Ecology

Ecology is the study of the relationships between living organisms and the interactions between them and their environment.

From the Big Bang to the Primordial Soup

Formation of the Universe

The Big Bang theory maintains that, 13.7 billion years ago, a very hot and dense environment grew from a single point to form the Universe.

The expansion and cooling of the generated mass created quarks, which then assembled into protons and neutrons. The first atoms appeared (hydrogen and helium).

Formation of the Solar System

The clouds of gas and cosmic dust created from the Big Bang eventually agglomerated into a mass, which contracted as it rotated around its own axis. As a result, our solar system appeared as a mass (called a protostar) and developed within one of the many galaxies being formed.

A wide variety of chemical compounds then appeared after the solar system had formed.

Formation of the Sun-Earth System

During the formation of the solar system, a proto-Sun emerged. Its core contained large amounts of hydrogen (H), oxygen (O), nitrogen (N) and carbon (C), and was surrounded by an atmosphere composed of hydrogen.

Elements from the centre of the proto-Sun combine with atmospheric hydrogen to form more complex chemical compounds: CH₄ (methane), NH₃ (ammonia) and H₂O (water vapour).

Rotating matter came together to form the Earth, which would have been in a degassing period, emitting gases such as H₂O, CO₂ and H₂S, as a result of certain phenomena such as volcanism.

Development of the Primitive Atmosphere

Soviet biochemist Alexander Oparin believed the primitive atmosphere of our planet was composed of an “inhospitable” mixture of methane (CH₄), ammonia (NH₃), water vapour (H₂O), carbon dioxide (CO₂) and hydrogen sulphide (H₂S).

Exposed to powerful solar radiation (especially UV rays), this mixture of gases created several simple organic molecules, such as amino acids which would later form proteins. These organic molecules evolved to generate the first living molecules. We call this mixture the primordial soup.
Note: Organic molecules are formed from the following atoms: C-H-O-N.

In 1953, an American scientist named Stanley Miller performed an experiment proving the Oparin hypothesis.

Evolution of the Primordial Soup

The organic molecules accumulated in lagoons and primitive seas continued to react over hundreds of millions of years.

As they were exposed to solar energy over time, these organic molecules combined into large complex organic molecules, such as nucleic acids, proteins, sugars and fats (lipids). These were the first biomolecules (polymers, chains of monomers) to develop. DNA, the basic molecule of life, is one of these biomolecules.

In order to evolve, these molecules needed to:

1. Create a protective envelope, so they could control exchanges with their environment (by osmosis and diffusion);

2. Use the environment’s resources (chemical products of fermentation) to meet their nutritional and energy needs. These are referred to as heterotrophic organisms;

3. Reproduce by making copies of themselves. This is the origin of the genetic code.

This started a “passive competition,” where the living organisms with the most advantages lived longer.

These organisms evolved into “proto-organisms” (more perfected), which were the ancestors of algae and bacteria.

It is important to know that the activation energy required for the first vital reactions came from molecules, such as glucose and ATP. This is known as the fermentation process.

Heterotrophs are organisms that obtain nourishment from the environment rather than creating it themselves, like autotrophs. Heterotrophs generate more and more waste in the form of carbon dioxide (CO₂).

As some organisms became “hungrier” and competed for food, they started feeding on carbon dioxide. This was the beginning of photosynthesis during which oxygen is released.