BIOL202 - Lectures 21-25

BIOL202 - Lectures 21-25 - LECTURE 21 SPECIES AND...

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LECTURE 21 SPECIES AND SPECIATION Systematics The study of the evolutionary relationships among organisms. Goals: 1) the identification of individual species 2) Discovering/describing the phylogeny of all life on Earth – the entire pattern of descent – the Great Tree of Life Taxonomy The naming and “classification” of living organisms, i.e., grouping living organisms into kingdoms, phyla, classes, families, etc., based on their similarities and evolutionary history
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SPECIES CONCEPTS What is a species? How do we sort individuals into species ? Species can be, and are, defined and identified in different ways: Morphological species a morphological species is a group of individuals in one or more populations that have the same basic form or morphology Sorting by morphology is often the first step taken in sorting extant individuals into species It is the only way to sort extinct, fossil organisms into species Biological species a biological species is a group of individuals in one or more populations that potentially can interbreed with one another and produce viable, fertile offspring identifying biological species requires detailed,extensive field observations of breeding behavior, reproductive success, etc. Genealogical species a genealogical species is a group of individuals in one or more populations that share common, unique“genetic markers ,” i.e., unique sequences of DNA which suggests that these individuals represent a separate and unique evolutionary lineage
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Morphological species: African ♂ robber flies Robber flies: aerial predators of the insect world Male genitalia When insect taxonomists are trying to sort morphologically similar individuals into species, then concentrate on the genitalia (genitals and associated organs). Why? If two individuals have differently structured genitalia, it strongly suggests they belong to different (biological) species. The lock-and-key phenomenon:
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Genitalia of two species of robber flies from Africa
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Biological Species : Baltimore and Bullock’s Orioles Baltimore Oriole, Icterus galbula Bullock’s Oriole, Icterus bullockii o Initially divided into two species based on morphology Mid-1900s: discovery of some mixed species pairs & hybrid individuals where the two species meet on the Great Plains (a “hybrid zone”) 1973: Based on initial reports of interbreeding, lumped into a single biological species, the Northern Oriole 1980s: Further research suggest hybridization was very rare and that hybrids were inferior; “hybid zone” was not expanding 1996: Two forms once again placed into separate species
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Identifying Genealogical Species: basic approach Extract a sample of DNA from individuals in two groups in questions o Examine the sequence of nucleotides (A, T, G, C) for specific regions of DNA Can use coding or non-coding DNA from either nucleus or mitochondria Different sequences referred to as alleles or haplotypes Note: Different allele/haplotypes are created by mutation
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BIOL202 - Lectures 21-25 - LECTURE 21 SPECIES AND...

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