NLiS Country Profile: Afghanistan

Mulch Delivered to Maryland and Northern Virginia

Definition of 'benign'
The indicator reflects the proportion of babies born in facilities that have been designated as Baby-friendly. It is often the finishing touch of a well-manicured garden. Global Nutrition Monitoring Framework: Mothers of children months receiving counselling, support or messages on optimal breastfeeding. A free market is a market in which buyers and sellers are generally free to decide what to exchange and under what terms.

Nonvascular plants

Natural landscape

As a group, ferns are either terrestrial or epiphytic growing upon another plant. Fern stems never become woody composed of secondary tissue containing lignin , because all tissues of the plant body originate at the stem apex. Ferns of the class Polypodiopsida typically possess a rhizome horizontal stem that grows partially underground; the deeply divided fronds leaves and the roots grow out of the rhizome. Fronds are characteristically coiled in the bud fiddleheads and uncurl in a type of leaf development called circinate vernation.

Fern leaves are either whole or variously divided. The leaf types are differentiated into rachis axis of a compound leaf , pinnae primary divisions , and pinnules ultimate segments of a pinna. Fern leaves often have prominent epidermal hairs and large chaffy scales.

Venation of fern leaves is usually open dichotomous forking into two equal parts. Each frond is a potential sporophyll spore-bearing leaf and as such can bear structures that are associated with reproduction. When growth conditions are favourable, a series of brown patches appear on the undersurface of the sporophylls.

Each one of the patches called a sorus is composed of many sporangia , or spore cases, which are joined by a stalk to the sporophyll. The spore case is flattened, with a layer of sterile, or nonfertile, cells surrounding the spore mother cells. Each spore mother cell divides by reduction division meiosis to produce haploid spores, which are shed in a way characteristic to the ferns. Each fern spore has the potential to grow into a green heart-shaped independent gametophyte plant prothallus capable of photosynthesis.

In contrast to bryophytes , in which the sporophyte is nutritionally dependent on the gametophyte during its entire existence, the fern sporophyte is dependent on the gametophyte for nutrition only during the early phase of its development; thereafter, the fern sporophyte is free-living.

In some ferns the sexes are separate, meaning a gametophyte will bear only male or female sex organs. Other species have gametophytes bearing both sex organs. Features important in the identification of ferns include such aspects of the mature sporophyte plant as differences in the stem, frond, sporophyll, sporangium, and position of the sporangium and the absence or presence, as well as the shape, of the indusium a membranous outgrowth of the leaf covering the sporangia.

Psilotopsida whisk ferns is a class represented by two living genera Psilotum and Tmesipteris and several species that are restricted to the subtropics.

This unusual group of small herbaceous plants is characterized by a leafless and rootless body possessing a stem that exhibits a primitive dichotomous type of branching: The photosynthetic function is assumed by the stem, and the underground rhizome anchors the plant.

The vascular tissue is organized into a poorly developed central cylinder in the stem. The family Ophioglossaceae , comprising four genera and some 80 species, is sometimes placed in the class Psilotopsida, though the taxonomy of the group is contentious. Equisetopsida also called horsetails and scouring rushes is a class represented by a single living genus Equisetum. It has a worldwide distribution but occurs in greater variety in the Northern Hemisphere.

Like the lycopods, this group was a diverse and prominent group of vascular plants during the Carboniferous Period , when some genera attained great size in the coal-forming swamp forests. Known as sphenophytes, these plants are differentiated into stem, leaf microphylls , and root. Green aerial stems have longitudinal ridges and furrows extending the length of the internodes, and stems are jointed articulated.

Surface cells are characteristically filled with silica. Branches, when they occur, are borne in whorls at the node, as are the scale leaves.

Sporangia are borne in terminal strobili. Equisetopsida had its origin in the Devonian Period Known as giant ferns, the class Marrattiopsida comprises a single extant family with four genera and some species of large tropical and subtropical ferns with stout erect stems. The leaves fronds may be very large, some reaching 4. The Marattiaceae generally are considered to be one of the most primitive families of ferns still living.

Gymnosperms and angiosperms flowering plants share with ferns a dominant, independent sporophyte generation; the presence of vascular tissue; differentiation of the plant body into root, stem, and leaf derived from a bipolar embryo having stem and root-growing apices ; and similar photosynthetic pigments. Unlike ferns, however, the seed plants have stems that branch laterally and vascular tissue that is arranged in strands bundles around the pith eustele.

