Speciation Concepts in Biology

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Questions and Answers

What term describes the inability of egg and sperm from different species to fuse, resulting in fertilization failure?

Allopatric Speciation

Hybrid Sterility

Postzygotic Isolation

Gametic Incompatibility (correct)

Which of the following best describes Haldane's Rule?

Hybrid offspring of two species are always sterile.

There are no exceptions to hybrid compatibility between all species.

The first generation of hybrids will always have equal fitness.

If one sex of a hybrid is absent or rare, it is usually the heterogametic sex. (correct)

What phenomenon occurs when hybrids between two species are sterile, but their parents are not?

Reproductive Isolation

Gametic Incompatibility

Allopatric Speciation

Hybrid Sterility (correct)

Which process involves the geographic separation of populations leading to the formation of new species?

Allopatric Speciation Signup and view all the answers

What factors influence the geography of speciation?

Habitat fragmentation and environmental barriers Signup and view all the answers

What is Haldane's Rule primarily concerned with?

The differential expression of hybrid breakdown in sexes Signup and view all the answers

Which of the following best describes hybrid sterility?

Hybrids are unable to reproduce successfully Signup and view all the answers

What mode of speciation is considered the most common?

Allopatric speciation Signup and view all the answers

Which of the following is an example of gametic incompatibility?

Sperm from one species unable to fertilize eggs of another species Signup and view all the answers

What does it mean if hybrid inviability occurs?

Hybrids suffer high mortality rates before reaching reproductive age Signup and view all the answers

Which of the following correctly describes hybrid breakdown?

Reduced fitness in subsequent generations of hybrids Signup and view all the answers

In the context of allopatric speciation, what is vicariance?

The physical separation of two populations by geographical features Signup and view all the answers

Which of the following species is most likely to be affected by Haldane's Rule?

Species where males have fewer chromosomes than females Signup and view all the answers

How does geographic isolation contribute to speciation?

By preventing individuals from mating with one another Signup and view all the answers

What is one of the first stages in the development of hybrid sterility?

There is a reduction in compatibility during mating Signup and view all the answers

What is a characteristic of sister species in relation to their habitats?

They are rarely sympatric. Signup and view all the answers

Which statement accurately describes allopatric speciation?

It arises from populations that are isolated on different islands. Signup and view all the answers

How does the Dobzhansky-Muller model explain hybrid incompatibility?

It describes how derived alleles may be incompatible due to lack of natural selection. Signup and view all the answers

What does Haldane's Rule state regarding hybrid species?

The heterogametic sex is often less viable or sterile. Signup and view all the answers

In the context of speciation, what is a key factor that reduces the likelihood of speciation on small islands?

Increased gene flow between populations. Signup and view all the answers

What is an example of hybrid sterility?

F1 generation from two different species that cannot reproduce. Signup and view all the answers

Which factor primarily influences the geographical aspect of speciation?

The isolation of populations due to geographical barriers. Signup and view all the answers

Which of the following factors is not typically associated with allopatric speciation?

Continuous gene flow between populations. Signup and view all the answers

Study Notes

Speciation

Haldane jokingly said the Creator had an "inordinate fondness for beetles" when asked about natural theology
Figure 9.1 shows diversity of cichlid fish in Lakes Tanganyika and Malawi. Rate of speciation is very high in these environments.
The biological species concept (BSC) defines species as groups of interbreeding populations reproductively isolated from others. Gene flow is the key, focusing on reproductive isolation more than phenotypic differences. Cryptic species share little phenotypic difference but are reproductively isolated.
Problems with BSC: asexuals lack gene flow, extinct groups cannot be assessed, and breeding is impractical for many species.
Other species concepts include phylogenetic (species distinguished by diagnosable differences in morphology or DNA), evolutionary, recognition, and genealogical species concepts
Evolution, as a process, has intermediate stages and fuzzy boundaries, meaning one unique classification will not work for all situations.

What are species?

Biological species concept (BSC): Groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups through gene flow that is not happening.
Focusing on gene flow (Reproductive Isolation), rather than phenotypic differences.
Cryptic species isolated but with little phenotypic differentiation.

Problems with the BSC

Asexuals: no gene flow
Extinct groups: Cannot conduct breeding experiments
Gene flow between species: How to observe flow of genes
Difficulty in breeding experiments

Other species concepts

Phylogenetic Species Concept: Populations are species if they are "diagnosably" different (morphology, DNA).
Evolutionary, Recognition/cohesion, and Genealogical Concepts

Issues with the single species concept

The search for a uniform species concept is unattainable given the diverse nature of evolution.

Example of Post-mating, Pre-zygotic Isolation

Researchers studied Callosobruchus beetles (maculate vs. subinnotatus) to look for post-mating, pre-zygotic isolation.

Extrinsic Isolation

Different food resources may result in varying evolutionary tracks, affecting post-zygotic isolation for Darwin's finches, for example.

Geographic Isolation of Speciation

Allopatric speciation: The most common mode of speciation, which involves geographic separation of populations.
- Populations become isolated and can evolve independently. If the barrier is removed, the two populations may be unable to interbreed or may have already evolved into distinct species through various evolutionary factors.

Further Points

Sympatric speciation: Speciation within the same geographic region.
Ecological isolation: Lack of opportunity to mate due to timing, habit, or space.
Behavioral/sexual isolation: Individuals prefer to mate with members of their own species.
Reproductive Isolation: Pre-zygotic/post-zygotic: events occurring before/after fertilization, respectively.

Haldane's Rule

The heterogametic sex is usually affected more severely by hybrid breakdown if the two sexes are different.

Empirical Evidence and Island Endemics

Empirical findings support the idea that sexual isolation is significant.
Studies on islands show that sister species are rarely found in sympatry (co-occurrence in the same geographic area).
Speciation is less likely in small island environments due to limited gene pools/restricted geographic opportunity.

Dobzhansky-Muller Model

There's a problem with single-locus incompatibilities.
Species diverge, then mate incompatibilities evolve.

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Description

This quiz explores various concepts of speciation including the biological species concept and its limitations. Additionally, it discusses alternative species concepts and the intricacies of evolutionary processes. Test your understanding of these vital biological principles!