Kematian

Dari Wikipedia bahasa Indonesia, ensiklopedia bebas

Tengkorak manusia di scrub, circa 1900-1910.

Kematian atau ajal adalah akhir dari kehidupan, ketiadaan nyawa dalam organisme biologis. Semua makhluk hidup pada akhirnya akan mati secara permanen, baik karena penyebab alami seperti penyakit atau karena penyebab tidak alami seperti kecelakaan. Setelah kematian, tubuh makhluk hidup mengalami pembusukan.
Istilah lain yang sering digunakan adalah meninggal, wafat, tewas, atau mati.

Penyebab-penyebab kematian

Seiring penuaan usia makhluk hidup, tubuh mereka akan perlahan-lahan mulai berhenti bekerja.
Jika tubuh tidak mampu melawan penyakit, atau tidak diobati.
Kecelakaan seperti tenggelam, tertabrak, terjatuh dari ketinggian, dll.
Lingkungan dengan suhu yang sangat dingin atau yang terlalu panas.
Pendarahan yang diakibatkan luka yang parah.
Kekurangan makanan, air, udara, dan perlindungan.
Diserang dan dimakan (pembunuhan).
Infeksi dari gigitan hewan berbisa maupun hewan yang terinfeksi virus berbahaya.
Kematian disaat tidak terbangun dari tidur.
Kematian sebelum lahir, karena perawatan janin yang tidak benar.

Januari 15, 2010

Dasyatnya Saat Kematian

Filed under: Dakwah Islam — po3tra78 @ 2:22 pm
Tags: kematian;dasyatnya;sakratul maut;malaikat

Perkarangan kuburan
Demi Allah, seandainya jenazah yang sedang tuan-tuan tangisi boleh berbicara sekejab, lalu menceritakan (pengalaman sakaratul mautnya) pada tuan-tuan, niscaya tuan-tuan akan melupakan jenazah tersebut, dan mulai menangisi diri tuan-tuan sendiri”. (Imam Ghazali mengutip atsar Al-Hasan).
Datangnya Kematian Menurut Al Qur’an :
1. Kematian bersifat memaksa dan siap menghampiri manusia walaupun kita berusaha menghindarkan risiko-risiko kematian.
Katakanlah: “Sekiranya kamu berada di rumahmu, niscaya orang-orang yang telah ditakdirkan akan mati terbunuh itu ke luar (juga) ke tempat mereka terbunuh”. Dan Allah (berbuat demikian) untuk menguji apa yang ada dalam dadamu dan untuk membersihkan apa yang ada dalam hatimu. Allah Maha Mengetahui isi hati. (QS Ali Imran, 3:154)
2. Kematian akan mengejar siapapun meskipun ia berlindung di balik benteng yang kukuh atau berlindung di sebalik teknologi kedoktoran yang canggih serta ratusan doktor terbaik yang ada di muka bumi ini.
Di mana saja kamu berada, kematian akan mendapatkan kamu, meskipun pun kamu di dalam benteng yang tinggi lagi kukuh, dan jika mereka memperoleh kebaikan, mereka mengatakan: “Ini adalah dari sisi Allah”, dan kalau mereka ditimpa sesuatu bencana mereka mengatakan: “Ini (datangnya) dari sisi kamu (Muhammad)”. Katakanlah: “Semuanya (datang) dari sisi Allah”. Maka mengapa orang-orang itu (orang munafik) hampir-hampir tidak memahami pembicaraan sedikit pun? (QS An-Nisa 4:7

3. Kematian akan mengejar siapapun walaupun ia lari menghindar.
Katakanlah: “Sesungguhnya kematian yang kamu lari daripadanya, maka sesungguhnya kematian itu akan menemui kamu, kemudian kamu akan dikembalikan kepada (Allah), yang mengetahui yang gaib dan yang nyata, lalu Dia beritakan kepadamu apa yang telah kamu kerjakan”. (QS al-Jumu’ah, 62:

