Minggu, 25 Maret 2012

Tips Wawancara Kerja

Tips Wawancara Kerja. 

TIPS WAWANCARA KERJA Wawancara kerja merupakan salah satu hal yang terpenting dalam proses melamar pekerjaan, karena dengan wawancara banyak aspek penilaian yang dapat diambil. Nah.. tidak ada salahnya khan apabila sobat membaca beberapa Tips Wawancara kerja berikut : 

1. Penampilan (berpakaian) Well, Dalam berpenampilan hendaknya sobat dapat memilih pakaian yang Pantas dan rapi. Buatlah penampilan sobat terlihat Profesional, dewasa, bisa diandalkan dan jangan berlebihan. untuk pria : Gunakan kemeja warna krem, abu-abu atau biru (yang tidak mencolok). dan jangan gunakan warna hitam, untuk menghindari kesan berkabung. Lebih tepatnya gunakan bahan yang tidak terlalu mencolok warnanya. Jangan lupa dasinya juga harus maching dengan pakaian. untuk wanita : Baju atau blouse yang simpel, gunakan bahan alami semacam wol, katun atau sutra. Warnya juga sama dengan pria krem, abu-abu atau biru (kalau wanita, hitam juga boleh). Dan yang terpenting make-up jangan berlebihan. 

2. Tepat waktu Datanglah tepat pada waktunya, ya kurang lebih 15 menit sebelum waktu yang dijanjikan sobat sudah ada di TKP. 

3. Bahasa Tubuh. Tips wawancara kerja ini akan mengesankan anda profesional dan tahu apa yang harus dilakukan. Saat memasuki ruang wawancara kerja. Anda harus mampu mengatur bahasa tubuh , jangan seperti sedang berjalan-jalan di mall. Berjalanlah secara tegap dengan kedua tangan mengibas bebas. Jangan lihat-lihat kesana kemari dan berkata wah ruanganya bagus, langsung berjalan lurus ke pewawancara kerja. Sodorkan tangan kepada si pewancara sambil tersenyum. Sambil menatap matanya, genggam keseluruhan tangan kemudian ayunkan satu sampai dua kali dan secara bersamaan ucapkan nama anda. Dan perlu diperhatikan…. Saat menghadapi wawancara kerja peting untuk jangan duduk sebelum dipersilahkan, jangan memasukkan tangan ke saku, jangan menggumam, jangan menyilangkan tangan di dada. Apalagi mengacungkan jari tengah, lebih nggak boleh lagi hehehe... Berusahalah senormal mungkin selayaknya berbicara, Gunakan ekspresi seperti senyum, mengerutkan dahi, sedikit mengangguk atau hal semacam itu. Dengan begitu akan memudahkan si pewawancara mengerti apa yang anda bicarakan. 

4. Kontak Mata. Tips wawancara kerja yang terakhir... adalah jangan pernah alihkan pandangan saat pewancara mengajukan pertanyaan wawancara kerja. Fokus dan tetap fokus kepada si pe-wawancara. Jangan lupa mata adalah cermin dari hati anda. Buat tatapan mata anda terlihat percaya diri dan berfikir positif. 

Cukup ini aja sob, Tips Wawancara Kerja nya, mudah mudahan dapat bermanfaat. http://gocengblog.blogspot.com/2011/10/tips-wawancara-kerja.html Copyright by gocengblog.blogspot.com Terima kasih sudah menyebarluaskan aritkel ini

