UNDER CONSTRUCTION

An important aspect of all biotechnology processes is the culture of either the microorganisms or plant and animal cells (or protoplasts in case of plants) or tissues and organs in artificial media. These possibilities led to significant advances and novel possibilities. While microbes in culture are used in recombinant DNA technology and in a variety of industrial processes, plant cells and tissues are used for a variety of genetic manipulations. For example, anther culture is used for haploid breeding; gametic and somatic cell tissue cultures are used for tapping gametoclonal and somaclonal variation or for production of artificial seeds. Transformation of protoplasts in culture leads to the production of useful transgenic plants. Embryo culture technique has also helped in extending the range of distant hybridization for plant breeding purposes. Similarly animal cells (e.g. egg cells) are used for multiplication of superior livestock using a variety of techniques like cloning of superior embryonic cells, transformation of cultured cells leading to the production of transgenic animals, and in vitro fertilization and transfer of embryos to surrogate mothers.

Ecosystems are composed of organisms interacting with each other and with their environment such that energy is exchanged and system-level processes, such as the cycling of elements, emerge. The ecosystem is a core concept in Biology and Ecology, serving as the level of biological organization in which organisms interact simultaneously with each other and with their environment. As such, ecosystems are a level above that of the ecological community (organisms of different species interacting with each other) but are at a level below, or equal to, biomes and the biosphere. Essentially, biomes are regional ecosystems, and the biosphere is the largest of all possible ecosystems.

Ecosystems include living organisms, the dead organic matter produced by them, theabiotic environment within which the organisms live and exchange elements (soils,water, atmosphere), and the interactions between these components. Ecosystems embody the concept that living organisms continually interact with each other and with the environment to produce complex systems with emergent properties, such that “the whole is greater than the sum of its parts” and “everything is connected”.

The spatial boundaries, component organisms and the matter and energy content and flux within ecosystems may be defined and measured. However, unlike organisms or energy, ecosystems are inherently conceptual, in that different observers may legitimately define their boundaries and components differently. For example, a single patch of trees together with the soil, organisms and atmosphere interacting with them may define a forest ecosystem, yet the entirety of all organisms, their environment, and their interactions across an entire forested region in the Amazon might also be defined as a single forest ecosystem. Some have even called the interacting system of organisms that live within the guts of most animals as an ecosystem, despite their residence within a single organism, which violates the levels of organization definition of ecosystems. Moreover, interactions between ecosystem components are as much a part of the definition of ecosystems as their constituent organisms, matter and energy. Despite the apparent contradictions that result from the flexibility of the ecosystem concept, it is just this flexibility that has made it such a useful and enduring concept.

History of the Ecosystem Concept

The term “ecosystem” was first coined by Roy Clapham in 1930, but it was ecologist Arthur Tansley who fully defined the ecosystem concept. In his classic article of 1935, Tansley defined ecosystems as “The whole system,… including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”. The ecosystem concept marked a critical advance in the science of ecology, as Tansely specifically used the term to replace the “superorganism” concept, which implied that communities of organisms formed something akin to a higher-level, more complex organism—a mistaken conception that formed a theoretical barrier to scientific research in ecology. Though Tansely and other ecologists also used the ecosystem concept in conjunction with the now defunct concept of the ecological “climax” (a “final”, or “equilibrium” type of community or ecosystem arising under specific environmental conditions), the concept of ecosystem dynamics has now replaced this. Eugene Odum, a major figure in advancing the science of ecology, deployed the ecosystem concept in a central role in his seminal textbook on ecology, defining ecosystems as: “Any unit that includes all of the organisms (ie: the “community”) in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, andmaterial cycles (ie: exchange of materials between living and nonliving parts) within the system is an ecosystem.”

Ecosystem Structure and Function

Ecosystem components (structure)

Ecosystems may be observed in many possible ways, so there is no one set of components that make up ecosystems. However, all ecosystems must include both biotic and abiotic components, their interactions, and some source of energy. The simplest (and least representative) of ecosystems might therefore contain just a single living plant (biotic component) within a small terrarium exposed to light to which a watersolution containing essential nutrients for plant growth has been added (abiotic environment). The other extreme would be the biosphere, which comprises the totality of Earth’s organisms and their interactions with each other and the earth systems (abiotic environment). And of course, most ecosystems fall somewhere in between these extremes of complexity.

