18.2 Formation of New Species
4 min read•june 14, 2024
and are crucial concepts in biology. They explain how organisms diversify and adapt to different environments over time. Understanding these processes helps us grasp the incredible variety of life on Earth and how it came to be.
Biological species, genetic factors, and isolation mechanisms all play key roles in speciation. From allopatric to , and , these processes shape the of life. Examples like Darwin's finches showcase the power of these mechanisms in action.
Species and Speciation
Biological species concept
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- Groups of interbreeding natural populations reproductively isolated from other such groups
- Emphasizes as the key factor in defining species boundaries
- Populations that can interbreed and produce viable, fertile offspring are considered the same species
- Populations that cannot interbreed due to reproductive barriers are separate species
Genetic factors in speciation
- Mutations introduce new genetic variation into populations can lead to new traits or adaptations (antibiotic resistance in bacteria)
- causes random changes in allele frequencies within a population more pronounced in small populations ()
- leads to differential survival and reproduction of individuals with advantageous traits drives to specific environments (industrial melanism in peppered moths)
- transfer of alleles between populations through migration or interbreeding can prevent or slow speciation by homogenizing gene pools (wolf-coyote hybridization)
- studies the distribution and changes in allele frequencies within populations
Prezygotic vs postzygotic isolation
- Prezygotic barriers prevent mating or fertilization between individuals of different species
- species occupy different environments and do not encounter each other (aquatic vs terrestrial organisms)
- species have different mating seasons or times of day for mating (diurnal vs nocturnal species)
- species have incompatible mating rituals or courtship behaviors (bird songs)
- incompatible reproductive structures prevent successful mating (flower shapes and pollinator mouthparts)
- gametes from different species are unable to fuse or survive (sea urchin sperm and egg incompatibility)
- Postzygotic barriers prevent the development of viable or fertile offspring after mating has occurred
- offspring do not survive due to genetic incompatibilities (mule)
- hybrid offspring are viable but unable to produce functional gametes (liger)
- hybrid offspring have reduced fitness or fertility in subsequent generations (second-generation hybrid plants)
Allopatric vs sympatric speciation
- occurs when populations are geographically isolated from one another
- a physical barrier separates a population into two or more subpopulations (mountain range, river)
- Divergence subpopulations evolve independently due to different selective pressures, genetic drift, or mutations
- Reproductive isolation subpopulations become reproductively isolated due to the accumulation of genetic differences
- occurs without geographic isolation, within the same habitat or region
- doubling of chromosome sets, often through hybridization, leading to instant reproductive isolation (bread wheat)
- subpopulations adapt to different microhabitats or niches within the same area (host plant specialization in insects)
- divergent mate preferences lead to reproductive isolation between subpopulations (cichlid fish color morphs)
- studies the distribution of species and ecosystems in geographic space and through geological time
Examples of adaptive radiation
- Rapid diversification of a single ancestral species into multiple descendant species, each adapted to a different
- Darwin's finches 15 species of finches in the Galápagos Islands, each with a unique beak shape adapted to different food sources (seeds, insects, cactus flowers)
- Hawaiian honeycreepers more than 50 species of birds in Hawaii, with diverse beak shapes and feeding habits, derived from a single finch-like ancestor (nectar feeders, insectivores, seed eaters)
- African cichlid fish over 1,500 species of cichlid fish in the Great Lakes of East Africa, with varied morphologies and feeding strategies (algae scrapers, piscivores, zooplankton feeders)
- Caribbean Anolis lizards more than 400 species of Anolis lizards in the Caribbean islands, each adapted to different microhabitats and niches (twig, trunk, grass, crown)
Evolution and Speciation
- Evolution is the change in heritable characteristics of biological populations over successive generations
- Adaptation is the process by which organisms become better suited to their environment through
- is the evolutionary history and relationships among species or groups of species
- proposed the theory of evolution by natural selection, which explains how species change over time
- Ecological niche refers to the role and position a species has in its environment, including how it meets its needs for food and shelter
Key Terms to Review (47)
(macroevolution): Macroevolution is the large-scale evolutionary changes that occur over long periods, leading to the emergence of new species and higher taxonomic groups. It contrasts with microevolution, which involves smaller evolutionary changes within a species.
