Speciation and its type
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Speciation is the process by which new biological species develop. It occurs through reproductive isolation, which can develop due to geographic barriers separating populations or behavioral/ecological factors preventing interbreeding. There are several types of speciation including allopatric, where populations are isolated geographically; parapatric, involving isolation in adjacent habitats; and sympatric, occurring without geographic separation through mechanisms like habitat differentiation. Reproductive barriers that maintain species include prezygotic barriers preventing fertilization and postzygotic barriers hindering viable offspring.
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best ever ppt on speciation by Nagesh sadili
1) The document discusses speciation in insects, including different species concepts, types of speciation, and mechanisms of speciation.
2) It describes four main species concepts: typological, nominalistic, biological, and evolutionary. The biological species concept, which defines species as groups of interbreeding natural populations reproductively isolated from other such groups, is most widely accepted.
3) Speciation occurs through the evolution of reproductive barriers between populations, including prezygotic barriers like habitat isolation and postzygotic barriers such as hybrid sterility. Disruptive selection can divide populations into distinct species.
Species concepts 4
The document discusses several species concepts:
- The typological concept views species as fixed types, ignoring variation.
- The biological concept defines species as groups of interbreeding populations reproductively isolated from others.
- The nominalistic concept views species as human constructs rather than natural categories.
It also notes difficulties in applying the biological concept, such as asexual reproduction, similar but isolated species, and ring species where isolation breaks down.
Species concept
Organisms are classified into a hierarchical classification that groups closely related individuals.
The species is the basic biological unit around which classifications are based.
Variation in taxonomic and systematic characters
There are three main types of variation: geographic, sexual, and individual. Geographic variation occurs over space and can lead to clinal variation correlated with environmental factors. Sexual variation involves differences between males and females, often involving primary and secondary sexual characteristics. Individual variation occurs within the lifetime of an organism and can be due to factors like age, environment, parasites, and genetics. Genetic variation includes sex-associated traits and non-sex associated continuous or discontinuous variation within populations.
Cladistic
Cladistics is a biological classification system that groups organisms based on shared traits and evolutionary relationships. It aims to trace ancestry back to common ancestors by constructing phylogenetic trees based on morphological and molecular data. Key terms in cladistics include plesiomorphy (ancestral traits), apomorphy (derived traits that define groups), and homoplasy (traits that evolved separately in different groups). Together, analysis of character states helps determine evolutionary relationships between taxa.
Natural Selection and its types
Natural selection is a process whereby organisms better adapted to their environment tend to survive and produce more offspring. There are three main types of natural selection: directional selection favors one extreme of a trait, disruptive selection favors both extremes of a trait, and stabilizing selection favors intermediate forms of a trait. Examples of natural selection in action include the evolution of different beak shapes in Galapagos finches and the increase of melanism in moths due to pollution. Sexual selection is a form of natural selection resulting from competition or choice of mates.
Speciation
Speciation is the splitting of one species into two distinct species. The biological species concept defines a species as a group that can interbreed and produce fertile offspring under natural conditions, while being reproductively isolated from other groups. Reproductive isolation occurs when two populations diverge genetically enough that their offspring are infertile or inviable. Allopatric speciation, where populations are isolated geographically, is the most common speciation mechanism. Over time, separated populations accumulate genetic differences due to random genetic drift and independent evolution, eventually becoming reproductively isolated.
Biosystematics, and types of taxonomy
1.Definition and basic concepts of Biosystematics, , Historical perspectives of Biosystematics and Taxonomy, Stages of taxonomic procedures-alpha taxonomy, Beta taxonomy and Gamma taxonomy,
Neo taxonomy.
Recommended
best ever ppt on speciation by Nagesh sadili
1) The document discusses speciation in insects, including different species concepts, types of speciation, and mechanisms of speciation.
2) It describes four main species concepts: typological, nominalistic, biological, and evolutionary. The biological species concept, which defines species as groups of interbreeding natural populations reproductively isolated from other such groups, is most widely accepted.
3) Speciation occurs through the evolution of reproductive barriers between populations, including prezygotic barriers like habitat isolation and postzygotic barriers such as hybrid sterility. Disruptive selection can divide populations into distinct species.