Rabu, 14 Maret 2012

Teknik Molekuler dalam Penentuan Variasi Genetik


Teknik Molekuler dalam Penentuan Variasi Genetik

Teknik-teknik yang digunakan dalam genetika modern banyak menggunakan penanda genetik sebagai alat bantu mengidentifikasi genotipe suatu individu atau sampel yang diambil. Penanda genetik disebut juga dengan penanda, marker, marka, atau markah. Penanda genetik merupakan ekspresi pada individu yang terlihat oleh mata atau terdeteksi dengan alat tertentu, yang menunjukkan dengan pasti genotipe suatu individu. Penanda genetik dapat diketahui lokasinya pada kromosom. Penanda yang lokasinya dapat diketahui pada kromosom memberikan informasi bagi sekuensing dan perbandingan antar genotipe, meskipun seringkali tidak praktis dalam aplikasinya. Aplikasi penanda genetik misalnya dalam bidang-bidang kedokteran, pertanian, ilmu pangan, lingkungan, antropologi, sejarah, hukum. Bidang-bidang tersebut menggunakan aplikasi penanda genetik  sebagai alat analisis atau alat pembuktian. Beberapa penanda genetik sangat terpercaya karena bersifat lembam dan tidak mudah berubah karena pengaruh lingkungan (Semagn et al., 2006)
1.   Prinsip pemanfaatan penanda genetik
Penanda genetik hanya berguna apabila ia polimorfik dan terpaut dengan sifat yang akan diamati atau dengan penanda genetik lain. Syarat polimorfik diperlukan karena penanda genetik harus bisa membedakan individu-individu dalam populasi yang diteliti. Suatu penanda genetik harus bisa mengelompokkan individu paling tidak dalam dua kelompok. Syarat terpaut dengan penanda, gen, atau sifat lain diperlukan karena fungsi penanda genetik adalah sebagai tanda pengenal yang harus melekat pada sifat yang diteliti. Penanda genetik juga mengikuti Hukum Pewarisan Mendel dalam suatu analisis genetik. Terdapat dua macam penanda genetik dalam kaitannya dengan Hukum Pewarisan Mendel, yaitu:
1.      Penanda yang bersifat kodominan, artinya dapat membedakan ketiga kelas genotipe pada generasi F2 (dua homozigot dan heterozigot)
2.      Penanda yang bersifat dominan, artinya tidak bisa memisahkan heterozigot dari salah satu kelas homozigot
2.   Macam-macam penanda Molekuler
a.       Hybridization-based marker-RFLP
RFLP (Restriction Fragment Length Polymorphism) berasal dari susunan DNA yang terjadi karena proses evolusi, mutasi titik pada situs enzim restriksi, insersi atau delesi dalam fragmen DNA. Dalam analisis RFLP, genomik DNA yang dipotong dengan enzim restriksi dipisahkan melalui gel elektroforesis, dan diblot ke membrane netroselulase. Dasar dari transfer DNA dari gel ke pensupport yang lebih solid adalah untuk mengawetkan posisi fragmen DNA dan menyebabkan hibridisasi dapat dilakukan. Pola banding yang spesifik divisualisasi dengan hibridisasi dengan probe yang dilabel. Probe biasanya probe lokus tunggal yang spesies-specific berukuran 0.5-3kb yang diperoleh dari cDNA library atau genomik library (Brown, 2002).
RFLP merupakan marker co-dominant. RFLP merupakan marker yang sangat dapat dpercaya dalam analisis linkage dan breeding dan dapat ditentukan dengan mudah jika karakter terdapat dalam bentuk homozigot atau heterozigot. Kekuatan dari marker RFLP adalah konsistensi yang tinggi, sifat pewarisan co-dominant, dapat diulang antar laboratorium, memberikan marker yang locus-specific, tidak memerlukan informasi sekuen, dan relative mudah discor karena perbedaan yang besar antar fragmen. Tetapi penggunaan RFLP memerlukan DNA dalam jumlah yang besar untuk pemotongan dengan enzim restriksi. Di samping itu penggunaan isotop radioaktif relatif mahal dan berbahaya. Waktu yang diperlukan juga cukup lama.
b.      RAPD (Random Amplified Polymorphic DNA)
Salah satu teknik molecular marker yang menggunakan PCR adalah RAPD. Metode standar RAPD menggunakan oligonukleotida tunggal pendek (10-12 basa) dengan urutan acak sebagai primer untuk mengamplifikasi genomik DNA dalam jumlah nanogram dengan temperatur annealing yang rendah. Produk amplifikasi PCR dipisahkan dengan agarose gel diwarnai dengan ethidium bromide. Primer decamer secara komersial tersedia di berbagai sumber (misalnya Operon Technologies Inc., Alameda, California atau University of British Columbia, Canada). Analisis RAPD berbeda dengan kondisi PCR standar dimana hanya menggunakan satu primer dan tidak memerlukan informasi sekuen DNA awal (Bardakci, 2001)
Pada temperature annealing yang tepat selama siklus thermal, oligonukleotida primers dengan urutan sekuen acak berikatan pada beberapa priming site pada sekuen komplementer pada template DNA genomik dan menghasilkan produk jika priming site berada dalam wilayah/jarak yang dapat diamplifikasi. Profil amplifikasi DNA tergantung pada homologi sekuen nukleotida antara template/cetakan DNA dengan oligonucleotide primer. Variasi nukleotida antar template DNA menghasilkan ada tidaknya band karena perubahan priming site.
Aplikasi analisis RAPD
Karena teknik RAPD yang sederhana dan biaya yang diperlukan lebih murah maka terdapat aplikasi yang sangat luas dari RAPD pada berbagai area biologi. Beberapa area tersebut antara lain:
1.      Kemampuan RAPD mendeteksi variasi intra-specifik dapat digunakan untuk melakukan screening untuk tingkat inbreeding pada tanaman komersial untuk mencegah peningkatan frekuensi alel resesif yang merugikan dalam populasi.
