Introduction to Evolution

Evolution is the change in the heritable characteristics of biological populations over successive generations. This change occurs through processes such as natural selection, genetic drift, and mutation.

Key Concepts

• Natural Selection: The process by which organisms with favorable traits are more likely to survive and reproduce, leading to the gradual change of a population over time.
• Genetic Drift: The random fluctuations in the frequency of alleles in a population, which can lead to changes in the gene pool.
• Mutation: The ultimate source of genetic variation, as new alleles can arise through mutations in DNA.

Evidence for Evolution

Several lines of evidence support the theory of evolution, including fossil records, comparative anatomy, embryology, and molecular biology.

Key Evidence

• Fossil Records: Show a progression of life forms over time, with simpler organisms appearing in older rock layers and more complex organisms in newer layers.
• Comparative Anatomy: Similarities in the structures of different species suggest a common ancestry, such as the pentadactyl limb found in mammals, birds, and reptiles.
• Embryology: Similarities in the early developmental stages of different organisms provide evidence of common ancestry.
• Molecular Biology: DNA and protein sequences can be compared between different species to determine their evolutionary relationships.

Principles of Classification

Classification is the process of grouping organisms based on their shared characteristics. The system of classification that we use today is called taxonomy, which was developed by Carl Linnaeus in the 18th century.

Key Principles

• Binomial Nomenclature: The system of naming species using two Latin words (genus and species), e.g., Homo sapiens for humans.
• Hierarchical Classification: Organisms are grouped into a hierarchical system of categories, from broadest to most specific, including kingdom, phylum, class, order, family, genus, and species.
• Evolutionary Relationships: Modern classification systems aim to reflect the evolutionary history of organisms, grouping them based on their shared ancestry.

Modern Classification Systems

Modern classification systems, such as the three-domain system, reflect our understanding of evolutionary relationships and genetic similarities between organisms.

Three-Domain System

• Domain Bacteria: Contains prokaryotic, unicellular organisms with distinct cell walls.
• Domain Archaea: Includes prokaryotic organisms that often live in extreme environments and have unique genetic and biochemical characteristics.
• Domain Eukarya: Consists of all eukaryotic organisms, including plants, animals, fungi, and protists.

Understanding evolution and classification is crucial for comprehending the diversity of life on Earth and its interconnectedness. Mastery of these topics provides a foundation for further studies in biology and related fields.