Adaptation: Adaptation refers to the process through which organisms become better suited to their environment over time, leading to changes in their traits that enhance survival and reproduction. This concept is fundamental to understanding how species evolve, how new species can emerge from common ancestors, and how organisms adjust to specific ecological niches and climates across different environments.
Adaptive radiation: Adaptive radiation is the evolutionary process in which a single ancestral species rapidly diversifies into a wide variety of forms to adapt to different environments and ecological niches. This phenomenon often occurs after the introduction of new habitats or following mass extinctions, enabling species to exploit various resources and reduce competition. It highlights the relationship between environmental factors and the diversification of life forms.
Allopatric speciation: Allopatric speciation occurs when a population is divided by a geographical barrier, leading to reproductive isolation and the formation of new species. Over time, genetic differences accumulate making interbreeding between the separated populations impossible even if they come back into contact.
Allopatric speciation: Allopatric speciation is the process by which new species arise due to geographical isolation. When populations of a species become separated by physical barriers, such as mountains, rivers, or distance, they can evolve independently. This process often leads to the accumulation of genetic differences that can result in reproductive isolation, ultimately giving rise to distinct species.
Allopolyploid: An allopolyploid is an organism that contains two or more sets of chromosomes derived from different species. This results from hybridization followed by chromosome doubling.
Autopolyploidy: Autopolyploidy is a condition in which an organism has more than two complete sets of chromosomes, all derived from a single species. This can result in new species formation through reproductive isolation.
Back mutations: Back mutations are genetic changes that restore the original sequence and function of a gene that had previously undergone mutation. These can occur naturally or be induced in a laboratory setting.
Behavioral isolation: Behavioral isolation occurs when two populations of the same species develop differences in courtship rituals or other behaviors that prevent them from interbreeding. This type of isolation can lead to speciation over time.
Behavioral isolation: Behavioral isolation is a form of reproductive isolation that occurs when two populations develop distinct behaviors or mating rituals that prevent them from interbreeding. This type of isolation can lead to the divergence of species, as differing mating preferences or practices become ingrained within each population, reducing the likelihood of hybridization. It highlights how behavior can play a critical role in speciation, emphasizing the importance of courtship and mating signals in maintaining species boundaries.
Biogeography: Biogeography is the study of the geographic distribution of species and ecosystems in relation to historical, climatic, and ecological factors. It aims to understand patterns of biodiversity and the processes that result in these patterns.
Biogeography: Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. It helps explain how species and populations evolve and adapt in different environments, influenced by various factors such as climate, geography, and historical events. By understanding biogeography, we can grasp how barriers and corridors affect the formation of new species and how reconnection between habitats can lead to varying rates of speciation.
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, emphasizing reproductive isolation as the key factor for species classification. This concept highlights the importance of gene flow and genetic similarity within a species while distinguishing it from other species, which do not share this ability to reproduce successfully. It is particularly useful in understanding how new species arise through the processes of speciation.
Charles Darwin: Charles Darwin was an English naturalist and biologist best known for his theory of evolution through natural selection, which he detailed in his 1859 work 'On the Origin of Species'. His ideas revolutionized our understanding of the development of life on Earth, linking the concept of species formation to the mechanisms of adaptation and survival in changing environments.
Dispersal: Dispersal is the movement of organisms from one place to another, often leading to gene flow between populations. It plays a crucial role in the formation of new species by enabling genetic variation and adaptation to new environments.
Ecological Niche: An ecological niche refers to the role and position a species has in its environment, including how it meets its needs for food, shelter, and reproduction. It encompasses all the interactions a species has with both biotic (living) and abiotic (non-living) factors in its habitat. Understanding ecological niches is crucial for grasping how species adapt and evolve, which is essential for the formation of new species.
Evolution: Evolution is the process by which different kinds of living organisms develop and diversify from earlier forms over time through changes in heritable traits. This concept is central to understanding the diversity of life on Earth, explaining how species adapt to their environments, and providing a framework for studying the relationships among organisms.