2.      Marker species-specific digunakan dalam inter-specific gene flow dan identifikasi hybrid. Sama halnya dengan marker population-specific akan bermanfaat dalam identifikasi populasi hibrid. Marker RAPD lebih cocok untuk organisme klonal dibandingkan organisme yang bereproduksi secara seksual. Karena bereproduksi secara aseksual, maka fragmen polimorfik antar individual dapat digunakan untuk menentukan identitas klonal.
Walaupun metode RAPD relatif cepat, murah dan gampang dilaksanakan dibandingkan metode marker DNA lain, isu konsistensi/reproducibility menjadi perhatian sejak dipublikasikannya teknik ini. RAPD sangat sensitif terhadap perubahan kondisi reaksi PCR. Problem reproducibility/konsistensi biasanya terjadi pada band dengan intensitas yang rendah. Hal ini mungkin terjadi karena primer tidak cocok secara sempurna pada sekuen priming site, amplifikasi pada beberapa siklus mungkin tidak terjadi sehingga band tetap samar (Bardakci, 2001)
c.       ISSR (Inter Simple Sequence Repeat)
ISSR melibatkan amplifikasi segmen DNA yang berada pada jarak yang dapat teramplifikasi antara dua daerah mikrosatelit berulang yang identik tetapi dengan orientasi arah yang berbeda. Teknik ini menggunakan primer mikrosatelit tunggal dalam reaksi PCR dengan target multiple-locus genomik untuk mengamplifikasi inter simple sequence repeats dengan ukuran yang berbeda. Mikrosatelit yang digunakan sebagai primer bisa berupa di-nucleotide, tri-nucleotide, tetranucleotide atau penta-nucleotide. Panjang primer ISSR yang digunakan adalah 15-30 mers dibandingkan dengan RAPD yang menggunakan primer 10 mers. Suhu annealing tergantung pada kandungan GC dari primer yang digunakan, biasanya berkisar 45 sampai 65C. Produk hasil amplifikasi biasanya berukuran 200-2000 bp dan dapat dideteksi dengan menggunakan gel agarosa atau poliakrilamid elektroforesis.
Mikrosatelit biasanya dibedakan dengan minisatelit pada derajat pengulangan sekuennya. Pada minisatelit ulangannya lebih sederhana dibandingkan dengan metode analisa mikrosatelit. Demikian pula panjang unit ulangan biasanya lebih panjang, sedangkan derajat ulangan minisatelit ditentukan pula berdasarkan ” sekuen intinya” sebagaimana pada mikrosatelit (Tautz, 1993).
Bentuk pengulangan sekuen DNA sederhana yang berulang-ulang menjadikan marka mikrosatelit sering disebut simple sequence repeat (SSR), short tandem repeats (STRs) atau simple sequence length polymorphisms (SSLPs) yang sekarang menjadi salah satu marka paling banyak digunakan secara luas untuk pemetaan genetik, analisis keragaman genetik, dan studi evolusi (Temykh et al., 2000). Marka ini muncul sebagai marka yang sangat variatif dan mudah diulang, menjadikan sangat ideal untuk pemetaan genom. Mikrosatelit ini merupakan salah satu tipe polimorfisme yang berulang-ulang, yang biasa dikelompokkan ke dalam simple tandem repeat polymorphism (STRP), karena perbedaan genetik di antara molekul-molekul DNA yang mengandung sejumlah kopi sekuen DNA pendek yang diulang beberapa kali. STRP yang memiliki pengulangan 2-9 pasang basa sering disebut mikrosatelit, sedangkan STRP dengan pengulangan 10-60 pasang basa sering disebut minisatelit atau variable number of tandem repeats (VNTR) (Hartl, 1988).
Mikrosatelit atau SSR dapat dideteksi dengan pewarnaan menggunakan teknik  Silver Staining PAGE (pewarnaan perak dengan teknik  Polyacrilamyde Gel Electrophoresis). Proses deteksi  SSR juga dapat diotomatisasi dengan menggunakan  fluorescently-labeled markers dan alat analisis genetik  (genetic analyzer). Kelebihan utama dari teknik ini adalah pembacaan fragmen  DNA lebih akurat  (ketelitian sampai 1 bp), lebih otomatis, dan  hightroughput (marka yang berbeda ukuran fragmen DNA dan warna labelnya dapat diproses bersamaan  dalam sekali pendeteksian (running) (Santoso, dkk; 2006).
Mikrosatelit, atau pengulangan urutan sederhana (simple sequence repeat) adalah sekuen sederhana yang berulang-ulang yang melimpah dalam genom suatu spesies. Mikrosatelit memiliki pengulangan sekuen yang berurutan dua sampai 4 motif sekuen nukleotida sebagai sekuen konservatif. Penciri  ini sangat berguna sebagai penciri genetik karena bersifat kodominan, sehingga dapat mendeteksi keragaman alel pada level yang tinggi, mudah dan ekonomis dalam pengaplikasiannya karena menggunakan proses PCR (Shen P et al., 2000). Penciri ini muncul sebagai marka yang sangat variatif dan mudah diulang, menjadikan sangat ideal untuk pemetaan genom.
Perbedaan panjang alel mikrosatelit pada lokus biasanya dikarenakan variasi pada jumlah ulangannya dan ketidaksepadanan pasangan nukleotida saat kejadian replikasi dipertimbangkan sebagai mekanisme utama yang menyebabkan panjangnya variasi alel  tersebut, bahkan munculnya alel-alel baru (Travis et al., 1996). Variasi  pada  lokus-lokus mikrosatelit dapat diuji dengan amplifikasi PCR menggunakan primer-primer  yang komplemen dengan sekuen  unit pengapit rangkaian nukleotida berulang, serta diikuti dengan elektroforesis produk PCR (Tauzt,  1993). Di bawah ini adalah hasil elektroforesis produk PCR DNA kerbau Blitar dengan menggunakan primer INRA 023.

