Hi. I'm Jensen Morgan. We're going to talk about some great concepts in environmental science. Today's topic is early life. So let's get started.
We're going to talk about early life formation on earth and its transition from water to land. Early life didn't just pop into existence. It was a process that took place over the course of millions of years.
At first, small, inorganic molecules in a water environment combined into larger, more complex organic molecules as a result of lightning. Then these molecules became encapsulated in a membrane over time.
Eventually, these membrane molecules gained the ability to replicate themselves. These were the earliest forms of life called prokaryotes, which formed about 3.8 billion years ago. Over time, they split into varying types which included bacteria. They developed the capacity to metabolize things, including each other. One of these types of metabolism was photosynthesis.
Photosynthetic metabolism led to free oxygen production. Some prokaryotes began to form symbiotic relationships with each other about 1.8 billion years ago. One would protect the other while the other focused on energy production. This relationship led to eukaryotes. About 600 million years ago, eukaryotes led to multi-celled organisms, where different cell types specialized in different tasks for the functioning of the whole. This led to fungi, algae, plants, and animals.
Eventually, water subsided from certain parts of the planet, which allowed enough dry land for plants to adapt to a terrestrial environment. As more terrestrial plants evolved, it provide a potential food source for animals to consume on land. Plants and animals faced other challenges to adapting to land, such as, drying out and dying if they couldn't find a water source, solar radiation could lead to mutations that killed organisms, and learning to move about outside of water with a different sense of gravity.
Organisms also had to adapt reproduction to life on land, because all such processes had previously relied on an aquatic environment. It wasn't until enough oxygen collected in the atmosphere and then reacted with solar radiation to form a thick enough ozone layer that protected organisms from radiation that land adaptation began in earnest.
Now let's have a recap. We talked about early life formation on earth and its transition from water to land. Well, that's all for this tutorial. I look forward to next time. Bye.