Core Principles of Evolution, Genetics, and Species Variation

Key Concepts in Genetics and Variation

Variations

Differences among individuals within a species.

Phenotypic Variations

Observable differences within individuals of a population (e.g., weight, height, color). These are the result of the environment and the influence of their genotypes.

Genotypic Variations

New features individuals acquire in each generation, typically caused by recombination and/or mutations.

Gene Pool

The sum total of genotypes of all individuals within a given population.

Mutations

Changes that occur in the genetic material. These can be spontaneous or induced and may act favorably or unfavorably on the development of a living being.

Genome

The entire genetic material contained in the cells of a particular organism.

Natural Selection

A process where organisms with unfavorable variations are eliminated, while organisms with favorable variations survive. This mechanism preserves and strengthens favorable variations over time.

Major Evolutionary Theories and Concepts

Defining Evolution

We define Evolution as a process involving changes in the characters of species over time, originating from simpler forms.

Historical Theories of Change

Lamarck's Theory

Lamarck's theory was based on two primary concepts:

1. Law of Use and Disuse of Organs: Organs became stronger if used and weaker if they ceased to be used.
2. Inheritance of Acquired Characteristics: Changes that occurred during an organism's lifetime were handed down from parent to offspring.

Darwin's Theory of Natural Selection

Darwin's theory laid the foundation for the modern understanding of evolution by introducing the concept of species change through a slow process of Natural Selection.

Synthetic Theory of Evolution (Neo-Darwinism)

Also called Neo-Darwinism, this theory emerged between 1930 and 1950, integrating contributions from three scientific disciplines:

• Genetics: Responsible for studying inheritance.
• Systematics: Responsible for the identification of species in nature.
• Paleontology: Responsible for studying the fossil record.

The modern theory of evolution holds that contemporary species are derived from other remote species through accumulated changes.

Fixist or Creationist Theory

The Fixist theory holds the immutability of species; that is, they do not change across time or space. Carolus Linnaeus (1707–1778) was a convinced fixist, yet his works suggest certain transformations. He realized that living things could be placed in a gradual succession of forms, where each species could be positioned according to its characteristics between the preceding and succeeding organization.