                                          Hasil produk PCR dari DNA Kerbau Blitar 
                                                            (Riyanto, 2010)

Berdasarkan gambar diatas menunjukkan bahwa adanya variasi jumlah alel pada tiap individu pada populasi kerbau. Alel mikrosatelit pada kerbau yang di identifikasi dapat digunakan sebagai penanda genetik, sehingga dapat menunjukkan variasi genetik. Misalnya pada sampel kerbau no 7 mempunyai variasi alel A, B, C sedangkan Sampel no 2 hanya mempunya variasi alel A, C artinya sampel no 7 lebih polimorf apabila dibandingkan sampel no 2. Semakin tinggi varisai alel maka variasi genetik juga semakin tinggi (Riyanto, 2010).

Selasa, 06 Maret 2012

Apakah evolusi sebuah teori, sistem, atau hipotesis?

Apakah evolusi sebuah teori, sistem, atau hipotesis
 

          Salah satu pemikir besar era kita, Pierre Teilhard de Chardin, pernah berkata
“Apakah evolusi sebuah teori, sistem, atau hipotesis? Saya kira ia lebih menyerupai suatu kenyataan yang paling tinggi dibanding teori, sistem, atau hipotesis manapun. Semua teori, sistem, dan hipotesis mesti diukur menggunakan evolusi ini. Ia merupakan cahaya yang menerangi segala kebenaran, sebuah lintasan yang mesti dilalui setiap garis yang ada.”
“Inilah evolusi!”

