آخـــر الـــمـــشـــاركــــات

نصوص استماع اللغة الانجليزية للصف الأول (mp3) - منهاج 2017-2018 » الكاتب: تمارا احمد » آخر مشاركة: أروى الصرايرة نصوص استماع اللغة الانجليزية للصف الثالث (mp3) - منهاج 2017-2018 » الكاتب: تمارا احمد » آخر مشاركة: أروى الصرايرة تحضير لغة أنجليزية صف تاسع ف1 الوحدة 3 Unit » الكاتب: منى زهران » آخر مشاركة: fbie خطة علاجية انجليزي صف سادس Corrective Plan for the 6th grade » الكاتب: تمارا احمد » آخر مشاركة: السفروت تدريبات اثرائية للوحدات 1-4 :منهاج اللغة الانجليزيةAction Pack 3 الفصل الاول. من اعداد الاستاذة نهاد حسن » الكاتب: nihadhasan » آخر مشاركة: محمد ابو ادريس تحضير لغة أنجليزية صف تاسع ف1 الوحدة 2 Unit » الكاتب: منى زهران » آخر مشاركة: fbie شرح وتحليل قصيدة قوة العلم - لغة عربية سابع ف1 (المنهاج المطور) » الكاتب: منى زهران » آخر مشاركة: ventos اليكم خطة لغة انجليزية للصف الخامس - الفصل الأول (المنهاج الاردني) » الكاتب: روح الأمل » آخر مشاركة: زينه زينه خطة لغة انجليزية للخامس ف2 .. حديثة » الكاتب: تمارا احمد » آخر مشاركة: ايمان بشير تحضير علوم صف ثامن الفصل الأول رقم 1 » الكاتب: اسراء » آخر مشاركة: ahmadmarouf
النتائج 1 إلى 2 من 2

الموضوع: The Carbon Cycle

  1. #1
    مشرفة الاقسام الاكاديمية الصورة الرمزية تمارا احمد
    تاريخ التسجيل
    Jul 2011
    الدولة
    الاردن - ماركا
    المشاركات
    14,544

    افتراضي The Carbon Cycle




    The concentration of carbon in living matter (18%) is almost 100 times greater than its concentration in the earth (0.19%). So living things extract carbon from their nonliving environment. For life to continue, this carbon must be recycled. That is our topic.

    carbon
    exists in the nonliving environment as:

    • carbon dioxide (CO2) in the atmosphere and dissolved in water (forming HCO3−)
    • carbonate rocks (limestone and coral = CaCO3)
    • deposits of coal, petroleum, and natural gas derived from once-living things
    • dead organic matter, e.g., humus in the soil

    carbon enters the biotic world through the action of autotrophs:

    • primarily photoautotrophs, like plants and algae, that use the energy of light to convert carbon dioxide to organic matter. Links to photosynthesis
    • and to a small extent, chemoautotrophsbacteria and archaea that do the same but use the energy derived from an oxidation of molecules in their substrate.

    carbon returns to the atmosphere and water by

    • respiration (as CO2)
    • burning
    • decay (producing CO2 if oxygen is present, methane (CH4) if it is not.

    The uptake and return of CO2 are not in balance.

    The carbon dioxide content of the atmosphere is gradually and steadily increasing. The graph shows the CO2 concentration at the summit of Mauna Loa in Hawaii from 1958 through 1999. The values are in parts per million (ppm). The seasonal fluctuation is caused by the increased uptake of CO2 by plants in the summer. (By November 2010, its concentration had risen to 389 ppm.)
    The increase in CO2 probably began with the start of the industrial revolution. Samples of air trapped over the centuries in the glacial ice of Greenland show no change in CO2 content until 300 years ago.
    Since measurements of atmospheric CO2 began late in the nineteenth century, its concentration has risen over 20%. This increase is surely "anthropogenic"; that is, caused by human activities:


    • burning fossil fuels (coal, oil, natural gas) which returns to the atmosphere carbon that has been locked within the earth for millions of years.
    • clearing and burning of forests, especially in the tropics. In recent decades, large areas of the Amazon rain forest have been cleared for agriculture and cattle grazing.

    Where is the missing carbon?

    Curiously, the increase in atmospheric CO2 is only about one-half of what would have been expected from the amount of fossil fuel consumption and forest burning.
    Where has the rest gone?
    Research has shown that increased CO2 levels lead to increased
    net production by photoautotrophs. There is evidence that at least some of the missing CO2 has been incorporated by

    • increased growth of forests, especially in North America;
    • increased amounts of photoautotrophic plankton in the oceans;
    • uptake by desert soils (mechanism as yet unknown).