At a basic functional level, ecosystems generally contain primary producers capable of harvesting energy from the sun by photosynthesis and of using this energy to convert carbon dioxide and other inorganic chemicals into theorganic building blocks of life. Consumers feed on this captured energy, and decomposers not only feed on this energy, but also break organic matter back into its inorganic constituents, which can be used again byproducers. These interactions among producers and the organisms that consume and decompose them are called trophic interactions, and are composed of trophic levels in an energy pyramid, with most energy and mass in the primary producers at the base, and higher levels of feeding on top of this, starting with primary consumers feeding on primary producers, secondary consumers feeding on these, and so on. Trophic interactions are also described in more detailed form as a food chain, which organizes specific organisms by their trophic distance from primary producers, and by food webs, which detail the feeding interactions among all organisms in an ecosystem. Together, these processes of energy transfer and matter cycling are essential in determining ecosystem structure and function and in defining the types of interactions between organisms and their environment. It must also be noted that most ecosystems contain a wide diversity of species, and that this diversity should be considered part of ecosystem structure.

Ecosystem processes (function)

By definition, ecosystems use energy and cycle matter, and these processes also define the basic ecosystem functions. Energetic processes in ecosystems are usually described in terms of trophic levels, which define the role of organisms based on their level of feeding relative to the original energy captured by primary producers. As always, energy does not cycle, so ecosystems require a continuous flow of high-quality energy to maintain their structure and function. For this reason, all ecosystems are “open systems” requiring a net flow of energy to persist over time—without the sun, the biosphere would soon run out of energy!

Energy input to ecosystems drives the flow of matter between organisms and the environment in a process known asbiogeochemical cycling. The biosphere provides a good example of this, as it interacts with and exchanges matter with thelithosphere, hydrosphere and atmosphere, driving the global biogeochemical cycles of carbon, nitrogen, phosphorus, sulfur and other elements. Ecosystem processes are dynamic, undergoing strong seasonal cycles in response to changes in solar irradiation, causing fluctuations in primary productivity and varying the influx of energy from photosynthesis and the fixation of carbon dioxide into organic materials over the year, driving remarkable annual variability in the carbon cycle—the largest of the global biogeochemical cycles. Fixed organic carbon in plants then becomes food for consumers and decomposers, who degrade the carbon to forms with lower energy, and ultimately releasing the carbon fixed by photosynthesis back into carbon dioxide in the atmosphere, producing the global carbon cycle. The biogeochemical cycling of nitrogen also uses energy, as bacteria fix nitrogen gas from the atmosphere into reactive forms useful for living organisms using energy obtained from organic materials and ultimately from plants and the sun. Ecosystems also cycle phosphorus, sulfur and other elements. As biogeochemical cycles are defined by the exchange of matter between organisms and their environment, they are classic examples of ecosystem-level proceses.

Ecosystem Research

Scientists who study entire ecosystems are generally called systems ecologists. However, most ecologists use the ecosystem concept and make measurements on ecosystem properties even if their work focuses on a single species or population.

Methods

Observing ecosystems

Researchers can make direct observations on ecosystems in the field and indirect observations using remote sensing. Direct measurements include sampling and measurement of soils and vegetation, characterization of community structure andbiodiversity, and the use of instruments for observing gas exchange and the fluxes of nutrients and water. As ecosystems can be very challenging to recreate under laboratory conditions, observational studies on existing ecosystems are a core methodology of ecosystem science.

Ecosystem experiments

Though it has historically been difficult, ecosystems are now often studied using the classic experimental methods of science, For example, small- and meso-scale ecosystems containing a significant set of interacting organisms and their environment may be created in the laboratory, or in enclosures in the field. There are also methods for excluding organisms or altering environmental conditions in the field, such as the addition of nutrients and artificially enhancing carbon dioxide concentrations, temperature ormoisture.