Species concepts 4
The document discusses several species concepts:
- The typological concept views species as fixed types, ignoring variation.
- The biological concept defines species as groups of interbreeding populations reproductively isolated from others.
- The nominalistic concept views species as human constructs rather than natural categories.
It also notes difficulties in applying the biological concept, such as asexual reproduction, similar but isolated species, and ring species where isolation breaks down.
Species concept
Organisms are classified into a hierarchical classification that groups closely related individuals.
The species is the basic biological unit around which classifications are based.
Variation in taxonomic and systematic characters
There are three main types of variation: geographic, sexual, and individual. Geographic variation occurs over space and can lead to clinal variation correlated with environmental factors. Sexual variation involves differences between males and females, often involving primary and secondary sexual characteristics. Individual variation occurs within the lifetime of an organism and can be due to factors like age, environment, parasites, and genetics. Genetic variation includes sex-associated traits and non-sex associated continuous or discontinuous variation within populations.
Cladistic
Cladistics is a biological classification system that groups organisms based on shared traits and evolutionary relationships. It aims to trace ancestry back to common ancestors by constructing phylogenetic trees based on morphological and molecular data. Key terms in cladistics include plesiomorphy (ancestral traits), apomorphy (derived traits that define groups), and homoplasy (traits that evolved separately in different groups). Together, analysis of character states helps determine evolutionary relationships between taxa.
Natural Selection and its types
Natural selection is a process whereby organisms better adapted to their environment tend to survive and produce more offspring. There are three main types of natural selection: directional selection favors one extreme of a trait, disruptive selection favors both extremes of a trait, and stabilizing selection favors intermediate forms of a trait. Examples of natural selection in action include the evolution of different beak shapes in Galapagos finches and the increase of melanism in moths due to pollution. Sexual selection is a form of natural selection resulting from competition or choice of mates.
Speciation
Speciation is the splitting of one species into two distinct species. The biological species concept defines a species as a group that can interbreed and produce fertile offspring under natural conditions, while being reproductively isolated from other groups. Reproductive isolation occurs when two populations diverge genetically enough that their offspring are infertile or inviable. Allopatric speciation, where populations are isolated geographically, is the most common speciation mechanism. Over time, separated populations accumulate genetic differences due to random genetic drift and independent evolution, eventually becoming reproductively isolated.
Biosystematics, and types of taxonomy
1.Definition and basic concepts of Biosystematics, , Historical perspectives of Biosystematics and Taxonomy, Stages of taxonomic procedures-alpha taxonomy, Beta taxonomy and Gamma taxonomy,
Neo taxonomy.
Darwinism and Neo Darwinism
The document summarizes Darwin's theory of evolution by natural selection. It discusses key concepts such as overproduction of offspring, the struggle for existence, variations and heredity, survival of the fittest, and the origin of species. It notes criticisms of Darwin's original theory, such as its inability to explain the origin of variations and intermediate forms. The document then outlines processes that can lead to variations, such as mutation and genetic drift. It also discusses inheritance of variations, natural selection maintaining constancy or promoting new species, and speciation occurring due to isolation.
Molecular taxonomy
Molecular taxonomy uses nucleotide sequence data to determine evolutionary relationships between organisms. It involves comparing the sequences of homologous molecules from each organism to determine differences, with more differences indicating more distant relationships. Walter Zimmerman and Willi Hennig pioneered using objective criteria like shared genetic attributes to determine phylogenetic relationships. Advances in molecular biology techniques and computing power allowed modeling large datasets to further molecular systematics. It helps resolve taxonomic problems, reorganize the tree of life, and has medical applications like tracking disease evolution.
Types of species
There are several types of species recognized, including:
- Species, which are groups of similar organisms capable of reproduction;
- Semi-species, which are transitional between species and subspecies and have some but not all species attributes;
- Allopatric species, which are related species with non-overlapping geographical ranges, such as the Indian and African lions.
Species concept
The document discusses various concepts and definitions of species in biology. It begins by explaining how species have traditionally been viewed as essential, fixed units but are now understood to evolve and diversify over time. It then examines different species concepts, including the biological species concept which defines a species as a population that can interbreed but is reproductively isolated from other species. The document also discusses concepts like nominalism which questions whether species are "real" categories. It explores recognition, cohesion and evolutionary species concepts, and defines types of species such as cryptic, endemic and polytypic species. Finally, it examines intraspecific categories below the species level like subspecies.
