2274 Slices
Medium 9781603442909

Recent Geologic Framework and Geomorphology of the Mississippi–Alabama Shelf, Northern Gulf of Mexico

Buster, Noreen A. Texas A&M University Press ePub

James G. Flocks, Nicholas F. Ferina, and Jack L. Kindinger

This paper provides a summary of previous studies and a synthesis of the surficial geology of the MississippiAlabama shelf, located between the modern Mississippi River Delta and the Florida carbonate platform. Presently, sedimentation processes on the shelf are a function of prevailing winds and currents; however, in the past, the shelf was the focus of numerous delta cycles. Major episodes of deposition and erosion on the shelf have been primarily in response to oscillations in sea level. As sea level fell during the last ice age, deltas moved across the shelf to the shelf edge, incising river valleys across the middle shelf and creating stacked delta sequences on the slope. The delta complexes regressed during the last sea-level rise, infilling valleys while also providing sediments for erosion. Shoals were formed throughout these processes and are found along the shelf and modern shoreline. Data collected from the shelf, incorporated into this summary, include bathymetric, geophysical, and sediment cores. The purpose of the report is to integrate past studies with archived data to provide a comprehensive overview of the geology and geomorphology of the shelf. In addition, areas of further study are identified in the summary as a bulleted list of future needs and goals.

See All Chapters
Medium 9781780643595

19 Agent-based Bayesian Spread Model Applied to Red Imported Fire Ants in Brisbane

Jarrad, F., Editor; Low-Choy, S., Editor CAB International PDF

19

Agent-based Bayesian Spread

Model Applied to Red Imported

Fire Ants in Brisbane

Jonathan M. Keith* and Daniel Spring

Monash University, Clayton, Australia

Abstract

19.1 Introduction

Red imported fire ants were first detected in

Brisbane in February 2001. Since then, the

National Red Imported Fire Ant Eradication

Program has been collecting data on the locations of detected nests and keeping a record of the areas searched and treated with baits. The result is an exceptionally large and detailed record of both the spread of the ant and the effects of human intervention on the invasion. In recent work, these data have been used to reconstruct the history of the invasion in terms of the trajectories of nest abundance and geographic range. A novel feature of the method is that it explicitly models individual nests and can thus reconstruct the invasion to a high level of spatial and temporal detail.

Some important lessons have been learned from this reconstruction. One is that an invasion can continue to expand its geographic range despite a drop in the number of invaders. Another is that immature nests – those not yet able to found new nests and generally too small to be detected – outnumbered mature nests at every stage of the invasion. Both of these lessons highlight the importance of sophisticated models to assist in monitoring an invasion and managing an eradication programme.

See All Chapters
Medium 9781607320470

14 Order Artiodactyla Even-toed Hoofed Mammals

David M. Armstrong University Press of Colorado ePub

The Artiodactyla is one of several orders of hoofed mammals, or ungulates. Ungulates (which, in addition to artiodactyls, include the living horses, tapirs, and rhinos as well as a rich diversity of extinct forms) are mostly adapted to covering large distances quickly, allowing them to exploit the abundant but often diffuse plant resources of open country. Usually the limbs are elongate, toes are reduced in number, and the collarbone (clavicle) is lost, with accompanying reduction in lateral mobility of the limb, a tradeoff for increased efficiency of fore-aft motion. Artiodactyls represent the zenith of these ungulate trends, and the order includes most of the living species of ungulates. In all artiodactyls the first digits (“thumb” in front, “big toe” behind) are missing. The second and fifth digits are reduced in more primitive living artiodactyls or lost completely in more advanced forms. The main weight of the body passes equally between the third and fourth digits in most species. One genus, Tayassu, the peccaries (family Tayassuidae), has 4 front toes per foot and 3 hind toes. In advanced artiodactyls the metacarpal bones of the front limbs and the meta-tarsal bones of the hind limbs are reduced in number and fused to form the cannon bones. The smallest of the artiodactyls is the mouse deer, Tragulus, which weighs about 8 kg, and the largest is Hippopotamus, which weighs up to 4,500 kg. For a technical appreciation of artiodactyls in particular, see Prothero and Foss (2007); Prothero and Schoch (2003) summarized ungulates in general, past and present. Some of the numerous taxonomic challenges within the artiodactyls were reviewed by Marcot (2007), synthesizing traditional “skin and skull” taxonomy with paleontology and molecular systematics.

See All Chapters
Medium 9781576336359

Human Nervous System: GED Biology

Ace Academics Ace Academics ePub
Medium 9781780643731

5: Genetic Engineering of Crop Plants to Sustain Drought Tolerance

Chakraborty, U., Editor CAB International PDF

5 

Genetic Engineering of Crop Plants to Sustain Drought Tolerance

J. Amudha* and G. Balasubramani

Central Institute for Cotton Research, Nagpur, Maharashtra, India

Abstract

The world today is faced with great challenges to produce adequate food, fibre, feed, industrial products and ecosystem services. Under the influence of global climate changes, the situation is getting worse by the destabilization of our ecosystem. With the increasing population, the challenge to develop ecosystem goods and services to meet human needs in the future is very important. Water scarcity, drought conditions and global climate change are major constraints in crop production worldwide. Uncertain rainfall is making conditions worse for farmers. Water stress along with other abiotic stresses is very complex in nature and is a serious challenge that needs to be met urgently in order to sustain and enhance productivity. Agriculture in India and other developing countries is a system which gambles with the monsoon and where irrigation is limited in major parts of the crop cultivation area. Genetic engineering techniques hold great promise for developing crop cultivars with high tolerance to drought. Biotechnological approaches can be utilized; drought and high salinity-tolerant genes can be discovered efficiently and subsequently cloned. Transgenic breeding is a new technology for the development of stress tolerance in crop plants. Drought stress is controlled by multiple polygenes, including signal transduction genes, transcriptional regulation genes and a series of genes for protection, defence and stress tolerance. It is very important to improve the drought tolerance of crops and to evolve plants with various mechanisms for adapting to adverse climatic environments. The introduction of transgenic technology to breeding crops has provided significant benefits to the industry; the first transgenic traits developed and commercialized were designed for insect and herbicide resistance in existing varieties. Eventually, by genetically enhanced technologies, current varieties must be improved or new varieties should be developed that adapt to environmental stresses and have the genetic potential to improve yield factors. This will lead to new levels of sustainable agriculture, with stable yield improvement.

See All Chapters

See All Slices