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Niche construction and the process of evolution
ALL life has a common ancestor, a cornerstone, that is, biology. And all the fields of biology are united under one theoretical umbrella. And this umbrella is Evolution. It’s not a very difficult concept, but very few people (which includes most biologists) have a satisfactory understanding to it. Too much of its understanding is based on fallacy. There are many concepts that have to be understood and recognized as yet.
Explain this: Environments shape up living things. Ever wondered why bee’s live in hives, rabbits in burrows and birds in nests! Not only these but also, why do different species of birds use different materials to build up their nests? This explains also that bees cannot live in burrows or earthworms in hives! Why we breathe air and not water? Why Polar bears live in the north while koalas cannot survive in that climate. So we understand that urroundings make their own choice of living things.
This also mean that the environment and geography compliment the life on it. And this is what we know as Natural selection. Most biologists say that it is the backbone of evolution. If natural selection is all they say about evolution then the perception seems to be quite limited and clearly tends to erase half of its definition. We may rather call it a conventional view. So according to this conventional view, evolution is a linear process. But Kevin Laland (who is a Royal Society University Research Fellow) and John Odling-Smee (a lecturer at the Institute of Biological Anthropology, University of Oxford) have proved that we need a rethink to the process of evolution. They explain that not only the environment is responsible for the nature of its inhabitants, but the living things in a certain environments also make prominently factual contributions toward bringing in major changes in their environments. And this is taken by niche construction. Laland and Odling-Smee have recognized niche construction as a neglected process in the whole process of evolution.
Influencing factors
Species and its environment compliment each other’s attitude to come up with any particular natural physical setup. Hence niche construction can be recognized as the driving force of the evolutionary process, thus a very important factor yet neglected. Niche construction also known as “ecosystem engineering” refers to the activities, choices and metabolic processes of organisms, through which they define, choose, modify and partly create their own niches. To varying degrees, organisms choose their own habitats, mates, and resources, and construct important components of their local environments such as nests, holes, burrows, paths, webs, dams, and chemical environments.
In addition, organisms may niche construct in ways that counteract natural selection, for example by digging a burrow or migrating to avoid the cold, or they may niche construct in ways which introduce novel selection pressures, for example by utilizing a new food resource which may later select for a new digestive enzyme.
They may also do both, for instance if counteractive niche construction itself establishes a novel selection pressure by acting on a second trait, for example, when nest building is further elaborated to enhance defence. In every case, however, the niche construction modifies one or more sources of natural selection in populations’ environments, and in doing so generates a form of feedback in evolution.
Niche construction is not only confined to animals. Plants too can change the chemical nature, the pattern of nutrient cycling, the temperature, the humidity, the fertility, the acidity, and the salinity of their soils and the patterns of light and shade in their habitats.
Impact
It has been found that the selection resulting from niche construction may sometimes override the independent sources of selection, driving populations along alternative evolutionary routes. They may also set off new evolutionary occurrences in a fixed external environment. Niche construction may affect or control the amount of genetic difference in a population. This can be due to the multi-generational assets of ecological legacy.
Niche construction has the power to generate remarkable evolutionary dynamics. Imagine this: Ancestral organisms to their descendants carry out the transmission of genes. And this is what the standard theory describes, but in addition, phenotypically selected and modified habitats, and artefacts are somehow transmitted to their descendants via their local environments. The environments met by descendents are more than mere templates, to which organisms adapt. Environments are partly determined by self-regulating environmental events (for instance, climatic, geological or chemical events), and partly by ‘inherited niche construction’.
The evolutionary importance of niche construction hangs primarily on the reaction that it generates. Many organisms modify their own selection forces, such that environment-altering characters co-evolve with traits whose fitness depends on alterable sources of natural selection in environments. Such feedback cycles may be indirect, so that they operate via a series of other environmental components, which may be biotic, such as other coevolving populations, or abiotic, for example, the soil, or a water resource. These indirect routes can become complicated, and may even incorporate entire biogeochemical cycles in ecosystems.
