Biological Sciences
Communities
Communities in biological sciences refer to groups of interacting species living in the same area. These interactions can include competition, predation, and mutualism, and they play a crucial role in shaping the structure and function of ecosystems. Understanding the dynamics of communities is essential for studying biodiversity, ecological processes, and conservation efforts.
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9 Key excerpts on "Communities"
eBook - PDF- Singh, Lalan Kumar, Arvind Kumar(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
Chapter 1 Community Ecology: A Critical Review Arvind Kumar Environmental Science Research Unit, Post Graduate Department of Zoology, S.K.M. University, Dumka – 814 101, Jharkhand, India Introduction Organisms of a particular species form a population, which has characteristics like natality, mortality, age structure, growth, dynamics etc. But when several populations share a common habitat and its resources and interact among themselves, they develop into a biotic community or simply a community. Thus, a community is a longer unit than a population, since it includes more than one species population. In other words, a community is a local association of several population of different species or a naturally occurring assemblage of plants and animals belonging to different species which live in the same environment, are mutually sustaining and interdependent, constitute a biotic community or biocenose. Microorganisms, plants and animal populations sharing a common habitat and interacting among themselves develop into biotic Communities. A biotic community has its own characteristics. Animal populations sharing a common habitat and interacting among themselves form an animal community and plant populations of an area form a plant community, but the concept of biotic community includes all populations of living organisms of a common habitat, ranging from a tract of forest to the whole of the forest, from a small pond to a large lake, and so on. The biological potential of each species population determines a tolerance range for environmental conditions. A taxon can tolerate a certain range of environmental condition which is called as its ecological amplitude. The composition of a biotic community in any habitat is dependent upon the This ebook is exclusively for this university only. Cannot be resold/distributed. prevalence of environmental conditions in that habitat and the ecological amplitude of species populations.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- University Publications(Publisher)
Biotic community , biological community, a nd ecological community are more common synonyms of biocenosis, all of which represent the same concepts. Three related descriptors within an ecosystem are: • zoocoenosis for the faunal community, • phytocoenosis for the floral community, • microbiocoenosis for the microbial community. The extent or geographical area of a biocenose is limited only by the requirement of a more or less uniform species composition. ________________________ WORLD TECHNOLOGIES ________________________ A freshwater aquatic and terrestrial food web. Ecosystems An ecosystem, as originally defined by Tansley (1935), is a biotic community (or biocoenosis) along with its physical environment (or biotope as defined by many known ecologists). The importance of the biocoenosis concept in ecology is its emphasis on the interrelationships among species in a geographical area. These interactions are as important as the physical factors to which each species is adapted and responding. In a ________________________ WORLD TECHNOLOGIES ________________________ very real sense, it is the specific biological community or biocoenosis that is adapted to conditions that prevail in a given place. Biotic Communities The side of a tide pool showing sea stars ( Dermasterias ), sea anemones ( Anthopleura ) and sea sponges in Santa Cruz, California. Biotic Communities may be of varying sizes, and larger ones may contain smaller ones. The inter actions between species are especially evident in food or feeding relationships. Therefore, a practical method of delineating biotic Communities is to map the food network to identify which species feed upon which others and then determine the system boundary as the one that can be drawn through the fewest consumption links relative to the number of species within the boundary.
eBook - PDF- David M. Hassenzahl, Mary Catherine Hager, Nancy Y. Gift, Linda R. Berg, Peter H. Raven(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
The organisms in a community are interdependent in a variety of ways. Species compete with one another for food, water, living space, and other resources. (Used in this con- text, a resource is anything from the environment that meets a particular species’ needs.) Some organisms kill and eat other organisms. Some species form intimate associations with one another, whereas other species seem only distantly connected. As discussed in Chapter 3, each organism plays one of three main roles in community life: producer, con- sumer, or decomposer. The unraveling of the many positive and negative, direct and indirect interactions of organisms living as a community is one of the goals of community ecologists. Communities vary greatly in size, lack precise boundar- ies, and are rarely completely isolated. They interact with and influence one another in countless ways, even when the inter- action is not readily apparent. Furthermore, Communities are nested within one another like Russian nesting dolls—that is, Communities exist within Communities. A forest is a commu- nity, but so is a rotting log in that forest. Insects, plants, and fungi invade a fallen tree as it undergoes a series of decay steps (Figure 5.11). Organisms exist in an abiotic (nonliving) environment that is as essential to their existence as is their biotic (living) environment. Minerals, air, water, and sunlight are just as much a part of a honeybee’s environment as the flowers it pol- linates and from which it takes nectar. A biological commu- nity and its abiotic environment form an ecosystem (Chapter 4 considered an ecosystem’s abiotic environment). Ecosystems can also include biological Communities managed by humans, such as farms. amount of precipitation, soil moisture, and availability of soil minerals. Those habitats that increase the likelihood of sur- vival and reproductive success for the individuals living there are called source habitats.
