Glossary

Speciation is the process by which new form. It's driven by factors like geographic isolation, , and . These forces can lead to between populations, eventually resulting in distinct species.

Understanding speciation is crucial for grasping how biodiversity arises. It explains the incredible variety of life on Earth, from to cichlid fish. Speciation also highlights the ongoing nature of and the interconnectedness of all living things.

Speciation

Definition and identification of species

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  • Species are groups of organisms that can interbreed and produce fertile offspring
  • distinguishes species based on physical characteristics (body shape, color patterns)
  • distinguishes species based on reproductive isolation
    • prevent fertilization from occurring
      • occurs when species occupy different habitats (different elevations, soil types)
      • occurs when species breed at different times (different seasons, times of day)
      • occurs when species have different mating rituals or behaviors (courtship displays, vocalizations)
      • occurs when physical differences prevent successful mating (incompatible genitalia, body sizes)
      • occurs when sperm and egg are incompatible (chemical barriers, sperm unable to penetrate egg)
    • prevent the development of viable, fertile offspring
      • occurs when hybrid offspring do not survive to adulthood (genetic incompatibilities, developmental abnormalities)
      • occurs when hybrid offspring are infertile (chromosomal differences, meiotic irregularities)
  • distinguishes species based on evolutionary relationships
    • include all descendants of a common ancestor (shared derived traits, genetic similarity)

Allopatric vs sympatric speciation

  • occurs when populations are geographically isolated
    • divides a population by a physical barrier (mountain range formation, river divergence)
    • occurs when a small group of individuals colonizes a new area (island colonization, wind-blown seeds)
    • Genetic drift causes random changes in allele frequencies leading to differences between isolated populations (, )
    • leads to populations adapting to different environmental conditions (climate, resource availability)
  • occurs without geographic isolation
    • results in an organism having more than two sets of chromosomes
      1. occurs when multiple sets of chromosomes come from the same species (spontaneous genome duplication, unreduced gametes)
      2. occurs when multiple sets of chromosomes come from different species (hybridization followed by genome duplication)
    • occurs when subpopulations specialize in different microhabitats (host plant preferences, soil type adaptations)
    • leads to divergence in mating preferences causing reproductive isolation (female choice, male competition)

Examples of adaptive radiation

  • is the rapid speciation and diversification of a single ancestral species into multiple descendant species adapted to different ecological niches
  • Darwin's finches in the Galápagos Islands
    • 15 species adapted to different food sources (seeds, insects, cactus flowers)
    • Variations in beak size and shape (large, crushing beaks for seeds; long, pointed beaks for insects)
    • Over 50 species adapted to different food sources and habitats (nectar, insects, seeds; forests, shrublands)
    • Variations in bill shape, plumage color, and body size (curved bills for nectar; stout bills for seeds; dull or bright coloration)
  • in the Great Lakes of East Africa
    • Over 1,500 species adapted to different feeding strategies (herbivory, insectivory, piscivory)
    • Variations in jaw and tooth morphology, body shape, and coloration (enlarged jaws for crushing; slender bodies for pursuit; vibrant colors for mate attraction)

Evolutionary processes in speciation

  • Natural selection drives to different environments, leading to divergence between populations
  • within populations provides the raw material for evolution and speciation
  • between populations can be reduced or eliminated during speciation, promoting genetic divergence
  • Adaptation to new environments can lead to the development of novel traits and reproductive isolation
  • Evolution through speciation results in the formation of new species and increased biodiversity

Key Terms to Review (40)