Modeling

To better understand how ecosystems function and change, modeling is often used to simulate ecosystem dynamics, including thebiogeochemical cycles of carbon and other elements, the role of specific species or functional groups in controlling ecosystem function, and even dynamic changes in ecosystem structure and function across landscapes and the entire biosphere.

The Future

Ecosystem science is evolving rapidly in both methodology and focus. Human alteration of ecosystems is now so pervasive globally that ecologists are working to integrate humans into ecosystem science at many levels—including the study of urban ecology,agroecology and global ecology. New techniques for ecosystem modelling are being developed all the time, as are new methods for observing ecosystems from space by remote sensing and aerial platforms, and even by networks of sensors embedded in soils andplants across ecosystems and on towers that can make observations on ecosystem exchanges with the atmosphere on a continuous basis. Examples of cutting edge ecosystem research are the Carnegie Airborne Observatory—an aerial remote sensing system capably of precisely mapping ecosystem carbon and species diversity, and the development of the National Ecological Observatory Network (NEON), a continental-scale research platform for discovering and understanding the impacts of climate change, land-use change, and invasive species on ecosystems.

More About Ecosystems

• Biosphere
• Biome
• Ecology
• Biogeochemical cycles
• Ecological energetics
• Biodiversity
• Millennium Ecosystem Assessment
• International Geosphere-Biosphere Programme (IGBP

Scientists claim to have found the ‘Holy Grail’ of science in an artificial leaf that could turn ever British home into its own power station.

The leaf, which is the same size as a playing card, mimics the process of photosynthesis that plants use to convert sunlight and water into energy.

Scientists behind the invention say it could provide an affordable solution to the third world’s growing energy crisis.

Holy Grail: The leaf, which is similar to this separate prototype, mimics the process of photosynthesis that plants use to convert sunlight and water into energy

Dr Daniel Nocera, who led the research team, said: ‘A practical artificial leaf has been one of the Holy Grails of science for decades.

‘We believe we have done it.

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‘The artificial leaf shows particular promise as an inexpensive source of electricity for homes of the poor in developing countries. Our goal is to make each home its own power station.

‘One can envision villages in India and Africa not long from now purchasing an affordable basic power system based on this technology.’

Future: The leaf splits water into its two components, hydrogen and oxygen which are stored in a fuel cell that converts energy into electricity

The device bears no resemblance to Mother Nature’s counterparts on oaks, maples and other green plants, which scientists have used as the model for their efforts to develop this new genre of solar cells. 

About the shape of a poker card but thinner, the device is fashioned from silicon, electronics and catalysts, substances that accelerate chemical reactions that otherwise would not occur, or would run slowly. 

Placed in a single gallon of water in a bright sunlight, the device could produce enough electricity to supply a house in a developing country with electricity for a day, Nocera said. 

It does so by splitting water into its two components, hydrogen and oxygen.

The hydrogen and oxygen gases would be stored in a fuel cell, which uses those two materials to produce electricity, located either on top of the house or beside it.

Nocera, who is with the Massachusetts Institute of Technology, points out that the ‘artificial leaf’ is not a new concept. 

The first artificial leaf was developed more than a decade ago by John Turner of the U.S. National Renewable Energy Laboratory in Boulder, Colorado. 

Although highly efficient at carrying out photosynthesis, Turner’s device was impractical for wider use, as it was composed of rare, expensive metals and was highly unstable — with a lifespan of barely one day.

Nocera’s new leaf overcomes these problems.

‘Our goal is to make each home its own power station’

Dr Daniel Nocera

It is made of inexpensive materials that are widely available, works under simple conditions and is highly stable. In laboratory studies, he showed that an artificial leaf prototype could operate continuously for at least 45 hours without a drop in activity.

The key to this breakthrough is Nocera’s recent discovery of several powerful new, inexpensive catalysts, made of nickel and cobalt, that are capable of efficiently splitting water into its two components, hydrogen and oxygen, under simple conditions. 

Right now, Nocera’s leaf is about 10 times more efficient at carrying out photosynthesis than a natural leaf. However, he is optimistic that he can boost the efficiency of the artificial leaf much higher in the future.

