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The performance (common measures include locomotion, growth, development, fecundity, and survivorship) of poikilotherms varies as a function of body temperature. As with plants (see Section 6.6, Figure 6.6), each species has minimum and maximum temperatures at which performance approaches zero (*T*min and *T*max) and a... | {
"Header 1": "7.9 Poikilotherms Regulate Body Temperature Primarily through Behavioral Mechanisms",
"token_count": 2036,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The maximal sustained swimming performance of estuarine crocodiles (*Crocodylus porosus*) shifts significantly with acclimation and coincides with mean body temperatures within each treatment (blue line, cold acclimation; red line, warm acclimation). Water temperatures for cold (blue) and warm (red) water treatment are... | {
"Header 1": "7.9 Poikilotherms Regulate Body Temperature Primarily through Behavioral Mechanisms",
"token_count": 372,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Homeothermic birds and mammals meet the thermal constraints of the environment by being endothermic. Their body temperature is maintained by the oxidization of glucose and other energy-rich molecules in the process of respiration. The process of oxidation is not 100 percent efficient, and in addition to the production ... | {
"Header 1": "7.10 Homeotherms Regulate Body Temperature through Metabolic Processes",
"token_count": 1165,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Prime examples of the trade-offs involved in the adaptations of organisms to their environment are endothermy and ectothermy, which are the two alternative approaches to regulation of body temperature in animals. Each strategy has advantages and disadvantages that enable the organisms to excel under different environme... | {
"Header 1": "7.11 Endothermy and Ectothermy Involve Trade-offs",
"token_count": 1118,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Species that sometimes function as homeotherms while at other times as poikilotherms are called temporal **heterotherms**. At different stages of their daily and seasonal cycle or in certain situations, these animals take on characteristics of endotherms or ectotherms. They can undergo rapid, drastic, repeated changes ... | {
"Header 1": "7.12 Heterotherms Take on Characteristics of Ectotherms and Endotherms",
"token_count": 1303,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Because of an animal's limited tolerance for heat, storing body heat does not seem like a sound option to maintain thermal balance in the body. But certain mammals, especially the camel, oryx, and some gazelles, do just that. The camel, for example, stores body heat by day and dissipates it by night, especially when wa... | {
"Header 1": "7.13 Some Animals Use Unique Physiological Means for Thermal Balance",
"token_count": 1292,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
One of the most fundamental factors defining the relationship between an organism and the environment is the place where it is found, its **habitat**. The millions of species that inhabit our planet are not found everywhere, nor are they distributed at random across Earth's environments. There is a correspondence betwe... | {
"Header 1": "7.14 An Animal's Habitat Reflects a Wide Variety of Adaptations to the Environment",
"token_count": 1433,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Body size is one of the most important phenotypic traits of animals, influencing virtually all physiological and ecological processes (Section 7.1). Variation in body size, both geographically and through time, is a common phenomenon and assumed to be a product of adaptation through natural selection (see Section 5.6).... | {
"Header 1": "Ecologica l Issues & Applications",
"Header 3": "Increasing Global Temperature Is Affecting the Body Size of Animals",
"token_count": 2023,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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#### Energy Exchange 7.7
Animals maintain a fairly constant internal body temperature, known as the body core temperature. They use behavioral and physiological means to maintain a heat balance in a variable environment. Layers of muscle fat and surface insulation of scales, feathers, and fur insulate the animal bo... | {
"Header 1": "Ecologica l Issues & Applications",
"Header 3": "Increasing Global Temperature Is Affecting the Body Size of Animals",
"token_count": 2009,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Princeton, NJ: Princeton University Press.
- This short book provides an excellent overview of the constraints imposed by body size in the evolution and ecology of animals from one of the leading figures in the field.
- French, A. R. 1988. "The patterns of mammalian hibernation." *American Scientist* 76:569–575.
