Organic Evolution - SS3 Biology Lesson Note

Organic evolution, also known as biological evolution, is the process by which populations of organisms change over time, resulting in the diversity of species on Earth. It refers to the gradual modification of species through genetic variation, natural selection, and other mechanisms, leading to the development of new species and the extinction of others.

Key points about organic evolution include:

1.       Descent with Modification: Organic evolution is based on the principle of "descent with modification," which means that new species arise from pre-existing species through a process of gradual change. Over generations, populations accumulate genetic variations, leading to heritable differences among individuals.

2.       Genetic Variation: Genetic variation is the raw material for evolution. It arises from mutations, genetic recombination, and other genetic processes. Genetic variations can result in differences in physical traits, behaviour, reproductive strategies, and other characteristics within a population.

3.       Natural Selection: Natural selection is the driving force of evolution. It is the process by which certain heritable traits become more or less common in a population over generations, depending on their fitness in a particular environment. Individuals with traits that confer advantages, such as better adaptation to the environment, increased reproductive success, or improved survival, are more likely to pass on their genes to future generations. Over time, these advantageous traits become more prevalent in the population.

4.       Speciation: Speciation is the process by which new species arise. It occurs when populations of the same species become reproductively isolated from each other, preventing gene flow. Over time, genetic differences accumulate between the isolated populations, leading to the formation of distinct species that are no longer able to interbreed.

5.       Extinction: Extinction is another important aspect of organic evolution. Species can become extinct due to various factors, such as environmental changes, competition, predation, or human activities. Extinction removes certain lineages from the evolutionary process, shaping the overall diversity of life on Earth.

Organic evolution is supported by extensive evidence from multiple scientific disciplines, including palaeontology, comparative anatomy, genetics, molecular biology, and biogeography. Together, these fields provide insights into the mechanisms and patterns of evolution and the interconnectedness of all living organisms.