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Chapter 45

Population and Community Ecology

Book Version 32
By Boundless
Boundless Biology
Biology
by Boundless
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Section 1
Population Demography
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Population Demography

Demography is the study of population dynamics, using statistical and mathematical tools.

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Population Size and Density

Scientists study population size and density using a variety of field sampling methods, including quadrats and mark-recapture.

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Species Distribution

Scientists gain insight into a species' biology and ecology from studying spatial distribution of individuals.

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The Study of Population Dynamics

Demography, or the study of population dynamics, is studied using tools such as life tables and survivorship curves.

Section 2
Environmental Limits to Population Growth
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Exponential Population Growth

When resources are unlimited, a population can experience exponential growth, where its size increases at a greater and greater rate.

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Logistic Population Growth

Logistic growth of a population size occurs when resources are limited, thereby setting a maximum number an environment can support.

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Density-Dependent and Density-Independent Population Regulation

Population regulation is a density-dependent process, meaning that population growth rates are regulated by the density of a population.

Section 3
Life History Patterns
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Life History Patterns and Energy Budgets

Energy budgets and life history strategies determine the type of reproductive capacity displayed by a population.

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Theories of Life History

Modern theories of life history incorporate life and survivorship factors with ecological concepts associated with r- and K-selection theories.

Section 4
Human Population Growth
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Human Population Growth

The exponential growth of the human population could lead to food shortages, global warming, and other issues of resource scarcity.

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Overcoming Density-Dependent Regulation

Humans have exceeded density-dependent limits on population by enacting various environmental changes to accommodate our needs for hygiene, shelter, and food.

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Age Structure, Population Growth, and Economic Development

A population's growth is strongly influenced by the proportions of individuals in different age brackets, which in turn is influenced by economic development.

Section 5
Community Ecology
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The Role of Species within Communities

Communities are shaped by foundation species and keystone species, while invasive species disrupt the natural balance of an area.

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Predation, Herbivory, and the Competitive Exclusion Principle

Predation and herbivory are two methods animals use to obtain energy; many species have developed defenses against them.

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Symbiosis

Commensalism, mutualism, and parasitism are three symbiotic ways organisms interact with each other with differing degrees of benefit.

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Ecological Succession

When disturbances occur, succession allows for communities to become re-established over periods of time.

Section 6
Innate Animal Behavior
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Introduction to Animal Behavior

BehaviorĀ is the change in activity of an organism in response to a stimulus and can be grouped as innate or learned.

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Movement and Migration

Innate behaviors, such as kinesis, taxis, and migration, are instinctual responses to external stimuli.

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Animal Communication and Living in Groups

Animals communicate using signals, which can be chemical (pheromones), aural (sound), visual (courtship displays), or tactile (touch).

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Altruism and Populations

Altruistic behaviors may be explained by the natural instinct to improve the chances of passing on one's genes.

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Mating Systems and Sexual Selection

In mating, there are two types of selection (intersexual, intrasexual) and three mating systems (monogamous, polygynous, polyandrous).

Section 7
Learned Animal Behavior
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Simple Learned Behaviors

Simple learned behaviors include habituation and imprinting, both of which are important to the maturation process of young animals.

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Conditioned Behavior

In classical conditioning, a behavior is paired with an unrelated stimulus; in operant conditioning, behaviors are modified by consequences.

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Cognitive Learning and Sociobiology

Cognitive learning relies on cognitive processes such as reasoning and abstract thinking; it is much more efficient than conditioning.

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Ecology and the Biosphere
  • The Scope of Ecology
  • Biogeography
  • Terrestrial Biomes
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  • Climate and the Effects of Global Climate Change
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Chapter 45
Population and Community Ecology
  • Population Demography
  • Environmental Limits to Population Growth
  • Life History Patterns
  • Human Population Growth
  • Community Ecology
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Ecosystems
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  • Biogeochemical Cycles
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