Taxonomic categories 6
This document discusses taxonomic hierarchy and categorization. It notes that Linnaeus originally established five categories (kingdom, class, order, genus, species, varieties) within the animal kingdom. Two additional categories were later adopted (phylum and family) to allow for finer divisions as more species were discovered. Examples of taxonomic categorization are provided for wolves and honey bees down to the species level. The document explains that additional intermediate categories have been inserted over time to provide more precise taxonomic positioning as the number of known species increased. It distinguishes that species are defined by isolating mechanisms in nature, while higher categories group species by emphasizing affinities rather than differences.
Species concept
The document discusses different species concepts:
1. The typological species concept defines a species as having an idealized, invariant pattern shared by all members. It considers variation as trivial.
2. The nominalistic species concept believes that only individuals exist in nature, not species, which are human constructs.
3. The biological species concept defines a species as a group of interbreeding natural populations reproductively isolated from other such groups. It is widely accepted but has limitations for asexual groups, cryptic species, and evolutionary intermediates.
4. The evolutionary species concept defines a species as a lineage evolving separately from other lineages with its own ecological niche. It aims to address limitations of the biological concept.
Species Concepts And Speciation
This document discusses different concepts of what defines a biological species, including historical, modern, and problematic concepts. It outlines the biological species concept, which defines a species as a group of interbreeding natural populations reproductively isolated from other such groups. However, it notes there are issues with this concept, as reproductive isolation evolves gradually and does not always correspond with morphological or genetic differences between forms. Other concepts discussed include the evolutionary species concept and problems identifying species without evidence of interbreeding.
Molecular taxonomy
presentation gives you information about different techniques and markers used in molecular taxonomy along with its advantages and disadvantages
typification
The type method is used to name taxonomic groups based on selecting a representative type specimen. The type specimen fixes the name of the taxonomic group and is permanently associated with it. There are several kinds of type specimens depending on how they were selected, including holotypes, isotypes, syntypes, paratypes, lectotypes, neotypes, and topotypes. The type specimen is usually a single preserved plant housed in a known herbarium and identified by collection details.
Variation (Genetics)
Variation-Genetic variation is the difference in DNA sequences between individuals within a population. Variation occurs in germ cells i.e. sperm and egg, and also in somatic (all other) cells. Only variation that arises in germ cells can be inherited from one individual to another and so affect population dynamics, and ultimately evolution.
Isolating mechanism and speciation in time 1
This document discusses isolating mechanisms and theories of speciation. It defines isolating mechanisms as any factors that prevent interbreeding between related groups. There are two main types of mechanisms: pre-mating (preventing mating) and post-mating (preventing hybrid formation). Theories of speciation include gradualism, where new species evolve slowly over long periods, and punctuated equilibrium, where species remain largely unchanged apart from brief periods of rapid change leading to speciation. The key differences between these theories are that gradualism involves continuous small changes while punctuated equilibrium involves long periods of stasis punctuated by sudden speciation events.
Taxonomic key
This document provides information about taxonomic keys, which are tools used in taxonomy to identify unknown organisms. It defines taxonomic keys and their purpose of using diagnostic characteristics to lead to the identification of a species or genus. It then describes different types of single access keys, including dichotomous, bracket, indented, serial, and grouped keys. It also discusses multi-access keys and styles of presenting keys, as well as advantages and disadvantages of using taxonomic keys.
Modern Synthetic Theory
The modern synthetic theory is the most widely accepted theory explaining organic evolution through genetics, molecular biology, and other modern fields of biology. It was first proposed by Dobzhansky in 1937 and further developed by Huxley, Muller, Fisher, Wright, Myer, and Stebbins. The theory explains that evolution occurs through five basic processes: gene mutation, chromosomal aberration, recombination, natural selection of adaptive characters, and reproductive isolation. Genetic drift and hybridization are also considered accessory factors in the modern synthesis theory of evolution.