    The Greenhouse Effect and Global Warming

    Despite these "sinks" for our greatly-increased CO2 production, the concentration of atmospheric CO2 continues to rise? Should we be worried?
    carbon dioxide is transparent to light but rather opaque to heat rays. Therefore, CO2 in the atmosphere retards the radiation of heat from the earth back into space — the "greenhouse effect".
    Has the increase in
    carbon
    dioxide led to global warming?
    Average temperatures do seem to have increased slightly (~0.7°C) in the last century.
    Some evidence:

    • Careful monitoring of both ocean and land temperatures.
    • Many glaciers and ice sheets are receding.
    • Woody shrubs are now growing in areas of northern Alaska that 50 years ago were barren tundra.
    • Many angiosperms in temperate climates are flowering earlier in the spring than they used to.
    • Many species of birds and butterflies are moving north and breeding earlier in the spring.

    Will continued increase in carbon dioxide lead to more global warming and, if so, how much?
    At this point, the answer depends on what assumptions you plug into your computer models. But as the different models have been improved, they seem to be converging on a consensus: a doubling of the CO2 concentration (expected by the end of this century) will cause the earth to warm somewhere in the range of 1.1–6.4°C.
    Other Greenhouse Gases

    Although their levels in the atmosphere are much lower than that of CO2,

    • methane (CH4),
    • nitrous oxide (N2O), and
    • hydrofluorocarbons (HFCs)

    are also potent greenhouse gases. Methane

    Although methane ("marsh gas") is released by natural processes (e.g. from decay occurring in swamps), human activities may now account for over two-thirds of the total.

    • mining, processing, and use of coal, oil, and natural gas;
    • growing rice in paddies;
    • burning forests;
    • raising cattle (fermentation in their rumens produces methane that is expelled from their GI tract).

    So burning of the tropical rain forest adds to the atmospheric methane budget in two ways:

    • incomplete combustion during burning and
    • release from the GI tract of the cattle that are later placed on the cleared land.

    The methane concentration in the air is presently some 1.7 parts per million (ppm). Although this concentration is far less than that of CO2, methane is 21 times as potent a greenhouse gas.
    The marked warming of the earth that occurred at the end of the
    Paleocene epoch
    is thought to have been caused by the release of large amounts of methane from the sea floor.

    عضو في أكاديمية ماركا التعليمية


  2. #2
    عضو مميز الصورة الرمزية قمر بلحاج
    تاريخ التسجيل
    Jul 2012
    المشاركات
    5,298

    افتراضي رد: The Carbon Cycle

    بارك الله بكم
    مشكورين

    عضو في أكاديمية ماركا التعليمية


معلومات الموضوع

الأعضاء الذين يشاهدون هذا الموضوع

الذين يشاهدون الموضوع الآن: 1 (0 من الأعضاء و 1 زائر)

المواضيع المتشابهه

  1. شرح درس دورة الكربون Carbon Cycle - علوم للصف الثامن فصل أول
    بواسطة مالك محمد في المنتدى شروحات وملخصات وأنشطة علوم صف ثامن
    مشاركات: 1
    آخر مشاركة: 07-08-2014, 09:52 PM
  2. Chiral Carbon
    بواسطة تمارا احمد في المنتدى .Organic chem
    مشاركات: 13
    آخر مشاركة: 17-09-2013, 02:09 AM
  3. بحث منسق عن التهجين في الكربون Hybridization of Carbon
    بواسطة ساره في المنتدى قسم الابحاث المدرسية
    مشاركات: 0
    آخر مشاركة: 22-07-2013, 09:55 PM
  4. Carbon Allotropes
    بواسطة تمارا احمد في المنتدى .Organic chem
    مشاركات: 2
    آخر مشاركة: 01-08-2012, 12:59 AM
  5. The Carbon Cycle What Goes Around Comes Around
    بواسطة مالك محمد في المنتدى قسم علوم الارض .. Geology
    مشاركات: 3
    آخر مشاركة: 19-04-2012, 03:43 PM

الاعضاء الذين قرؤوا الموضوع: 0

الكلمات الدلالية لهذا الموضوع

المفضلات

ضوابط المشاركة

  • لا تستطيع إضافة مواضيع جديدة
  • لا تستطيع الرد على المواضيع
  • لا تستطيع إرفاق ملفات
  • لا تستطيع تعديل مشاركاتك
  •