- Th... | {
"Header 1": "Ecologica l Issues & Applications",
"Header 3": "Increasing Global Temperature Is Affecting the Body Size of Animals",
"token_count": 583,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 8.1 Organisms May Be Unitary or Modular
- 8.2 The Distribution of a Population Defines Its Spatial Location
- 8.3 Abundance Reflects Population Density and Distribution
- 8.4 Determining Density Requires Sampling
- 8.5 Measures of Population Structure Include Age, Developmental Stage, and Size
- 8.6 Sex Ratios in Pop... | {
"Header 1": "Chapter Guide",
"token_count": 476,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
A population is considered to be a group of individuals, but what constitutes an individual? For most of us, defining an individual would seem to be no problem. We are individuals, and so are dogs, cats, spiders, insects, fish, and so on throughout much of the animal kingdom. What defines us as individuals is our unita... | {
"Header 1": "**8.1** Organisms May Be Unitary or Modular",
"token_count": 1039,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Department of Biological Sciences, University of Wisconsin-Milwaukee
umerous plant species reproduce both sexually and asexually. For example, many grass species form dense mats of ramets through the growth of rhizomes or stolons, yet also produce new offspring by flowering and through seed production (new genets). F... | {
"Header 1": "8.2 The Distribution of a Population Defines Its Spatial Location",
"Header 3": "FIELD STUDIES Filipe Alberto",
"token_count": 2046,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
each red dot in Figure 8.4 represents an individual's position within a population on the landscape, we can draw a line (shown in blue) defining the population distribution—a spatial boundary within which all individuals in the population reside. When the defined area encompasses all the individuals of a species, the... | {
"Header 1": "8.2 The Distribution of a Population Defines Its Spatial Location",
"Header 3": "FIELD STUDIES Filipe Alberto",
"token_count": 1639,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Whereas distribution defines the spatial extent of a population, **abundance** defines its size—the number of individuals in the population. In Figure 8.4, the population abundance is the total number of red dots (individuals) within the blue line that defines the population distribution.
Abundance is a function of t... | {
"Header 1": "**8.3** Abundance Reflects Population Density and Distribution",
"token_count": 1338,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Population size (abundance) is a function of population density and the area that is occupied (geographic distribution). In other words, population size + density × area. But how is density determined? When both the distribution (spatial extent) and abundance are small—as in the case of many rare or endangered species—... | {
"Header 1": "8.4 Determining Density Requires Sampling",
"token_count": 1657,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Abundance describes the number of individuals in the population but provides no information on their characteristics—that is, how individuals within the population may differ from one another. Unless each generation reproduces and dies in a single season, not overlapping the next generation (such as annual plants and m... | {
"Header 1": "8.5 Measures of Population Structure Include Age, Developmental Stage, and Size",
"token_count": 1572,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Populations of sexually reproducing organisms in theory tend toward a 1:1 sex ratio (the proportion of males to females). The primary sex ratio (the ratio at conception) also tends to be 1:1. This statement may not be universally true, and it is, of course, difficult to confirm.
In most mammalian populations, includi... | {
"Header 1": "8.6 Sex Ratios in Populations May Shift with Age",
"token_count": 547,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
At some stage in their lives, most organisms are mobile to some degree. The movement of individuals directly influences their local density. The movement of individuals in space is referred to as **dispersal**, although the term *dispersal* most often refers to the more specific movement of individuals away from one an... | {
"Header 1": "8.7 Individuals Move within the Population",
"token_count": 1461,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Dispersal has the effect of shifting the spatial distribution of individuals and consequently the localized patterns of population density. Emigration may cause density in some areas to decline, whereas immigration into other areas increases the density of subpopulations or even establishes new subpopulations in habita... | {
"Header 1": "8.8 Population Distribution and Density Change in Both Time and Space",
"token_count": 501,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Dispersal is a key feature of the life histories of all species, and a diversity of mechanisms have evolved to allow plant and animal species to move across the landscape and seascape. In plants, seeds and spores can be dispersed by wind, water, or through active dispersal by animals (see Section 15.14). In animals, th... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Humans Aid in the Dispersal of Many Species, Expanding Their Geographic Range",
"token_count": 2035,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The distribution of a population is influenced by the occurrence of suitable environmental conditions. Within the geographic range of a population, individuals are not distributed equally throughout the area. Therefore, the distribution of individuals within the population can be described as a range of different spati... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Humans Aid in the Dispersal of Many Species, Expanding Their Geographic Range",
"token_count": 871,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
#### Classic Studies
Cook, R. E. 1983. "Clonal plant populations." *American Scientist* 71:244–253.
An introduction to the nature of modular growth in plants and its implications for the study of plant populations.
