Life’s Fundamental Principles: Characteristics and Evolutionary Theories
Characteristics of Living Organisms
Living organisms perform vital functions. They are able to:
- Exchange matter and energy with their environment, processed and transformed by processes called metabolism. To maintain life activity, nutrition is essential.
- Create replicas or copies of themselves through the function of reproduction. This function requires the duplication of genetic information.
- Receive and respond to environmental information, a function of relation.
Living things are composed of molecules arranged in cells. These organic molecules are biomolecules unique to living beings, along with some inorganic molecules. These molecules gather to form organelles and structures that constitute cells. As the cell theory states, all living beings are composed of cells.
Chemical Evolution: Origins of Life
According to Alexander Oparin, approximately 3.5 billion years ago, under conditions of an Earth atmosphere different from today’s (not composed of gases like oxygen, but rather hydrogen (H2), ammonia (NH3), and carbon dioxide (CO2)), and within an aqueous medium like a ‘soup’ or ‘broth,’ aggregates of primitive organic substances could form. These led to microvesicles, called coacervates, which were precursor cells.
Biological Evolution: The Development of Life
A compartment, though not isolated from the environment, allows and regulates the entry and exit of substances. It is capable of processing molecular substances within, performing transformations necessary to obtain energy and other molecules, thus maintaining its structure. It also contains molecules with information necessary for reproduction.
These microvesicles could have evolved into protocells. These protocells had properties similar to primitive bacteria, meaning they were prokaryotes: lacking a distinct nucleus or organelles.
Subsequently, an association of cells in colonies allowed for specialization within the group. Thus, cells within the colony specialized in specific tasks, beginning the evolutionary path that led to multicellular organisms, such as protoctists and fungi.
The Endosymbiosis Theory
According to the theory of endosymbiosis or symbiogenesis, eukaryotic cells originated from smaller prokaryotes that were engulfed by larger ones. A large anaerobic prokaryotic cell with a great capacity for phagocytosis could engulf other prokaryotes. Instead of being digested, these engulfed prokaryotes survived in symbiosis, relying on the host cell and eventually forming different organelles within an aerobic eukaryotic cell.
The main foundations of this theory are based on the fact that mitochondria and chloroplasts have the following features:
- Size and shape similar to bacteria.
- Bacterial-sized ribosomes.
- Their own circular DNA, like today’s bacteria.
- Enzymes necessary to transcribe RNA and translate a small number of their own proteins.
Evolutionism: Meaning, Evidence, and Theory
Evolution: a gradual change from one state to another.
The fact of evolution: The gradual change in the characteristics of species over time is an observable fact, supported by the fossil record. Changes identified due to environmental shifts are undeniable examples.
The theory of evolution: Considering the observed changes as the explanation for the origin of every species that populates the planet constitutes a sufficiently proven scientific theory.
Fixism and Creationism
The belief that species remain identical to themselves forever from their origin, having been created as they are and as we see them, is known as Fixism. Creationism is closely related. Carl Linnaeus, for example, proposed his system of natural classification of organisms, which he intended to reflect the divine plan of creation.