‘Nature is powered by photosynthesis, and I think that the future world will be powered by photosynthesis as well in the form of this artificial leaf,’ said Nocera, a chemist at Massachusetts Institute of Technology in Cambridge, 

• Carbon dating suggests it is around 2,500 years old
• Archaeologists baffled at how brain has survived

Archaeologists believe they have discovered one of the world’s oldest brains that once belonged to a man in Iron Age Britain who was sacrificed in a ritual killing.

Scientists found the cranium in a muddy pit when they were excavating a site before a new campus was to be built at the University of York. When a researcher reached inside the skull, she was stunned to discover the soft tissue of the 2,500-year-old brain still preserved.

Fractures and marks on the bones suggest the man, who was aged between 26 and 45, died most probably from hanging, after which he was carefully decapitated and his head was then buried on its own.

Grey matter: The 2,500-year-old preserved brain has baffled scientists after it was found during an excavation at the University of York

Scientists have been baffled by how the brain tissue - which usually rots after a couple at years - managed to remain intact for so long.

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‘The survival of brain remains where no other soft tissues are preserved is extremely rare,’ said Sonia O’Connor, research fellow in archaeological sciences at the University of Bradford.

‘This brain is particularly exciting because it is very well preserved, even though it is the oldest recorded find of this type in the UK, and one of the earliest worldwide.’

Philip Duffey, a neurologist at York Hospital who scanned the skull, said: ‘I’m amazed and excited that scanning has shown structures which appear to be unequivocally of brain origin.’

Baffled: Dr Sonia O Connor, from the University of Bradford, examines the remains of the brain

‘I think that it will be very important to establish how these structures have survived, whether there are traces of biological material within them and, if not, what is their composition.’

Experts from York Archaeological Trust were commissioned by the university to carry out the exploratory dig last year before building work on the £750million campus expansion started.

They discovered the solitary skull face-down in the pit in dark brown organic rich, soft sandy clay.

The university put together a team of scientists, archaeologists, chemists, bio-archaeologists and neurologists, to establish how the man’s brain, could have survived when all the other soft tissue had decayed leaving only the bone.

Remains: Archaeologists sift through the muddy pit at the site near the University of York where the brain was found

The team is also investigating details of the man’s death and burial that may have contributed to the survival of what is normally highly vulnerable soft tissue. 

The research, which was funded by the University of York and English Heritage, is published in the Journal of Archaeological Science.

Since the discovery, the brain and skull have been kept in strictly controlled conditions, but scientists have examined samples using a range of sophisticated equipment, including a CT scanner at York Hospital and mass spectrometers at the University of York.

Samples of brain material had a DNA sequence that matched sequences found only in a few individuals from Tuscany and the Near East. Carbon dating suggests the remains date from between 673-482BC.

Fractures on the second neck vertebrae point to some kind of trauma before the man died and and a cluster of about nine horizontal fine cut-marks made by a thin-bladed instrument, such as a knife, can be seen on the front of the brain.

Preserved: Brain material shows as dark folded matter at the top of the head in this computer-generated view of the skull

Clean: Scientists said there was no trace on the brain of the usual preservation methods such as embalming or smoking

Scientists are now investigating how lipids and proteins found in the brain preserved the brain and what happened between the man dying and his burial.

Dr O’Connor said: ‘It is rare to be able to suggest the cause of death for skeletonised human remains of archaeological origin. The preservation of the brain in otherwise skeletonised remains is even more astonishing but not unique.

‘This is the most thorough investigation ever undertaken of a brain found in a buried skeleton and has allowed us to begin to really understand why a brain can survive thousands of years after all the other soft tissues have decayed.’

Despite the place that ‘trophy heads’ appear to have played in Iron Age societies and evidence for the preservation of human remains in the Bronze Age, the researchers say there is no evidence for that in this case. They found no marks indicating deliberate preservation by embalming or smoking.

