THE FUNDAMENTALS OF BIOLOGY AND ITS BRANCHES
The word biology- from Greek bios, life and logos, studied- was coined more than two hundred years ago;Biology had its origins as a purely observational discipline and was of a naturalistic type, which is why it was called "natural history", it is currently developed within the framework of the scientific method, and is defined as a branch of sciences that aimsIdentify all causes related to the different processes that occur in nature and that affect different ways about the living world. Within biology it is considered that it is very unlikely that a phenomenon responds to a single cause, its analysis often becomes a bit complex. This complexity causes multiple approaches to be able to explain them, since it is necessary to characterize processes and patterns at different spaces of space and time.
It can be said that the foundations of biology began as a compendium of ideas and observations that tried to explain the notion of life: how do you explain what something is alive?, What attributes should you have to consider it as such?, What is the origin of so many different ways of life?, How do they reproduce? The first works focused on answering these questions and eventually concepts and theories arose that would allow structuring knowledge within biology. The first debate consisted of defining what should be the attributes that an entity should possess to be considered alive.
Fundamental biological characteristics of living organisms
An organism is a way of life -uni or multicellular- that share fundamental characteristics in common, these allow them to be considered as "living" entities: they use an energy source to remain alive and reproduce. For example, a marine grass uses light energy to perform photosynthesis. They are formed by a series of units, – more or less independent – locked by membranes, known as cells. They have hereditary genetic information encoded in the genes that the organism uses to continuously renew its organs (for example the skin) and that also responds to the conditions of the immediate environment. They have the power of replication, such as viruses or bacteria. They are the product of evolution and each new set of organisms (population) will have the intrinsic capacity to continue evolving.
In addition to this the questions arose: what is a cell formed from? And what is its origin? With the emergence of cell theory and the theory of evolution, these questions could be addressed. Currently, both theories are considered as key foundations that contributed to the unification of biology.
Unifying principles of biology
Cell theory
It emerged in 1665, after the observations made by Robert Hooke. Hooke used a simple microscope to study the cork, which is the tissue of the oak tree bark. This experiment allowed him to observe the small cork compartments – imperceptible to the naked eye – and called them cells. Subsequently, Anton Van Leeuwenhoek built a microscope with an amplification capacity of 300 increases with which he studied a water sample, in it he appreciated the existence of a wide variety of unicellular organisms he called “animals”. He also made and recorded his observations of the structure of human blood cells and sperm. In 1670, after a study of stems and plants, it was concluded that they were formed by individual cells. As progress were made in the field of microscopy, at the beginning of the 19th century it could be declared that all organisms were formed by cells.
From the point of view of contemporary biology a cell is defined as a compartment divided into perfectly organized structures called organelles (nucleus, nucleolus, mitochondria, etc.) that are immersed in chemical substances concentrated in an aqueous solution and that are surrounded by a thin structure called plasma membrane. From the study of each of the organelles it was determined that all the reactions that support life, occur inside the cell.
The second part of cell theory comes from the answer to the questions: what is the origin of the cells of an organism?, Where do they come from? For which the hypothesis that "one cell only comes from another cell" by German Rudolph Virchow was enunciated. The response and confirmation of this came from the Louis Pasteur experiment, he set out to experimentally verify the hypotheses of the spontaneous generation against which he stated that one cell only has its origin from another cell. The popular Pasteur experiment, made in a swan neck flask, allowed us to conclude that "cells are only born from other previous cells, not spontaneously from matter not life".
The second theory and foundation that gave rise to biology was proposed, independently, by the English Darwin and Wallace. It was extensively detailed in the book "The origin of the species" by Charles Darwin.
Theory of evolution by natural selection
This theory was very controversial for the progress of biology and experiment a process of development similar to that of cell theory, was stated at the same time as her and formulated two statements that generated debates in her time:
- Species share common ancestors, as opposed to the idea of divine origin and
- The characteristics of the species change from one generation to another. This theory was opposed to the idea of the unchanged permanence of species over time (and from generation to generation).
Through the work of several scientists (in addition to Darwin and Wallace) a model could be proposed that explained the relationship between species and how evolution operates, this process was called the natural selection and the premises that allowed us to understand how the processes occurredEvolutionary:
- Individuals of a population vary depending on inheritable characteristics.
- In specific environments, certain variants (versions) of the same inheritable feature helps them increase their survival or their chances of leaving offspring.
For example the birch moths;This species, before being subjected to an environment full of contamination floating in the air, used to be white, after industrialization (in England) specimens arose that became dark or mottled in order to reduce the number of predators. Over time the population almost entirely became dark. This phenomenon constitutes biology the clearest example of how natural selection operates.
The basic idea is that, if a variation of a trait that is inheritable generates greater success in the probability of leaving offspring, then the frequency of that feature in the population will increase. This is a key concept in biology: evolution acurs at the individual level but change only affects the population.
At the same time that the concept of natural selection was proposed, concepts such as fitness and adaptation arose. Fitness refers to the biological success of leaving a) a viable offspring and that, in turn, is able to reproduce and b) that it is a large offspring. Adaptation: From the biological point of view, it is a feature that increases the biological efficacy of an individual in the presence of a given environment.
After the recognition of the natural selection process, which operates in all populations, a phenomenon was also documented that consisted of the divergence of populations by the effect of natural selection, and that made one species arise from another, this process was called speciation. Research on this phenomenon provided evidence that all species are the result of previous species and that all share a single ancestor in common.
Cell theory and evolution theory (and natural selection) facilitated the understanding and connection between all the processes that occur between all species, so that it was considered that using the unifying principles of biology should be able to rebuild the tree genealogical or tree of the life of all current and past species.
Phylogenetic tree or tree of life
With the generation of a tree of life or phylogenetic tree, kinship relationships of all species that have been – until current times – on earth and in which “an ancestral species should be considered in thebase". With this, the term phylogenesis (origin of the tribe) was introduced into biology, which refers to the genealogical relationships between all organisms.
This great advance occurred when the idea was raised that the chemical components of the organisms began to be analyzed as a means of understanding what were the evolutionary relationships they shared. For this, it was proposed that the molecules that were present in all organisms be.
The RNA has a simple structure composed of a sequence of four nucleotides (ribonucleotides) identified with letters A (adenine), G (guanine), C (cytocin) and U (urasilo) and whose sequence is not identical between the organism (oreven among individuals of the same species). The antecedent under which the proposal was made was that if all organisms came from a common ancestor, similar sequences should be presented among all those who had a close relationship of kinship, but not so much among those who were not so close.
This premise was tested by studying the RNA of different species;The objective was to create a diagram that reflected the phylogenesis of the organisms studied. Eventually the creation of these phylogenetic trees has allowed establishing the evolutionary process that species have suffered, in which the closest branches represent closely related species and with a common ancestor;While the farthest reflect divergences that occurred in a distant time, so it is suggested that these are species that separated at an early time from the evolutionary process. From the emergence of phylogeny how a primary branch in the study of the biology of an organism, another branch emerged that focused on classifying organism groups called taxonomy. Both branches are responsible for facilitating the understanding of the diversity of known organisms to date.
We currently know that biology is a branch of multidisciplinary approach science, for each question that arises there are different possible legitimate answers, which will depend on the main objective pursued and the approach and the original initial question.
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