equation

(b)                    For example, a species may bias its life history toward maximizing either rmax or K

(c)                    That is, some organisms are good at increasing their population size rapidly in environments which lack limits (e.g., weeds) while other species (e.g., gorillas) are good at maintaining population sizes at carrying capacity in environments that have limits

(d)                    A species that is better at maintaining a population at carrying capacity in a stable environment is said to be more K-selected

(e)                    A typical K-selected species is shown to the right à

(f)                      [equilibrial populations (Google Search)] [index]

(29) r-selected populations (opportunistic populations)

(a)                    A species that is good at growing rapidly in, for example, disturbed environments, but is significantly less capable of maintaining its population at carrying capacity in undisturbed (i.e., stable) environments is termed r-selected


(c)                    [opportunistic populations (Google Search)] [index]

(30) r and K selection compared

(a)                    Few species are purely r- or K-selected; e.g., there certainly exist populations that are able to increase rapidly but may also thrive in mature ecosystems

(b)                    "It has been difficult to demonstrate a direct relationship between population growth rate and specific life history characteristics. Increasingly, ecologists are recognizing that most populations show a mix of the traditional r-selected and K-selected characteristics; life history evolves in the context of a complex interplay of factors."

(c)                    Nevertheless, consider the following generalizations (adapted from




Unstable environment, density independent


Stable environment, density dependent interactions

Organism size



Energy used to make each individual



# Offspring produced



Timing of maturation



(with much parental care)

Life expectancy



Lifetime reproductive events


More than one

Survivorship curve

Type III

Type I or II


(d)                    “Plants and animals whose young are subject to high mortality rates often produce large numbers of offspring. Thus, plants that colonize disturbed environments usually produce many small seeds, most of which will not reach a suitable environment. Small size might actually benefit such seeds if it enables them to be carried long distances… In other organisms, extra investment on the part of the parent greatly increases the offspring’s change of survival.” (pp. 1158, Campbell, & Reece, 2002)

(e)                    Question: are humans K selected, or are we r selected? In other words, do we wisely maintain our populations at or below carrying capacity? Or do we have a tendency to moronically grow our populations until our local environment, and then our entire planet, has been turned into a sewer? (hey, don’t worry, I’m sure wallowing for eternity in our own excrement has its upsides… though off hand none have occurred to me)




(31) Density-dependent factors

(a)                    Density-dependent limits on population growth are ones that stem from intraspecific competition

(b)                    Typically, the organisms best suited to compete with another organism are those from the same species

(c)                    Thus, the actions of conspecifics can very precisely serve to limit the environment (e.g., eat preferred food, obtain preferred shelter, etc.)

(d)                    Actions of that serve to limit the environment for conspecifics—e.g., eating, excreting wastes, using up non-food resources, taking up space, defending territories—are those that determine carrying capacity

(e)                    They are referred to as density dependent because the greater the density of the population, the greater their effects

(f)                      Density-dependent factors may exert their effect by reducing birth rates, increasing death rates, extending generation times, or by forcing the migration of conspecifics to new regions

(g)                    “The impact of disease on a population can be density dependent if the transmission rate of the disease depends on a certain level of crowding in the population.” (p. 1165, Campbell & Reece, 2002)

(h)                    “A death rate that rises as population density rises is said to be density dependent, as is a birth rate that falls with rising density. Density-dependent rates are an example of negative feedback, a type of regulation you learned about in Chapter 1. In contrast, a birth rate or death rate that does not change with population density is said to be density independent… Negative feedback prevents unlimited population growth.” (pp. 1163-1164, Campbell & Reece, 2002)

(i)                      Predation can also be density dependent since predators often can switch prey preferences to match whatever prey organisms are most plentiful in a given environment

(j)                      “Many predators, for example, exhibit switching behavior: They begin to concentrate on a particularly common species of prey when it becomes energetically efficient to do so (see the discussion of optimal foraging in Chapter 51).” (p. 1165, Campbell & Reece, 2002)

(k)                   See Figure 52.14, Decreased fecundity at high population densities

(l)                      See Figure 52.15, Decreased survivorship at high population densities

(m)                  [density-dependent factors (Google Search)] [index]

(32) Density-independent factors

(a)                    Density-independent effects on population sizes (or structures) occur to the same extent regardless of population size

(b)                    These can be things like sudden changes in the weather

(c)                    "Over the long term, many populations remain fairly stable in size and are presumably close to a carrying capacity that is determined by density-dependent factors. Superimposed on this general stability, however, are short-term fluctuations due to density-independent factors."

(d)                    See Figure 52.18, Extreme population fluctuations

(e)                    [density-independent factors (Google Search)] [index]




(33) Vocabulary

(a)                    Age structure

(b)                    Allocation of limited resources

(c)                    birth rate

(d)                    Carrying capacity

(e)                    Cohort

(f)                      Death rate

(g)                    Demographics

(h)                    Density-dependent factors

(i)                      Density-independent factors

(j)                      Equilibrial populations

(k)                    Exponential growth

(l)                      Fecundity

(m)                  Generation time

(n)                    Intrinsic rate of population increase

(o)                    Iteroparity

(p)                    K

(q)                    K-selected populations

(r)                     Life history

(s)                     Limits on population growth

(t)                      Logistic growth

(u)                    Opportunistic populations

(v)                    Patterns of dispersion

(w)                  Population

(x)                    Population density

(y)                    Population ecology

(z)                     Population growth

(aa)                 Population size

(bb)                r max

(cc)                 r-selected populations

(dd)                Semelparity

(ee)                 Sex ratio

(ff)                    Survivorship curves

(gg)                 Type I survivorship curves

(hh)                 Type II survivorship curves

(ii)                     Type III survivorship curves