Dr O’Connor added: ‘The hydrated state of the brain and the lack of evidence for putrefaction suggests that burial, in the fine-grained, anoxic sediments of the pit, occurred very rapidly after death. This is a distinctive and unusual sequence of events, and could be taken as an explanation for the exceptional brain preservatioN

Read more: http://www.dailymail.co.uk/sciencetech/article-1371012/Scientists-discover-worlds-oldest-brains-belonging-Iron-Age-man-ritual-killing.html#ixzz1I2f5Otga

The cyclic reproduction changes of the human female are marked by menstruation, during which some cells, uncloatted blood from ruptured blood vessels, other fluids and uterine endometrium are released through the cervix and vagina. Each menstrual cycle occurs about every 28 days and last for 4 - 5 days. The menstruation occurs 12 to 14 days after the ovum is released from the ovary (ovulation), about once in four weeks. The periodicity of cycle varies with individuals. After fertilization, menstruation ceases and it is the first indication of pregnancy.

The menstrual (destructive phase) the uterus lining i.e. endometrium and its blood vessels break, and is discharge with in blood, mucus, cells debris, and other fluid as the menses by way of the vagina. This may last for 4 – 5 days. The menses occur when fertilization does not take place.

The proliferate (follicular) phase

Occur between the end of the menses and the ovulation. In this phase, under the stimulation of estrogen the uterine endometrium undergoes a process of growth (proliferation) and a new thick endometrium is formed. In the ovary, the follicles begin to develop in to a graafian follicles. This phase include cycle days 6- 13 or 14 in a 28 day cycle. The ovulatory phase indicates the rupture of the graafian follicle and released of the ovum (ovulation). It occurs some 14 days after the start of menstruation during this phase the concentration of estrogen is high in blood, and it stimulates the ovulation. The blood vessels enlarge and grow in the endometrial wall, and some secretary cells or glands are formed.

The secretory (luteal) phase

Occur between ovulation and the onset of menses, i.e. the phase last about 14 days (cycle days 15- 28). The endometrium, which is under the influence of progesterone and estrogen, increases in size, becomes thick, the endometrium glands become enlarged, undergo maximum secretory activity and its blood vessels become coiled and enlarged.

The ovum released in ovulatory phase may or may not be fertilize. If the ovum is fertilized, it becomes embedded in the endometrium (implantation), the corpus luteum remains to secrete progesterone which helps the embryo to grow with in the uterus. If the ovum is not fertilized, the corpus luteum disintegrates and the progesterone level falls sharply. 14 days after ovulation unless fertilization occurs, the menstruation begins again.

Hormonal control of menstrual cycle

The menstruation reflects not only the health of the uterus but also the health of the endocrine glands that control it, i.e. the ovaries and the pituitary gland.

Following hormones regulates the menstrual cycle. These hormones have profound effects on the ovaries and the uterus.

The anterior pituitary glands produces to gonadotrophic hormones

The follicle stimulating hormnones (FSH) and the luteinizing hormone (LH).

The FSH stimulates the ovarian follicle to mature and secondly, it stimulates the  Follicle to produce the estrogen. The estrogen brings about healing and repair of  uterine wall (endometrium) following menstruation.

In next two weeks the high concentration of estrogen in blood stream stimulates the anterior pituitary to produce second hormone called luteinizing hormone (LH). LH brings about ovulation and changes the graphian follicle into a corpus luteum.

The corpus leuteum secrets yet another hormone, the progesterone whose main function is to prepare uterus for pregnancy. The luteotrophic hormone (LTH) of corpus luteum seems to be responsible for production of progesterone, and maintenance of corpus luteum. If corpus luteum is not maintained, the implanted fertilized egg is carried away in the menstrual flow(abortion)

In the absence of pregnancy, corpus luteum stops secreting progesterone, anterior pituitary starts secreting FSH again, and the cycle is repeated.

The disorders of the female reproductive system are frequently involved in the menstrual disorders.  Some of them are:

Amenorrhoea

Amenorrhoeameans without monthly flow, i.e. the absence of menstruation.  If a woman has never menstruated, the condition is calledPrimary amenorrhoea. This can be caused by endocrine disorders, most often in the pituitary gland and hypothalamus or by genetically caused abnormal development of the ovaries or uterus.