Neodarwinism or synthetic theory of evolution
Neo-Darwinism is a modified version of Darwin's theory of evolution by natural selection. It incorporates genetic variation as the raw material for evolution. Genetic variation arises from sources like mutations, recombination, and chromosomal changes. Natural selection leads to differential reproduction of adaptive variants, increasing their frequency over generations. Reproductive isolation maintains distinctiveness between species. According to Neo-Darwinism, evolution occurs through the appearance of genetic variation, its spread through populations by natural selection, and reproductive isolation leading to speciation.
Mechanism Of Speciation
Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.There are few mechanisms through which this process can be well understood.
Rep isolating mechanism evolution final
Speciation occurs through reproductive isolation of populations. Isolating mechanisms like geographic barriers, behavioral differences, or incompatible gametes can prevent interbreeding and lead to the evolution of new species over time. Speciation increases biodiversity and is an important part of evolution. Reproductive isolation can have prezygotic causes like differences in mating behaviors, or postzygotic causes if hybrids are inviable or infertile. Examples of speciation include the diverse finch species that evolved on the Galapagos Islands.
Kinds of taxonomic publications,taxonomic review ,revision, monograph,atlas,s...
kinds of taxonomic publication mainly deals with different types of taxonomic publications.the taxonomy deals with several types of publications mainly that help to over all exchange of taxonomic information,its is a world wide taxonomic communication.
Speciation
This presentation is uploaded by Mahar Tanvir ul Hassan Tibbi Tarhana Samandry Faisalabad Pakistan. I am enrolled in University of Sargodha in MSc Zoology.
Cladistics
- Cladistics is a method of classifying organisms based on their evolutionary relationships and phylogenetic branching rather than physical similarities. It groups organisms into clades of monophyletic groups that share a common ancestor.
- Key terms include synapomorphy (shared derived trait), plesiomorphy (ancestral trait), apomorphy (derived trait), monophyletic/polyphyletic/paraphyletic taxa.
- Cladograms visually depict these evolutionary relationships through branching diagrams showing how groups split from common ancestors over time. They do not show passage of time or degree of change.
Isolating mechanisms - kashmeera
This document summarizes isolating mechanisms - factors that prevent gene exchange between populations. There are prezygotic mechanisms, which act before fertilization, including habitat isolation where species occupy different habitats, seasonal isolation with differences in breeding times, and behavioral isolation from variations in courtship displays. Postzygotic mechanisms occur after fertilization, such as gametic mortality where sperm are killed before reaching eggs, hybrid inviability where zygotes do not develop, and hybrid sterility where offspring are viable but infertile. Isolating mechanisms have a genetic basis and act together to maintain species boundaries where populations meet.
Speciation and domestication
The document discusses speciation, which is the process by which new species develop from existing species. There are several factors that can lead to speciation, including geographical isolation, reproductive isolation, genetic drift, and variations due to natural selection. The main types of speciation discussed are allopatric (geographical isolation), sympatric (evolution of new niches), parapatric (non-random mating reduces gene flow), and peripatric (isolation of small populations). Examples are given of each type, including Darwin's finches through allopatric speciation and apple maggot flies through sympatric speciation. Reproductive isolating mechanisms that can occur both before and after mating are also outlined.
Speciation
Speciation occurs through reproductive isolation over long periods of time. There are three main types of speciation: allopatric speciation which occurs when populations become geographically isolated; parapatric speciation at habitat borders; and sympatric speciation within the same habitat. Reproductive barriers like behavioral, ecological, and mechanical isolation prevent interbreeding and lead to the evolution of new species. Over time, small changes through microevolution accumulate into macroevolutionary changes between species.
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The document summarizes Darwin's theory of evolution by natural selection. It discusses key concepts such as overproduction of offspring, the struggle for existence, variations and heredity, survival of the fittest, and the origin of species. It notes criticisms of Darwin's original theory, such as its inability to explain the origin of variations and intermediate forms. The document then outlines processes that can lead to variations, such as mutation and genetic drift. It also discusses inheritance of variations, natural selection maintaining constancy or promoting new species, and speciation occurring due to isolation.
Molecular taxonomy
Molecular taxonomy uses nucleotide sequence data to determine evolutionary relationships between organisms. It involves comparing the sequences of homologous molecules from each organism to determine differences, with more differences indicating more distant relationships. Walter Zimmerman and Willi Hennig pioneered using objective criteria like shared genetic attributes to determine phylogenetic relationships. Advances in molecular biology techniques and computing power allowed modeling large datasets to further molecular systematics. It helps resolve taxonomic problems, reorganize the tree of life, and has medical applications like tracking disease evolution.