Elton, C. S. 1958. *The ecology of invasions by animals and plants*. London: Methuen and Co. Ltd. ... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Further Readings",
"token_count": 851,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 9.1 Population Growth Reflects the Difference between Rates of Birth and Death
- 9.2 Life Tables Provide a Schedule of Age-Specific Mortality and Survival
- 9.3 Different Types of Life Tables Reflect Different Approaches to Defining Cohorts and Age Structure
- 9.4 Life Tables Provide Data for Mortality and Survivorsh... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Chapter guide",
"token_count": 417,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Suppose we were to undertake an experiment in which we monitor a population of an organism that has a very simple life cycle, such as a population of freshwater hydra (**Figure 9.2**) growing in an aquarium in the laboratory. Most reproduction is asexual, involving a process termed *budding*, in which a new hydra devel... | {
"Header 1": "9.1 Population Growth Reflects the Difference between Rates of Birth and Death",
"token_count": 2031,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The model of exponential growth (d*N*/d*t* = *rN*) predicts the rate of population change over time. If we wish to define the equation to predict population size, *N*(*t*), under conditions of exponential growth [*N*(*t*) at any given value of *t*], it is necessary to integrate the differential equation presented pre... | {
"Header 1": "9.1 Population Growth Reflects the Difference between Rates of Birth and Death",
"token_count": 807,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As we established in the previous section, change in population abundance over time is a function of the rates of birth and death, as represented by the per capita growth rate *r.* But how do ecologists estimate the per capita growth rate of a population? For the hydra population, where all individuals can be treated a... | {
"Header 1": "9.2 Life Tables Provide a Schedule of Age-Specific Mortality and Survival",
"token_count": 2047,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
x
$$n_x$$
$T_x$
$e_x$
0
530
578.0
1.09
1
159
233.5
1.47
2
80
114.0
1.43
3
48
50.0
1.06
4
21
15.5
0.75
5
5
2.5
0.50
$$= T_0 / n_0 = 578 / 530 = 1.09$$
$$= T_2 / n_2 = 114 / 80 = 1.43$$
Note that life expectancy changes with age. On average, at birth gray squirrel individuals can expect to live for ... | {
"Header 1": "9.2 Life Tables Provide a Schedule of Age-Specific Mortality and Survival",
"token_count": 341,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
There are two basic kinds of life tables. The first type is the **cohort** or **dynamic life table**. This is the approach used in constructing the gray squirrel life table presented in Table 9.1. The
fate of a group of individuals, born at a given time, is followed from birth to death—for example, a group of individ... | {
"Header 1": "9.3 Different Types of Life Tables Reflect Different Approaches to Defining Cohorts and Age Structure",
"token_count": 1067,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Although we can graphically display data from any of the columns in a life table, the two most common approaches are the construction of (1) a mortality curve based on the *qx* column and (2) a survivorship curve based on the *lx* column. A mortality curve plots mortality rates in terms of *qx* as a function of age. Mo... | {
"Header 1": "9.4 Life Tables Provide Data for Mortality and Survivorship Curves",
"token_count": 1082,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
A standard convention in demography (the study of populations) is to express birthrates as births per 1000 individuals of a population per unit of time. This figure is obtained by dividing the number of births that occurred during some period of time (typically a year) by the estimated population size at the beginning ... | {
"Header 1": "9.5 Birthrate Is Age-Specific",
"token_count": 524,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
We can use the gray squirrel population as the basis for constructing a fecundity, or fertility, table (Table 9.4). The **fecundity table** uses the survivorship column, *lx*, from the life
| Table 9.4 | Gray Squirrel Fecundity Table | | | | | |
|-----------|-------------------------------|------|------|... | {
"Header 1": "9.6 Birthrate and Survivorship Determine Net Reproductive Rate",
"token_count": 764,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Age-specific mortality rates (*qx*) from the life table together with the age-specific birthrates (*bx*) from the fecundity table can be combined to project changes in the population into the future. To simplify the process, the values for age-specific mortality are converted to age-specific survival. If *qx* is the pr... | {
"Header 1": "9.7 Age-Specific Mortality and Birthrates Can Be Used to Project Population Growth",
"token_count": 1457,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The population projection table demonstrates two important concepts of population growth: (1) the rate of population growth, as estimated by λ, is a function of the age-specific rates of survival (*sx*) and birth (*bx*), and (2) the constant rate of
| Table 9.6 | Population Projection Table, Squirrel Population |
|... | {
"Header 1": "9.7 Age-Specific Mortality and Birthrates Can Be Used to Project Population Growth",
"token_count": 796,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The construction of life tables and their use in the development of population projection tables are important approaches in studying the dynamics of age-structured populations. We can represent the steps involved in the construction of the population projection table presented in Table 9.6 graphically using a life his... | {
"Header 1": "QUANTIFYING ECOLOGY 9.2 Life History Diagrams and Population Projection Matrices",
"token_count": 1995,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
This can be shown simply by multiplying both sides of the equation for $\lambda$ shown previously by the current population size, N(t), giving:
$$N(t+1) = N(t)\lambda$$
We can predict the population size at year 1 by multiplying the initial population size N(0) by $\lambda$ , and for year 2 by multiplying N(1) b... | {
"Header 1": "QUANTIFYING ECOLOGY 9.2 Life History Diagrams and Population Projection Matrices",
"token_count": 1037,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Thus far we have considered population growth as a deterministic process. Because the rates of birth and death are assumed to be constant for a given set of initial conditions — values of r or $\lambda$ and N(0) — both the exponential and geometric models of population growth will predict only one exact outcome. Reca... | {
"Header 1": "9.8 Stochastic Processes Can Influence Population Dynamics",
"token_count": 681,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
When deaths exceed births, populations decline. $R_0$ becomes less than 1.0, and r becomes negative. Unless the population reverses the trend, it may become so low that it declines toward extinction (see Figure 9.4).
