Geography of cretaceous extinctions: Data base development

Data bases built from the source literature are plagued by problems of data quality. Unless the data acquisition is done by experts, working slowly, the data base may contain so much garbage that true signals and patterns cannot be detected. On the other hand, high quality data bases develop so slowly that satisfactory statistical analysis may never be possible due to the small sample sizes. Results of a test are presented of the opposite strategy: rapid data acquisition by non-experts with minimal control on data quality. A published list of 186 species and genera of fossil invertibrates of the latest Cretaceous Age (Maestrichtian) were located through a random search of the paleobiological and geological literature. The geographic location for each faunal list was then transformed electronically to Maestrichtian latitude and longitude and the lists were further digested to identify the genera occurring in each ten-degree, latitude-longitude block. The geographical lists were clustered using the Otsuka similarity coefficient and a standard unweight-pair-group method. The resulting clusters are remarkably consistent geographically, indicating that a strong biogeographic signal is visible despite low-quality data. A further test evaluated the geographic pattern of end-Cretaceaous extinctions. All genera in the data base were compared with Sepkoski's compendium of time ranges of genera to determine which of the reported genera survived the Cretaceous mass extinction. In turn, extinction rates for the ten-degree, latitude-longitude blocks were mapped. The resulting distribution is readily interpretable as a robust pattern of the geography of the mass extinction. The study demonstrates that a low-quality data base, built rapidly, can provide a basis for meaningful analysis of past biotic events

Extintion: bad genes or bad luck?

La extinción de especies y taxones superiores se ve generalmente como una fuerza constructiva en evolución, ya que se supone que los organismos mejor adaptados sobrevivenmás fácilmente. Esposible, sinembargo, que gran parte de la extinción no sea selectiva y que los cambios observados en la composición taxonómica de la biota sean el resultado de efectos aleatorios. En este trabajo se  evaluan dos guiones para la extinción no selectiva: uno utiliza un modelo de tiempo de  nacimiento-muerte homogéneo y el otro postula exterminaciones intermitentes, catastróficas de gran numero de  especies. En el estado actual de nuestros conocimientos, ninguno deestos dosguiones es  matemáticamente plausible. Esto podria serdebido a que la extinción es, de hecho, selectiva, o bien podria ser que nuestras estimaciones de las diversidades del pasado y las tasas de avance evolutivo  fueran erróneas.Si la extinción es selectiva, el modelo de tiempo homcgéneo sugiere que los  Trilobites abarcan especies conduraciones de l14 al 28 por cientomás cortas que lo normal para los invertebrados marinos del  Paleozoico

LAND VALUES AND ENVIRONMENTAL REGULATION

Environmental Economics and Policy, Land Economics/Use,

Avalanche dynamics in Bak-Sneppen evolution model observed with standard distribution width of fitness

We introduce the standard distribution width of fitness to characterize the global and individual features of a ecosystem in the Bak-Sneppen evolution model. Through tracking this quantity in evolution, a different hierarchy of avalanche dynamics, $w_{0}$ avalanche is observed. The corresponding gap equation and the self-organized threshold $w_{c}$ are obtained. The critical exponents $\tau ,$ $\gamma$and $\rho$, which describe the behavior of the avalanche size distribution, the average avalanche size and the relaxation to attractor, respectively, are calculated with numerical simulation. The exact master equation and $\gamma$ equation are derived. And the scaling relations are established among the critical exponents of this new avalanche.Comment: 14 pages, 3 figure

Entropic Sampling and Natural Selection in Biological Evolution

With a view to connecting random mutation on the molecular level to punctuated equilibrium behavior on the phenotype level, we propose a new model for biological evolution, which incorporates random mutation and natural selection. In this scheme the system evolves continuously into new configurations, yielding non-stationary behavior of the total fitness. Further, both the waiting time distribution of species and the avalanche size distribution display power-law behaviors with exponents close to two, which are consistent with the fossil data. These features are rather robust, indicating the key role of entropy

Dorsal inlay buccal mucosal graft (Asopa) urethroplasty for anterior urethral stricture

