BI102

General Biology

Spring 2010

Dr. Brian K. Penney

Goulet 2320

603 641-7149

bpenney@anselm.edu

Brian K. Penney 's web page

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1. Compare the definitions, advantages and disadvantages of the two major species concepts

   Reliable definitions of a “species” are required both for studies of evolution and taxonomy (the science of naming/classifying life)

   • Morphological species concept: classification based on observable and measurable phenotypic traits
   • Biological species concept: a species is a population or group thereof whose members potentially interbreed and produce fertile offspring
   • Other species concepts (genealogical, ecological) may be more applicable to specific problems or taxa

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2. Describe five types of prezygotic barriers and three types of postzygotic barries that prevent populations belonging to closely related species from interbreeding

   Reproductive barriers may evolve as populations diverge, and can be classified as:

   • Prezygotic: temporal, habitat, behavioral, mechanical, gametic
   • Postzygotic: hybrid inviability, hybrid sterility, hybrid breakdown
   • You should consult Table 14.3 and understand the definitions of all these mechanisms!
   • Reproductive isolation may be studied in hybrid zones

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3. Explain two major ways that populations can fragment leading to speciation, with two examples of each.

   Divergence (reduction of gene flow) can happen through two major groups of mechanisms

   • allopatric speciation (geographic isolation): e.g. canyon formation, founders arriving on islands, etc.
   • sympatric speciation: polyploidy, resource isolation, etc.

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4. Compare the gradualism model with the punctuated equilibrium model of evolution, and explain how each model applies to the fossil record.

   One current debate concerns the tempo of evolution and what gaps in the fossil record indicate.

   • gradualism: species evolve gradually from the ancestral population as differences accumulate. Gaps in fossil record are soleley from incomplete preservation of species.
   • punctuated equilibrium: species undergo long periods of evolutionary stasis, and new species arise during short bursts of change. Some gaps in fossil record may be because species changed extremely quickly (for geologic time)

Copyright 2007-2010, Brian K. Penney

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