Evolutionary acquisition

The sense of smell, with which we can enjoy a bursting rosebud on a summer s day, or a fine Cabernet, is a relatively recent evolutionary acquisition. For most of evolutionary time our ancestors did not breathe air and gained information about their surroundings by tasting their aquatic environments. The so-called olfactory rosettes in the heads of... 

In this methodology, the user is provided the best possible capability within each increment, and continuous user feedback is important. The requirements for future increments are dependent on the feedback from users and technology maturation. It is an iterative process designed to assess the viability of technologies while simultaneously refining user requirements. Spiral development complements an evolutionary approach by continuing in parallel with the acquisition process to speed the identification and development of the technologies necessary for follow-on increments. Each incremental spiral provides the best possible capability. Spiral development is a form of evolutionary acquisition. 

I suggest that we take the acquisition of the total set of species-typical traits (however that is to be measured empirically) to be a maximum specification of the process of development. Anything more exhaustive than species-typical might entail that new species could not evolve. As a minimum bound, I suggest the following evolutionary specification - development is the acquisition of the capacity to reproduce. It will become clear in a moment why I bracket the process of development in this way. First, though, let us consider the sorts of questions about development at multiple levels of evolutionary transition that must be addressed if we are to understand units of evolutionary transition in terms of the propagation of developmental capacities. 

In order to analyze the process of reproduction, two more basic concepts are needed progeneration and development. Development was described briefly above. Here, I will adopt the evolutionary minimum concept of development as the acquisition of the capacity to reproduce. The evolutionary minimum concept is very general, although limited to the context of evolutionary processes. More precise notions of development could be substituted that specify mechanisms by which the capacity to reproduce can be realized, although it remains to be seen whether more precise, non-evolutionary concepts can be general enough to apply to all levels of evolutionary transition. 

The evolution of parasitic phenotypes in nematodes is a topic of active practical and theoretical research (Skorping el al., 1991 Read and Skorping, 1995a,b). Understanding the mode and tempo of acquisition of particular phenotypes associated with succesful parasitism will permit fuller appreciation of the evolutionary constraints experienced by organisms adapting to new hosts. 

The acquisition and assimilation of bioelements are the most fundamental processes in an organism s struggle for life. It is therefore obvious that in complex natural systems the competition between thousands of species for limited quantities of a small number of elements is a major evolutionary factor. However, the individual contributions of the physical and biochemical aspects of nutrition to the fitness of an organism are widely unknown. The frequent observation that biodegradation processes, e.g. in soil remediation, are limited by physical obstacles to substrate acquisition, rather than by biochemical incapacities, points at the importance of substrate mobilisation strategies. 

A fundamental change occurred in the biochemistry of the ancestor that allowed ingested PAs to be detoxified, retained, and transported safely throughout the larval body. The acquisition of the PA-specihc monooxygenase may have been the critical evolutionary innovation for the Arctiinae that sealed their intimate relationship with PA-containing plants. This specific enzyme allows them simultaneously to detoxify the PAs and render them mobile. Once sequestered, PAs could deter predators. 

The adaptation to an anaerobic lifestyle with the aid of hydrogenosomes required the acquisition of an (oxygen-sensitive) hydrogenase. The evolution of fumarate respiration in N. ovalis shows that an adaptation to life in anaerobic environments can occur in steps - by evolutionary tinkering. 

Hall, B.G. (1982) Evolution on a Petri dish the evolved /3-galac-tosidase system as a model for studying acquisitive evolution in the laboratory. Evolutionary Biol. 15, 85-150. 

The sequencing of a- and /3-spectrin, a-actinin, and dystrophin has revealed similarities not only within the spectrin repeat, but also the other domains and motifs present within these proteins. Subsequent analyses have revealed an evolutionary pathway for the divergence of spectrin and dystrophin from a common a-actinin ancestor via a series of rearrangements, duplications, and evolution of repeats and other domains, as well as the acquisition of unique domains such as PH, WW, and SHS (Fig. 2). 

The finite resources available to organisms must be allocated to several life processes including growth, reproduction, maintenance, defense, and further resource acquisition. It is often assumed that a resource allocated to one process incurs a cost to the remaining processes because the resource is diverted away from them.7 8 It is also assumed that natural selection acts to optimize the allocation of resources to best suit the life history and environment for a particular organism, of course, within evolutionary and ecological constraints. 

Acquisition of new metabolic activities by microorganisms has been studied deliberately since the early 1960s. Most of those studies, many of which are reviewed in detail in Mortlock,1 were conducted using well-characterized laboratory strains of Escherichia coli, Klebsiella, or Pseudomonas aeruginosa and were intended to provide insights into evolutionary processes. In most cases the new activities were catabolic functions simply because the organisms in question were already capable of all required anabolic functions. There is no reason, however, why the methods outlined below should not be applicable to isolation of mutants with novel biosynthetic capabilities, provided that a sufficiently strong selection for those capabilities can be devised. The purpose of this chapter is to provide some... 

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