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 compared to the original population. This can result in certain alleles becoming more common or entirely absent, significantly influencing the evolutionary trajectory of the new population. The founder effect can play a crucial role in the emergence of new species, population evolution, and the understanding of population genetics.
Gametic barrier: Gametic barrier is a prezygotic reproductive isolation mechanism where sperm from one species cannot fertilize the eggs of another species. This can occur due to incompatibility in gamete recognition or biochemical differences.
Gametic isolation: Gametic isolation is a prezygotic reproductive barrier that occurs when the gametes (sperm and egg) of two different species are incompatible, preventing fertilization. This type of isolation helps maintain species boundaries by ensuring that even if individuals from different species come into contact, their gametes cannot successfully combine to form a zygote. It highlights the importance of reproductive mechanisms in the formation of new species by reducing hybridization.
Gene flow: Gene flow is the transfer of genetic material between populations, which can occur through the movement of individuals or their gametes. This process can introduce new alleles into a population, impacting genetic diversity and potentially affecting evolutionary pathways, such as the formation of new species and adaptive traits within populations.
Genetic drift: Genetic drift is a mechanism of evolution that involves random changes in the frequency of alleles (gene variants) in a population over time, primarily due to chance events. This process can lead to significant changes in small populations, impacting their genetic diversity and potentially leading to the fixation or loss of certain alleles, which influences evolutionary dynamics and speciation.
Geographic isolation: Geographic isolation occurs when a population of organisms is separated from exchanging genetic material with other populations of the same species, often due to physical barriers such as mountains, rivers, or distance. This separation can lead to distinct evolutionary paths for the isolated populations, contributing significantly to the formation of new species over time through processes like mutation, natural selection, and genetic drift.
Habitat differentiation: Habitat differentiation refers to the process by which populations of a species evolve distinct adaptations to different environmental conditions within the same geographic area, leading to reduced competition and facilitating coexistence. This phenomenon is crucial in promoting biodiversity as it allows multiple species or populations to exploit various niches, thereby reducing direct competition for resources.
Habitat isolation: Habitat isolation is a type of reproductive barrier that occurs when two species live in different habitats and thus do not meet and mate, even if they are in the same geographical area. This can prevent gene flow between populations, leading to the potential formation of new species over time as they adapt to their respective environments.
Hybrid: A hybrid is an organism resulting from the crossbreeding of two different species or distinct genetic lines. Hybrids often possess a combination of traits from both parent species.
Hybrid Breakdown: Hybrid breakdown refers to a phenomenon where the hybrid offspring of two different species are viable and fertile in the first generation but produce offspring that are inviable or sterile in subsequent generations. This concept highlights the complexities of reproductive isolation and the mechanisms through which new species can emerge, emphasizing how genetic incompatibility can manifest over generations.
Hybrid inviability: Hybrid inviability refers to a reproductive barrier that occurs when hybrid offspring resulting from the mating of two different species fail to develop properly or survive to maturity. This concept is important in understanding speciation, as it illustrates one of the mechanisms that prevent gene flow between species and maintain their distinct identities. It showcases how even if mating occurs, the resulting hybrids may not be viable, highlighting the complexities of reproductive isolation.
Hybrid sterility: Hybrid sterility is a reproductive barrier that occurs when hybrids produced from the mating of two different species are unable to reproduce. This phenomenon plays a crucial role in the formation of new species, as it prevents gene flow between the parent species and reinforces reproductive isolation, which is essential for speciation.
Mechanical isolation: Mechanical isolation is a reproductive barrier that occurs when two species are physically unable to mate due to differences in their reproductive structures or mechanisms. This form of isolation plays a crucial role in the process of speciation by preventing the interbreeding of distinct species, allowing them to evolve separately and develop unique traits over time.
Mutation: A mutation is a change in the DNA sequence of an organism's genome, which can lead to alterations in traits or characteristics. Mutations can occur spontaneously or be induced by environmental factors, and they play a crucial role in genetic diversity and evolution. They can be beneficial, harmful, or neutral, impacting an organism's ability to survive and reproduce in its environment.
Natural selection: Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring. Over time, this leads to the evolution of species as advantageous traits become more common in a population.