Small populations—because of their greater vulnerability to demographic and environmental stochasti... | {
"Header 1": "9.9 A Variety of Factors Can Lead to Population Extinction",
"token_count": 610,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
A multitude of ecological studies over the past several decades have documented a pattern of population decline and extinction for an ever-growing number of plant and animal species across the planet (Figure 9.14). The primary cause of current population extinctions is the loss of habitat as a result of human activitie... | {
"Header 1": "The Leading Cause of Current Population Declines and Extinctions Is Habitat Loss",
"token_count": 2050,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As the time interval over which population change is evaluated decreases, approaching zero, the change in population size is expressed as a continuous function, and the resulting pattern is termed *exponential population growth.* The difference in the instantaneous per capita rates of birth and death is defined as *r,*... | {
"Header 1": "The Leading Cause of Current Population Declines and Extinctions Is Habitat Loss",
"token_count": 1686,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 10.1 The Evolution of Life Histories Involves Trade-offs
- 10.2 Reproduction May Be Sexual or Asexual
- 10.3 Sexual Reproduction Takes a Variety of Forms
- 10.4 Reproduction Involves Both Benefits and Costs to Individual Fitness
- 10.5 Age at Maturity Is Influenced by Patterns of Age-Specific Mortality
- 10.6 Reprodu... | {
"Header 1": "The Leading Cause of Current Population Declines and Extinctions Is Habitat Loss",
"Header 3": "Chapter Guide",
"token_count": 509,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
If reproductive success (the number of offspring that survive to reproduce) is the measure of fitness, imagine designing an organism with the objective of maximizing its fitness. It would reproduce as soon as possible after birth, and it would reproduce continuously, producing large numbers of large offspring that it w... | {
"Header 1": "10.1 The Evolution of Life Histories Involves Trade-offs",
"token_count": 372,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In Chapter 5, we explored how genetic variation among individuals within a population arises from the shuffling of genes and chromosomes in sexual reproduction. In sexual reproduction between two diploid individuals, the individuals produce haploid (one-half the normal number of chromosomes) gametes—egg and sperm—that ... | {
"Header 1": "**10.2** Reproduction May Be Sexual or Asexual",
"token_count": 868,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Sexual reproduction takes a variety of forms. The most familiar involves separate male and female individuals. It is common to most animals. Plants with that characteristic are called **dioecious** (Greek *di*, "two," and *oikos*, "home"; **Figure 10.1a**).
In some species, individual organisms possess both male and ... | {
"Header 1": "10.3 Sexual Reproduction Takes a Variety of Forms",
"token_count": 965,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
To understand how trade-offs function to influence natural selection requires an understanding of the balance between benefits and costs associated with a phenotypic trait. If the objective of reproduction is to maximize the relative fitness of the individual, then the benefit of increasing the number of offspring prod... | {
"Header 1": "10.4 Reproduction Involves Both Benefits and Costs to Individual Fitness",
"token_count": 1291,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
When should an organism begin the process of reproduction? Some species begin reproduction early in their life cycle, whereas others have a period of growth and development before
**Figure 10.7*... | {
"Header 1": "10.5 Age at Maturity Is Influenced by Patterns of Age-Specific Mortality",
"token_count": 2039,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Laboratory studies and comparative data from natural populations, as well as a number of long-term experiments in which patterns of mortality have been manipulated, support the prediction that natural selection favors earlier maturation when adult survival is reduced, and conversely, that it favors delayed maturation... | {
"Header 1": "10.5 Age at Maturity Is Influenced by Patterns of Age-Specific Mortality",
"token_count": 430,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Fecundity is the number of offspring produced per unit of time $(b_x)$ , but the energetic costs of reproduction include a wide variety of physiological and behavioral activities in addition to the energy and nutrient demands of the reproductive event,
**Figure 10.10** Experiment in wh... | {
"Header 1": "10.6 Reproductive Effort Is Governed by Trade-offs between Fecundity and Survival",
"token_count": 2053,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The dashed line represents the sum of the values for current and future reproduction for any given allocation to reproduction (value along *x*-axis). The dashed line reaches its maximum value
Figure 10.15 Examples of the trade-off between number of offspri... | {
"Header 1": "10.6 Reproductive Effort Is Governed by Trade-offs between Fecundity and Survival",
"token_count": 339,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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In theory, a given allocation to reproduction can potentially produce many small offspring or fewer large ones (Figure 10.15). The number of offspring affects the parental investment each receives. If the parent produces a large number of young, it can afford only minimal investment in each one. In such cases,
Figure... | {
"Header 1": "10.7 There Is a Trade-off between the Number and Size of Offspring",
"token_count": 889,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
How should an organism invest its allocation to reproduction through time? Thus far we have focused on age-structured populations in which reproduction begins with the onset of maturity and continues over some period of time until either reproduction ceases (postreproductive period) or senescence occurs. Organisms that... | {
"Header 1": "10.8 Species Differ in the Timing of Reproduction",
"token_count": 646,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
any of the life history characteristics discussed in this chapter involve trade-offs, and understanding the nature of trade-offs involves the analysis of costs and benefits for a particular trait.