Types of species
There are several types of species recognized, including:
- Species, which are groups of similar organisms capable of reproduction;
- Semi-species, which are transitional between species and subspecies and have some but not all species attributes;
- Allopatric species, which are related species with non-overlapping geographical ranges, such as the Indian and African lions.
Species concept
The document discusses various concepts and definitions of species in biology. It begins by explaining how species have traditionally been viewed as essential, fixed units but are now understood to evolve and diversify over time. It then examines different species concepts, including the biological species concept which defines a species as a population that can interbreed but is reproductively isolated from other species. The document also discusses concepts like nominalism which questions whether species are "real" categories. It explores recognition, cohesion and evolutionary species concepts, and defines types of species such as cryptic, endemic and polytypic species. Finally, it examines intraspecific categories below the species level like subspecies.
Taxonomic categories 6
This document discusses taxonomic hierarchy and categorization. It notes that Linnaeus originally established five categories (kingdom, class, order, genus, species, varieties) within the animal kingdom. Two additional categories were later adopted (phylum and family) to allow for finer divisions as more species were discovered. Examples of taxonomic categorization are provided for wolves and honey bees down to the species level. The document explains that additional intermediate categories have been inserted over time to provide more precise taxonomic positioning as the number of known species increased. It distinguishes that species are defined by isolating mechanisms in nature, while higher categories group species by emphasizing affinities rather than differences.
Species concept
The document discusses different species concepts:
1. The typological species concept defines a species as having an idealized, invariant pattern shared by all members. It considers variation as trivial.
2. The nominalistic species concept believes that only individuals exist in nature, not species, which are human constructs.
3. The biological species concept defines a species as a group of interbreeding natural populations reproductively isolated from other such groups. It is widely accepted but has limitations for asexual groups, cryptic species, and evolutionary intermediates.
4. The evolutionary species concept defines a species as a lineage evolving separately from other lineages with its own ecological niche. It aims to address limitations of the biological concept.
Species Concepts And Speciation
This document discusses different concepts of what defines a biological species, including historical, modern, and problematic concepts. It outlines the biological species concept, which defines a species as a group of interbreeding natural populations reproductively isolated from other such groups. However, it notes there are issues with this concept, as reproductive isolation evolves gradually and does not always correspond with morphological or genetic differences between forms. Other concepts discussed include the evolutionary species concept and problems identifying species without evidence of interbreeding.
Molecular taxonomy
presentation gives you information about different techniques and markers used in molecular taxonomy along with its advantages and disadvantages
typification
The type method is used to name taxonomic groups based on selecting a representative type specimen. The type specimen fixes the name of the taxonomic group and is permanently associated with it. There are several kinds of type specimens depending on how they were selected, including holotypes, isotypes, syntypes, paratypes, lectotypes, neotypes, and topotypes. The type specimen is usually a single preserved plant housed in a known herbarium and identified by collection details.
Variation (Genetics)
Variation-Genetic variation is the difference in DNA sequences between individuals within a population. Variation occurs in germ cells i.e. sperm and egg, and also in somatic (all other) cells. Only variation that arises in germ cells can be inherited from one individual to another and so affect population dynamics, and ultimately evolution.
Isolating mechanism and speciation in time 1
This document discusses isolating mechanisms and theories of speciation. It defines isolating mechanisms as any factors that prevent interbreeding between related groups. There are two main types of mechanisms: pre-mating (preventing mating) and post-mating (preventing hybrid formation). Theories of speciation include gradualism, where new species evolve slowly over long periods, and punctuated equilibrium, where species remain largely unchanged apart from brief periods of rapid change leading to speciation. The key differences between these theories are that gradualism involves continuous small changes while punctuated equilibrium involves long periods of stasis punctuated by sudden speciation events.
Taxonomic key
This document provides information about taxonomic keys, which are tools used in taxonomy to identify unknown organisms. It defines taxonomic keys and their purpose of using diagnostic characteristics to lead to the identification of a species or genus. It then describes different types of single access keys, including dichotomous, bracket, indented, serial, and grouped keys. It also discusses multi-access keys and styles of presenting keys, as well as advantages and disadvantages of using taxonomic keys.
