The Organic evolution , Also known as biological evolution, is the result of genetic changes in populations of certain species that have been heritages over several generations.
These changes can be either large or small, obvious or not so obvious, minimal or substantial; That is to say, slight changes in a species or alterations that lead to the diversification of a type of organism in several subspecies or in unique and different species.
Biological evolution is not simply about changes in time. Many organisms exhibit changes over time such as loss of leaves in trees, weight loss in mammals, metamorphosis of insects or changes in the skin of some reptiles.
These are not considered evolutionary changes because there is no genetic change that is being transmitted to the next generation.
Evolution transcends the simple life cycle of a single individual organism; Encompasses the inheritance of genetic information between generations.
Organic evolution: microevolution and macroevolution
For these events to really be considered as an evolutionary step, the changes must occur at a genetic level in a population and be transmitted to offspring. These small-scale changes are defined as micro evolution.
The definition of macro evolution considers that all living organisms are connected in an evolutionary history, and can be traced back many generations to a common ancestor.
Organic evolution as theory and natural selection
Evolution involves modifications to existing species, not the development of new species. This idea was developed and proposed by Charles Darwin As a scientific theory based on observations and experiments.
This theory tries to explain how the events related to living organisms in the natural world work and it was called Darwinism Or the general theory of evolution.
Darwinism states that the struggle of species to exist and survive was forcing their body systems to adapt to conditions, acquiring new characteristics that responded to the needs of the environment.
Different conditions can trigger a process of adaptation and eventually an evolutionary genetic change in a species, such as climate, terrain, environment, temperature, pressure, excess or lack of food, excess or absence of predators, isolation, etc.
According to Darwin, the set of these processes is called natural selection and acts on populations, not on individuals.
The first traces of change can occur in a single individual. If that change helps him to survive where another of his own species does not, transmitting it to the next generations, the change ends up being written in the DNA Of other individuals and eventually in whole populations.
Natural selection
Genetic variations occurring in a population occur randomly, but the process of natural selection does not. Natural selection is the result of interactions between genetic changes in a population and the conditions of the environment or environment.
The environment determines which variation is most favorable. Individuals who possess more favorable characteristics in their environment will survive to reproduce and give life to other individuals.
Consequently, the most optimal features are transmitted to the population as a whole. The following conditions must occur for the processes of evolutionary changes to occur in populations of species:
1- Individuals in a population must produce more offspring than the surrounding conditions can sustain
This increases the chances of survival of individuals of the same species, since at least a small portion of the offspring would reach maturity to reproduce and transmit their genes.
2- Individuals when mating must have different characteristics
Changes in organisms arise from DNA mutations in a mixture of genetic information during sexual reproduction, in a process called genetic recombination.
It occurs during meiosis that provides a way to produce new combinations of alleles on a single chromosome. Sexual reproduction also allows the removal of unfavorable gene combinations in a population.
Organisms that reproduce asexually do not bring evolutionary changes, since the process simply produces exact copies of the same individual.
3- The offspring must inherit the characteristics of the parents with the transmission of genes
4- The organisms with the characteristics most suitable for their environmental environment, are more likely to survive and reproduce
This point is the heart of natural selection. If there is competition for survival and not all organisms are equal, those with the best traits will have the advantage.
If these traits can be transmitted, then the next generation will show more of these advantages.
If these four conditions are met, the following generations will always be different from the previous individuals in frequency and distribution of genetic traits; Then we could say that a species has evolved satisfactorily.
Cetaceans as an example of organic evolution
Aquatic mammals, such as cetaceans, are a clear example of adaptation to the environment. They retain traits typical of all mammals such as internal gestation in a womb and breastfeed their offspring.
But its life cycle was completely dissociated from the mainland millions of years ago. Their limbs were adapted by developing swimming fins and their bodies to provide the least possible resistance when moving through the water.
The way they store and distribute oxygen within their body systems allows them to dive and even stay underwater for a long time. They can reduce their rate of oxygen consumption in immersion conditions by almost 30%.
Muscle tissues can store 50% oxygen and blood 40% and your lungs perform gas exchange more efficiently.
With the exhalations, they manage to eliminate up to 90% of the carbon dioxide of the alveoli, where a terrestrial mammal achieves only 20%.
The nostrils adapted to become a nasal orifice that moved to the top of the skull, thus facilitating the intake of air by just peeking the top of the head on the surface.
References
- Francisco J. Ayala (2003). Evolution, Biological. Encyclopedia of Science and Religion. Retrieved from encyclopedia.com.
- Understanding Evolution team. Welcome to Evolution 101! Understanding Evolution. Retrieved from evolution.berkeley.edu.
- Regina Bailey (2017). Biological Evolution. Retrieved from thoughtco.com.
- NW Creation Network. Biological evolution. Encyclopedia or Creation and Science. Retrieved from creationwiki.org.
- What is organic evolution? Retrieved from reference.com.
- Bruno Almón (2001). The Marine Mammals. Hydronauta. Recovered from hydronauta.com.
- Rene Fester Kratz. Natural Selection and Biological Evolution. Dummies. Retrieved from dummies.com.