OpenStax Biology 2e
Life in an ecosystem is often about competition for limited resources, a characteristic of the theory of natural selection. Competition in communities (all living things within specific habitats) is observed both within species and among different species. The resources for which organisms compete include organic material, sunlight, and mineral nutrients, which provide the energy for living processes and the matter to make up organisms’ physical structures. Other critical factors influencing community dynamics are the components of its physical and geographic environment: a habitat’s latitude, amount of rainfall, topography (elevation), and available species. These are all important environmental variables that determine which organisms can exist within a particular area.
An ecosystem is a community of living organisms and their interactions with their abiotic (nonliving) environment. Ecosystems can be small, such as the tide pools found near the rocky shores of many oceans, or large, such as the Amazon Rainforest in Brazil.
There are three broad categories of ecosystems based on their general environment: freshwater, ocean water, and terrestrial. Within these broad categories are individual ecosystem types based on the organisms present and the type of environmental habitat.
Ocean ecosystems are the most common, comprising over 70 percent of the Earth’s surface and consisting of three basic types: shallow ocean, deep ocean water, and deep ocean surfaces (the low depth areas of the deep oceans). The shallow ocean ecosystems include extremely biodiverse coral reef ecosystems, and the deep ocean surface is known for its large numbers of plankton and krill (small crustaceans) that support it. These two environments are especially important to aerobic respirators worldwide as the phytoplankton perform 40 percent of all photosynthesis on Earth. Although not as diverse as the other two, deep ocean ecosystems contain a wide variety of marine organisms. Such ecosystems exist even at the bottom of the ocean where light is unable to penetrate through the water.
Freshwater ecosystems are the rarest, occurring on only 1.8 percent of the Earth’s surface. Lakes, rivers, streams, and springs comprise these systems. They are quite diverse, and they support a variety of fish, amphibians, reptiles, insects, phytoplankton, fungi, and bacteria.
Terrestrial ecosystems, also known for their diversity, are grouped into large categories called biomes, such as tropical rain forests, savannas, deserts, coniferous forests, deciduous forests, and tundra. Grouping these ecosystems into just a few biome categories obscures the great diversity of the individual ecosystems within them. For example, there is great variation in desert vegetation: the saguaro cacti and other plant life in the Sonoran Desert, in the United States, are relatively abundant compared to the desolate rocky desert of Boa Vista, an island off the coast of Western Africa.
Ecosystems are complex with many interacting parts. They are routinely exposed to various disturbances, or changes in the environment that effect their compositions: yearly variations in rainfall and temperature and the slower processes of plant growth, which may take several years. Many of these disturbances result from natural processes. For example, when lightning causes a forest fire and destroys part of a forest ecosystem, the ground is eventually populated by grasses, then by bushes and shrubs, and later by mature trees, restoring the forest to its former state. The impact of environmental disturbances caused by human activities is as important as the changes wrought by natural processes. Human agricultural practices, air pollution, acid rain, global deforestation, overfishing, eutrophication, oil spills, and waste dumping on land and into the ocean are all issues of concern to conservationists.
Equilibrium is the steady state of an ecosystem where all organisms are in balance with their environment and with each other. In ecology, two parameters are used to measure changes in ecosystems: resistance and resilience. Resistance is the ability of an ecosystem to remain at equilibrium in spite of disturbances. Resilience is the speed at which an ecosystem recovers equilibrium after being disturbed. Ecosystem resistance and resilience are especially important when considering human impact. The nature of an ecosystem may change to such a degree that it can lose its resilience entirely. This process can lead to the complete destruction or irreversible altering of the ecosystem.
Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/details/books/biology-2e
Research Article: On the prevalence of uninformative parameters in statistical models applying model selection in applied ecology
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Research Article: Combining Public Health Education and Disease Ecology Research: Using Citizen Science to Assess Chagas Disease Entomological Risk in Texas
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Date Published: March 11, 2014 Publisher: Public Library of Science Author(s): Deborah M. Gordon Abstract: Networks of local interactions regulate biological systems. Ecological constraints set by resource distribution, operating costs, and the threat of rupture produce similar collective behavior in ants, cells, and gene transcription. Partial Text: Collective behavior operates without central control to regulate … Continue reading
Date Published: December 22, 2003 Publisher: Public Library of Science Author(s): Thomas Brooks Abstract: Will reconciliation ecology — sharing our habitats deliberately with other species — help ameliorate the rapid loss of species from the world? Partial Text: This important book relates much the most optimistic treatise on conservation that I have ever read: many … Continue reading
Date Published: July 16, 2018 Publisher: Public Library of Science Author(s): Hannah Fraser, Tim Parker, Shinichi Nakagawa, Ashley Barnett, Fiona Fidler, Jelte M. Wicherts. http://doi.org/10.1371/journal.pone.0200303 Abstract: We surveyed 807 researchers (494 ecologists and 313 evolutionary biologists) about their use of Questionable Research Practices (QRPs), including cherry picking statistically significant results, p hacking, and hypothesising after … Continue reading
Date Published: August 5, 2011 Publisher: Public Library of Science Author(s): Paul E. Smaldino, Mark Lubell, Attila Szolnoki. http://doi.org/10.1371/journal.pone.0023019 Abstract: Recent research has revived Long’s “ecology of games” model to analyze how social actors cooperate in the context of multiple political and social games. However, there is still a paucity of theoretical work that considers the … Continue reading
Date Published: May 13, 2019 Publisher: Public Library of Science Author(s): Sonja Lehtinen, François Blanquart, Marc Lipsitch, Christophe Fraser, Erwin Schurr. http://doi.org/10.1371/journal.ppat.1007763 Abstract: Resistance against different antibiotics appears on the same bacterial strains more often than expected by chance, leading to high frequencies of multidrug resistance. There are multiple explanations for this observation, but these … Continue reading
Date Published: May 16, 2018 Publisher: Public Library of Science Author(s): Allison S. Quan, Michael B. Eisen, Joseph Schacherer. http://doi.org/10.1371/journal.pone.0196440 Abstract: The fruit fly, Drosophila melanogaster, is preferentially found on fermenting fruits. The yeasts that dominate the microbial communities of these substrates are the primary food source for developing D. melanogaster larvae, and adult flies … Continue reading