Evolution:- Evolution is the process by which species of organisms change over time through the mechanisms of genetic variation, natural selection, and adaptation. It is the fundamental process that has shaped the diversity of life on Earth. Evolutionary theory, first proposed by Charles Darwin in the mid-19th century, provides a comprehensive framework to understand how species originate, diversify, and change over generations. At the core of evolution is the concept of genetic variation. Genetic variation refers to the differences in the genetic makeup (DNA sequences) of individuals within a population. This variation arises from a variety of sources, including random mutations, genetic recombination during reproduction, and the introduction of new genetic material through migration or gene flow between populations. Natural selection acts on this genetic variation. It is the process by which certain traits become more or less common in a population over time. Individuals ...
The cell theory is a fundamental principle in biology that states that all living organisms are composed of cells, cells are the basic units of structure and function in living organisms, and all cells arise from preexisting cells through cell division. This theory revolutionized our understanding of life and provided a unifying framework for the study of biology. The cell theory originated in the early 19th century and was formulated independently by the German botanist Matthias Schleiden and the German zoologist Theodor Schwann. Schleiden studied plant tissues and concluded that plants are composed of cells, while Schwann extended this idea to animals. Their combined efforts led to the proposal of the cell theory, which was further refined and expanded upon by subsequent scientists. The first component of the cell theory states that all living organisms are composed of cells. This observation arose from the early microscopic studies of Antonie van Leeuwenhoek, who used si...