Nothing in Biology Makes Sense Except in the Light oEvolution


Nothing in Biology Makes Sense Except in the Light of Evolution
 Theodosius Dobzhansky,
"Nothing in biology makes sense except in the light of evolution." The American Biology Teacher, March 1973
As recently as 1966, sheik Abd el Aziz bin Baz asked the king of Saudi Arabia to suppress a heresy that was spreading in his land. Wrote the sheik:
"The Holy Koran, the Prophet's teachings, the majority of Islamic scientists, and the actual facts all prove that the sun is running in its orbit... and that the earth is fixed and stable, spread out by God for his mankind.... Anyone who professed otherwise would utter a charge of falsehood toward God, the Koran, and the Prophet."
The good sheik evidently holds the Copernican theory to be a "mere theory," not a "fact." In this he is technically correct. A theory can be verified by a mass of facts, but it becomes a proven theory, not a fact. The sheik was perhaps unaware that the Space Age had begun before he asked the king to suppress the Copernican heresy. The sphericity of the earth has been seen by astronauts, and even by many earth-bound people on their television screens. Perhaps the sheik could retort that those who venture beyond the confines of God's earth suffer hallucinations, and that the earth is really flat.
Parts of the Copernican world model, such as the contention that the earth rotates around the sun, and not vice versa, have not been verified by direct observations even to the extent the sphericity of the earth has been. Yet scientists accept the model as an accurate representation of reality. Why? Because it makes sense of a multitude of facts which are otherwise meaningless or extravagant. To non-specialists most of these facts are unfamiliar. Why then do we accept the "mere theory" that the earth is a sphere revolving around a spherical sun? Are we simply submitting to authority? Not quite: we know that those who took the time to study the evidence found it convincing.
The good sheik is probably ignorant of the evidence. Even more likely, he is so hopelessly biased that no amount of evidence would impress him. Anyway, it would be sheer waste of time to attempt to convince him. The Koran and the Bible do not contradict Copernicus, nor does Copernicus contradict them. It is ludicrous to mistake the Bible and the Koran for primers of natural science. They treat of matters even more important: the meaning of man and his relations to God. They are written in poetic symbols that were understandable to people of the age when they were written, as well as to peoples of all other ages. The king of Arabia did not comply with the sheik's demand. He knew that some people fear enlightenment, because enlightenment threatens their vested interests. Education is not to be used to promote obscurantism.
The earth is not the geometric center of the universe, although it may be its spiritual center. It is a mere speck of dust in the cosmic spaces. Contrary to Bishop Ussher's calculations, the world did not appear in approximately its present state in 4004 BC. The estimates of the age of the universe given by modern cosmologists are still only rough approximations, which are revised (usually upward) as the methods of estimation are refined. Some cosmologists take the universe to be about 10 billion years old; others suppose that it may have existed, and will continue to exist, eternally. The origin of life on earth is dated tentatively between 3 and 5 billion years ago; manlike beings appeared relatively quite recently, between 2 and 4 million years ago. The estimates of the age of the earth, of the duration of the geologic and paleontologic eras, and of the antiquity of man's ancestors are now based mainly on radiometric evidence the proportions of isotopes of certain chemical elements in rocks suitable for such studies.
Shiek bin Baz and his like refuse to accept the radiometric evidence, because it is a "mere theory." What is the alternative? One can suppose that the Creator saw fit to play deceitful tricks on geologists and biologists. He carefully arranged to have various rocks provided with isotope ratios just right to mislead us into thinking that certain rocks are 2 billion years old, others 2 million, which in fact they are only some 6,000 years old. This kind of pseudo-explanation is not very new. One of the early anti-evolutionists, P. H. Gosse, published a book entitled Omphalos ("the Navel"). The gist of this amazing book is that Adam, though he had no mother, was created with a navel, and that fossils were placed by the Creator where we find them now -- a deliberate act on His part, to give the appearance of great antiquity and geologic upheavals. It is easy to see the fatal flaw in all such notions. They are blasphemies, accusing God of absurd deceitfulness. This is as revolting as it is uncalled for.
Diversity of Living Beings
The diversity and the unity of life are equally striking and meaningful aspects of the living world. Between 1.5 and 2 million species of animals and plants have been described and studied; the number yet to be described is probably as great. The diversity of sizes, structures, and ways of life is staggering but fascinating. Here are just a few examples.
The foot-and-mouth disease virus is a sphere 8-12 mm in diameter. The blue whale reaches 30 m in length and 135 t in weight. The simplest viruses are parasites in cells of other organisms, reduced to barest essentials minute amounts of DNA or RNA, which subvert the biochemical machinery of the host cells to replicate their genetic information, rather than that of the host.
It is a matter of opinion, or of definition, whether viruses are considered living organisms or peculiar chemical substances. The fact that such differences of opinion can exist is in itself highly significant. It means that the borderline between living and inanimate matter is obliterated. At the opposite end of the simplicity complexity spectrum you have vertebrate animals, including man. The human brain has some 12 billion neurons; the synapses between the neurons are perhaps a thousand times numerous.
Some organisms live in a great variety of environments. Man is at the top of the scale in this respect. He is not only a truly cosmopolitan species but, owing to his technologic achievements, can survive for at least a limited time on the surface of the moon and in cosmic spaces. By contrast, some organisms are amazingly specialized. Perhaps the narrowest ecologic niche of all is that of a species of the fungus family Laboulbeniaceae, which grows exclusively on the rear portion of the elytra of the beetle Aphenops cronei, which is found only in some limestone caves in southern France. Larvae of the fly Psilopa petrolei develop in seepages of crude oil in California oilfields; as far as is known they occur nowhere else. This is the only insect able to live and feed in oil, and its adult can walk on the surface of the oil only as long as no body part other than the tarsi are in contact with the oil. Larvae of the fly Drosophila carciniphila develop only in the nephric grooves beneath the flaps of the third maxilliped of the land crab Geocarcinus ruricola, which is restricted to certain islands in the Caribbean.
