Life's Origins and Biological Classification Systems

The Origin of Life: Hypotheses and Evidence

The Panspermia Hypothesis

The hypothesis of extraterrestrial origin, known as Panspermia, proposes that the first organisms arrived on Earth from other parts of the universe, transported by meteorites. While this theory does not explain the ultimate origin of these beings, there is increasing evidence of organic matter arriving on Earth via meteorites.

Oparin's Hypothesis and Miller's Experiment

According to Oparin's hypothesis, the existing conditions on the early Earth allowed for the synthesis of a multitude of possible organic molecules. These molecules fell into the oceans, forming a nutrient broth or "primordial soup" where they accumulated. The affinity between larger and smaller molecules led them to associate, creating more complex structures, eventually forming hollow microscopic spheres called coacervates.

Those coacervates that survived were subject to autoselection and would have acquired the capacity for self-replication, which would constitute the first cells. It is not known how long it took for these coacervates to evolve into real organisms. Probably, during thousands or millions of years, they were perfected to become protocells.

Stanley Miller demonstrated that Oparin's ideas were correct, showing that organic matter could appear spontaneously from suitable inorganic conditions in a laboratory setting, simulating early Earth's atmosphere.

Classification of Living Beings: Taxonomy and Phylogeny

Linnaean Taxonomy

Taxonomy is the ordering and classification of living beings into categories. The system currently used is based on Carl Linnaeus's Systema Naturae, which proposed a hierarchical taxonomy where different living beings were grouped according to their similarities.

Linnaeus also devised binomial nomenclature, where all species are designated by two Latin words: the genus and the species name. For example, Homo sapiens.

Drawbacks of Linnaean Classification

However, Linnaeus's proposed classification has its drawbacks:

• It groups beings based on artificial criteria, such as superficial similarities, without taking into account their evolutionary relationships, which we now understand.
• This system would only be suitable if species were fixed and immutable, which is not the case according to modern evolutionary theory.

Phylogeny: Evolutionary History

Phylogeny establishes a kind of evolutionary history, tracing the lineage of all living things and linking them together back to their common origin.