is a cornerstone of biology, explaining how species change over time. Darwin's theory of revolutionized our understanding, proposing that organisms with beneficial traits are more likely to survive and reproduce, passing these traits to offspring.
Modern evolutionary theory combines Darwin's ideas with genetics and molecular biology. It explains how genetic arises through mutations and recombination, and how acts on this variation. studies these changes in within populations.
Darwin's Theory of Evolution and Modern Evolutionary Theory
Darwin's theory vs prevailing views
Prevailing views before Darwin held that species were created separately and remained unchanging ()
Carolus Linnaeus developed a hierarchical classification system for living things () based on shared characteristics
Georges Cuvier proposed that species go extinct and are replaced by new, distinct species rather than evolving from existing ones
Darwin's theory of evolution proposed that species change over time through the process of natural selection
Organisms with advantageous traits (better camouflage) are more likely to survive and reproduce, passing these traits to their offspring
Over many generations, the accumulation of advantageous traits leads to changes in populations and the emergence of new species
Darwin's theory differed from prevailing views by suggesting that species are not fixed and can change over time
Provided a mechanism for how species change (natural selection) based on observations from his travels ()
Contradicted the idea of creationism and the fixity of species, challenging the dominant religious and scientific views of the time
Development of modern evolutionary theory
and independently developed the theory of evolution by natural selection in the mid-19th century
Darwin published his seminal work "" in 1859, detailing evidence for evolution and the mechanism of natural selection
Evidence for evolution comes from various sources:
Fossil record shows gradual changes in species over millions of years ( as a transitional form between dinosaurs and birds)
Comparative anatomy reveals structural similarities between related species, suggesting common ancestry ( like vertebrate limbs)
Embryology shows that related species share similar developmental stages, indicating a shared evolutionary history (pharyngeal arches in vertebrate embryos)
Biogeography explains the distribution of species across the globe based on evolutionary history and geographical barriers (marsupials in Australia)
, the evolutionary history and relationships among species, provides additional evidence for common ancestry and evolutionary patterns
The of evolutionary theory combines Darwin's ideas with Mendelian genetics and advances in molecular biology
Explains how genetic variation arises through mutations and recombination and is acted upon by natural selection
Incorporates knowledge of DNA, gene expression, and the molecular basis of inheritance into the understanding of evolutionary processes
Population genetics in evolutionary changes
Population genetics is the study of genetic variation within and between populations
Focuses on changes in allele frequencies (different versions of a gene) over time
Genetic variation is the foundation for evolutionary change
Caused by mutations (changes in DNA sequence), recombination (mixing of genetic material during sexual reproduction), and (transfer of alleles between populations)
Provides the raw material for natural selection to act upon, as some variants may be more advantageous than others
The is a mathematical model that describes a non-evolving population
Assumes no , no migration, no natural selection, large population size, and random mating
Deviations from Hardy-Weinberg equilibrium indicate evolutionary changes in the population
refers to changes in allele frequencies within a population over time
Can be caused by natural selection (differential survival and reproduction), (random changes in allele frequencies), gene flow (migration), and mutation
Examples include pesticide resistance in insects and antibiotic resistance in bacteria
refers to evolutionary changes above the species level, such as the formation of new species ()
Results from the accumulation of microevolutionary changes over long periods of time
Examples include the evolution of birds from dinosaurs and the diversification of mammals after the extinction of the dinosaurs
Mechanisms of Evolutionary Change
Natural selection: The process by which organisms with advantageous traits are more likely to survive and reproduce
Genetic drift: Random changes in allele frequencies within a population, especially in small populations
Mutation: Changes in DNA sequence that introduce new genetic variations into a population
Gene flow: The transfer of genetic variation between populations through migration
: The process by which organisms become better suited to their environment through natural selection
Key Terms to Review (31)
Adaptation: Adaptation refers to the process by which organisms evolve characteristics that enhance their survival and reproductive success in a specific environment. These changes can occur over generations and may involve structural, behavioral, or physiological modifications that better suit the organism to its surroundings.