Is there an explanation, to make intelligible to reason this colossal diversity of living beings? Whence came these extraordinary, seemingly whimsical and superfluous creatures, like the fungus Laboulbenia, the beetle Aphenops cronei, the flies Psilopa petrolei and Drosophila carciniphila, and many, many more apparent biologic curiosities? The only explanation that makes sense is that the organic diversity has evolved in response to the diversity of environment on the planet earth. No single species, however perfect and however versatile, could exploit all the opportunities for living. Every one of the millions of species has its own way of living and of getting sustenance from the environment. There are doubtless many other possible ways of living as yet unexploited by any existing species; but one thing is clear: with less organic diversity, some opportunities for living would remain unexploited. The evolutionary process tends to fill up the available ecologic niches. It does not do so consciously or deliberately; the relations between evolution and environment are more subtle and more interesting than that. The environment does not impose evolutionary changes on its inhabitants, as postulated by the now abandoned neo-Lamarckian theories. The best way to envisage the situation is as follows: the environment presents challenges to living species, to which the later may respond by adaptive genetic changes.
An unoccupied ecologic niche, an unexploited opportunity for living, is a challenge. So is an environmental change, such as the Ice Age climate giving place to a warmer climate. Natural selection may cause a living species to respond to the challenge by adaptive genetic changes. These changes may enable the species to occupy the formerly empty ecologic niche as a new opportunity for living, or to resist the environmental change if it is unfavorable. But the response may or may not be successful. This depends on many factors, the chief of which is the genetic composition of the responding species at the time the response is called for. Lack of successful response may cause the species to become extinct. The evidence of fossils shows clearly that the eventual end of most evolutionary lines is extinction. Organisms now living are successful descendants of only a minority of the species that lived in the past and of smaller and smaller minorities the farther back you look. Nevertheless, the number of living species has not dwindled; indeed, it has probably grown with time. All this is understandable in the light of evolution theory; but what a senseless operation it would have been, on God's part, to fabricate a multitude of species ex nihilo and then let most of them die out!
There is, of course, nothing conscious or intentional in the action of natural selection. A biologic species does not say to itself, "Let me try tomorrow (or a million years from now) to grow in a different soil, or use a different food, or subsist on a different body part of a different crab." Only a human being could make such conscious decisions. This is why the species Homo sapiens is the apex of evolution. Natural selection is at one and the same time a blind and creative process. Only a creative and blind process could produce, on the one hand, the tremendous biologic success that is the human species and, on the other, forms of adaptedness as narrow and as constraining as those of the overspecialized fungus, beetle, and flies mentioned above.
Anti-evolutionists fail to understand how natural selection operates. They fancy that all existing species were generated by supernatural fiat a few thousand years ago, pretty much as we find them today. But what is the sense of having as many as 2 or 3 million species living on earth? If natural selection is the main factor that brings evolution about, any number of species is understandable: natural selection does not work according to a foreordained plan, and species are produced not because they are needed for some purpose but simply because there is an environmental opportunity and genetic wherewithal to make them possible. Was the Creator in a jocular mood when he made Psilopa petrolei for California oil fields and species of Drosophila to live exclusively on some body-parts of certain land crabs on only certain islands in the Caribbean? The organic diversity becomes, however, reasonable and understandable if the Creator has created the living world not by caprice but by evolution propelled by natural selection. It is wrong to hold creation and evolution as mutually exclusive alternatives. I am a creationist and an evolutionist. Evolution is God's, or Nature's method of creation. Creation is not an event that happened in 4004 BC; it is a process that began some 10 billion years ago and is still under way.
Unity of Life
The unity of life is no less remarkable than its diversity. Most forms of life are similar in many respects. The universal biologic similarities are particularly striking in the biochemical dimension. From viruses to man, heredity is coded in just two, chemically related substances: DNA and RNA. The genetic code is as simple as it is universal. There are only four genetic "letters" in DNA: adenine, guanine, thymine, and cytosine. Uracil replaces thymine in RNA. The entire evolutionary development of the living world has taken place not by invention of new "letters" in the genetic "alphabet" but by elaboration of ever-new combinations of these letters.
Not only is the DNA-RNA genetic code universal, but so is the method of translation of the sequences of the "letters" in DNA-RNA into sequences of amino acids in proteins. The same 20 amino acids compose countless different proteins in all, or at least in most, organisms. Different amino acids are coded by one to six nucleotide triplets in DNA and RNA. And the biochemical universals extend beyond the genetic code and its translation into proteins: striking uniformities prevail in the cellular metabolism of the most diverse living beings. Adenosine triphosphate, biotin, riboflavin, hemes, pyridoxin, vitamins K and B12, and folic acid implement metabolic processes everywhere.
