Name: how photosynthesis changed earth
Uploaded: 2026-03-12T13:57:27.000Z
Duration: 1 min 26 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Environmental Science

Earth's Systems

9-12.EVS.3.4

Origin of Photosynthesis

Fotosentez, fotosentetik organizmaların ışık enerjisini kimyasal enerjiye dönüştürme süreci, muhtemelen yaklaşık 3,5 milyar yıl önce başlamıştır.Fotosentezin en erken formu muhtemelen oksijensizdi; hidrojen sülfür veya demir gibi birkaç alternatif elektron donörü kullanılarak oksijen yerine kükürt veya oksitlenmiş demir salgılanıyordu.Daha sonra, siyanobakteriler suyu elektron bağışçısı olarak kullanarak oksijenik fotosentez yapma yeteneği geliştirmiş ve yan ürün olarak oksijen salgılamıştır.Siyanobakteriler tarafından salınan oksijen, okyanuslarda çözünmüş demirle reaksiyona girerek, deniz tabanında bantlı demir oluşumları olarak çöken çözünmeyen demir oksitleri oluşturdu.Bu arada, siyanobakteriler katmanlı mikrobiyal matlar oluşturdu ve bunlar sonunda stromatolitlere fosilleşti.Okyanusun çözünmüş demirinin çoğu oksitlenip okyanuslardaki büyük oksijen batımı giderek daha doygunlaştıkça, serbest oksijen sonunda atmosferde birikebildi.Atmosferik oksijendeki bu artış, yaklaşık 2,4 milyar yıl önce Büyük Oksidasyon Olayı'nı tetikledi ve aerobik metabolizmayı ve ozon tabakası oluşumunu mümkün kıldı.

fotosentezin kökeni

Fotosentez, Dünya'nın atmosferini dönüştüren ve karmaşık yaşamın yolunu açan temel bir biyolojik süreci temsil eder. Yaklaşık 3,4–3,8 milyar yıl önce ortaya çıkan en erken fotosentetik organizmalar, ışık enerjisini kullanarak organik bileşikler üretmiştir. Bu anoksijenik fototroflar, su yerine hidrojen sülfür (H₂S) veya demirli demir (Fe²⁺) gibi elektron donörleri kullanıyor ve yan ürün olarak moleküler oksijen (O₂) salgılamamıştı. Yeşil kükürt ve mor bakteriler dahil olmak üzere çeşitli gruplar bu erken fototrofik çeşitliliğe katkıda bulundu.Önemli bir evrimsel dönüm noktası, siyanobakteriler tarafından oksijenik fotosentezin geliştirilmesiydi. Bu mikroorganizmalar, elektron bağışçısı olarak suyu kullanarak yan ürün olarak moleküler oksijen üretti. Siyanobakteriler sığ deniz ortamlarını kolonileştirerek geniş mikrobiyal matlar oluşturdu. Zamanla, bu matlar tortular ve çökeltmeler biriktirerek stromatolitlere fosilleşerek yaşamın bilinen en eski kanıtlarından bazılarını oluşturmuştur. Yerel olarak oksijen seviyeleri arttıkça, deniz suyunda bol çözünmüş demirle reaksiyona girerek demir oksitleri olarak çökelmiştir. Bu oksitler deniz tabanına yerleşerek, erken atmosfer değişiminin önemli jeolojik göstergeleri olan bantlı demir oluşumları (BIF'ler) oluşturdu.Okyanusun demirinin çoğu oksitlendikten sonra, fazla oksijen atmosfere yayılmaya başladı ve yaklaşık 2,4 milyar yıl önce Büyük Oksidasyon Olayı'nı (GOE) tetikledi. Bu geçiş, Dünya'nın kimyasını ve biyolojisini köklü şekilde değiştirdi. Atmosfer oksijenindeki artış, anaerobik metabolizmadan çok daha fazla enerji sağlayan aerobik solunumun evrimini mümkün kıldı. Ayrıca, gezegeni zararlı ultraviyole radyasyondan koruyan ve hayatın karaya yayılmasının yolunu açan stratosferik ozon (O₃) tabakasının oluşmasına yol açtı.GOE evrimsel yeniliği teşvik ederken, oksidatif stresi de getirdi ve birçok anaerobik organizmanın yok olmasına neden oldu. Buna rağmen, oksijenik fotosentezin ortaya çıkışı, Dünya tarihindeki en önemli evrimsel gelişmelerden biri olmaya devam etmektedir.

Fotosentezin Kökeni

Photosynthesis represents a fundamental biological process that transformed Earth's atmosphere and paved the way for complex life. Emerging roughly ...

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Education

JoVE Core

Microbiology

Mikrobiyoloji

Unit

Birim

Microbial Evolution

Mikrobiyal Evrim

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

how photosynthesis changed earth

Photosynthesis changed Earth’s atmosphere and made complex life possible. It began about 3.4 to 3.8 billion years ago, when the first photosynthetic organisms used light energy to build organic compounds. These early organisms were anoxygenic phototrophs, which means they made food from light but did not release oxygen.

Early photosynthesis used hydrogen sulfide (H2S) or ferrous iron (Fe2+) as electron donors instead of water. Because of that, it did not produce molecular oxygen (O2) as a waste product. Green sulfur bacteria and purple bacteria were among the groups that helped shape this early phototrophic diversity.

A major turning point came with cyanobacteria and oxygenic photosynthesis. Cyanobacteria used water as the electron donor and released oxygen. They lived in shallow marine environments and formed large microbial mats. Over time, those mats trapped sediments and precipitates and later became stromatolites, which are some of the oldest evidence of life.

As oxygen built up in local waters, it reacted with dissolved iron in the sea. This formed iron oxides that sank to the seafloor and created banded iron formations, or BIFs. These rocks are important markers of early changes in Earth’s atmosphere and oceans.

After most of the iron in the oceans had been oxidized, oxygen began to enter the atmosphere. This led to the Great Oxidation Event, or GOE, around 2.4 billion years ago. The rise in oxygen changed Earth’s chemistry and biology in major ways.

More oxygen allowed aerobic respiration, which releases much more energy than anaerobic metabolism. It also helped form the stratospheric ozone (O3) layer, which protects life from harmful ultraviolet radiation. That protection helped set the stage for life to spread onto land.

The Great Oxidation Event also had harmful effects. Oxygen created oxidative stress and caused many anaerobic organisms to die out. Even so, the rise of oxygenic photosynthesis remains one of the most important events in Earth’s history.

How Photosynthesis Changed Earth

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key terms and concepts

Explore how early photosynthesis, cyanobacteria, stromatolites, and the Great Oxidation Event transformed Earth’s atmosphere and enabled complex life.

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9-12.EVS.3.5

How Photosynthesis Changed Earth

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