Asopa described the inlay of a graft into Snodgrass\u27s longitudinal urethral plate incision using a ventral sagittal urethrotomy approach in 2001. He claimed that this technique was easier to perform and led to less tissue ischemia due to no need for mobilization of the urethra. This approach has subsequently been popularized among reconstructive urologists as the dorsal inlay urethroplasty or Asopa technique. Depending on the location of the stricture, either a subcoronal circumferential incision is made for penile strictures, or a midline perineal incision is made for bulbar strictures. Other approaches for penile urethral strictures include the non-circumferential penile incisional approach and a penoscrotal approach. We generally prefer the circumferential degloving approach for penile urethral strictures. The penis is de-gloved and the urethra is split ventrally to exposure the stricture. It is then deepened to include the full thickness of the dorsal urethra. The dorsal surface is made raw and grafts are fixed on the urethral surface. Quilting sutures are placed to further anchor the graft. A Foley catheter is placed and the urethra is retubularized in two layers with special attention to the staggering of suture lines. The skin incision is then closed in layers. We have found that it is best to perform an Asopa urethroplasty when the urethral plate is ≥1 cm in width. The key to when to use the dorsal inlay technique all depends on the width of the urethral plate once the urethrotomy is performed, stricture etiology, and stricture location (penile vs. bulb)

Mechanical basis of morphogenesis and convergent evolution of spiny seashells

Convergent evolution is a phenomenon whereby similar traits evolved independently in not closely related species, and is often interpreted in functional terms. Spines in mollusk seashells are classically interpreted as having repeatedly evolved as a defense in response to shell-crushing predators. Here we consider the morphogenetic process that shapes these structures and underlies their repeated emergence. We develop a mathematical model for spine morphogenesis based on the mechanical interaction between the secreting mantle edge and the calcified shell edge to which the mantle adheres during shell growth. It is demonstrated that a large diversity of spine structures can be accounted for through small variations in control parameters of this natural mechanical process. This physical mechanism suggests that convergent evolution of spines can be understood through a generic morphogenetic process, and provides unique perspectives in understanding the phenotypic evolution of this second largest phylum in the animal kingdom.\ud \ud Homoplasy, the appearance of similar traits in separate evolutionary lineages as a result of convergence, parallelism, or evolutionary reversals, is a major concern in phylogenetic analysis for which it is viewed as noise. However, over the past two decades, homoplasy has also become a subject of increasing interest, stimulated by the rise of evolutionary developmental biology (evo devo) and the wish to uncover the developmental basis of this phenomenon (1⇓–3). Spines constitute the most prominent ornamentation of mollusk shells and have evolved in many distantly related fossil and current mollusk species (at least 55 genera and 21 families of current gastropods; 10 genera and 8 families of current bivalves; 11 genera and 8 families of ammonoids; and 6 fossil nautiloid genera; see Fig. 1 for examples). Convergent evolution of spines in mollusks has been addressed in functional terms, these structures being interpreted as having evolved as a defense in response to shell-crushing predators (4⇓–6). This hypothesis is itself the basis of the widely cited “escalation hypothesis,” according to which long-term trends in the fossil record were caused by the evolutionary response of prey to predation pressure (7). The idea that convergent evolution of similar mollusk ornamentations might be fully explained in functional terms is based on the premise that similar characters, perceived as well designed for a presumed function, cannot conceivably have independently evolved fortuitously. Therefore, natural selection is thought to have repeatedly shaped similar functional traits out of random variations

Extremal dynamics on complex networks: Analytic solutions

The Bak-Sneppen model displaying punctuated equilibria in biological evolution is studied on random complex networks. By using the rate equation and the random walk approaches, we obtain the analytic solution of the fitness threshold $x_c$ to be 1/(_f+1), where _f=/ (=) in the quenched (annealed) updating case, where is the n-th moment of the degree distribution. Thus, the threshold is zero (finite) for the degree exponent \gamma 3) for the quenched case in the thermodynamic limit. The theoretical value x_c fits well to the numerical simulation data in the annealed case only. Avalanche size, defined as the duration of successive mutations below the threshold, exhibits a critical behavior as its distribution follows a power law, P_a(s) ~ s^{-3/2}.Comment: 6 pages, 2 figure

Biological Effects of Stellar Collapse Neutrinos

Massive stars in their final stages of collapse radiate most of their binding energy in the form of MeV neutrinos. The recoil atoms that they produce in elastic scattering off nuclei in organic tissue create radiation damage which is highly effective in the production of irreparable DNA harm, leading to cellular mutation, neoplasia and oncogenesis. Using a conventional model of the galaxy and of the collapse mechanism, the periodicity of nearby stellar collapses and the radiation dose are calculated. The possible contribution of this process to the paleontological record of mass extinctions is examined.Comment: gzipped PostScript (filename.ps.Z), 12 pages. Final version, Phys. Rev. Lett., in pres