What do these biochemical or biologic universals mean? They suggest that life arose from inanimate matter only once and that all organisms, no matter now diverse, in other respects, conserve the basic features of the primordial life. (It is also possible that there were several, or even many, origins of life; if so, the progeny of only one of them has survived and inherited the earth.) But what if there was no evolution and every one of the millions of species were created by separate fiat? However offensive the notion may be to religious feeling and to reason, the anti-evolutionists must again accuse the Creator of cheating. They must insist that He deliberately arranged things exactly as if his method of creation was evolution, intentionally to mislead sincere seekers of truth.
The remarkable advances of molecular biology in recent years have made it possible to understand how it is that diverse organisms are constructed from such monotonously similar materials: proteins composed of only 20 kinds of amino acids and coded only by DNA and RNA, each with only four kinds of nucleotides. The method is astonishingly simple. All English words, sentences, chapters, and books are made up of sequences of 26 letters of the alphabet. (They can be represented also by only three signs of the Morse code: dot, dash, and gap.) The meaning of a word or a sentence is defined not so much by what letters it contains as by the sequences of these letters. It is the same with heredity: it is coded by the sequences of the genetic "letters" the nucleotides in the DNA. They are translated into the sequences of amino acids in the proteins.
Molecular studies have made possible an approach to exact measurements of degrees of biochemical similarities and differences among organisms. Some kinds of enzymes and other proteins are quasi-universal, or at any rate widespread, in the living world. They are functionally similar in different living beings, in that they catalyze similar chemical reactions. But when such proteins are isolated and their structures determined chemically, they are often found to contain more or less different sequences of amino acids in different organisms. For example, the so-called alpha chains of hemoglobin have identical sequences of amino acids in man and the chimpanzee, but they differ in a single amino acid (out of 141) in the gorilla. Alpha chains of human hemoglobin differ from cattle hemoglobin in 17 amino acid substitutions, 18 from horse, 20 from donkey, 25 from rabbit, and 71 from fish (carp).
Cytochrome C is an enzyme that plays an important role in the metabolism of aerobic cells. It is found in the most diverse organisms, from man to molds. E. Margoliash, W. M. Fitch, and others have compared the amino acid sequences in cytochrome C in different branches of the living world. Most significant similarities as well as differences have been brought to light. The cytochrome C of different orders of mammals and birds differ in 2 to 17 amino acids, classes of vertebrates in 7 to 38, and vertebrates and insects in 23 to 41; and animals differ from yeasts and molds in 56 to 72 amino acids. Fitch and Margoliash prefer to express their findings in what are called "minimal mutational distances." It has been mentioned above that different amino acids are coded by different triplets of nucleotides in DNA of the genes; this code is now known. Most mutations involve substitutions of single nucleotides somewhere in the DNA chain coding for a given protein. Therefore, one can calculate the minimum numbers of single mutations needed to change the cytochrome C of one organism into that of another. Minimal mutational distances between human cytochrome C and the cytochrome C of other living beings are as follows:
Monkey
1
Chicken
18
Dog
13
Penguin
18
Horse
17
Turtle
19
Donkey
16
Rattlesnake
20
Pig
13
Fish (tuna)
31
Rabbit
12
Fly
33
Kangaroo
12
Moth
36
Duck
17
Mold
63
Pigeon
16
Yeast
56
It is important to note that amino acid sequences in a given kind of protein vary within a species as well as from species to species. It is evident that the differences among proteins at the level of species, genus, family, order, class, and phylum are compounded of elements that vary also among individuals within a species. Individual and group differences are only quantitatively, not qualitatively, different. Evidence supporting the above propositions is ample and is growing rapidly. Much work has been done in recent years on individual variations in amino acid sequences of hemoglobin of human blood. More that 100 variants have been detected. Most of them involve substitutions of single amino acids - substitutions that have arisen by genetic mutations in the persons in whom they are discovered or in their ancestors. As expected, some of these mutations are deleterious to their carriers, but others apparently are neutral or even favorable in certain environments. Some mutant hemoglobins have been found only in one person or in one family; others are discovered repeatedly among inhabitants of different parts of the world. I submit that all these remarkable findings make sense in the light of evolution: they are nonsense otherwise.
Comparative Anatomy and Embryology
The biochemical universals are the most impressive and the most recently discovered, but certainly they are not the only vestiges of creation by means of evolution. Comparative anatomy and embryology proclaim the evolutionary origins of the present inhabitants of the world. In 1555 Pierre Belon established the presence of homologous bones in the superficially very different skeletons of man and bird. Later anatomists traced the homologies in the skeletons, as well as in other organs, of all vertebrates. Homologies are also traceable in the external skeletons of arthropods as seemingly unlike as a lobster, a fly, and a butterfly. Examples of homologies can be multiplied indefinitely.
Embryos of apparently quite diverse animals often exhibit striking similarities. A century ago these similarities led some biologists (notably the German zoologist Ernst Haeckel) to be carried by their enthusiasm as far as to interpret the embryonic similarities as meaning that the embryo repeats in its development the evolutionary history of its species: it was said to pass through stages in which it resembles its remote ancestors. In other words, early-day biologists supposed that by studying embryonic development one can, as it were, read off the stages through which the evolutionary development had passed. This so-called biogenetic law is no longer credited in its original form. And yet embryonic similarities are undeniable impressive and significant.