Alfred Russel Wallace: Alfred Russel Wallace was a British naturalist and biogeographer, best known for independently conceiving the theory of evolution through natural selection alongside Charles Darwin. His work laid foundational concepts that helped explain how populations change over time due to environmental pressures and survival of the fittest, making significant contributions to our understanding of biodiversity.
Allele frequencies: Allele frequencies refer to how often a specific allele appears in a population's gene pool relative to all alleles for that gene. This concept is fundamental in understanding population genetics and how genetic variation can change over time, which is essential for studying evolution and natural selection.
Allopatric speciation: Allopatric speciation occurs when a population is geographically separated into two groups that evolve independently. Over time, genetic differences accumulate, leading to the formation of distinct species.
Analogous structures: Analogous structures are body parts in different species that have similar functions but evolved separately, not from a common ancestor. They arise due to convergent evolution where different organisms adapt similarly to comparable environments.
Archaeopteryx: Archaeopteryx is a prehistoric creature that lived around 150 million years ago during the Late Jurassic period, recognized as one of the earliest known birds and an important link between reptiles and birds. Its unique combination of avian and dinosaur features, such as feathers, wings, and a bony tail, provides critical insight into the evolutionary transition from dinosaurs to modern birds.
Charles Darwin: Charles Darwin was a British naturalist known for developing the theory of evolution through natural selection, which explains how populations change over time. His observations and writings, particularly in 'On the Origin of Species,' laid the groundwork for understanding the processes that drive biological diversity and adaptation in various species.
Creationism: Creationism is the belief that the universe and living organisms originate from specific acts of divine creation, as opposed to the scientific explanation of evolution. This perspective emphasizes the idea that a supernatural being, often referred to as God, is responsible for the creation of all life and the universe. It stands in contrast to evolutionary theory, which posits that species change over time through natural selection and genetic variation.
Divergent evolution: Divergent evolution is the process by which two or more related species become increasingly different over time. This typically occurs when populations of a species adapt to different environments and accumulate distinct traits.
Evolution: Evolution is the process through which species change over time, driven by mechanisms such as natural selection, genetic drift, and gene flow. This concept explains the diversity of life on Earth and how organisms adapt to their environments, linking various aspects of biology, including genetics, ecology, and the relationships among species.
Galápagos finches: Galápagos finches are a group of bird species found exclusively on the Galápagos Islands, renowned for their diverse beak shapes and sizes, which evolved to adapt to varying food sources. This adaptive radiation serves as a classic example of evolution in action, showcasing how environmental pressures can lead to significant changes within populations over time.
Gene flow: Gene flow is the transfer of genetic material between populations through migration and interbreeding, which can change the genetic composition of both source and recipient populations. This process plays a crucial role in maintaining genetic diversity, facilitating adaptation, and influencing evolutionary trajectories.
Gene pool: The gene pool is the complete set of genetic information within all individuals in a population. It includes all alleles for every gene present in that population.
Genetic drift: Genetic drift is the change in the frequency of alleles (gene variants) in a population due to random sampling of organisms. This process can lead to significant changes in the genetic makeup of small populations over time and can contribute to the evolution of species, highlighting how chance events can impact genetic diversity and population dynamics.
Hardy-Weinberg equilibrium: Hardy-Weinberg equilibrium is a principle that describes the genetic variation in a population that remains constant from one generation to the next in the absence of evolutionary influences. This principle serves as a null hypothesis for population genetics, indicating that allele frequencies will remain stable unless acted upon by forces such as natural selection, mutation, gene flow, or genetic drift. It provides a baseline to understand how populations change over time and the mechanisms behind those changes.
Homologous structures: Homologous structures are anatomical features in different species that share a common ancestry, even though they may serve different functions. These structures reveal the evolutionary relationships among species and illustrate how adaptations to different environments can lead to variations of a common trait. The presence of homologous structures supports the concept of descent with modification, demonstrating how species have diverged from their common ancestors over time.