Secondary amenorrhoea, the skipping of one or more periods, is commonly experienced by women at some time during their life. Changes in body weight, either gains or losses often cause amenorrhoea. Obesity may disturb ovarian function, and similarly the extreme weight loss that characterizes anorexia nervosa often leads to a suspension of menstrual flow.  When amenorrhoea is not related with the changes in body weight, its causative factor may be the deficiencies of pituitary and ovarian hormone. Amenorrhoea may also be caused by continuous involvement in rigorous atheletic training.

Dysmenorrhoea

It refers to pain associated with menstruation and the term is usually reserved to describe an individual with menstrual symptoms that are severe enough to prevent her from functioning normally for one or more days each month.  Primary dysmenorrhoea is painful menstruation with no detectable organic disease. The pain in this condition is thought to result from uterine contractions, probably associated with uterine muscle ischemia and Prostaglandin’s produced by the uterus. Prostaglandins are known to stimulate uterine contractions, but they cannot do so in the presence of high levels of progesterone (a hormone secreted by ovary). Progesterone levels are high during the last half of the menstrual cycle, and during this time Prostaglandin’s are apparently inhibited by progesterone from producing uterine contractions. However, in the absence of pregnancy progesterone levels drop rapidly and prostaglandin production increases. This causes the uterus to contract and slough off its lining, which may result in dysmenorrhoea. In addition to pain, other signs and symptoms may include headache, nausea, diarrhoea or constipation and increased urinary frequency. Secondary dysmenorrhoea is painful menstruation that is frequently associated with a pelvic pathology. In some cases it is caused by uterine tumours, ovarian cysts, pelvic inflammatory disease, endometriosis and intrauterine devices.

Abnormal Uterine Bleeding

This refers to menstruation of excessive duration or excessive amount, diminished menstrual flow; too frequent menstruation, intermenstrual bleeding and post-menstrual bleeding. The causative factors for all such conditions may be the disordered hormonal regulation, emotional imbalance and any tumour in the uterus.

Premenstrual Syndrome

PMS, or premenstrual syndrome, is a condition that affects a lot of women before the onset of their menstrual period. PMS commonly occurs during the week or two before the start of your period and can last until menstruation starts. The symptoms usually increase in severity until the onset of menstruation and then dramatically disappear. Symptoms are diverse as overall discomfort, oedema, weight gain, painful or swollen breast and tenderness, abdominal distension, backache, joint pain, constipation, skin eruptions, fatigue and lethargy, insomnia, depression or anxiety, irritability, headache, clumsiness and even uncharacteristically aggressive behavior. Some may even experience no symptoms at all. The basic cause of this state is not known. 

Yoga can help by relieving the discomfort and keep you fit, strong, clear thinking and with bliss. There are poses that are particularly useful during the menstrual period. These poses ease menstrual cramps, heavy bleeding, pelvic discomfort and the low back pain associated with menses. They are also effective in smoothing out the emotional rough edges some women encounter at this time of their cycle.

Yoga Poses Recommended During the Menstrual Period 

Svastikasana

Virasana

Padmasana

Gomukhasana

Paschimothansana

Baddha-konaasana

Relieves menstrual discomfort and sciatica also helps relieve the symptoms of menopause. 

Janu Sirsasana

It is recommended to perform the asana without coming forward, keeping your back spine concave and front torso long during pregnancy (up to second trimester).  These poses are calming.  Lower abdominal and pelvic compression  aids cramps and heavy bleeding. Relieves menstrual discomfort and sciatica also helps relieve the symptoms of menopause.

Trikonasana

Ardhachandrasana

These poses are helpful for backache associated with menses.

Supported Setubandhasana

This pose is calming, It also relieves pelvic discomfort.

Supta-Vajrasana , Matsyasana, done with support of belts, bolsters and blankets

Shavasana.

Pranayama

Ujjayi and Viloma pranayama in Shavasana.

If the menstruation is normal without giving any pain, headache, irritation, anxiety, suffocation, depression one can do Ujjayi and Viloma pranayamas in a sitting position.

This asanas relax the muscles and nerves which are under constant stress, strain and irritation. If done above asanas restfully, it checks the over bleeding, soothes the abdomen and makes the throbbing brain-cells rest. These asanas help those who suffer from head-ache, backache, heavy bleeding, abdominal cramps and fatigue.