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.
Adaptive radiation: Adaptive radiation is the evolutionary process where organisms rapidly diversify and adapt to fill different ecological niches. This phenomenon often occurs when a new habitat or environmental change opens up opportunities, allowing a single ancestral species to evolve into a variety of forms that each exploit different resources or environments. It highlights how evolution can lead to a variety of species from a common ancestor in response to environmental challenges.
African cichlids: African cichlids are a diverse group of freshwater fish found primarily in the Great Lakes of Africa, known for their vibrant colors and unique behaviors. They are a prime example of adaptive radiation, showcasing how species can evolve rapidly to exploit various ecological niches, which makes them significant in the study of speciation.
Allopatric speciation: Allopatric speciation is the process by which new species arise due to geographic isolation, leading to the divergence of populations. This occurs when a population is separated by physical barriers such as mountains, rivers, or distances, preventing gene flow between groups. Over time, the isolated populations may evolve independently through natural selection and genetic drift, ultimately resulting in the formation of distinct species.
Allopolyploidy: Allopolyploidy is a form of polyploidy that occurs when two different species hybridize and the resulting offspring possess multiple sets of chromosomes from both parent species. This process can lead to the emergence of new species and contributes to the diversity of plant life, especially in flowering plants. Allopolyploidy is significant in speciation as it allows for genetic variation and adaptability, which are crucial for evolution.
Autopolyploidy: Autopolyploidy is a condition in which an organism has more than two sets of chromosomes that are all derived from a single species. This process can lead to genetic diversity and contribute to the formation of new species through mechanisms like hybridization and reproductive isolation. Autopolyploidy can play a significant role in speciation by providing a way for plants and some animal species to adapt to changing environments or ecological niches.
Behavioral isolation: Behavioral isolation is a form of reproductive isolation that occurs when different species or populations develop distinct behaviors or mating rituals that prevent them from interbreeding. This type of isolation plays a crucial role in speciation, as it ensures that mating occurs only between individuals of the same species, thus maintaining genetic differences and supporting the formation of new species.
Biological species concept: The biological species concept defines a species as a group of organisms that can interbreed and produce fertile offspring in natural conditions. This concept emphasizes reproductive isolation, which means that members of different species do not mate with each other or, if they do, their offspring are typically sterile. By focusing on reproductive compatibility, this concept helps to clarify how new species arise through speciation.
Darwin's finches: Darwin's finches refer to a group of about 15 species of finches that are found on the Galápagos Islands, known for their diverse beak shapes and sizes. These variations are key examples of adaptive radiation, showcasing how environmental pressures can lead to evolutionary changes and the development of new species from a common ancestor.
Dispersal: Dispersal is the movement of individuals or organisms from their birthplace to other locations where they establish and reproduce. It plays a critical role in gene flow, population dynamics, and speciation processes.
Dispersal: Dispersal refers to the movement of organisms from one location to another, often in search of new habitats, resources, or mates. This process is crucial for the colonization of new environments and can influence genetic diversity within populations. Dispersal mechanisms can include wind, water, or animal movement, and play a significant role in how species adapt and evolve over time.
Endemic species: An endemic species is a plant or animal that exists only in one geographic region. These species are not found naturally anywhere else in the world.
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.
Founder effect: The founder effect is a genetic phenomenon that occurs when a small group of individuals establishes a new population, leading to reduced genetic diversity and the potential for certain traits to become more common in the new population. This can have significant implications for how populations evolve over time, as the genetic makeup of the founders can shape the future genetic variation and adaptation of the descendants.
Gametic isolation: Gametic isolation is a reproductive barrier that prevents fertilization between different species. This occurs when the sperm of one species cannot successfully fertilize the eggs of another species, even if they come into contact. This isolation mechanism helps maintain species boundaries and promotes speciation by ensuring that only compatible gametes combine to produce viable offspring.
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.
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.
Genetic variation: Genetic variation refers to the differences in DNA sequences among individuals within a population, which contribute to the diversity of traits and characteristics. This variation is essential for evolution, as it provides the raw material for natural selection to act upon, allowing populations to adapt to changing environments over time. Genetic variation arises from mutations, gene flow, and sexual reproduction, influencing both individual survival and species development.
Habitat differentiation: Habitat differentiation refers to the process by which populations of the same species adapt to different habitats within a shared environment, leading to the development of distinct ecological niches. This adaptation can promote speciation as populations become more specialized in their respective habitats, often resulting in reduced competition and increased resource use efficiency. It is a crucial mechanism in understanding how biodiversity arises in ecosystems.
Habitat isolation: Habitat isolation is a type of reproductive barrier where two species live in different habitats and, as a result, do not encounter each other to mate. This form of isolation can prevent gene flow between populations and is a key mechanism in the process of speciation. When species occupy different environments, they may adapt to their specific conditions, leading to the emergence of distinct traits and, eventually, new species.
Hawaiian honeycreepers: Hawaiian honeycreepers are a group of small, colorful songbirds native to Hawaii, known for their remarkable diversity in form and behavior. This unique group has evolved through processes of adaptive radiation, allowing them to occupy various ecological niches in the Hawaiian Islands. Their evolution showcases how geographic isolation and environmental pressures can lead to speciation, resulting in a wide range of specialized feeding strategies and physical adaptations.