4. Kematian datang secara tiba-tiba.
Sesungguhnya Allah, hanya pada sisi-Nya sajalah pengetahuan tentang Hari Kiamat; dan Dia-lah Yang menurunkan hujan, dan mengetahui apa yang ada dalam rahim. Dan tiada seorang pun yang dapat mengetahui (dengan pasti) apa yang akan diusahakannya besok. Dan tiada seorang pun yang dapat mengetahui di bumi mana dia akan mati. Sesungguhnya Allah Maha Mengetahui lagi Maha Mengenal. (QS, Luqman 31:34)
5. Kematian telah ditentukan waktunya, tidak dapat ditunda atau dipercepat
Dan Allah sekali-kali tidak akan menangguhkan (kematian) seseorang apabila datang waktu kematiannya. Dan Allah Maha Mengetahui apa yang kamu kerjakan. (QS, Al-Munafiqun, 63:11)
Dahsyatnya Rasa Sakit Saat Sakaratul Maut
Sabda Rasulullah SAW : “Sakaratul maut itu sakitnya sama dengan tusukan tiga ratus pedang” (HR Tirmidzi)
Sabda Rasulullah SAW : “Kematian yang paling ringan ibarat sebatang pohon penuh duri yang menucuk di selembar kain sutera. Apakah batang pohon duri itu dapat diambil tanpa membawa serta bahagian kain sutera yang terobek ?” (HR Bukhari)
Pendapat para sahabat Rasulullah SAW .
Ka’b al-Ahbar r.a berpendapat : “Sakaratul maut ibarat sebatang pohon berduri yang dimasukkan kedalam perut seseorang. Lalu, seorang lelaki menariknya dengan sekuat-kuatnya sehingga ranting itu pun membawa semua bahagian tubuh yang menyangkut padanya dan meninggalkan yang tersisa itu”.
Imam Ghazali rah, berpendapat : “Rasa sakit yang dirasakan selama sakaratul maut meruntum jiwa dan menyebar ke seluruh anggota tubuh sehingga bahagian orang yang sedang sekarat merasakan dirinya ditarik-tarik dan dicerai-ceraikan dari setiap urat nadi, urat syaraf, persendian, dari setiap akar rambut dan kulit kepala hingga kaki”.
Imam Ghazali rah juga mengambil satu riwayat ketika sekelompok Bani Israil yang sedang melewati sebuah pekuburan berdoa pada Allah SWT agar Ia menghidupkan satu mayat dari pekuburan itu sehingga mereka boleh mengetahui gambaran sakaratul maut. Dengan izin Allah melalui suatu cara tiba-tiba mereka dihadapkan pada seorang wanita yang muncul dari salah satu kuburan. “Wahai manusia !”, kata wanita tersebut. “Apa yang kalian kehendaki dariku? Limapuluh tahun yang lalu aku mengalami kematian, namun hingga kini rasa perih bekas sakaratul maut itu belum juga hilang dariku.”
Proses sakaratul maut bisa memakan waktu yang berbeza untuk setiap orang, dan tidak dapat dihitung dalam ukuran masa seperti hitungan waktu dunia ketika kita menyaksikan detik-detik terakhir kematian seseorang.
Rasa sakit sakaratul maut akan di alami setiap manusia, dengan berbagai macam tingkatan rasa sakit, ini tidak berkait dengan tingkatan keimanan atau kezaliman seseorang selama ia hidup. Sebuah riwayat bahkan mengatakan bahwa rasa sakit sakaratul maut merupakan suatu proses pengurangan kadar siksaan akhirat kita kelak.
Demikianlah perancangan Allah. Wallahu a’lam bis shawab.
Sakaratul Maut Orang-orang Zalim
Imam Ghazali mengambil satu riwayat yang menceritakan tentang keinginan Ibrahim as untuk melihat wajah Malaikatul Maut ketika mencabut nyawa orang zalim. Allah SWT pun memperlihatkan gambaran rupa Malaikatul Maut sebagai seorang lelaki bertubuh besar berkulit gelap, rambut menegak, berbau busuk, memiliki dua mata, satu didepan satu dibelakang, mengenakan pakaian serba hitam, sangat menakutkan, dari mulutnya keluar jilatan api, ketika melihatnya Ibrahim as pun pengsan tidak sadarkan diri. Setelah sedar Ibrahim as pun berkata bahawa dengan memandang wajah Malaikatul Maut rasanya sudah cukup bagi seorang pelaku kejahatan untuk menerima ganjaran hukuman kejahatannya, padahal hukuman akhirat Allah jauh lebih dahsyat dari semua itu.
Di akhir sakaratul maut, seorang manusia akan diperlihatkan padanya wajah dua Malaikat Pencatat Amal. Kepada orang zalim, si malaikat akan berkata, “Semoga Allah tidak memberimu balasan yang baik, engkaulah yang membuat kami terpaksa hadir ke tengah-tengah perbuatan kejimu, dan membuat kami hadir menyaksikan perbuatan burukmu, memaksa kami mendengar ucapan-ucapan burukmu. Semoga Allah tidak memberimu balasan yang baik ! “ Ketika itulah orang itu menatap lesu ke arah kedua malaikat itu.
Ketika sakaratul maut hampir selesai, dimana tenaga mereka telah hilang dan roh mulai merayap keluar dari jasad mereka, maka tibalah saatnya Malaikatul Maut mengabarkan padanya rumahnya kelak di akhirat. Rasulullah SAW pernah bersabda, “Tak seorangpun diantara kalian yang akan meninggalkan dunia ini kecuali telah diberikan tempat kembalinya dan diperlihatkan padanya tempatnya di surga atau di neraka”.
Dan inilah ucapan malaikat ketika menunjukkan rumah akhirat seorang zalim di neraka, “Wahai musuh Allah, itulah rumahmu kelak, bersiaplah engkau merasakan seksa neraka”. Naudzu bila min dzalik!
Sakaratul Maut Orang-orang Yang Bertaqwa
Sebaliknya Imam Ghazali mengatakan bahawa orang beriman akan melihat rupa Malaikatul Maut sebagai pemuda yang tampan, berpakaian indah dan menyebarkan wangi yang sangat harum.
Dan dikatakan kepada orang-orang yang bertakwa: “Apakah yang telah diturunkan oleh Tuhanmu?” Mereka menjawab: “(Allah telah menurunkan) kebaikan”. Orang-orang yang berbuat baik di dunia ini mendapat (pembalasan) yang baik. Dan sesungguhnya kampung akhirat adalah lebih baik dan itulah sebaik-baik tempat bagi orang yang bertakwa, (yaitu) surga Adn yang mereka masuk ke dalamnya, mengalir di bawahnya sungai-sungai, di dalam surga itu mereka mendapat segala apa yang mereka kehendaki. Demikianlah Allah memberi balasan kepada orang-orang yang bertakwa. (yaitu) orang-orang yang diwafatkan dalam keadaan baik oleh para malaikat dengan mengatakan (kepada mereka): “Assalamu alaikum, masuklah kamu ke dalam surga itu disebabkan apa yang telah kamu kerjakan”. (QS, An-Nahl, 16 : 30-31-32)
Dan saat terakhir sakaratul mautnya, malaikatpun akan menunjukkan surga yang akan menjadi rumahnya kelak di akhirat, dan berkata padanya, “Bergembiaralah, wahai sahabat Allah, itulah rumahmu kelak, bergembiralah dalam masa-masa menunggumu”.
Semoga Allah memberikan taufik untuk kita amal dan sampaikan.