Extended phenotype
The changes that organisms cause in their niches, and the resulting dynamics, are hardly ever investigated in empirical evolutionary studies, or included into population genetic models. One theoretical construct, which captures some of the consequences of niche construction, is Dawkins’ ‘extended phenotype’. Dawkins argues that genes also express themselves outside the bodies of the organisms that carry them which in other words mean that genes have the ability to build up environmental states. For instance, the beaver’s dam is an extended phenotypic effect of beaver genes. Like any other aspect of the phenotype, extended phenotypes play an evolutionary role by influencing the chances that the genes responsible for the extended phenotypic trait will be passed onto the next generation.
Dawkins emphasizes just this one aspect of the evolutionary feedback from niche construction. However, the beaver’s dam sets up a host of selection pressures which feed back to act not only on the genes responsible for the extended phenotype, but also on other genes which may influence the expression of other traits in beavers such as their teeth, tail, feeding behaviour, their susceptibility to predation or disease, their social system, and many other aspects of their phenotypes. It may also affect many future generations of beavers that may ‘inherit’ the dam, its lodge, and the altered river, as well as many other species of organisms that now have to live in a world with a lake in it.
Adaptation of habitats
There are processes that supply all organisms with the knowledge that organizes their adaptations. Every species is informed by naturally selected genes, many are also informed by complex, information-acquiring ontogenetic processes such as learning or the immune system.
Web spiders marking web or building dummy spiders or woodpecker finch, by learning to grub with a tool, alleviates selection for a woodpecker’s bill can be easy examples of modified activities.
Similarly, ants, bees, wasps and termites, construct nests, which often themselves become the source of selection for many nest regulatory, maintenance and defence behaviour patterns. Many ant and termite species regulate temperature by plugging nest entrances at night, or in the cold, by adjusting the height or shape of their mounds to optimise the intake of the sun’s rays, or by carrying their brood around their nest to the place with the optimal temperature and humidity for the brood’s development.
Most cases of niche construction, however, do not involve the building of artefacts, but merely the selection or modification of habitats. For instance, many insects choose particular host plants as oviposition sites, greatly influencing the developmental (and hence selective) environment of the emerging larvae.
Impact of change
All organisms constantly interact with their local environments, and they constantly change them by doing so. If, in each generation, populations of organisms only modify their local environment uniquely, or variably, then there will be no modification of natural selection pressures, and hence, no significant evolutionary consequence. Web spiders provide an example. Individual spiders repeatedly build webs in their local environments, generation after generation, presumably because they repeatedly inherit genes expressed in web construction. The consistent presence of a web in each spider’s environment has, over many generations, fed back to become the source of new natural selection pressures for further phenotypic changes in the population of spiders, such as the marking of the web to enhance crypsis, differential responses to the frequency of web vibration, or the building of dummy spiders in their webs by Cyclosa to divert the attention of bird predators away from themselves.
In more complicated cases, inherited genes may be expressed in a modification of the environments of offspring, rather than in organisms’ own environments. For example, cuckoo parents repeatedly select host nests for their offspring, thereby bequeathing modified selection pressures as well as genes to their chicks. These modified selection pressures have probably favored adaptations in the offspring of cuckoos, such as their short incubation periods, or the behavioral ejection by cuckoo chicks of host eggs from the parasitized nests.
Driving force
Close assessments of the niche constructing behaviors of countless organisms, from bacteria to humans have made us certain that this is a chief evolutionary process. A focus on niche construction can also provide tools to the ecologists for linking species to eco-system with a considerable approach. By doing so, ecologists make predictions such as invasion of certain type of species in a different community and the changes they bring in, in accordance with the ability of the species to tolerate or adapt the effects of other populations.
Niche construction introduces eco-system as super-constructions formed by shared behaviors of their basic organisms. Niche construction may find in it medicine for the sick ecosystem. Hence perseverance of niche construction of animals and plants is very crucial.
The writer regularly contributes IT related articles
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