One trade-off in reproductive effort discussed in Section 10.7 involves the number and size of offspring produced. The gr... | {
"Header 1": "10.8 Species Differ in the Timing of Reproduction",
"Header 3": "QUANTIFYING ECOLOGY 10.1 Interpreting Trade-offs",
"token_count": 739,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Natural selection acts on phenotypic variation among individuals within the population and variation in life history characteristics, such as age at maturity, allocation to reproduction, and the average number and size of offspring produced, is common
Figure 3
In wet environments, whe... | {
"Header 1": "10.9 An Individual's Life History Represents the Interaction between Genotype and the Environment",
"token_count": 1439,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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In all sexually reproducing species there is a social framework involving the selection of mates. The pattern of mating between males and females in a population is called the **mating system** (also see Chapter 5). The structure of mating systems in animal species ranges from **monogamy**, which involves the formation... | {
"Header 1": "10.10 Mating Systems Describe the Pairing of Males and Females",
"token_count": 1509,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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For females, the production and care of offspring represents the largest component of reproduction expenditure. For males, however, the acquisition of a mate is often the major energetic expenditure that influences fitness.
The flamboyant plumage of the peacock (Figure 10.20c) presented a troubling problem for Charle... | {
"Header 1": "10.11 Acquisition of a Mate Involves Sexual Selection",
"token_count": 2047,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The results suggest that sexual selection through female choice will influence the relative fitness of males. The benefit of having a long sword is the increased probability of mating. But what is the cost? Locomotion accounts for a large part of the energy budget of fish, and the elongated caudal fin (sword) of the ma... | {
"Header 1": "10.11 Acquisition of a Mate Involves Sexual Selection",
"token_count": 1239,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
A female exhibits two major approaches in choosing a mate. In the sexual selection discussed previously, the female selects a mate for characteristics such as exaggerated plumage or displays that are indirectly related to the health and quality of the male as a mate. The second approach is that the female bases her cho... | {
"Header 1": "10.12 Females May Choose Mates Based on Resources",
"token_count": 938,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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Nature presents us with a richness of form and function in the diversity of life that inhabits our planet. Some species are large, and others are small. Some mature early, and others mature later in their lives. Some organisms produce only a few offspring over their lifetime, whereas other species produce thousands in ... | {
"Header 1": "10.13 Patterns of Life History Characteristics Reflect External Selective Forces",
"token_count": 1760,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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The history of the human population presents what appears to be a classic example of exponential population growth, yet on closer inspection, what emerges is a story of a species that has redefined its life history through a series of technological, cultural, and economic changes over the past two centuries.