Among seed plants, as in ferns, the stem tissues that arise directly from the shoot apex are called primary tissues. Primary tissues contribute to the longitudinal growth of the stem, or primary growth. Secondary growth, resulting in an increase in the width of the axis, is produced by meristematic tissue between the primary xylem and phloem called vascular cambium. This meristem consists of a narrow zone of cells that form new secondary xylem wood and secondary phloem secondary vascular tissues.

Major evolutionary advancements of these plants are demonstrated by the generally more complex plant body and by reproduction via seeds. Seeds represent an important evolutionary innovation within the plant kingdom. Each seed has an embryonic plant sporophyte , food-storage tissue, and hardened protective covering seed coat.

The seed thus contains and protects the embryonic plant and, as the primary dispersal unit of the seed plants, represents a significant improvement over the spore, with its limited capacity for survival.

In comparing ferns and seed plants and their life histories, certain significant differences are seen. The gametophyte in seed plants has been reduced in size, usually consisting of a few to a dozen cells. Thus, it is no longer itself a plant body, as in the bryophytes and ferns. The gametophyte is not free-living but is embedded in the sporophyte and thus less vulnerable to environmental stress than the gametophytes of bryophytes and ferns. Finally, the spores of seed plants are male and female, as are the sporangia that contain them.

The spores are not dispersed as in the bryophytes and ferns but develop into gametophytes within the sporangia. In the most advanced seed plants, the male gametes sperm are carried to the egg by a later extension of the pollen grain called the pollen tube. The advantage of this system is that the nonflagellated sperm are no longer dependent on water to reach the egg. Another terrestrial adaptation of the seed plants not found in ferns is pollen dispersed by wind or animals.

Pollen is a unit of genetic material as well as part of the seed-formation process. The dispersal of pollen by wind or animals, in addition to dispersal of seeds, promotes genetic recombination and distribution of the species over a wide geographic area. The cone-bearing gymnosperms are among the largest and oldest living organisms in the world. They dominated the landscape about million years ago. Today gymnosperms are of great economic value as major sources of lumber products, pulpwood, turpentine, and resins.

Conifer stems are composed of a woody axis containing primitive water- and mineral-conducting cells called tracheids. Tracheids are interconnected by passages called bordered pits. Leaves are often needlelike or scalelike and typically contain canals filled with resin.

The leaves of pine are borne in bundles fascicles , and the number of leaves per fascicle is an important distinguishing feature. Most gymnosperms are evergreen, but some, such as larch and bald cypress , are deciduous the leaves fall after one growing season. The leaves of many gymnosperms have a thick cuticle and stomata below the leaf surface.

The tree or shrub is the sporophyte generation. In conifers, the male and female sporangia are produced on separate structures called cones or strobili. Individual trees are typically monoecious male and female cones are borne on the same tree. A cone is a modified shoot with a single axis, on which is borne a spirally arranged series of pollen- or ovule-bearing scales or bracts. The male cone, or microstrobilus , is usually smaller than the female cone megastrobilus and is essentially an aggregation of many small structures microsporophylls that encase the pollen in microsporangia.

The extant cycads division Cycadophyta are a group of ancient seed plants that are survivors of a complex that has existed since the Mesozoic Era They are presently distributed in the tropics and subtropics of both hemispheres. Cycads are palmlike in general appearance, with an unbranched columnar trunk and a crown of large pinnately compound divided leaves.

The sexes are always separate, resulting in male and female plants i. Most species produce conspicuous cones strobili on both male and female plants, and the seeds are very large.

The ginkgophytes division Ginkgophyta , although abundant, diverse, and widely distributed in the past, are represented now by a sole surviving species, Ginkgo biloba maidenhair tree. The species was formerly restricted to southeastern China, but it is now likely extinct in the wild. The plant is commonly cultivated worldwide, however, and is particularly resistant to disease and air pollution.

The ginkgo is multibranched, with stems that are differentiated into long shoots and dwarf spur shoots. A cluster of fan-shaped deciduous leaves with open dichotomous venation occurs at the end of each lateral spur shoot. Sexes are separate, and distinct cones are not produced. Female trees produce plumlike seeds with a fleshy outer layer and are noted for their foul smell when mature. The gnetophytes division Gnetophyta comprise a group of three unusual genera.

