Understanding Speciation and the Biological Species Concept

What is speciation?

The process by which one species splits into two or more species, responsible for the diversity of life.

What does the biological species concept emphasize?

Reproductive isolation, defining a species as a group of populations that can interbreed and produce viable, fertile offspring.

How does speciation explain similarities between species?

Species that result from speciation share characteristics because they descend from a common ancestral species.

What is the significance of gene flow in species?

Gene flow is the transfer of alleles between populations, which holds the gene pool of a species together and maintains genetic similarity.

What is reproductive isolation?

Biological factors that impede members of two species from interbreeding and producing viable, fertile offspring.

What are prezygotic barriers?

Barriers that prevent fertilization from occurring, including habitat isolation, temporal isolation, and behavioral isolation.

What are postzygotic barriers?

Barriers that occur after fertilization, which may lead to reduced survival among hybrid embryos or infertility in hybrids.

What is habitat isolation?

A prezygotic barrier where two species occupy different habitats and rarely encounter each other.

What is temporal isolation?

A prezygotic barrier where species breed at different times of the day, seasons, or years, preventing gamete mixing.

What is behavioral isolation?

A prezygotic barrier where unique courtship rituals and behaviors prevent interbreeding between closely related species.

What is mechanical isolation?

A prezygotic barrier where morphological differences prevent successful mating between species.

What role does speciation play in macroevolution?

Speciation is a key mechanism that leads to the origin of new groups of organisms through a series of speciation events.

How does Darwin's view on speciation relate to the Galápagos Islands?

Darwin noted that species on the Galápagos Islands were unique and likely originated from ancestral species that migrated from the mainland.

What is the relationship between microevolution and macroevolution?

Speciation serves as a bridge between microevolution (changes in allele frequencies) and macroevolution (broad patterns of evolution).

What does the term 'hybrid' refer to?

Offspring that result from the mating of individuals from different species.

What is the main focus of Chapter 24 in the context of evolution?

To explore the mechanisms by which new species originate from existing ones.

Why is the biological species concept important in classifying species?

It provides a clear definition based on reproductive compatibility rather than just physical appearance.

What can lead to the formation of new species?

The absence of gene flow and the presence of reproductive barriers can lead to speciation.

What is the significance of DNA similarities in speciation?

DNA similarities can indicate close relationships between species, supporting the idea of common ancestry.

How does the concept of species challenge traditional classifications?

It raises questions about whether organisms are truly divided into discrete units or if classifications are arbitrary.

What is the 'mystery of mysteries' that captivated Darwin?

The first appearance of new beings on Earth, which relates to the process of speciation.

What does the term 'viable offspring' mean?

Offspring that are capable of surviving and reproducing.

What is an example of a hybrid barrier after fertilization?

Developmental errors that reduce survival among hybrid embryos.

What is the potential outcome when two species interbreed?

They may produce hybrids, but reproductive barriers often prevent the production of viable, fertile offspring.

What is gametic isolation?

A type of reproductive barrier where sperm of one species cannot fertilize the eggs of another species.

What does reduced hybrid viability refer to?

When hybrid offspring do not develop properly or are frail, leading to low survival rates.

What is reduced hybrid fertility?

When hybrids are viable but sterile, preventing them from producing offspring.

What is hybrid breakdown?

When first-generation hybrids are viable and fertile, but their offspring in the next generation are weak or sterile.

Provide an example of reduced hybrid viability.

Most hybrids of certain salamander subspecies do not complete development or are frail.

What is an example of a hybrid that is robust but sterile?

A mule, which is the offspring of a male donkey and a female horse.

What is the biological species concept?

A definition of species based on the ability to interbreed and produce viable, fertile offspring.

What is a limitation of the biological species concept?

It cannot be applied to fossils or asexual organisms, such as prokaryotes.

What is the morphological species concept?

A definition that characterizes species by body shape and structural features.

What is a disadvantage of the morphological species concept?

It relies on subjective criteria, leading to potential disagreements among researchers.

What does the ecological species concept emphasize?

The interactions of a species with its environment and its ecological niche.

What is the phylogenetic species concept?

A definition that identifies species as the smallest group sharing a common ancestor, forming a branch on the tree of life.