With the... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "The Life History of the Human Population Reflects Technological and Cultural Changes",
"token_count": 1952,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
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#### Trade-offs 10.1
Organisms face trade-offs in life history characteristics related to reproduction. Trade-offs are necessitated by the constraints of physiology, energetics, and the prevailing physical and biotic environment. Trade-offs involve conflicting demands on resources or negative correlation among traits... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "S ummary",
"token_count": 1928,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 11.1 The Environment Functions to Limit Population Growth
- 11.2 Population Regulation Involves Density Dependence
- 11.3 Competition Results When Resources Are Limited
- 11.4 Intraspecific Competition Affects Growth and Development
- 11.5 Intraspecific Competition Can Influence Mortality Rates
- 11.6 Intraspecific C... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "CHAPTER GUIDE",
"token_count": 289,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The exponential model of population growth that we developed in Chapter 9 [dN/dt = (b - d)N] is based on several assumptions about the environment in which the population is growing. The model assumes that essential resources (space, food, etc.) are unlimited and that the environment is constant, but this is not the ca... | {
"Header 1": "11.1 The Environment Functions to Limit Population Growth",
"token_count": 1112,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
We can solve for the population size at which b = d by setting the equation for population growth developed in Section 11.1 equal to zero and solving for N:
$$\frac{dN}{dt} = [(b_0 - aN) - (d_0 + cN)]N = 0$$
$(b_0 - aN)N - (d_0 + cN)N = 0$ (move the term for death rate to the right side of the equation)
$$(b_0 - ... | {
"Header 1": "11.1 The Environment Functions to Limit Population Growth",
"Header 3": "QUANTIFYING ECOLOGY 11.1 Defining the Carrying Capacity (K)",
"token_count": 1595,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The concept of carrying capacity suggests a negative feedback between population increase and resources available in the environment. As population density increases, the per capita availability of resources declines. The decline in per capita resources eventually reaches some crucial level at which it functions to reg... | {
"Header 1": "**11.2** Population Regulation Involves Density Dependence",
"token_count": 547,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Implicit in the concept of carrying capacity is competition among individuals for essential resources. **Competition** occurs when individuals use a common resource that is in short supply relative to the number seeking it. Competition among individuals of the same species is referred to as **intraspecific competition*... | {
"Header 1": "11.3 Competition Results When Resources Are Limited",
"token_count": 515,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Because the intensity of intraspecific competition is usually density dependent, it increases gradually, and at first affects growth and development. Later, it affects individual survival and reproduction.
As population density increases toward a point at which resources are insufficient to provide for all individual... | {
"Header 1": "11.4 Intraspecific Competition Affects Growth and Development",
"token_count": 1387,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In addition to suppressing the growth of individuals, competition for resources at high population densities can function to reduce survival (Figure 11.8). In turn, mortality functions to increase per capita resource availability, allowing for increased growth of the surviving individuals. This link between densitydepe... | {
"Header 1": "11.5 Intraspecific Competition Can Influence Mortality Rates",
"token_count": 1049,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Besides directly influencing the survival and growth of individuals, competition within a population can reduce fecundity. The timing of the response depends on the nature of the population, and the mechanisms by which competition influences reproductive rate can vary with species. Harp seals (*Phoca groenlandica*) bec... | {
"Header 1": "11.6 Intraspecific Competition Can Reduce Reproduction",
"token_count": 1301,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As a population reaches a high density, individual living space can become restricted. Often, aggressive contacts among individuals increase. One hypothesis of population regulation in animals is that increased crowding and social contact cause stress. Such stress triggers hormonal changes that can suppress growth, cur... | {
"Header 1": "11.7 High Density Is Stressful to Individuals",
"token_count": 2049,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In addition to the influence of the ENSO cycle, Sillett and his colleagues observed density-dependent regulation of fecundity rates at the New Hampshire site over the period of study. Using a series of experiments in which population density of areas of the study site were manipulated through the removal of breeding ... | {
"Header 1": "11.7 High Density Is Stressful to Individuals",
"token_count": 613,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Instead of coping with stress, some animals disperse, leaving the population to seek vacant habitats (Section 8.7). Although dispersal is most apparent when population density is high, it occurs all the time. Some individuals leave the parent population whether it is crowded or not. There is no hard-and-fast rule about... | {
"Header 1": "11.8 Dispersal Can Be Density Dependent",
"token_count": 466,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Intraspecific competition can express itself in social behavior, or the degree to which individuals of the same species tolerate one another. Social behavior appears to be a mechanism that limits the number of animals living in a particular habitat, having access to a common food supply, and engaging in reproductive ac... | {
"Header 1": "11.9 Social Behavior May Function to Limit Populations",
"token_count": 870,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The area that an animal normally uses during a year is its **home range**. Overall size of the home range varies with the available food resources, mode of food gathering, body size, and metabolic needs. Among mammal species, the home-range size is related to body size (Figure 11.16), which reflects the link between bo... | {
"Header 1": "11.10 Territoriality Can Function to Regulate Population Growth",
"token_count": 1198,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Plants are not territorial in the same sense that animals are, but plants can capture and hold onto space. Plants from dandelions to trees occupy a certain amount of space and exclude individuals of their own and other species. When a dandelion plant spreads its rosettes of leaves on the ground, it eliminates all other... | {
"Header 1": "11.11 Plants Preempt Space and Resources",
"token_count": 971,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In contrast to the model of declining rates of birth and survival with increasing population size presented in Section 11.1 (see Figure 11.1), density-dependent mechanisms have also been identified that function to reduce rates of birth and survival at low population densities. This is referred to as the **Allee effect... | {
"Header 1": "11.12 A Form of Inverse Density Dependence Can Occur in Small Populations",
"token_count": 1575,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
We have seen that population growth and fecundity are heavily influenced by density-dependent responses. But there are other, often overriding influences on population growth that do not relate to density. These influences are termed **density independent**. Factors such as temperature, precipitation, and natural disas... | {
"Header 1": "11.13 Density-Independent Factors Can Influence Population Growth",
"token_count": 821,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Human activities and associated habitat loss have resulted in population decline for an ever-increasing number of plant and animal species (see Chapter 9, *Ecological Issues & Applications*). Often, these populations are restricted to protected areas (nature reserves, etc.), and an adequate conservation plan requires t... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "The Conservation of Populations Requires an Understanding of Minimum Viable Population Size and Carrying Capacity",
"token_count": 2040,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
#### Competition and Reproduction 11.6
High population density and competition can also function to delay reproduction in animals and reduce fecundity in both plants and animals.