Modern Synthetic Theory
The modern synthetic theory is the most widely accepted theory explaining organic evolution through genetics, molecular biology, and other modern fields of biology. It was first proposed by Dobzhansky in 1937 and further developed by Huxley, Muller, Fisher, Wright, Myer, and Stebbins. The theory explains that evolution occurs through five basic processes: gene mutation, chromosomal aberration, recombination, natural selection of adaptive characters, and reproductive isolation. Genetic drift and hybridization are also considered accessory factors in the modern synthesis theory of evolution.
Neodarwinism or synthetic theory of evolution
Neo-Darwinism is a modified version of Darwin's theory of evolution by natural selection. It incorporates genetic variation as the raw material for evolution. Genetic variation arises from sources like mutations, recombination, and chromosomal changes. Natural selection leads to differential reproduction of adaptive variants, increasing their frequency over generations. Reproductive isolation maintains distinctiveness between species. According to Neo-Darwinism, evolution occurs through the appearance of genetic variation, its spread through populations by natural selection, and reproductive isolation leading to speciation.
Mechanism Of Speciation
Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.There are few mechanisms through which this process can be well understood.
Rep isolating mechanism evolution final
Speciation occurs through reproductive isolation of populations. Isolating mechanisms like geographic barriers, behavioral differences, or incompatible gametes can prevent interbreeding and lead to the evolution of new species over time. Speciation increases biodiversity and is an important part of evolution. Reproductive isolation can have prezygotic causes like differences in mating behaviors, or postzygotic causes if hybrids are inviable or infertile. Examples of speciation include the diverse finch species that evolved on the Galapagos Islands.
Kinds of taxonomic publications,taxonomic review ,revision, monograph,atlas,s...
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Speciation
This presentation is uploaded by Mahar Tanvir ul Hassan Tibbi Tarhana Samandry Faisalabad Pakistan. I am enrolled in University of Sargodha in MSc Zoology.
Cladistics
- Cladistics is a method of classifying organisms based on their evolutionary relationships and phylogenetic branching rather than physical similarities. It groups organisms into clades of monophyletic groups that share a common ancestor.
- Key terms include synapomorphy (shared derived trait), plesiomorphy (ancestral trait), apomorphy (derived trait), monophyletic/polyphyletic/paraphyletic taxa.
- Cladograms visually depict these evolutionary relationships through branching diagrams showing how groups split from common ancestors over time. They do not show passage of time or degree of change.
Isolating mechanisms - kashmeera
This document summarizes isolating mechanisms - factors that prevent gene exchange between populations. There are prezygotic mechanisms, which act before fertilization, including habitat isolation where species occupy different habitats, seasonal isolation with differences in breeding times, and behavioral isolation from variations in courtship displays. Postzygotic mechanisms occur after fertilization, such as gametic mortality where sperm are killed before reaching eggs, hybrid inviability where zygotes do not develop, and hybrid sterility where offspring are viable but infertile. Isolating mechanisms have a genetic basis and act together to maintain species boundaries where populations meet.
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The document discusses speciation, which is the process by which new species develop from existing species. There are several factors that can lead to speciation, including geographical isolation, reproductive isolation, genetic drift, and variations due to natural selection. The main types of speciation discussed are allopatric (geographical isolation), sympatric (evolution of new niches), parapatric (non-random mating reduces gene flow), and peripatric (isolation of small populations). Examples are given of each type, including Darwin's finches through allopatric speciation and apple maggot flies through sympatric speciation. Reproductive isolating mechanisms that can occur both before and after mating are also outlined.
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Speciation occurs through reproductive isolation over long periods of time. There are three main types of speciation: allopatric speciation which occurs when populations become geographically isolated; parapatric speciation at habitat borders; and sympatric speciation within the same habitat. Reproductive barriers like behavioral, ecological, and mechanical isolation prevent interbreeding and lead to the evolution of new species. Over time, small changes through microevolution accumulate into macroevolutionary changes between species.
