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Understanding Species Classification in Biology

Explore how biologists classify organisms through interbreeding, hybridization, and phylogenetic analysis. Learn about biological species, evolutionary history, cladistics, and more in this insightful guide. Discover the complexities of species identification and taxonomy.

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Understanding Species Classification in Biology

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  1. Chapter 14 Section 2 How Biologists Classify Organisms Grade 10 Biology Spring 2011

  2. What is a Species? • Biological species: a group of natural populations that are interbreeding or that could interbreed, and that are reproductively isolated from other such groups

  3. What is a Species? • Hybrids: sometimes individuals of different species interbreed and produce offspring • Species are closely related when they can interbreed and produce fertile hybrids

  4. Evaluating the Biological Species Concept • Works well for most members of kingdom Animalia • Some species are able to form fertile offspring with closely related species • Fails to describe species that reproduce asexually • Biologist recognize species by studying an organism’s features

  5. Evolutionary History • Classification based on similarities should reflect an organism’s phylogeny • Its evolutionary history • This can be misleading, not all characters are inherited from a common ancestor • Wings of bird vs. wings of insect

  6. Evolutionary History • Convergent evolution: similarities evolve in organisms not closely related to one another, often because the organisms live in similar habitats • Analogous structures: similarities that arise through convergent evolution

  7. Evolutionary History • Divergent evolution: similarities evolve in organisms not closely related to one another

  8. Cladistics • Cladistics: method of analysis that reconstructs phylogenies by inferring relationships based on shared characters • Can be used to hypothesize the sequence in which different groups of organisms evolved

  9. Cladistics • Ancestral character: with respect to two different groups, a character is defined as an ancestral character if it evolved in a common ancestor of both groups • Ex. Birds and mammals, backbone is an ancestral character

  10. Cladistics • Derived character: evolved in an ancestor of one group but not of the other • Ex. Feathers evolved in an ancestor of birds that was not also ancestral to mammals

  11. Cladistics • Cladogram: branching diagram, shows the evolutionary relationships among groups of organisms

  12. Evolutionary Systematics • Evolutionary systematics: taxonomists give varying degrees of importance to characters and thus produce a subjective analysis of evolutionary relationships • Phylogenetic tree: branching diagram based on evolutionary systematics

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