Death

From Wikipedia, the free encyclopedia

For other uses, see Death (disambiguation) and Dead (disambiguation). For the process of coloring, see Dyeing.

"Deceased" redirects here. For the band, see Deceased (band).

The human skull is a universal symbol for death.

Death is the termination of the biological functions that sustain a living organism. The word refers both to the particular processes of life's cessation as well as to the condition or state of a formerly living body. Phenomena which commonly bring about death include predation, malnutrition, accidents resulting in terminal injury, and disease.
The nature of death has been for millennia a central concern of the world's religious traditions and of philosophical enquiry, and belief in some kind of afterlife or rebirth has been a central aspect of religious belief. In modern scientific enquiry, the origin and nature of consciousness has yet to be fully understood; any such view about the existence or non-existence of consciousness after death therefore remains speculative.^[1]

Etymology

The word death comes from Old English deað, which in turn comes from Proto-Germanic dauthaz (reconstructed by etymological analysis). This comes from the Proto-Indo-European stem dheu- meaning the 'Process, act, condition of dying'.
Dauthaz was reconstructed through the use of the daughter tongues of Proto-Germanic, such as doth from Old Saxon, dath from Old Frisian, dood from Dutch, tod from Old High German, dauði from Old Norse, död from Swedish, and dauþas from Gothic.^[2]

Senescence

Almost all animals fortunate enough to survive hazards to their existence eventually die from senescence. The only exception is the jellyfish Turritopsis nutricula, thought to be, in effect, immortal.^[3] Causes of death in humans as a result of intentional activity include suicide, homicide and war. From all causes, roughly 150,000 people die around the world each day.^[4]
Physiological death is now seen as less an event than a process: conditions once considered indicative of death are now reversible.^[5] Where in the process a dividing line is drawn between life and death depends on factors beyond the presence or absence of vital signs. In general, clinical death is neither necessary nor sufficient for a determination of legal death. A patient with working heart and lungs determined to be brain dead can be pronounced legally dead without clinical death occurring. Precise medical definition of death, in other words, becomes more problematic, paradoxically, as scientific knowledge and medicine advance.