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Evolutionary mechanisms of reproductive isolation prevent interbreeding between species and promote biodiversity. There are pre-zygotic isolation mechanisms that prevent fertilization, including differences in habitat, timing of reproduction, courtship behaviors, physical incompatibility of reproductive organs, and sperm/egg incompatibilities. Post-zygotic mechanisms allow fertilization but cause hybrid inviability or sterility, such as failure of early embryo development, sterile hybrid offspring, or weak/sterile offspring in subsequent generations. Speciation occurs through geographic isolation of populations, ecological isolation within the same habitat, or gradual isolation with gene flow.
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This document discusses speciation and the evolution of new species. It describes barriers to gene flow that can lead to allopatric speciation when populations are isolated geographically. Mechanisms of speciation include prezygotic and postzygotic isolation that prevent interbreeding. Speciation occurs through gradual divergence or punctuated bursts and is visualized using evolutionary trees. Adaptive radiation and extinction further shape the diversity of life over time.
Ch 16 notes
This document discusses population genetics and the process of speciation. It explains that variations in genotype can arise through mutation, recombination, and random pairing of gametes. Genetic equilibrium occurs when genotype frequencies remain stable between generations under certain conditions. Equilibrium can be disrupted by factors like mutation, gene flow, genetic drift, and natural selection. Speciation is the formation of new species and can occur through geographic (allopatric) isolation or reproductive (sympatric) isolation within the same area.
EVOLUTION THE HISTORY
Evolution is a very complex, irreversible and extremely slow process. the events related to theories of evolution and evidences of evolution are discussed. Theories of origin of life are as follows. 1)Theory of Special creation or devine origin 2) The theory of spontaneous generation/ Abiogenesis 3)Spallanzani experiment 4) Redi Experiment (1680) 5) Pasteurs Experiment (1864) 6) Panspermia 7) Theory of Catastrophism ( G,Cuvier) 8) Naturalistic theory ( Oparin & Haldane, 1920)
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Speciation and its type
- 2. • Can be caused by a change in just 1 gene or a set of genes causing some sort of isolation Speciation • Development of a new species through a variety of factors • Rate of speciation depends on generation time, environmental conditions, etc.
- 3. Biological Species Concept Species-Group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable offspring with members of other groups. What maintains species? Gene flow Reproductive isolation (biological)
- 4. Smallest group of organisms that share a common ancestor Other Species Definitions Morphological Species Concept Characterizes by body shape and other structures Ecological Species Concept Characterizes in terms of ecological niche Phylogenetic Species Concept
- 5. • block fertilization from happening • Prevent different species from attempting to mate • Prevent an attempted mating from being successful • Hindering fertilization Prezygotic Barriers- Postzygotic Barriers • occur after zygote is formed • Developmental errors • Birth defects cause death • Infertile offspring
- 6. Behavioral isolation- Absence of cross-attraction between individuals of separate species inhibiting any courtship initiation or individual behavior during copulation does not allow normal fertilization to occur. Ecological isolation-Variations in the ecology of species give rise to barriers: Habitat isolation-Even when living in the same common locality, species occupy diverse habitats due to different biological or genetic tendencies thereby limiting gene flow during breeding seasons. Temporal isolation-Species living in the same area have different breeding seasons preventing gene flow. Pollinator isolation-Flowering plants have varying interactions with pollinators thereby reducing gene flow. Mechanical isolation-Reproductive structures are incompatible between species inhibiting copulation or pollination. Gametic isolation-Gametes that are transferred during copulation or pollination are ineffectual for fertilization due to problems with storage or transfer of gametes or because of conspecific pollen or sperm partiality. Prezygotic Reproductive Isolating Barriers
- 7. Types of Speciation Sympatric Speciation--occurs in populations that live in the same geographic area • Less common than allopatric speciation • Happens when gene flow is diminished by: • Polyploidy Habitat differentiation Sexual selection Allopatric Speciation-gene flow is interrupted when a population is divided into geographically isolated subpopulations Parapatric Speciation-occurs when part of a population enters a new habitat bordering the range of the parent species Some gene flow may occur between populations in border zone
- 8. Allopatric Peripatric Parapatric Sympatric Initiation of speciation Evolution of reproductive isolation New distinct species after equilibration of new ranges Barrier formation In isolation New niche entered In isolation niche New niche entered In adjacent niche Genetic polymorphism With population