Hybrid inviability: Hybrid inviability refers to a reproductive barrier where hybrid offspring, produced by the mating of two different species, do not develop properly and fail to reach maturity. This phenomenon highlights the genetic incompatibility between species and is an important factor in the speciation process, as it prevents the successful establishment of hybrid populations.
Hybrid Sterility: Hybrid sterility is a reproductive barrier that occurs when hybrids—offspring resulting from the mating of individuals from different species—are unable to produce viable gametes. This phenomenon serves as an important mechanism in speciation, preventing the successful interbreeding of distinct species and maintaining their genetic integrity. Hybrid sterility can be a significant factor in the process of speciation, as it reinforces reproductive isolation, which is crucial for the divergence of species over time.
Mechanical isolation: Mechanical isolation is a reproductive barrier that occurs when differences in the physical structures of organisms prevent successful mating and fertilization. This type of isolation can arise due to variations in the size or shape of reproductive organs, leading to incompatibility between species. As a result, mechanical isolation plays a crucial role in speciation by maintaining distinct species through limited gene flow.
Monophyletic groups: Monophyletic groups, or clades, are sets of organisms that consist of a common ancestor and all its descendants. This concept is critical in understanding the evolutionary relationships among species, as it helps to classify organisms based on shared characteristics inherited from a common ancestor, which is essential for constructing accurate phylogenetic trees.
Morphological species concept: The morphological species concept defines species based on their physical characteristics, such as size, shape, and structure. This approach emphasizes observable traits that can be used to distinguish one species from another, making it a practical tool for identifying and classifying organisms in the study of biodiversity.
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.
Phylogenetic species concept: The phylogenetic species concept defines a species as the smallest group of individuals that share a common ancestor and form one branch on the tree of life. This concept emphasizes the importance of evolutionary relationships and genetic divergence in classifying organisms, distinguishing species based on their unique evolutionary history rather than solely on morphological traits or reproductive isolation.
Polyploidy: Polyploidy is a condition in which an organism has more than two complete sets of chromosomes, which can arise through errors in cell division during meiosis or fertilization. This phenomenon is especially common in plants, leading to increased genetic diversity and the potential for new species to form. Polyploidy can impact evolution and adaptation by allowing for larger cell sizes and greater resilience to environmental stresses.
Population bottlenecks: Population bottlenecks refer to significant reductions in the size of a population, often due to environmental events or human activities, leading to a decrease in genetic diversity. This can result in a limited gene pool, which impacts the ability of a species to adapt and survive in changing environments. These events can set the stage for speciation by creating isolated populations that undergo divergent evolution.
Postzygotic barriers: Postzygotic barriers are reproductive isolation mechanisms that occur after fertilization, preventing hybrid offspring from developing into viable, fertile adults. These barriers play a crucial role in the speciation process by ensuring that even if different species mate and produce offspring, these hybrids will either not survive or will be sterile, thus maintaining the distinctiveness of each species.
Prezygotic barriers: Prezygotic barriers are reproductive mechanisms that prevent mating or fertilization between different species before a zygote is formed. These barriers play a crucial role in speciation by maintaining species boundaries and reducing gene flow, ensuring that distinct species remain separate despite overlapping habitats. Various types of prezygotic barriers include temporal, behavioral, mechanical, and ecological factors that influence whether or not two species can successfully mate.
Reproductive isolation: Reproductive isolation refers to a set of mechanisms that prevent different species from interbreeding, thereby maintaining species integrity and promoting speciation. This concept is crucial in understanding how populations evolve into distinct species, as it helps to explain the barriers that can arise during the process of speciation, including temporal, behavioral, mechanical, and ecological differences.
Sexual selection: Sexual selection is a form of natural selection where individuals with certain inherited traits are more likely than others to obtain mates. This process can lead to the development of secondary sexual characteristics, such as elaborate feathers or mating calls, which may enhance an individual's attractiveness to potential partners. It plays a crucial role in speciation by influencing reproductive isolation and divergence between populations.
Species: A species is a group of organisms that can interbreed and produce fertile offspring under natural conditions, sharing common characteristics and genetic makeup. This definition connects to the processes by which new species emerge and how organisms are classified and organized in the natural world. Understanding the concept of species helps clarify biodiversity, the relationship between different organisms, and their evolutionary paths.
Sympatric speciation: Sympatric speciation occurs when new species evolve from a single ancestral species while inhabiting the same geographic region. This process often involves genetic mutations, ecological niches, or behavioral changes that reduce interbreeding.
Sympatric speciation: Sympatric speciation is the process through which new species arise from a single ancestral species while inhabiting the same geographic region. This type of speciation often occurs due to reproductive isolation mechanisms such as behavioral changes, polyploidy, or ecological differences, allowing populations to diverge genetically without physical barriers separating them.
Temporal isolation: Temporal isolation is a form of reproductive isolation where different species or populations breed at different times, preventing them from interbreeding. This can occur due to differences in mating seasons, times of day for activity, or even variations in the timing of flowering in plants. By isolating species temporally, it plays a critical role in the process of speciation by allowing populations to evolve independently over time.
Vicariance: Vicariance is the process by which a population is geographically divided by a physical barrier, leading to the separation and subsequent evolution of distinct species. This can occur due to various factors such as continental drift, rising mountains, or the formation of rivers that isolate populations, ultimately affecting genetic diversity and speciation. The concept highlights how environmental changes can shape the distribution and diversity of organisms over time.
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