Signs of death

Signs of death or strong indications that a person is no longer alive are:

Cessation of breathing
No pulse (cardiac arrest)
Pallor mortis, paleness which happens in the 15–120 minutes after death
Livor mortis, a settling of the blood in the lower (dependent) portion of the body
Algor mortis, the reduction in body temperature following death. This is generally a steady decline until matching ambient temperature
Rigor mortis, the limbs of the corpse become stiff (Latin rigor) and difficult to move or manipulate
Decomposition, the reduction into simpler forms of matter, accompanied by a strong, unpleasant odor.

Diagnosis

Problems of definition

A flower, a skull and an hourglass stand in for Life, Death and Time in this 17th-century painting by Philippe de Champaigne

The concept of death is a key to human understanding of the phenomenon.^[6] There are many scientific approaches to the concept. For example, brain death, as practiced in medical science, defines death as a point in time during which brain activity ceases.^[7]^[8]^[9]^[10] One of the challenges in defining death is in distinguishing it from life. As a point in time, death would seem to refer to the moment at which life ends. However, determining when death has occurred requires drawing precise conceptual boundaries between life and death. This is problematic because there is little consensus over how to define life. It is possible to define life in terms of consciousness. When consciousness ceases, a living organism can be said to have died. One of the notable flaws in this approach, however, is that there are many organisms which are alive but probably not conscious (for example, single-celled organisms). Another problem with this approach is in defining consciousness, which has many different definitions given by modern scientists, psychologists and philosophers. This general problem of defining death applies to the particular challenge of defining death in the context of medicine.
Other definitions for death focus on the character of cessation of something.^[11] In this context "death" describes merely the state where something has ceased, for example, life. Thus, the definition of "life" simultaneously defines death.
Historically, attempts to define the exact moment of a human's death have been problematic. Death was once defined as the cessation of heartbeat (cardiac arrest) and of breathing, but the development of CPR and prompt defibrillation have rendered that definition inadequate because breathing and heartbeat can sometimes be restarted. Events which were causally linked to death in the past no longer kill in all circumstances; without a functioning heart or lungs, life can sometimes be sustained with a combination of life support devices, organ transplants and artificial pacemakers.
Today, where a definition of the moment of death is required, doctors and coroners usually turn to "brain death" or "biological death" to define a person as being clinically dead; people are considered dead when the electrical activity in their brain ceases. It is presumed that an end of electrical activity indicates the end of consciousness. However, suspension of consciousness must be permanent, and not transient, as occurs during certain sleep stages, and especially a coma. In the case of sleep, EEGs can easily tell the difference.
However, the category of "brain death" is seen by some scholars to be problematic. For instance, Dr. Franklin Miller, senior faculty member at the Department of Bioethics, National Institutes of Health, notes: "By the late 1990s, however, the equation of brain death with death of the human being was increasingly challenged by scholars, based on evidence regarding the array of biological functioning displayed by patients correctly diagnosed as having this condition who were maintained on mechanical ventilation for substantial periods of time. These patients maintained the ability to sustain circulation and respiration, control temperature, excrete wastes, heal wounds, fight infections and, most dramatically, to gestate fetuses (in the case of pregnant "brain-dead" women)."^[12]
Those people maintaining that only the neo-cortex of the brain is necessary for consciousness sometimes argue that only electrical activity should be considered when defining death. Eventually it is possible that the criterion for death will be the permanent and irreversible loss of cognitive function, as evidenced by the death of the cerebral cortex. All hope of recovering human thought and personality is then gone given current and foreseeable medical technology. However, at present, in most places the more conservative definition of death – irreversible cessation of electrical activity in the whole brain, as opposed to just in the neo-cortex – has been adopted (for example the Uniform Determination Of Death Act in the United States). In 2005, the Terri Schiavo case brought the question of brain death and artificial sustenance to the front of American politics.
Even by whole-brain criteria, the determination of brain death can be complicated. EEGs can detect spurious electrical impulses, while certain drugs, hypoglycemia, hypoxia, or hypothermia can suppress or even stop brain activity on a temporary basis. Because of this, hospitals have protocols for determining brain death involving EEGs at widely separated intervals under defined conditions.