What is a challenge with the phylogenetic species concept?

Determining the degree of difference required to classify separate species.

What is an example of hybridization between closely related species?

The hybrid offspring of grizzly bears and polar bears, known as 'grolar bears'.

What type of reproductive barrier is likely present if two bird species do not interbreed in nature but can produce viable offspring in captivity?

Behavioral isolation, as they occupy different ecological niches.

What can the presence of gene flow between species indicate?

It suggests that natural selection may maintain distinct species despite some interbreeding.

What is the significance of reproductive isolation in speciation?

It is crucial for the evolution of new species by preventing gene flow between populations.

How do postzygotic barriers differ from prezygotic barriers?

Postzygotic barriers occur after fertilization, while prezygotic barriers prevent fertilization from occurring.

What is an example of gametic isolation in aquatic animals?

Sea urchins have sperm and eggs that do not fuse due to poor binding between their proteins.

What role does natural selection play in species divergence?

Natural selection can lead to the development of distinct species by favoring different adaptations in varying environments.

What is the importance of understanding species concepts in biology?

It helps clarify how species originate and evolve, guiding research and conservation efforts.

What is the relationship between speciation and geographic isolation?

Speciation can occur with or without geographic separation, depending on reproductive barriers.

What are the two main types of speciation?

Allopatric speciation and sympatric speciation.

What is allopatric speciation?

Speciation that occurs when gene flow is interrupted due to geographic isolation of populations.

What does the term 'allopatric' mean?

From the Greek 'allos' meaning 'other' and 'patra' meaning 'homeland'.

Give an example of allopatric speciation.

The separation of antelope squirrels on opposite rims of the Grand Canyon.

How can allopatric speciation occur without geologic changes?

When individuals colonize a remote area and become geographically isolated from the parent population.

What factors determine how formidable a geographic barrier is for allopatric speciation?

The ability of organisms to move about; some can cross barriers while others cannot.

What happens to gene pools after geographic separation in allopatric speciation?

They may diverge due to mutations, natural selection, and genetic drift.

How did the mosquitofish illustrate reproductive isolation?

Different body shapes evolved in high-predation versus low-predation ponds, leading to mating preferences that isolated populations.

What evidence supports allopatric speciation in snapping shrimp?

Morphological and genetic data show sibling species on either side of the Isthmus of Panama, indicating they arose from geographic separation.

What is the significance of geographic isolation in biodiversity?

Regions that are isolated or subdivided by barriers typically have more species than similar regions without such features.

What did studies on dusky salamanders reveal about reproductive isolation?

Reproductive isolation increased with the geographic distance between populations.

What is the relationship between distance and reproductive isolation?

As the distance between populations increases, the degree of reproductive isolation generally increases.

What role do environmental conditions play in speciation?

Different environmental conditions can lead to intrinsic reproductive barriers developing in isolated populations.

What is sympatric speciation?

Speciation that occurs without geographic separation, often through mechanisms like polyploidy or behavioral changes.

What is the role of natural selection in allopatric speciation?

Natural selection can lead to different adaptations in isolated populations, contributing to speciation.

How does genetic drift contribute to speciation?

Genetic drift can alter allele frequencies in separated populations, leading to divergence and potential speciation.

What is the significance of the Galápagos Islands in the study of speciation?

They provide examples of species that evolved from ancestral forms due to geographic isolation.

How does the concept of gene flow relate to speciation?

Gene flow must be interrupted for speciation to occur, allowing populations to diverge genetically.

What is the importance of studying speciation?

Understanding speciation helps explain biodiversity and the evolutionary processes that shape life on Earth.

What are biological reproductive barriers?

Intrinsic barriers within organisms that prevent interbreeding between different populations.

What organism was used in Diane Dodd's experiment on speciation?

The fruit fly Drosophila pseudoobscura.

What mediums were used to raise the fruit flies in Dodd's experiment?

Starch medium and maltose medium.

What was the outcome of Dodd's experiment after 40 generations?

Divergent evolution occurred, with populations adapting to their respective food sources.

What factors can reduce gene flow in sympatric populations?

Polyploidy, habitat differentiation, and sexual selection.

