How is natural selection related to the concept of niche? What is an example of an ecological niche? What is the difference between a broad vs. Do humans have a niche? What is it? See all questions in Biodiversity.
Impact of this question views around the world. You can reuse this answer Creative Commons License. Abundance patterns of species in communities have some predictability. Most species in a community tend to have intermediate abundance levels. A few tend to be extremely common, and a few are rare. The shape of this distribution fits the predicted pattern with an increased number of sample collections.
The distribution of abundance in communities can be described by a lognormal curve Preston For example, Figure 2 depicts the abundances, or number of individuals, for fish species collected in the Wabash River during a year period.
Figure 2: Abundances of fish species in the Wabash River The abundances of fish species that were collected in the Wabash River from The majority of species occurred in low abundance, and a few species were extremely abundant.
Data are from Pyron et al. Comparisons among communities frequently result in patterns of species that coexist, or species that tend not to coexist. A potential explanation for patterns of why species do not coexist is competition. This may be observed if two species tend to occur in similar communities, but never occur together in a single community. If the two species use similar resources they have overlapping niches.
Studies of niche overlap can be for resources of food, habitats, or timing for use of habitats. An example of two species with similar niches, and that do not occur together are the redfin shiner and the Ouachita Mountain shiner in the Little River watershed of Oklahoma and Arkansas. Both species are small minnows that inhabit rocky pools in small to medium streams, and consume aquatic macroinvertebrates. Food webs describe the trophic, or feeding relationships among the members of a community.
Trophic relationships refer to where and how organisms obtain their energy. For example, primary producers are organisms that convert energy from light or heat into organic tissue. Plants are an example of a primary producer.
Consumers are organisms that get their energy from eating primary producers. A rabbit is a consumer that eats grasses. Predators are organisms that eat consumers. A wolf is a predator that eats rabbits. Food webs can be simple or they can be complex, depending upon the number of species in a community. Food webs can vary in complexity by the number of connections between member species. Spatial and temporal comparisons of communities provide information about the things that cause differences in species occurrence and abundance patterns.
A spatial comparison refers to comparing similar communities that occur in different locations. This allows an ecologist to test if there are differences in climate, landscape features, geology, or habitats that occur with different species assemblages. For example, in small streams, the fish species that occur in a riffle habitat stream location with change in height of the stream bottom tend to be different than the fish species that occur in pool habitats stream location with constant stream bottom height.
In other words the fish assemblages of riffles differ from the fish assemblages of pools. The assemblage differences are largely due to the fact that the habitats are so different. Riffles have higher gradients, increased flows, and larger substrates than the pool habitats of streams.
At a larger scale, fish assemblages in larger rivers differ from fish assemblages in small streams. A temporal comparison refers to comparing the same community at different times. The species composition of communities and assemblages changes with time. Change may occur following disturbance events, or change may occur due to stochasticity in assemblages. The predictable change that occurs to assemblages in the context of a natural disturbance regimen, is frequently interpreted as succession.
Communities can be characterized by natural disturbance regimes. Disturbance events are characterized by their frequency and impact. Disturbances can include variation in climate, variation in flooding frequency or drought frequency, or frequencies of storm events. Species have adaptations that were shaped by exposure to natural disturbance regimes during their evolutionary history. For example, insects that occur in temperate headwater streams frequently have life history adaptations that result in larval stages being present during the season when leaf inputs from terrestrial plants are high.
Insects that occur in desert streams might have adaptations for surviving unpredictable flood events. The life histories of organisms are a product of their local environment, including the predictability of disturbance regimes. Organisms can be classified in three general life history modes. An interesting product of this classification exercise was that species in these three groups differ in their ability to survive disturbances.
For example, fish species with low juvenile survivorship, low number of offspring, and with early maturity tend to be successful in habitats with unpredictable droughts or floods. Species with a different suite of life history traits such as low juvenile survivorship, high number of offspring, and late maturity cannot survive unpredictable flood or drought disturbances. Gotelli, N. Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness.
Ecology Letters 4 , Pyron, M. Stability of the fish assemblages of the Wabash River from Freshwater Biology 51 , Taylor, C. Regional parapatry of the congeneric cyprinids Lythrurus snelsoni and L. Copeia , Winemiller, K. Patterns of life history diversification in North American fishes: implications for population regulation.
Canadian Journal of Fisheries and Aquatic Sciences 49 , Predation, Herbivory, and Parasitism. Biodiversity is increased by genetic change and evolutionary processes and reduced by habitat destruction, population decline and extinction. There is a growing recognition that the level of biodiversity is an important factor in influencing the resilience of ecosystems to disturbance. Biodiversity is a complex term that includes not only the variety of different animals species diversity but also the difference between animals of the same species genetic diversity and between ecosystems ecosystem diversity.
Genetic Diversity is the diversity of genetic characteristics expressed or recessive within a species i. This component of biodiversity is important because it allows populations to adapt to environmental changes through the survival and reproduction of individuals within a population that have particular genetic characteristics that enable them to withstand these changes.
The maintenance of high genetic diversity within populations is therefore a conservation and management priority as this provides the greatest capacity for any population to adapt to a broad range of environmental changes.
Conversely, failure to maintain genetic diversity limits the capacity for a population to adapt, making it vulnerable to even small changes in the environment and increasing the likelihood of extinction. Species Diversity is simply the number and relative abundance of species found in a given biological organisation population, ecosystem, Earth.
Species are the basic units of biological classification and hence, this is the measure most commonly associated with the term 'biodiversity'.
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