#### Density and Stress 11.7
In animals, the stress of crowding may cause delayed reproduction, abnormal behavior, and reduced abilit... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "The Conservation of Populations Requires an Understanding of Minimum Viable Population Size and Carrying Capacity",
"token_count": 657,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- **1.** What is the difference between the exponential and logistic models of population growth?
- **2.** What is the difference between density-dependent and density-independent population regulation?
- **3.** We have seen from many examples in Chapter 11 that competition among individuals within a population can res... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Study Q ues ti ons",
"token_count": 1181,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 12.1 Species Interactions Can Be Classified Based on Their Reciprocal Effects
- 12.2 Species Interactions Influence Population Dynamics
- 12.3 Species Interactions Can Function as Agents of Natural Selection
- 12.4 The Nature of Species Interactions Can Vary across Geographic Landscapes
- 12.5 Species Interactions Ca... | {
"Header 1": "Ecologic al Issues & Applications",
"Header 3": "Chapter Guide",
"token_count": 873,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
If we designate the positive effect of one species on another as +, a detrimental effect as -, and no effect as 0, we can use this qualitative description of the different ways in which populations of two species interact to develop a classification of possible interactions between two co-occurring species (Table 12.1)... | {
"Header 1": "12.1 Species Interactions Can Be Classified Based on Their Reciprocal Effects",
"token_count": 581,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The varieties of species interactions outlined in the previous section typically involve the interaction of individual organisms. A predator captures a prey or a bacterium infects a host organism. Yet through their beneficial or detrimental effects on the individuals involved, these interactions influence the collectiv... | {
"Header 1": "12.2 Species Interactions Influence Population Dynamics",
"token_count": 1825,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
hen individuals of two different species (represented as populations $N_1$ and $N_2$ ) share a common limiting resource that defines the carrying capacity for each population ( $K_1$ and $K_2$ ), there is potential for competition between individuals of the two species (interspecific competition). Thus, the popula... | {
"Header 1": "Incorporating Competitive Interactions in Models of Population Growth",
"token_count": 1221,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
For a number of reasons, the interaction between two species will not influence all individuals within the respective populations equally. First, interactions among species involve a diverse array of physiological processes and behavioral activities that
are influenced by phenotypic characteristics (physiological, mo... | {
"Header 1": "**12.3** Species Interactions Can Function as Agents of Natural Selection",
"token_count": 2036,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In the extreme case, the interaction can become obligate, where the degree of specialization in phenotypic characteristics results in the two species being dependent on each other for survival and successful reproduction. We will examine the evolution of obligate species interactions in detail later (Chapter 15).
