Biology Chapter 24 Flashcards

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Questions and Answers

Distinguish between anagenesis and cladogenesis.

Anagenesis is a state in which an unbranched lineage transforms into a new species, while cladogenesis is the budding of one or more new species from a parent species resulting in diversification.

Explain the concept of morphospecies and its usefulness to biologists.

Morphospecies is used to define species by their anatomical features.

Explain the concept of biological species.

A biological species is a population whose members have the potential to interbreed in nature to produce fertile offspring.

Describe some limitations of the biological species concept.

It does not apply to asexual organisms, extinct species represented only by fossils, and cases where geographically separated species might reproduce if together. Signup and view all the answers

Distinguish between prezygotic and postzygotic isolating mechanisms.

Prezygotic mechanisms are reproductive barriers occurring before fertilization, while postzygotic mechanisms occur after fertilization, often resulting in hybrid sterility. Signup and view all the answers

Explain the following prezygotic isolating mechanisms: geographic isolation, habitat isolation, behavioral isolation, temporal isolation, mechanical isolation, and gametic isolation.

Geographic isolation is physical separation; habitat isolation refers to similar species living in different habitats; behavioral isolation involves unique mating behaviors; temporal isolation occurs when species breed at different times; mechanical isolation is anatomical incompatibility; and gametic isolation prevents fertilization between species. Signup and view all the answers

Define the following postzygotic isolating mechanisms: reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.

Reduced hybrid viability means the hybrid may abort due to genetic incompatibility; reduced hybrid fertility means the hybrid is unable to reproduce; hybrid breakdown means the first generation hybrid is viable but later generations may be feeble or sterile. Signup and view all the answers

Explain the concept of adaptive radiation.

Adaptive radiation is the emergence of multiple species from a single common ancestor introduced to a diverse environment. Signup and view all the answers

Describe allopatric speciation.

Allopatric speciation results from a population being separated by a geographical barrier that prevents gene flow. Signup and view all the answers

Describe sympatric speciation and explain how polyploidy can cause reproductive isolation.

Sympatric speciation occurs within the range of the parent species without geographic isolation, while polyploidy causes reproductive isolation by making organisms sterile. Signup and view all the answers

Distinguish between autopolyploidy and allopolyploidy.

Autopolyploidy is when an organism doubles its chromosome number from a single parent, while allopolyploidy results from hybridization between two different parent species. Signup and view all the answers

Compare and contrast the two schools of thought on the tempo of speciation: gradualism and punctuated equilibrium.

Gradualism involves slow, incremental changes over long periods, while punctuated equilibrium involves rapid changes followed by long periods of stability. Signup and view all the answers

Describe the concept of a hybrid zone and factors that may prevent gene flow between populations across the hybrid zone.

A hybrid zone is where two species meet in adjacent habitats, and gene flow can be prevented by geographic or habitat isolation, or mechanical or behavioral isolation. Signup and view all the answers

Study Notes

Speciation Concepts

Anagenesis vs. Cladogenesis: Anagenesis involves the transformation of an unbranched lineage into a new species, while cladogenesis is the process of a parent species diverging into one or more new species, promoting diversification.
Morphospecies: This concept defines species based on anatomical features, aiding biologists in field identification and classification of species based on observable traits.
Biological Species Concept: Defines a species as a population capable of interbreeding in nature to produce fertile offspring.

Limitations of Biological Species Concept

Inapplicable to asexual organisms, extinct species represented only by fossils, or geographically separated species that could potentially interbreed.
Some species that do not interbreed may still be genetically connected through a shared ancestral population.

Isolating Mechanisms

Prezygotic Mechanisms: Includes barriers preventing mating or fertilization. Types are:
- Geographic Isolation: Physical separation by location.
- Habitat Isolation: Species occupy different habitats within the same area.
- Behavioral Isolation: Unique mating behaviors or signals hinder mating.
- Temporal Isolation: Species breed at different times or seasons.
- Mechanical Isolation: Anatomical incompatibility prevents successful mating.
- Gametic Isolation: Gametes from different species usually do not fuse.
Postzygotic Mechanisms: Barriers that occur after fertilization. Types include:
- Reduced Hybrid Viability: Hybrids may develop poorly or die due to genetic incompatibility.
- Reduced Hybrid Fertility: Hybrids may be sterile and unable to reproduce.
- Hybrid Breakdown: First-generation hybrids are viable, but their descendants are feeble or sterile.

Speciation Types

Adaptive Radiation: Rapid emergence of multiple species from a common ancestor due to diverse environmental opportunities and challenges.
Allopatric Speciation: Occurs when a population is split by a geographical barrier, preventing gene flow and leading to the development of new species.
Sympatric Speciation: Happens within the same geographical area without a physical barrier, often caused by reproductive isolation, such as polyploidy leading to sterility.

Polyploidy

Autopolyploidy: Resulting from a single parent species doubling its chromosome number.
Allopolyploidy: Arises from the hybridization of two different parent species, producing a new polyploid organism.

Speciation Tempo

Gradualism: Suggests speciation occurs through slow, gradual changes over long periods, leading to major transformations.
Punctuated Equilibrium: Proposes that species remain stable for long periods, interspersed with rapid evolutionary changes.

Hybrid Zones

Hybrid Zone: Area where two species meet and interbreed, which can be influenced by geographical or habitat isolation and mechanical or behavioral barriers that restrict gene flow.

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Description

This quiz covers key concepts from Chapter 24 of biology, focusing on the differences between anagenesis and cladogenesis, as well as the concept of morphospecies. Test your understanding of these evolutionary terms and their significance in biodiversity and species classification.