Natural selection: Natural selection is the process by which certain traits become more or less common in a population based on their impact on the survival and reproduction of individuals. It serves as a key mechanism of evolution, driving adaptation and influencing the genetic makeup of populations over time.
Phylogeny: Phylogeny is the evolutionary history and the relationships among various biological species or entities, which is often represented in a tree-like diagram known as a phylogenetic tree. This concept not only helps in understanding how different species are related through common ancestors but also plays a vital role in classifying organisms and understanding the formation of new species.
Polyploidy: Polyploidy refers to the condition where an organism has more than two complete sets of chromosomes. This phenomenon can lead to significant genetic variation and is a major driver in the formation of new species through processes such as hybridization and genome duplication. Polyploid organisms often exhibit traits that allow them to adapt to different environments, making them important players in evolution and speciation.
Population genetics: Population genetics is the study of genetic variation within populations and the factors that influence this variation over time. This field connects evolutionary theory and genetic principles, highlighting how evolutionary processes such as natural selection, genetic drift, and gene flow shape the genetic makeup of populations. Understanding these genetic dynamics is crucial for exploring the mechanisms behind evolution and speciation.
Postzygotic barrier: Postzygotic barriers are mechanisms that reduce the viability or reproductive capacity of hybrid offspring. These barriers occur after fertilization and can prevent hybrids from developing into fertile adults.
Postzygotic isolation: Postzygotic isolation refers to reproductive barriers that occur after fertilization, preventing the successful development and reproduction of hybrid offspring. This concept is critical in understanding how new species form, as it helps maintain distinct species by limiting gene flow between populations that may interbreed.
Prezygotic barrier: Prezygotic barriers are mechanisms that prevent fertilization from occurring between different species. They ensure reproductive isolation by hindering mating or the fusion of gametes before zygote formation.
Prezygotic isolation: Prezygotic isolation refers to mechanisms that prevent mating or fertilization between different species before a zygote can form. These mechanisms play a critical role in the formation of new species by ensuring that distinct species remain reproductively isolated, even when they inhabit the same geographic area. By preventing interbreeding, prezygotic isolation promotes genetic divergence, which is essential for speciation.
Reproductive isolation: Reproductive isolation refers to the mechanisms that prevent different species from interbreeding, ensuring that they remain distinct entities. This concept is essential for understanding how new species form and maintain their uniqueness over time, as it plays a critical role in the speciation process. By hindering gene flow between populations, reproductive isolation contributes to the divergence of species and can influence the rates at which new species arise and reconnect.
Sexual selection: Sexual selection is a form of natural selection where certain traits increase an individual's chances of attracting mates, leading to reproductive success. This process can drive the evolution of traits that may not necessarily enhance survival but improve mating opportunities, such as bright colors or elaborate courtship behaviors. Sexual selection can lead to the development of new species by creating distinct reproductive strategies and preferences within populations, as well as promote adaptive evolution by favoring traits that enhance mating success in specific environments.
Speciation: Speciation is the evolutionary process through which new biological species arise from a common ancestral species. This process is crucial for understanding the diversity of life, as it highlights how populations can diverge genetically over time, leading to the formation of distinct species that adapt to different environments and ecological niches.
Species: A species is a group of organisms that can interbreed and produce fertile offspring under natural conditions. They share common characteristics and genetic similarities, distinguishing them from other groups.
Sympatric speciation: Sympatric speciation occurs when new species evolve from a single ancestral species while inhabiting the same geographic region. This process often involves reproductive isolation mechanisms such as behavioral changes or genetic mutations.
Sympatric speciation: Sympatric speciation is the process by which new species arise from a single ancestral species while inhabiting the same geographic region. This type of speciation often occurs through mechanisms such as polyploidy, sexual selection, or habitat differentiation, leading to reproductive isolation despite the lack of physical barriers. It plays a crucial role in understanding how biodiversity evolves and how species adapt in shared environments.
Temporal isolation: Temporal isolation is a type of reproductive barrier that occurs when two or more species breed at different times, preventing them from mating even if they inhabit the same location. This can happen due to differences in mating seasons, times of day, or even environmental triggers. Such isolation is crucial in the formation of new species as it reduces gene flow between populations, allowing them to evolve independently.