Macroevolution: Macroevolution refers to large-scale evolutionary changes that occur over long periods of time, resulting in the emergence of new species and major shifts in biodiversity. It encompasses processes such as speciation, extinction, and the evolution of complex structures or systems, highlighting how populations change and adapt through various environmental pressures and genetic changes.
Microevolution: Microevolution refers to the small-scale changes in allele frequencies within a population over time, resulting in subtle evolutionary shifts. These changes can occur through processes such as mutation, gene flow, genetic drift, and natural selection, ultimately leading to variations within a species. Understanding microevolution helps explain how populations adapt to their environments and evolve over generations.
Modern synthesis: Modern synthesis is the fusion of Mendelian genetics with Darwinian evolution, forming a cohesive theory of evolution. It explains how genetic variation and natural selection drive evolutionary changes in populations.
Modern Synthesis: Modern Synthesis is a comprehensive theory in evolutionary biology that combines Darwin's theory of natural selection with Mendelian genetics, explaining how populations change over time. It emphasizes the role of genetic variation in evolution, integrating findings from various biological fields such as paleontology, genetics, and ecology to provide a clearer understanding of how species evolve and adapt to their environments.
Mutation: A mutation is a change in the DNA sequence of an organism's genome, which can lead to variations in traits and can affect an organism's fitness in its environment. These changes can be caused by various factors, including environmental influences, replication errors during cell division, or even spontaneous alterations. Mutations are crucial for evolution, as they provide the raw genetic material upon which natural selection can act, leading to adaptations and evolutionary changes over time.
Natural selection: Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring. It is a key mechanism of evolution, first proposed by Charles Darwin.
Natural selection: Natural selection is a process where organisms better adapted to their environment tend to survive and produce more offspring. This mechanism plays a crucial role in shaping the diversity of life on Earth by promoting traits that enhance survival and reproduction, connecting it to various biological concepts and evolutionary processes.
On the Origin of Species: On the Origin of Species is a groundbreaking scientific work by Charles Darwin published in 1859, which introduced the theory of evolution through natural selection. This book fundamentally changed our understanding of how populations evolve over time and the mechanisms that drive changes in species. It emphasizes the importance of variation, competition, and adaptation within populations as key factors influencing survival and reproduction.
Phylogeny: Phylogeny is the study of the evolutionary history and relationships among species or groups of organisms. It helps in understanding how different life forms are related through common ancestors.
Phylogeny: Phylogeny refers to the evolutionary history and the relationships among species or groups of organisms. It illustrates how different species have evolved from common ancestors over time, often represented as a branching tree-like diagram known as a phylogenetic tree. Understanding phylogeny helps clarify how populations change through evolutionary processes and provides insight into the organization of life on Earth.
Population genetics: Population genetics is the study of genetic variation within populations and the changes in allele frequencies that occur over time due to evolutionary processes. It connects the principles of Mendelian inheritance and natural selection, helping to explain how populations evolve and adapt to their environments.
Speciation: Speciation is the evolutionary process through which new biological species arise, often due to the accumulation of genetic changes that lead to reproductive isolation between populations. This process is crucial for understanding how populations adapt and evolve over time, ultimately leading to biodiversity on Earth.
Taxonomy: Taxonomy is the scientific process of classifying organisms into structured categories based on shared characteristics. It helps organize biological diversity and facilitates understanding and studying life forms.
Taxonomy: Taxonomy is the scientific discipline that involves classifying and naming living organisms based on shared characteristics and relationships. This systematic categorization helps scientists organize biological diversity, identify organisms, and understand their evolutionary connections. By establishing a framework for naming and grouping species, taxonomy plays a crucial role in studying how populations evolve, how life on Earth is organized, and how different organisms are related to one another.
Variation: Variation is the differences in physical traits or behaviors among individuals within a population. These differences can be genetic, environmental, or a combination of both.