Probably everybody knows the sedentary barnacles which seem to have no similarity to free-swimming crustaceans, such as the copepods. How remarkable that barnacles pass through a free-swimming larval stage, the nauplius! At that stage of its development a barnacle and a Cyclops look unmistakably similar. They are evidently relatives. The presence of gill slits in human embryos and in embryos of other terrestrial vertebrates is another famous example. Of course, at no stage of its development is a human embryo a fish, nor does it ever have functioning gills. But why should it have unmistakable gill slits unless its remote ancestors did respire with the aid of gills? It is the Creator again playing practical jokes?
Adaptive radiation: Hawaii's Flies
There are about 2,000 species of drosophilid flies in the world as a whole. About a quarter of them occur in Hawaii, although the total area of the archipelago is only about that of the state of New Jersey. All but 17 of the species in Hawaii are endemic (found nowhere else). Furthermore, a great majority of the Hawaiian endemics do not occur throughout the archipelago: they are restricted to single islands or even to a part of an island. What is the explanation of this extraordinary proliferation of drosophilid species in so small a territory? Recent work of H. L. Carson, H. T. Spieth, D. E. Hardy, and others makes the situation understandable.
The Hawaiian Islands are of volcanic origin; they were never parts of any continent. Their ages are between 5.6 and 0.7 million years. Before man came there inhabitants were descendants of immigrants that had been transported across the ocean by air currents and other accidental means. A single drosophilid species, which arrived in Hawaii first, before there were numerous competitors, faced the challenge of an abundance of many unoccupied ecologic niches. Its descendants responded to this challenge by evolutionary adaptive radiation, the products of which are the remarkable Hawaiian drosophilids of today. To forestall a possible misunderstanding, let it be made clear that the Hawaiian endemics are by no means so similar to each other that they could be mistaken for variants of the same species; if anything, they are more diversified than are drosophilids elsewhere. The largest and the smallest drosophilid species are both Hawaiian. They exhibit an astonishing variety of behavior patterns. Some of them have become adapted to ways of life quite extraordinary for a drosophilid fly, such as being parasites in egg cocoons of spiders.
Oceanic islands other than Hawaii, scattered over the wide Pacific Ocean, are not conspicuously rich in endemic species of drosophilids. The most probable explanation of this fact is that these other islands were colonized by drosophilid after most ecologic niches had already been filled by earlier arrivals. This surely is a hypothesis, but it is a reasonable one. Anti-evolutionists might perhaps suggest an alternative hypothesis: in a fit of absentmindedness, the Creator went on manufacturing more and more drosophilid species for Hawaii, until there was an extravagant surfeit of them in this archipelago. I leave it up to you to decide which hypothesis makes sense.
Strength and Acceptance of the Theory
Seen in the light of evolution, biology is, perhaps, intellectually the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts some of them interesting or curious but making no meaningful picture as a whole.
This is not to imply that we know everything that can and should be known about biology and about evolution. Any competent biologist is aware of a multitude of problems yet unresolved and of questions yet unanswered. After all, biologic research shows no sign of approaching completion; quite the opposite is true. Disagreements and clashes of opinion are rife among biologists, as they should be in a living and growing science. Anti-evolutionists mistake, or pretend to mistake, these disagreements as indications of dubiousness of the entire doctrine of evolution. Their favorite sport is stringing together quotations, carefully and sometimes expertly taken out of context, to show that nothing is really established or agreed upon among evolutionists. Some of my colleagues and myself have been amused and amazed to read ourselves quoted in a way showing that we are really anti-evolutionists under the skin.
Let me try to make crystal clear what is established beyond reasonable doubt, and what needs further study, about evolution. Evolution as a process that has always gone on in the history of the earth can be doubted only by those who are ignorant of the evidence or are resistant to evidence, owing to emotional blocks or to plain bigotry. By contrast, the mechanisms that bring evolution about certainly need study and clarification. There are no alternatives to evolution as history that can withstand critical examination. Yet we are constantly learning new and important facts about evolutionary mechanisms.
It is remarkable that more than a century ago Darwin was able to discern so much about evolution without having available to him the key facts discovered since. The development of genetics after 1900 especially of molecular genetics, in the last two decades has provided information essential to the understanding of evolutionary mechanisms. But much is in doubt and much remains to be learned. This is heartening and inspiring for any scientist worth his salt. Imagine that everything is completely known and that science has nothing more to discover: what a nightmare!
Does the evolutionary doctrine clash with religious faith? It does not. It is a blunder to mistake the Holy Scriptures for elementary textbooks of astronomy, geology, biology, and anthropology. Only if symbols are construed to mean what they are not intended to mean can there arise imaginary, insoluble conflicts. As pointed out above, the blunder leads to blasphemy: the Creator is accused of systematic deceitfulness.
One of the great thinkers of our age, Pierre Teilhard de Chardin, wrote the following: "Is evolution a theory, a system, or a hypothesis? It is much more it is a general postulate to which all theories, all hypotheses, all systems much henceforward bow and which they must satisfy in order to be thinkable and true. Evolution is a light which illuminates all facts, a trajectory which all lines of though must follow this is what evolution is. Of course, some scientists, as well as some philosophers and theologians, disagree with some parts of Teilhard's teachings; the acceptance of his worldview falls short of universal. But there is no doubt at all that Teilhard was a truly and deeply religious man and that Christianity was the cornerstone of his worldview. Moreover, in his worldview science and faith were not segregated in watertight compartments, as they are with so many people. They were harmoniously fitting parts of his worldview. Teilhard was a creationist, but one who understood that the Creation is realized in this world by means of evolution.