eBook - PDFMicrobial Ecology
An Evolutionary Approach
- J Vaun McArthur(Author)
- 2006(Publication Date)
- Academic Press(Publisher)
Living Together in Communities IV Characteristics of Communities and Diversity 11 Community Structure and Energetics It is difficult to ascertain the true nature of microbial Communities. This problem is more acute for Communities than for populations or for the study of individuals. Through modern molecular techniques, we are able to perform in situ hybridizations that can provide visual estimates of the numbers of various species and perhaps some understanding of their spatial distribution. However, in all cases, sampling is destruc-tive, and knowing the actual level of association between organisms identified in a particular sample is difficult at best and perhaps impossible. The act of sampling destroys habitat integrity and increases the homogeneity within a sample. Fine-scale interactions between individual cells or micro-colonies is lost, and although we can with some confidence identify members of different species or groups, we cannot know exactly their spatial distributions or which species were interacting before sam-pling. Undaunted, we press forward into the study of these important aspects of the ecology of an organism: the interspecific interactions and what factors create and maintain community structure. Are associations of microbes Communities, assemblages, or random haphazard groups? Before we can answer that question, we must define community and assem-blage. We also must determine what important ecological and evolutionary interac-tions take place in these mixed-species groupings. There are levels of organization above ecological Communities. It is important to know whether microbes interact with the environment at the ecosystem, biome, or biosphere scales and the extent of any measurable effects. These important considerations require separate treatment. The study of biology ranges from molecules to astrobiology.
eBook - PDFOcean Ecology
Marine Life in the Age of Humans
- J. Emmett Duffy(Author)
- 2021(Publication Date)
- Princeton University Press(Publisher)
These influences were traditionally the purview of paleontology and biogeography and have been underappreciated in community and ecosystem ecology. But it is increasingly recognized that they are every bit as important to the struc-ture of Communities as are local interactions, if not more so (Ricklefs 1987, Ricklefs and Schluter 1993, Hubbell 2001, Vellend 2016). Dispersal and species richness Nearly all local Communities are connected via dispersal to a larger network of populations. As a re-sult, the dynamics of marine species happen at a much larger scale than what we think of as the local community. The large population sizes and variety of conditions among the connected Communities mean that competitive exclusion and extinction are very slow at the regional scale. Thus, regional community dynamics and evolutionary dynamics converge on similar time scales, making speciation an integral component of community dynamics (Hubbell 2001, Ricklefs 2004). To what extent is species diversity in a community determined by local interactions versus dis-persal from the larger region around it? Comparisons of local richness across regions offer key evi-dence to answer this question. The logic is as follows (Ricklefs 1987, Srivastava 1999): If local inter-actions, such as competition for resources, determine diversity, then the number of species in a community should be maintained below some limit determined by local resources. In this case, simi-lar habitats in different regions should converge on a similar number of species, regardless of how many species arrive from surrounding regions. In other words, local richness reaches saturation at a point determined by the local environment and is unrelated to richness of the surrounding region (Terborgh and Faaborg 1980, Ricklefs 1987) ( figure 8.5 ).
eBook - PDF- Fred D. Singer(Author)
- 2016(Publication Date)
- Cambridge University Press(Publisher)
Thus our task is huge. Not only do we need to continue to test new hypotheses, we also need to identify when a particular hypoth-esis is likely to apply. For example, several researchers have shown that in their study system, species diversity is not greatest at intermediate levels of disturbance (Fox 2013 ). Ecolo-gists need to develop a deeper understanding of when a par-ticular factor will have an important impact on species diversity, and when and how multiple factors will interact to in fl uence species diversity. We have shown that biotic and abiotic factors interact to in fl uence species diversity. Armed with this understanding, we can now turn to the question of what species diversity contrib-utes to an ecological community. Does a diverse community have certain properties that distinguish it from a simple community? 17.3 WHAT IS THE RELATIONSHIP BETWEEN SPECIES DIVERSITY AND COMMUNITY STABILITY? Intuitively, we might expect that a diverse community would be better in some ways than a simple community. That type of thinking begs the question of what we mean by “ better. ” One possible answer is that a diverse community might be more productive, producing via photosynthesis more biomass over a de fi ned period of time than does a simple community. A second possible answer is that a diverse community may be more stable – tending to retain its current structure and functioning even when disturbed by biotic or abiotic forces. Stability can have a number of different meanings. Resistance is a community ’ s ability to avoid signi fi cant change in structure or function when disturbed, while resilience is the speed with which a commu-nity returns to its former structure and functioning following a shift caused by disturbance. In 1973 , Robert May published a landmark book entitled Stability and Complexity in Model Ecosystems . He reminded ecolo-gists that stability can apply to the community as a whole, or to populations within the community.