Inversions during menstrual period

Inversions (like head stand, shoulder stand) are not recommended during the menstrual period for philosophic as well as physiologic reasons. During menstruation if one does inversions the blood flow will be arrested. It may lead to fibroids, cysts, endometriosis and cancer, damaging the system.
According to Ayurveda philosophy, during menses the direction of energy is down and out of the body. This flow should not be obstructed or reversed as it is in inversions.

Urine, faeces, phlegm are weast products in the body and so are thrown out of the system So you cannot hold, mucus etc. If they are retained within they invite all diseases.

The Inversions are very important to the health because they produce a revitalizing effect on the entire body. Although Inversions are not recommended during the menstrual period, the inversions have their own characteristics. when done during pregnancy they hold the foetus safely and healthily. It is greatly advantageous for those who have frequent miscarriage.

 
Note

Avoid physical exertion during menstruation.

The flow has to stop completely before one can resume the practice of inversion. As soon as the flow stops, begin with the practice of inversions.

It is recommended to read “Yoga: A Gem for Women” by Geeta Iyengar.

Geeta and her father B.K.S. Iyengar were the first yoga masters of the twentieth century to strongly address the need for women to nurture and honour their bodies by adjusting the way they practice yoga during the different cycles in life.

It’s a natural part of life to have sexual feelings. As people pass from childhood, through adolescence, to adulthood, their sexual feelings develop and change.

Adolescence Is a Time of Change

During the teen years, sexual feelings are awakened in new ways because of the hormonal and physical changes of puberty. These changes involve both the body and the mind, and teens may wonder about new — and often intense — sexual feelings.

It takes time for many people to understand who they are and who they’re becoming. Part of that understanding includes a person’s sexual feelings and attractions.

The term sexual orientation refers to the gender (that is, male or female) to which a person is attracted. There are several types of sexual orientation that are commonly described:

• Heterosexual. People who are heterosexual are romantically and physically attracted to members of the opposite sex: Heterosexual males are attracted to females, and heterosexual females are attracted to males. Heterosexuals are sometimes called “straight.”
• Homosexual. People who are homosexual are romantically and physically attracted to people of the same sex: Females who are attracted to other females are lesbian; males who are attracted to other males are often known as gay. (The term gay is sometimes also used to describe homosexual individuals of either gender.)
• Bisexual. People who are bisexual are romantically and physically attracted to members of both sexes.

Teens — both guys and girls — often find themselves having sexual thoughts and attractions. For some, these feelings and thoughts can be intense — and even confusing or disturbing. That may be especially true for people who are having romantic or sexual thoughts about someone who is the same sex they are. “What does that mean,” they might think. “Am I gay?”

Thinking sexually about both the same sex and the opposite sex is quite common as people sort through their emerging sexual feelings. This type of imagining about people of the same or opposite sex doesn’t necessarily mean that a person fits into a particular type of sexual orientation.

Some teens may also experiment with sexual experiences, including those with members of the same sex, during the years they are exploring their own sexuality. These experiences, by themselves, do not necessarily mean that a person is gay or straight.

Do People Choose Their Sexual Orientation?

Most medical professionals, including organizations such as the American Academy of Pediatrics and the American Psychological Association, believe that sexual orientation involves a complex mixture of biology, psychology, and environmental factors. A person’s genes and inborn hormonal factors may play a role as well. These medical professionals believe that — in most cases — sexual orientation, whatever its causes, is not simply chosen.

Not everyone agrees. Some believe that individuals can choose who they are attracted to — and that people who are gay have chosen to be attracted to people of the same gender. No matter what someone’s sexual orientation is, in some cases it may be affected by the life experiences that person has had.

There are lots of opinions and stereotypes about sexual orientation, though, and some of these can be hurtful to people of all orientations. For example, having a more “feminine” appearance or interest does not mean that a guy is gay. And having a more “masculine” appearance doesn’t mean a girl is lesbian. As with most things, making assumptions just based on looks can lead to the wrong conclusion.

The Importance of Talking

No matter what someone’s sexual orientation is, learning about sexuality and relationships can be difficult. It can help to talk to someone about the confusing feelings that go with growing up, perhaps a parent or other family member, a close friend or sibling, or a school counselor. It’s not always easy to find somebody to talk to, but many people find that confiding in someone they trust and feel close to, even if they’re not completely sure how that person will react, turns out to be a positive experience.