Legal

[edit] Misdiagnosed

Causes

The leading cause of death in developing countries is infectious disease. The leading causes of death in developed countries are atherosclerosis (heart disease and stroke), cancer, and other diseases related to obesity and aging. These conditions cause loss of homeostasis, leading to cardiac arrest, causing loss of oxygen and nutrient supply, causing irreversible deterioration of the brain and other tissues. Of the roughly 150,000 people who die each day across the globe, about two thirds die of age-related causes.^[4] In industrialized nations, the proportion is much higher, reaching 90%.^[4] With improved medical capability, dying has become a condition to be managed. Home deaths, once commonplace, are now rare in the developed world.

The body of Pope John Paul II lying in state in St. Peter's Basilica, 2005

In developing nations, inferior sanitary conditions and lack of access to modern medical technology makes death from infectious diseases more common than in developed countries. One such disease is tuberculosis, a bacterial disease which killed 1.7 million people in 2004.^[18] Malaria causes about 400–900 million cases of fever and 1–3 million deaths annually.^[19] AIDS death toll in Africa may reach 90–100 million by 2025.^[20]^[21]
According to Jean Ziegler, who was the United Nations Special reporter on the Right to Food from 2000 to March 2008; mortality due to malnutrition accounted for 58% of the total mortality rate in 2006. Ziegler says worldwide approximately 62 million people died from all causes and of those deaths more than 36 million died of hunger or diseases due to deficiencies in micronutrients.^[22]
Tobacco smoking killed 100 million people worldwide in the 20th century and could kill 1 billion people around the world in the 21st century, a WHO Report warned.^[23]^[24]
Many leading developed world causes of death can be postponed by diet and physical activity, but the accelerating incidence of disease with age still imposes limits on human longevity. The evolutionary cause of aging is, at best, only just beginning to be understood. It has been suggested that direct intervention in the aging process may now be the most effective intervention against major causes of death.^[25]

Autopsy

An autopsy, also known as a postmortem examination or an obduction, is a medical procedure that consists of a thorough examination of a human corpse to determine the cause and manner of a person's death and to evaluate any disease or injury that may be present. It is usually performed by a specialized medical doctor called a pathologist.

Rembrandt turns an autopsy into a masterpiece: The Anatomy Lesson of Dr. Nicolaes Tulp

Autopsies are either performed for legal or medical purposes. A forensic autopsy is carried out when the cause of death may be a criminal matter, while a clinical or academic autopsy is performed to find the medical cause of death and is used in cases of unknown or uncertain death, or for research purposes. Autopsies can be further classified into cases where external examination suffices, and those where the body is dissected and an internal examination is conducted. Permission from next of kin may be required for internal autopsy in some cases. Once an internal autopsy is complete the body is generally reconstituted by sewing it back together. Autopsy is important in a medical environment and may shed light on mistakes and help improve practices.
A "necropsy" is an older term for a postmortem examination, unregulated, and not always a medical procedure. In modern times the term is more often used in the postmortem examination of the corpses of animals.

Life extension

Main article: Life extension

Life extension refers to an increase in maximum or average lifespan, especially in humans, by slowing down or reversing the processes of aging. Average lifespan is determined by vulnerability to accidents and age or lifestyle-related afflictions such as cancer, or cardiovascular disease. Extension of average lifespan can be achieved by good diet, exercise and avoidance of hazards such as smoking. Maximum lifespan is determined by the rate of aging for a species inherent in its genes. Currently, the only widely recognized method of extending maximum lifespan is calorie restriction. Theoretically, extension of maximum lifespan can be achieved by reducing the rate of aging damage, by periodic replacement of damaged tissues, or by molecular repair or rejuvenation of deteriorated cells and tissues.
Researchers of life extension are a subclass of biogerontologists known as "biomedical gerontologists". They try to understand the nature of aging and they develop treatments to reverse aging processes or to at least slow them down, for the improvement of health and the maintenance of youthful vigor at every stage of life. Those who take advantage of life extension findings and seek to apply them upon themselves are called "life extensionists" or "longevists". The primary life extension strategy currently is to apply available anti-aging methods in the hope of living long enough to benefit from a complete cure to aging once it is developed, which given the rapidly advancing state of biogenetic and general medical technology, could conceivably occur within the lifetimes of people living today.