Ephedra occurs as a shrub in dry regions in tropical and temperate North and South America and in Asia, from the Mediterranean Sea to China. Species of Gnetum occur as woody shrubs, vines, or broad-leaved trees and grow in moist tropical forests of South America, Africa, and Asia.

Welwitschia , restricted to extreme deserts less than 25 mm [1 inch] of rain per year in a narrow belt about 1, km miles long in southwestern Africa, is an unusual plant composed of an enormous underground stem and a pair of long strap-shaped leaves that lie along the ground.

The three genera differ from all other gymnosperms in possessing vessel elements as compared with tracheids in the xylem and in specializations in reproductive morphology. The gnetophytes have figured prominently in the theories about gymnospermous origins of the angiosperms. Approximately million years ago, flowering plants angiosperms evolved from gymnosperms, although the identity of the specific gymnospermous ancestral group remains unresolved.

The primary distinction between gymnosperms and angiosperms is that angiosperms reproduce by means of flowers. Flowers are modified shoots bearing a series of leaflike modified appendages and containing ovules immature seeds surrounded and protected by the female reproductive structure, the carpel or pistil. Along with other features, angiospermy, the enclosed condition of the seed, gave the flowering plants a competitive advantage and enabled them to come to dominate the extant flora.

Flowering plants have also fully exploited the use of insects and other animals as agents of pollination the transfer of pollen from male to female floral structures. In addition, the water-conducting cells and food-conducting tissue are more complex and efficient in flowering plants than in other land plants. Finally, flowering plants possess a specialized type of nutritive tissue in the seed, endosperm.

Endosperm is the chief storage tissue in the seeds of grasses; hence, it is the primary source of nutrition in corn maize , rice , wheat , and other cereals that have been utilized as major food sources by humans and other animals. Many of the flowering plants are commonly represented by two basic groups, the monocotyledons and the dicotyledons , distinguished by the number of embryonic seed leaves cotyledons , number of flower parts, arrangement of vascular tissue in the stem, leaf venation, and manner of leaf attachment to the stem.

However, one of the major changes in the understanding of the evolution of the angiosperms was the realization that the basic distinction among flowering plants is not between monocotyledon groups monocots and dicotyledon groups dicots. This group of typical dicots is now known as the eudicots, and molecular-based evidence supports their having a single evolutionary lineage monophyletic.

Other angiosperm groups, such as the Magnoliids , do not fit the traditional paradigm of monocot and dicot and are considered to have more-ancient lineages. The plant body of angiosperms consists of a central axis of two parts, the shoot and the root. Shoots have two kinds of organs, the stem and the leaves , while roots have one type of organ, the root itself. Systems of classification are often based upon the longevity of the portions of plant aboveground.

Woody plants are trees and shrubs whose shoots are durable and survive over a period of years. They are further classified into deciduous and evergreen plants. Deciduous plants drop their leaves at the end of every growing season , whereas evergreens keep their leaves for up to several years. Herbaceous plants have soft, flexible aerial portions and commonly die back each year. Another system of classification, based on the duration of the life history, is particularly applicable to angiosperms of the temperate region.

Annuals are plants that complete the entire life history germinate from seeds, mature, flower, and produce seed in one growing season. Examples of annuals are corn , wheat , and peas. Biennials complete their life history in two seasons, blooming during the second season. Beets , celery , cabbage , carrots , and turnips are biennials, but their flowers are rarely seen because they are harvested during the first season.

Annuals and biennials are both generally herbaceous plants. Perennials are plants that live from year to year. Trees and shrubs are perennials , but some herbaceous plants are also perennials. A number of modifications of the stem occur in angiosperms, and many of these modifications provide a means for herbs to become dormant and survive for a period of years.

Rhizomes are horizontally growing underground stems that serve as organs of asexual reproduction and food storage. Similar to rhizomes, tubers are thickened underground stem portions that primarily serve as food storage for example, potato. Corms are short upright underground stems surrounded by a few thin scale leaves as in Crocus and Gladiolus. Bulbs have a greatly reduced stem with thick fleshy scale leaves surrounding it as in the onion.

Runners and stolons are surface stems characteristic of such plants as strawberries ; new plants may form on the runner or stolon as it spreads along the ground. Many of the most prolific weeds have runners or stolons by which they propagate asexually.

In herbaceous dicotyledonous stems, the vascular conducting tissue xylem and phloem is organized into discrete strands or vascular bundles , each containing both xylem and phloem. The cells between the vascular bundles are thin-walled and often store starch. They enjoyed an especially benign climate.