Unl... | {
"Header 1": "**12.3** Species Interactions Can Function as Agents of Natural Selection",
"token_count": 445,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
We have examined how natural selection can result in genetic differentiation, that is, genetic differences among local populations. Species with wide geographic distributions generally encounter a broader range of physical environmental conditions than species whose distribution is more restricted. The variation in phy... | {
"Header 1": "12.4 The Nature of Species Interactions Can Vary across Geographic Landscapes",
"token_count": 1263,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The examples of species interactions that we have discussed thus far focus on the direct interaction between two species. However, most interactions (e.g., predator–prey, competitors, mutually beneficial) are not exclusive nor involve only two species. Rather, they involve a number of species that form diffuse associat... | {
"Header 1": "**12.5** Species Interactions Can Be Diffuse",
"token_count": 950,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The diversity of species inhabiting our planet reflect different evolutionary solutions to the same basic processes of assimilation and reproduction, and that the characteristics that distinguish each species often reflect adaptations (products of natural selection) that allow individuals of that species to survive, gr... | {
"Header 1": "12.6 Species Interactions Influence the Species' Niche",
"token_count": 1967,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Adaptive radiation is the process by which one species gives rise to multiple species that exploit different features of the environment, such as food resources or habitats (see Section 5.9, Figure 5.22). Different features of the environment exert the selective pressures that push populations in various directions (ph... | {
"Header 1": "12.7 Species Interactions Can Drive Adaptive Radiation",
"token_count": 1203,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
As we will see in the chapters that follow, species interactions are ubiquitous in nature and play a fundamental role in the structuring of ecological communities. Perhaps no other interaction, however, has as great an impact on the diverse array of plants and animals that inhabit our planet as their interaction with t... | {
"Header 1": "Ecologic al Issues & Application",
"Header 3": "Urbanization Has Negatively Impacted Most Species while Favoring a Few",
"token_count": 1963,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
This combination of negative interactions with the majority of native species—while enhancing a small subset of often non-native species, which we have manipulated to serve our needs, facilitated through dispersal, or created urban environments in which their populations flourish—is resulting in what urban and conser... | {
"Header 1": "Ecologic al Issues & Application",
"Header 3": "Urbanization Has Negatively Impacted Most Species while Favoring a Few",
"token_count": 710,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- **1.** Contrast amensalism and competition. What do ecologists mean when they refer to amensalism as a form of asymmetrical competition?
- **2.** Why will the interaction between two species not equally influence all individuals within the respective populations?
- **3.** Do you think all species interactions influen... | {
"Header 1": "Ecologic al Issues & Application",
"Header 3": "Study Ques tions",
"token_count": 1231,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
- 13.1 Interspecific Competition Involves Two or More Species
- 13.2 The Combined Dynamics of Two Competing Populations Can Be Examined Using the Lotka–Volterra Model
- 13.3 There Are Four Possible Outcomes of Interspecific Competition
- 13.4 Laboratory Experiments Support the Lotka–Volterra Model
- 13.5 Studies Suppor... | {
"Header 1": "Chapter Guide",
"token_count": 354,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
A relationship that affects the populations of two or more species adversely (--) is interspecific competition. In interspecific competition, as in intraspecific competition, individuals seek a common resource in short supply (see Chapter 11). But in interspecific competition, the individuals are of two or more species... | {
"Header 1": "**13.1** Interspecific Competition Involves Two or More Species",
"token_count": 525,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In the early 20th century, two mathematicians—the American Alfred Lotka and the Italian Vittora Volterra—independently arrived at mathematical expressions to describe the relationship between two species using the same resource (consumption competition). Both men began with the logistic equation for population growth t... | {
"Header 1": "13.2 The Combined Dynamics of Two Competing Populations Can Be Examined Using the Lotka– Volterra Model",
"token_count": 2037,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The zero-growth isocline for each species is defined as the combinations of (*N*1, *N*2) for which d*N*/d*t* = 0 (zero population growth). In the area (combined values of [*N*1, *N*2]) below the line, population growth is positive and the population increases (as indicated by the arrows); for combined values of (*N*1, ... | {
"Header 1": "13.2 The Combined Dynamics of Two Competing Populations Can Be Examined Using the Lotka– Volterra Model",
"token_count": 256,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
To interpret the combined dynamics of the two competing species, their isoclines must be drawn on the same *x*–*y* graph. Although there are an infinite number of isoclines that can be constructed by using different values of $K_1$ , $K_2$ , $\alpha$ , and $\beta$ , there are only four qualitatively different ways ... | {
"Header 1": "13.3 There Are Four Possible Outcomes of Interspecific Competition",
"token_count": 1937,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
The theoretical Lotka-Volterra equations stimulated studies of competition in the laboratory, where under controlled conditions an outcome is more easily determined than in the field. One of the first to study the Lotka–Volterra competition model experimentally was the Russian biologist G. F. Gause. In a series of expe... | {
"Header 1": "13.4 Laboratory Experiments Support the Lotka–Volterra Model",
"token_count": 645,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
In three of the four situations predicted by the Lotka–Volterra equations, one species drives the other to extinction. The results of the laboratory studies just presented tend to support the mathematical models. These and other observations have led to the concept called the **competitive exclusion principle**, which ... | {
"Header 1": "13.5 Studies Support the Competitive Exclusion Principle",
"token_count": 490,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
Interspecific competition involves individuals of two or more species vying for the same limited resource. However, features of the environment other than resources also directly influence the growth and reproduction of species (see Chapters 6 and 7) and therefore can influence the outcome of competitive interactions. ... | {
"Header 1": "13.6 Competition Is Influenced by Nonresource Factors",
"token_count": 1010,
"source_pdf": "datasets/websources/biochem/Smith_Smith_2015.pdf"
} |
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