What is polyploidy?

A condition where a species has more than two sets of chromosomes, often leading to speciation.

What is an autopolyploid?

An individual with more than two chromosome sets derived from a single species.

How can autopolyploidy lead to reproductive isolation?

It can generate reproductive isolation without geographic separation by producing offspring with different chromosome numbers.

What is allopolyploidy?

A form of polyploidy that occurs when two different species interbreed and produce hybrid offspring.

What is the significance of Tragopogon miscellus?

It is a tetraploid hybrid species that originated from European species introduced to the Pacific Northwest.

How do polyploids relate to agriculture?

Many important crops, such as wheat and cotton, are polyploids, often resulting from hybridization events.

Why were all flies in the mating preference tests reared on a standard medium?

To control for environmental factors and isolate the effects of genetic differences on mating preferences.

What is the role of natural selection in Dodd's experiment?

Natural selection favored flies that efficiently digested their specific food sources, leading to divergent evolution.

What does the term 'reproductive barrier' refer to?

Any mechanism that prevents mating and successful reproduction between different species or populations.

What is the outcome of mating between starch and maltose flies in Dodd's experiment?

Flies tended to mate with like-adapted partners, indicating the formation of a reproductive barrier.

What is the diploid number represented as in the text?

2n, where n represents the number of chromosome sets.

What is a triploid organism?

An organism with three sets of chromosomes, often resulting from hybridization.

What is the significance of meiotic errors in polyploidy?

They can lead to the formation of polyploid individuals, contributing to speciation.

What is an example of a plant that has undergone polyploid speciation?

The gray tree frog Hyla versicolor, which is thought to have originated from polyploidy.

How can scientists induce polyploidy in the laboratory?

By using chemicals that induce meiotic and mitotic errors.

What is the chromosome number of the allopolyploid hybrid derived from two parent species?

It has a diploid chromosome number equal to the sum of the diploid numbers of the two parent species.

What is the primary mechanism that can lead to the formation of new species in plants?

Polyploidy, which can occur through both autopolyploidy and allopolyploidy.

How can sympatric speciation occur in the North American apple maggot fly?

It can occur when genetic factors enable a subpopulation to exploit a different host plant than the parent population, leading to natural selection and reproductive barriers.

What role does sexual selection play in speciation?

Sexual selection can drive speciation by influencing mate choice based on traits such as coloration, which can create reproductive barriers between populations.

What was the conclusion of Seehausen and van Alphen's experiment with cichlids?

They concluded that mate choice based on male breeding coloration is the main reproductive barrier that keeps the gene pools of two cichlid species separate.

What happens to cichlid mating behavior under monochromatic orange light?

Under monochromatic orange light, females responded indiscriminately to males of both species, suggesting that visual cues are crucial for mate selection.

What are some processes that can lead to genetic changes in allopatric populations?

Genetic changes can occur due to natural selection, genetic drift, and sexual selection under different environmental conditions.

What is a hybrid zone?

A hybrid zone is a region where members of different species meet and mate, producing offspring of mixed ancestry.

What can happen when species with incomplete reproductive barriers come into contact?

They may form a hybrid zone, where interbreeding occurs, potentially leading to gene flow between the species.

What is polyploidy and how does it relate to sympatric speciation?

Polyploidy is a condition where an organism has extra sets of chromosomes, which can lead to reproductive isolation and sympatric speciation.

What is the significance of the cichlid species in Lake Victoria?

Cichlid species in Lake Victoria demonstrate rapid speciation, likely due to adaptation to different food sources and sexual selection.

How does gene flow affect sympatric populations?

Gene flow can decrease in sympatric populations due to reproductive barriers, making sympatric speciation more likely.

What is the difference between allopatric and sympatric speciation?

Allopatric speciation occurs due to geographic isolation, while sympatric speciation occurs without geographic barriers, often through reproductive isolation mechanisms.

What is the role of natural selection in sympatric speciation?

Natural selection can drive sympatric speciation by favoring traits that allow a subpopulation to exploit different resources or habitats.

How does sexual selection contribute to reproductive isolation?

Sexual selection can create preferences for certain traits, leading to reproductive isolation as individuals choose mates based on those traits.