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

A fotossíntese, o processo pelo qual organismos fotossintéticos convertem energia luminosa em energia química, provavelmente começou há cerca de 3,5 bilhões de anos.A forma mais antiga de fotossíntese provavelmente era anoxigênica, utilizando vários doadores alternativos de elétrons, como sulfeto de hidrogênio ou ferro ferroso, e liberando enxofre ou ferro oxidado em vez de oxigênio.Mais tarde, as cianobactérias evoluíram a capacidade de realizar fotossíntese oxigênica usando água como doador de elétrons e liberando oxigênio como subproduto.O oxigênio liberado por cianobactérias reagiu com ferro dissolvido nos oceanos, formando óxidos de ferro insolúveis que se estabeleceram como formações de ferro em faixas no fundo do mar.Enquanto isso, as cianobactérias formaram tapetes microbianos em camadas, que eventualmente se fossilizaram em estromatólitos.À medida que a maior parte do ferro dissolvido do oceano se oxidava e os principais sumidouros de oxigênio nos oceanos se tornavam cada vez mais saturados, o oxigênio livre acabou se acumulando na atmosfera.Esse aumento do oxigênio atmosférico desencadeou o Grande Evento de Oxidação há cerca de 2,4 bilhões de anos, possibilitando o metabolismo aeróbico e a formação da camada de ozônio.

origem da fotossíntese

A fotossíntese representa um processo biológico fundamental que transformou a atmosfera da Terra e abriu caminho para uma vida complexa. Surgindo há cerca de 3,4 a 3,8 bilhões de anos, os primeiros organismos fotossintéticos aproveitaram a energia luminosa para produzir compostos orgânicos. Esses fotótrofos anioxigénicos usavam doadores de elétrons como sulfeto de hidrogênio (H₂S) ou ferro ferroso (Fe²⁺), em vez de água, e não liberavam oxigênio molecular (O₂) como subproduto. Diversos grupos, incluindo enxofre verde e bactérias roxas, contribuíram para essa diversidade fototrófica inicial.Um marco evolutivo significativo foi o desenvolvimento da fotossíntese oxigênica por cianobactérias. Esses microrganismos utilizavam água como doador de elétrons, produzindo oxigênio molecular como subproduto. As cianobactérias colonizaram ambientes marinhos rasos, formando extensos tapetes microbianos. Com o tempo, esses tapetes acumularam sedimentos e precipitados, fossilizando-se em estromatólitos — algumas das evidências mais antigas conhecidas de vida. À medida que os níveis de oxigênio aumentavam localmente, ele reagia com a abundância de ferro dissolvido na água do mar, precipitando como óxidos de ferro. Esses óxidos se depositaram no fundo do mar, gerando formações de ferro em faixas (BIFs), que servem como marcadores geológicos chave das primeiras mudanças atmosféricas.Uma vez que a maior parte do ferro oceânico foi oxidada, o excesso de oxigênio começou a se difundir na atmosfera, desencadeando o Grande Evento de Oxidação (GOE) há cerca de 2,4 bilhões de anos. Essa transição alterou drasticamente a química e a biologia da Terra. O aumento do oxigênio atmosférico possibilitou a evolução da respiração aeróbica, que fornece muito mais energia do que o metabolismo anaeróbico. Também levou à formação da camada estratosférica de ozônio (O₃), protegendo o planeta da radiação ultravioleta nociva e abrindo caminho para a expansão da vida em terra.Embora o GOE tenha promovido a inovação evolutiva, também introduziu estresse oxidativo e causou a extinção de muitos organismos anaeróbicos. No entanto, o advento da fotossíntese oxigênica continua sendo um dos desenvolvimentos evolutivos mais significativos da história da Terra.

Origem da fotossíntese

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

Microbiologia

Unit

Unidade

Microbial Evolution

Evolução Microbiana

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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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