EVOLUTION IN BRIEF

The word evolution is derived from the Latin “evolver” meaning to roll forth. It is defined as a gradual, orderly, and continuous process of change and development from one condition or state to another. It encompasses all aspects of life, including physical, psychologic, sociologic, cultural, and intellectual development, and involves a progressive advancement from a simple to a more complex form of state through the processes of modification, differentiation, and growth.

In genetics it is the theory of origin and propagation of all plant and animal species, including humans, and their development from lower to more complex forms through the natural selection of variants produced through genetic mutations, hybridization, and inbreeding.

Natural selection is the natural evolutionary processes by which those organisms best suited for adaptation to the environment tend to survive and propagate the species, where as those unfit are eliminated. On the contrary, the artificial selection is the process by which the genotypes (the full set of chromosomes; all the inheritance traits of organism) of successive plant and animal generations are determined through controlled breeding.

Evolution does not conform to an uniformitarian principle. When animals originated in a bewilderingly fast and psychedelic 30-50 million years, was an event in which evolution pushed itself to greater heights. The evolution of sight, of burrowing, of active predation, all these innovations allowed animals to explore evolutionary avenues that were until then closed off.

Evolution is a cumulative process where each step builds on the previous steps. The best evidence for evolution through natural selection is comparative molecular biology. By comparing the genomes of all species, you can create an exact tree of “cousinship” by literally counting the number of letters (of DNA) that they have in common. The molecular evidence is overwhelming and the chimpanzee – human resemblance is over 99 percent, however, all this has happened over a long period of time.

The genes affect the body in which they sit. The effect or the physical manifestation of the genes on the body is known as phenotype. In other words, the genes that sit in the body survive by virtue of making the body survive and everything about a body is part of its phenotype. The phenotypes by which genes survive don’t have to be in the body. For example, a bird’s nest is made by the bird’s behavior but the nest is not part of the bird’s body and it is considered an extended phenotype. Natural selection is working on the bird’s genes to influence the phenotype of the bird to make a perfect nest.

Some organisms can change their appearance, physiology and development in response to changes in the environment. This is called phenotypic plasticity. Examples are body builders in humans, water fleas that develop a spiny helmet in the presence of predators or even the effect of learning on the brain – it’s a ubiquitous phenomenon.

The most phenotypically plastic organisms are plants. Unlike animals, plants are evolved to be plastic in their physiology and development, with the best example of this being heterophylly, the ability of many wetland plants to change leaf structure and physiology in global warming, drought and in flood conditions. (Hetero = different; Philly = related to leaf). Phenotypic plasticity is one of the larger areas of current research from developmental biology, ecology, and evolution.

The evolution of genes, a system of heredity and information flow and storage, fundamentally changed how evolution worked. The evolution of multicellularity blew open the concept of individuality. The evolution in unicellular organisms is radically different than in multicellular organisms. Similarly, the evolution of language and culture are representative of new domains for evolution to grow into, where it will work in new ways.

Major evolutionary transition is the coming together of individuals into a single reproductive group: from genes to genome, genomes to cell, cells to multicellular organisms to eusocial colony. Major evolutionary transitions could also be defined by an increase in complexity. A multicellular eukaryote is more complex than a unicellular bacterium. Some transitions are characterized by new inheritance mechanisms - this unites the origin of life, genes, and language. The discoveries of endosymbiosis and of widespread horizontal gene transfer led to acceptance that evolution is no longer as simple as gene frequency changes between populations.

When developmental biology was brought into the picture it led to a major evolutionary transitions paper in 1995. A new Synthesis that acknowledges and explicitly includes all of these developments, has not yet been reached. According to professor Richard Dawkins: “we understand the whole life but we need to understand how that first step was taken – (how we got to) the first self-replicating molecule. There are lots of theories and the truth probably lies somewhere around the ones we’ve already got".

SOURCES

1. McNamara, Alexander. A life in science – An interview with Prof. Richard Dawkins. Focus Science and Technology, November 3, 2015

2. Srour, Marc. Teaching Biology. Phenotypic Plasticity, May 2, 2013

3. Srour, Marc. Teaching Biology. Major Transitions in Evolution, November 7, 2015