This plunge came in a time of relatively benign economic conditions. More Synonyms of benign. Word origin of 'benign'. Medicine doing little or no harm; not malignant; specif. Example sentences containing 'benign' These examples have been automatically selected and may contain sensitive content. But under the surface, things look considerably less benign.

Times, Sunday Times She looked at me blankly, with the kind of benign smile that suggested I might have imagined it. Times, Sunday Times The proteins could also distinguish between tumours that were benign and malignant. Times, Sunday Times It could have cost me my job had my bosses been less benign.

Times, Sunday Times We are not in a benign economic environment. The Sun Why would something so benign feel so scary? Christianity Today He had a benign smile and forearms like hams. Times, Sunday Times This is presumably not a trend being reflected in the relatively benign employment statistics. Times, Sunday Times The curators of the exhibition take a more benign view.

Times, Sunday Times Some benign tumours tend to become malignant. Mayes, Adrienne The Dictionary of Nutritional Health The privatisation programme is being launched against a relatively benign economic background. Folke et al state that the likelihood of sustaining development is raised by "Managing for resilience" [1] whilst Perman et al. The challenge of applying the concept of ecological resilience to the context of sustainable development is that it sits at odds with conventional economic ideology and policy making.

Resilience questions the free market model within which global markets operate. Inherent to the successful operation of a free market is specialisation which is required to achieve efficiency and increase productivity.

This very act of specialisation weakens resilience by permitting systems to become accustomed to and dependent upon their prevailing conditions. In the event of unanticipated shocks; this dependency reduces the ability of the system to adapt to these changes. Berkes and Folke table a set of principles to assist with "building resilience and sustainability" which consolidate approaches of adaptive management , local knowledge-based management practices and conditions for institutional learning and self-organisation.

Scientific research associated with resilience is beginning to play a role in influencing policy-making and subsequent environmental decision making. Ecological resilience and the thresholds by which resilience is defined are closely interrelated in the way that they influence environmental policy-making, legislation and subsequently environmental management.

The ability of ecosystems to recover from certain levels of environmental impact is not explicitly noted in legislation, however, because of ecosystem resilience, some levels of environmental impact associated with development are made permissible by environmental policy-making and ensuing legislation.

From Wikipedia, the free encyclopedia. Redirected from Resilience ecology. For other uses, see Resilience disambiguation. Climate change mitigation Climate resilience Ecology and Society Resilience of coral reefs Resistance ecology Regeneration ecology Stability ecology Socio-ecological system Soil resilience Sustainable development Sustainability Vulnerability Homeostasis.

Building Adaptive Capacity in a World of Transformations". Annual Review of Ecology, Evolution, and Systematics. Annual Review of Ecology and Systematics. The need of sustainable and efficient practices". Estuarine, Coastal and Shelf Science. Environmental Facts Archived at the Wayback Machine. What is it and what does it mean for marine policymakers? Archived from the original on International Tanker Owners Pollution Federation. Ecological resilience and sustainable development".

Submission to TfC e-Journal. Journal of Law and Society. Climate change and Water. New South Wales Department of the Environment. Queensland Department of the Environment and Resource Management. Chemoorganoheterotrophy Decomposition Detritivores Detritus. Archaea Bacteriophage Environmental microbiology Lithoautotroph Lithotrophy Microbial cooperation Microbial ecology Microbial food web Microbial intelligence Microbial loop Microbial mat Microbial metabolism Phage ecology.

Ascendency Bioaccumulation Cascade effect Climax community Competitive exclusion principle Consumer-resource systems Copiotrophs Dominance Ecological network Ecological succession Energy quality Energy Systems Language f-ratio Feed conversion ratio Feeding frenzy Mesotrophic soil Nutrient cycle Oligotroph Paradox of the plankton Trophic cascade Trophic mutualism Trophic state index. Animal coloration Antipredator adaptations Camouflage Deimatic behaviour Herbivore adaptations to plant defense Mimicry Plant defense against herbivory Predator avoidance in schooling fish.

Abundance Allee effect Depensation Ecological yield Effective population size Intraspecific competition Logistic function Malthusian growth model Maximum sustainable yield Overpopulation in wild animals Overexploitation Population cycle Population dynamics Population modeling Population size Predator—prey Lotka—Volterra equations Recruitment Resilience Small population size Stability.

Definition of the kingdom