25: Population Ecology
Ecology
Ecology is the study of the interaction of organisms with their biotic (living) and abiotic (non-living) environment. Plant ecologists study plants across many different biomes, both terrestrial and aquatic. They may be interested in studying plants at different levels of organization, such as the population level, the community level, or the ecosystem level. Many plant ecologists are interested in conservation biology, protecting the diversity of plants from human impacts. Understanding the connections between plants and other organisms helps us solve scientific problems and understand our world better.
Population Ecology
Researchers study ecology at various levels. For example, at the organismal level, a scientist might be interested in the adaptations that enable individuals to live in specific habitats. These adaptations could be morphological (pertaining to the study of form or structure), physiological, or behavioral. In this chapter, we will focus on population ecology. A population is a group of interbreeding organisms that are members of the same species living in the same area at the same time. Organisms that are all members of the same species, a population, are called conspecifics (Figure \(\PageIndex{2}\)). A population is identified, in part, by where it lives; its area of population may have natural or artificial boundaries. Natural boundaries might be rivers, mountains, or deserts, while examples of artificial boundaries include mowed grass or manmade structures such as roads. The study of population ecology focuses on the number of individuals in an area and how and why population size changes over time. Population ecologists are particularly interested in counting the Karner blue butterfly, for example, because it is classified as federally endangered.
Attributions
Modified by Kammy Algiers from the following sources:
- Population and Community Ecology from General Biology by OpenStax (licensed CC-BY )
- Organismal Ecology & Population Ecology from General Biology by Boundless (licensed CC-BY-SA )
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- 25.1: Population Size and Density
- Populations are characterized by their population size and their population density. Various methods can be used to measure the size and density of a population. For example, scientists often use quadrats to do this for plants. Dispersion patterns can give scientists information about a particular population. Three common dispersion patters are uniform, random, and clumped.
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- 25.2: Life Histories and Natural Selection
- All species have evolved a pattern of living, called a life history strategy, in which they partition energy for growth, maintenance, and reproduction. These patterns evolve through natural selection. There are different life strategies that species may exhibit. A species may reproduce early in life to ensure surviving to a reproductive age or reproduce later in life to become larger and healthier. A species may reproduce once (semelparity) or many times (iteroparity) in its life.
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- 25.3: Environmental Limits to Population Growth
- Populations with unlimited resources grow exponentially, with an accelerating growth rate. When resources become limiting, populations follow a logistic growth curve. The population of a species will level off at the carrying capacity of its environment.
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- 25.4: Population Dynamics and Regulation
- Populations are regulated by a variety of density-dependent and density-independent factors. Species are divided into two categories based on a variety of features of their life history patterns: r-selected species, which have large numbers of offspring, and K-selected species, which have few offspring.