Location

Before about 1930, most people died in their own homes, surrounded by family, and comforted by clergy, neighbors, and doctors making house calls.^[26] By the mid-20th century, half of all Americans died in a hospital.^[27] By the start of the 21st century, only about 20 to 25% of people in developed countries died in the community.^[27]^[28]^[29] The shift away from dying at home, towards dying in a professionalized medical environment, has been termed the "Invisible Death".^[27]

Society and culture

Main article: Death and culture

Death haunts even the beautiful: an early 20th-century artist says, "All is Vanity"

Death is the center of many traditions and organizations, and is a feature of every culture around the world. Much of this revolves around the care of the dead, as well as the afterlife and the disposal of bodies upon the onset of death. The disposal of human corpses does, in general, begin with the last offices before significant time has passed, and ritualistic ceremonies often occur, most commonly interment or cremation. This is not a unified practice, however, as in Tibet for instance the body is given a sky burial and left on a mountain top. Proper preparation for death and techniques and ceremonies for producing the ability to transfer one's spiritual attainments into another body (reincarnation) are subjects of detailed study in Tibet.^[30] Mummification or embalming is also prevalent in some cultures, to retard the rate of decay.
Legal aspects of death are also part of many cultures, particularly the settlement of the deceased estate and the issues of inheritance and in some countries, inheritance taxation.

Gravestones in Kyoto, Japan

Capital punishment is also a culturally divisive aspect of death. In most jurisdictions where capital punishment is carried out today, the death penalty is reserved for premeditated murder, espionage, treason, or as part of military justice. In some countries, sexual crimes, such as adultery and sodomy, carry the death penalty, as do religious crimes such as apostasy, the formal renunciation of one's religion. In many retentionist countries, drug trafficking is also a capital offense. In China human trafficking and serious cases of corruption are also punished by the death penalty. In militaries around the world courts-martial have imposed death sentences for offenses such as cowardice, desertion, insubordination, and mutiny.^[31]
Death in warfare and in suicide attack also have cultural links, and the ideas of dulce et decorum est pro patria mori, mutiny punishable by death, grieving relatives of dead soldiers and death notification are embedded in many cultures. Recently in the western world, with the supposed increase in terrorism following the September 11 attacks, but also further back in time with suicide bombings, kamikaze missions in World War II and suicide missions in a host of other conflicts in history, death for a cause by way of suicide attack, and martyrdom have had significant cultural impacts.
Suicide in general, and particularly euthanasia, are also points of cultural debate. Both acts are understood very differently in different cultures. In Japan, for example, ending a life with honor by seppuku was considered a desirable death, whereas according to traditional Christian and Islamic cultures, suicide is viewed as a sin. Death is personified in many cultures, with such symbolic representations as the Grim Reaper, Azrael and Father Time.

In biology

After death the remains of an organism become part of the biogeochemical cycle. Animals may be consumed by a predator or a scavenger. Organic material may then be further decomposed by detritivores, organisms which recycle detritus, returning it to the environment for reuse in the food chain. Examples of detritivores include earthworms, woodlice and dung beetles.
Microorganisms also play a vital role, raising the temperature of the decomposing matter as they break it down into yet simpler molecules. Not all materials need be decomposed fully, however. Coal, a fossil fuel formed over vast tracts of time in swamp ecosystems, is one example.

Natural selection

Main articles: competition (biology), natural selection, and extinction

Contemporary evolutionary theory sees death as an important part of the process of natural selection. It is considered that organisms less adapted to their environment are more likely to die having produced fewer offspring, thereby reducing their contribution to the gene pool. Their genes are thus eventually bred out of a population, leading at worst to extinction and, more positively, making the process possible, referred to as speciation. Frequency of reproduction plays an equally important role in determining species survival: an organism that dies young but leaves numerous offspring displays, according to Darwinian criteria, much greater fitness than a long-lived organism leaving only one.

Extinction

Main article: Extinction

A dodo, the bird that became a byword in English for species extinction^[32]

Extinction is the cessation of existence of a species or group of taxa, reducing biodiversity. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to breed and recover may have been lost before this point). Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence. New species arise through the process of speciation, an aspect of evolution. New varieties of organisms arise and thrive when they are able to find and exploit an ecological niche – and species become extinct when they are no longer able to survive in changing conditions or against superior competition.

Evolution of aging

Main article: Evolution of ageing

Inquiry into the evolution of aging aims to explain why so many living things and the vast majority of animals weaken and die with age (a notable exception being hydra, which may be biologically immortal). The evolutionary origin of senescence remains one of the fundamental puzzles of biology. Gerontology specializes in the science of human aging processes.

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Rabu, 04 Mei 2011