Biology Tutorials > The Origins of Life > Evolution of Life – Ancient Earth

Evolution of Life – Ancient Earth

Evolution of Life - Ancient Earth

The first life forms on Earth were probably the ones with biomolecules carrying “genetic code”.

Continuing from the previous tutorial investigating the origins of life on Earth….

Life began to flourish, and the autotrophic organisms had tapped a new niche allowing the biomass of Earth at the time to dramatically increase.

The autotrophs en masse were absorbing carbon and light. The light invariably would always be an available source for synthesizing energy, while the carbon was not.

CO2 was constantly being absorbed by these organisms, and after the biological reactions responsible for creating energy in them, oxygen would be released as a by-product.

Aerobic Organisms

This meant that oxygen began to accumulate in the oceans where life existed. This new material would, in turn, be taken advantage of by the adapting organisms, leading to the creation of aerobic organisms that used oxygen as a component of their energy creation. This is another example of life diversifying to adapt to its environment and exploit the niches that it could occupy.

This type of evolution continued, where the supply of potential energy making elements and compounds outstretched the requirements of life, therefore organisms continued to adapt to fill all available niches as opposed to competing with one another.

Infraspecific / Intraspecific Competition

Pathogens existed by this time and were able to leech resources from their single-cell hosts, kill them, and move on to the next host after multiplying. On top of this, resources for all organisms alive at the time were being stretched by the increasing population of species and also the diversity of unique species.

The exhaustible materials used by species were limited and they would have to ‘fight for their right’ to survive.

To do this, natural selection would give them a competitive advantage over other organisms and perhaps relieve stress caused by competition within the species (intraspecific).


One noted event in the origins of life is the emergence of protists. Although these organisms were single-celled like all other organisms, they were notably bigger, some being visible to the human eye. This adaptation must have been a selective advantage at the time, either over competitors or taking advantage of an ecological niche.

In fact, adaptive change is believed to be anatomical. Unlike other organisms, the protists contained cell organelles, which meant that a fundamental difference in the way life operated had arisen in the case of the protists. The occurrence of the protists was so unique that the diversity of them substantiates the Animalia and Plantae classifications because differentiating characteristics were noted, i.e. the presence of organelles.

Basically, protists are unique because they possess a nucleus which contains the genetic information of the cell and the organism. Previous species were more simple in their nature and did not possess such a complex cellular structure.

The next tutorial investigates how these protists survived in the times, progressing through our evolutionary timeline on Earth…..


Credit: Science Channel


Write True, if the sentence is correct, or False, if the sentence is incorrect.

1. While carbon dioxide is absorbed by the autotrophs oxygen is released as a byproduct in a process called photosynthesis.
2. Aerobes used oxygen, which was beginning to accumulate from the photosynthetic activity of autotrophs, as a reactant during chemical energy synthesis.
3. The competition occurring between same species is called interspecific.
4. One of the most notable events in the origins of life is the emergence of early protists that possessed the genetic material in their nucleus.
5. Natural selection is one of the reasons that led to the diversification of organisms.

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Biology Tutorials > The Origins of Life > Evolution of Life – Ancient Earth

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