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Speciation is the evolutionary process by which new species arise. It occurs when populations of a single species become reproductively isolated and evolve independently. Types of Speciation: 1. Allopatric Speciation (Geographic Isolation): Occurs when a population is physically separated by a barrier such as mountains, rivers, or oceans. Example: Darwin’s finches evolved into different species … Read more
Charles Darwin traveled on the HMS Beagle from 1831 to 1836, studying diverse species in South America, the Galápagos Islands, and other locations. His key observations included: 1. Variation in Species: Darwin noticed that finches on different Galápagos Islands had different beak shapes, suited to their specific diets. Some had long, pointed beaks for insects, … Read more
Darwin’s theory of evolution by natural selection explains how species change over time due to differences in survival and reproduction. The key principles of this theory are: 1. Overproduction: Organisms produce more offspring than can survive. For example, a frog lays hundreds of eggs, but only a few tadpoles reach adulthood. 2. Variation: Individuals in … Read more
Selection is a fundamental mechanism of evolution, as it determines which individuals survive, reproduce, and pass on their traits to the next generation. It plays a major role in shaping the genetic structure of populations over time. There are two main types of selection: 1. Natural Selection: Proposed by Charles Darwin, natural selection explains how … Read more
Variation refers to the differences in characteristics among individuals of the same species. It plays a crucial role in evolution, as it provides the raw material for natural selection to act upon. Variations arise due to differences in genetic composition, environmental influences, and interactions between genes and the environment. Sources of Variation: Genetic Mutations: These … Read more
Evolution: The gradual change in species over time due to genetic variation and natural selection. Homologous organs: Structures that have a similar basic design but different functions, indicating a common ancestry. Speciation: The process by which new species evolve from existing ones due to genetic differences and reproductive isolation. Natural selection: A process where organisms … Read more
Palaeontology is the study of fossils, which are preserved remains or traces of ancient life. Fossils provide direct evidence of how organisms have changed over millions of years. Types of Fossil Evidence: Transitional Fossils: These show intermediate forms between ancient and modern species. Example: Archaeopteryx, which had both reptilian (teeth, claws) and avian (feathers, wings) … Read more
Selective breeding, also known as artificial selection, is a process in which humans breed organisms to enhance specific traits. Unlike natural selection, where nature determines which traits are advantageous, in selective breeding, humans choose desirable characteristics. Examples of Selective Breeding: Agriculture: Farmers have bred wheat for higher yield and disease resistance. Livestock: Dairy cows have … Read more
Genetic mutations are sudden changes in the DNA sequence that create new genetic variations within a species. They can occur due to errors during DNA replication, exposure to radiation, chemicals, or viruses. Types of Mutations: Beneficial Mutations: These provide an advantage, such as antibiotic resistance in bacteria. Neutral Mutations: These do not affect survival, such … Read more