eBook - PDFCoexistence in Ecology
A Mechanistic Perspective
- Mark A. McPeek(Author)
- 2022(Publication Date)
- Princeton University Press(Publisher)
This is because species composition in one part of a local food web intimately depends on the species that occupy other parts of the food web. In fact, a food web repre- sents much (but not all) of the causal network of species interactions that consti- tutes a biological community. For some taxa and some types of questions, only adjacent portions of the local interaction network are necessary. For others, link- ages between the networks in multiple locations are critical (Holyoak et al. 2005, Leibold and Chase 2017). I have organized this book to systematically work through the exploration of these interaction networks and how various features of the networks foster or constrain various features of Communities (i.e., opportuni- ties for new types of species to establish, consequences of species perturbations or deletions, patterns of species distributions, and abundances among Communities scattered along environmental gradients). THE WHY QUESTION Understanding this network of species interactions is also key to understanding why each species is successful or unsuccessful in a community, namely, the mech- anism for why it can coexist. Testing whether a species can invade a community is in principle a fairly simple exercise (but exceedingly difficult in practice for most Communities), and such tests can be accomplished without any reference to why the species has a positive per capita population growth rate when it is rare. However, each coexisting species in a community is present because of its 1 6 C H A P T E R 1 abilities to balance the conflicting demographic demands of the various species interactions it faces at its position in the food web. Understanding comes from not simply asking whether this or that species is coexisting; rather, understanding comes from asking why this species is able to coexist in this community.
eBook - PDF- Michael Begon, Robert W. Howarth, Colin R. Townsend(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
From populations to Communities Chapter 9 ■ 247 In this section we consider how abiotic and biotic factors combine to determine the dynamics of species populations. Then, in Section 9.2, we revisit one of the major themes of this book—the importance of patchiness and dispersal between patches—and discuss especially the importance of the concept of the metapopulation. In Section 9.3, we deal with temporal patterns in com- munity composition, including community succession. We acknowledge that disturbances, such as forest fires and the storm-battering of seashores, play an impor- tant role in the dynamics of many populations and the composition of most Communities. We trace the pat- terns of reestablishment of species that are played out after each disturbance against a background of chang- ing conditions, resources, and population interactions. Finally, in Section 9.4 we broaden our view further to examine food webs, like the one illustrated in Figure 9.1, with usually at least three trophic levels (plant– herbivore–predator). We emphasize the importance not only of direct but also of indirect effects that a spe- cies may have on others on the same trophic level or on levels below or above it. Why are some species rare and others common? Why does a species occur at low population densities in some places and at high densities in others? What factors cause fluctuations in a species’ abundance? These are crucial questions when we wish to con- serve rare species, or control pests, or manage natural living resources, or when we wish simply to under- stand the patterns and dynamics of the natural world. To provide complete answers for even a single species in a single location, we need to know the physi- cochemical conditions, the level of resources avail- able, the organism’s life cycle, and the influence of competitors, predators, parasites, and so on—and how all these factors influence abundance through effects on birth, death, dispersal, and migration.
No longer available |Learn more- Cecie Starr, Christine Evers, Lisa Starr, , Cecie Starr, Christine Evers, Lisa Starr(Authors)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
A description of a plant’s niche would include details of its requirements for soil, water, light, and pollinators. Species interactions also affect community structure. In some cases, the effect is indirect. For example, when songbirds eat caterpillars, the birds indirectly benefit the trees that the caterpillars feed on. Other interactions are direct; the actions of one species helps or harms another. Such direct interactions are the subject of the next section. Figure 17.2 Tropical diversity. Two of the 12 or so fruit-eating pigeon species that live in New Guinea’s tropical rain forests (left). Top, a Victoria crowned pigeon, which is the size of a turkey. Below, the smaller superb crowned fruit pigeon. Left, Donna Hutchins; right, top, © Martin Harvey, Gallo Images/Corbis; bottom, © Len Robinson, Frank Lane Picture Agency/Corbis. Take-Home Message 17.2 What factors shape a community? • Communities vary in their species diversity as a result of nonbiological factors such as differences in incoming sunlight, temperature, and soil quality. • Biological factors such as species requirements for survival and reproduction, as well as interactions with other species, also influence community structure. community All populations of all species in some area. habitat The type of place in which a species lives. niche The role of a species in its community. species diversity The number of species and their relative abundance within a community. Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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