In many communities, resources such as youth groups composed of teens who are facing similar issues can provide opportunities for people to talk to others who understand. Psychologists, psychiatrists, family doctors, and trained counselors can help teens cope — confidentially and privately — with the difficult feelings that go with their developing sexuality. These experts also can help teens find ways to deal with any peer pressure, harassment, and bullying they may face.

Whether gay, straight, bisexual, or just not sure, almost all teens have questions about physically maturing and about sexual health (for example, avoiding STDs). It’s important to find a doctoror health professional to discuss these issues with — someone who can provide reliable health advice.

Although sexual feelings and behavior are important parts of human development, there are still many unanswered questions about human sexuality. Researchers are constantly learning new information, and undoubtedly people will know more about sexual orientation in the coming years.

ScienceDaily (Mar. 16, 2011) — Its head looks like a turkey’s, its body resembles a chicken’s — now scientists can explain why one of the poultry world’s most curious specimens has developed such a distinctive look.

The Transylvanian naked neck chicken — once dubbed a Churkey or a Turken because of its hybrid appearance — has developed its defining feature because of a complex genetic mutation.

Researchers at The Roslin Institute at The University of Edinburgh found that a vitamin A-derived substance produced around the bird’s neck enhanced the effects of the genetic mutation.

This causes a protein — BMP12 — to be produced, suppressing feather growth and causing the bird to have an outstanding bald neck.

The findings could help poultry production in hot countries, including in the developing world, because chickens with naked necks are much better equipped to withstand the heat.

The discovery also has implications for understanding how birds — including vultures — evolved to have featherless necks due to their metabolism of vitamin A selectively in neck skin.

Transylvanian naked necks, which are thought to have originated from the north of Romania, have been around for hundreds of years and were introduced to Britain in the 1920s.

The research, published in the journal PLoS Biology, was funded by the Biotechnology and Biological Sciences Research Council.

Dr Denis Headon, who led the research at The Roslin Institute, said: “Not only does this help our understanding of developmental biology and give insight into how different breeds have evolved but it could have practical implications for helping poultry production in hot countries including those in the developing world.”

Researchers analysed DNA samples from naked neck chickens in Mexico, France and Hungary to find the genetic mutation. Skin samples from embryonic chickens were also analysed using complex mathematical modelling to identify the genetic trigger.

Bt cotton

Cotton and other monocultured crops require an intensive use of pesticides as various types of pests attack these crops causing extensive damage. Over the past 40 years, many pests have developed resistance to pesticides.

So far, the only successful approach to engineering crops for insect tolerance has been the addition of Bt toxin, a family of toxins originally derived from soil bacteria. The Bt toxin contained by the Bt crops is no different from other chemical pesticides, but causes much less damage to the environment. These toxins are effective against a variety of economically important crop pests but pose no hazard to non-target organisms like mammals and fish. Three Bt crops are now commercially available: corn, cotton, and potato.

As of now, cotton is the most popular of the Bt crops: it was planted on about 1.8 million acres (728437 ha) in 1996 and 1997. The Bt gene was isolated and transferred from a bacterium bacillus thurigiensis to American cotton. The American cotton was subsequently crossed with Indian cotton to introduce the gene into native varieties.

The Bt cotton variety contains a foreign gene obtained from bacillus thuringiensis. This bacterial gene, introduced genetically into the cotton seeds, protects the plants from bollworm (A. lepidoptora), a major pest of cotton. The worm feeding on the leaves of a BT cotton plant becomes lethargic and sleepy, thereby causing less damage to the plant.

Field trials have shown that farmers who grew the Bt variety obtained 25%–75% more cotton than those who grew the normal variety. Also, Bt cotton requires only two sprays of chemical pesticide against eight sprays for normal variety. According to the director general of the Indian Council of Agricultural Research, India uses about half of its pesticides on cotton to fight the bollworm menace.

Use of Bt cotton has led to a 3%–27 increase in cotton yield in countries where it is grown.