Identifying Species: Using the Species Concept

1. Identifying Species: Using the Species Concept • Morphological Species Concept 2. Biological Species Concept 3. Phylogenetic Species Concept

2. 1. Morphological Species Concept • Focus on the morphology of an organism • Morphology refers to: body size, shape, and other structural features • Organisms are compared and scientists decide whether similar organisms represent different species

3. 1. Morphological Species con’t ADVANTAGE: • Simple to use • Most widely used by people in general DISADVANTAGE: • Too much variation within a species

4. 2. Biological Species Concept • Focus on similar characteristics AND the ability of organisms to interbreed in nature and produce viable, fertile offspring

5. 2. Biological Species con’t ADVANTAGE: • It is widely used by scientists DISADVANTAGE: • Can’t be applied for species the reproduce asexually • Uncertain for populations that are physically separated and don’t have the opportunity to breed naturally • Can’t be applied to fossil species, which are no longer reproducing

6. 3. Phylogenetic Species Concept • Focus on evolutionary relationships among organisms • A species is defined as a cluster of organisms that is distinct from other clusters and shows a pattern of relationship among organism

7. 3. Phylogenetic Species con’t ADVANTAGES: • Can be applied to extinct species • Considers information about relationships among organisms learned from DNA analysis DISADVANTAGE: • Evolutionary histories are not known for all species

8. Phylogeny....we need to know a bit about evolution • Evolution: the scientific theory that describes changes in species over time and their shared ancestry. • All living things are descended from a common ancestor. • When scientists say that two species are closely related, it means that they share a common ancestor in their recent, evolutionary, history.

9. Problems with Morphological based classification

11. Which are more closely related?

12. More About Phylogeny • Phylogeny refers to the evolutionary history of a species • Phylogenies are determined through: • Developmental Traits (Embryology) • Structural Traits (Homology) • Molecular Traits (Genetics & Molecular Biology)

13. Phylogeny con’t: Organisms likely share a common ancestry if: • They show similar stages of embryological development • They have similar anatomical structures, regardless of function • They are genetically similar

14. Evidence of common ancestry: Embryological Similarities • It has been observed that the early stages of embryo development are similar in closely related species • All vertebrate embryos go through a state in which they have gill pouches similar to those of fish and a postanal tail.

15. History: Recapitulation Theory: • Theory proposed by embryologists in the 19th century (Ernst Haeckel) • The notion that “ontogeny recapitulates phylogeny” is an overstatement. Some scientists proposed that the stages of embryonic development was a replay of its evolutionary history. This is generally not accepted; however, what recapitulation does occur is a replay of embryonic states, not a sequence of adultlike states of ever more advanced vertebrates Ontogeny: the development of an individual organism Phylogeny: evolutionary history of the species Recapitulates: replay

16. Evidence of common ancestry: Anatomical Similarities - Homology • Homologous Structures: structures of different organisms that are similar in form

17. Evidence of Common Ancestry: Molecular Similarities • Evolutionary relationships among species are reflected in DNA and proteins • Two species that have matching gene and protein sequences would share a common ancestor • Humans and chimpanzee share 99.9% identical DNA sequence

18. International Barcode of Life Project (2010) U of Guelph • http://ibol.org/ • Use DNA technology to create a DNA profile of every species in the form of a barcode • Field biologists can then use a hand-held device to identify species using a small sample of DNA (ie: feathers, hair, meat etc) • Malaise project!

19. Phylogenetic Trees • Based on common ancestry, phylogenetic trees can be made

20. Importance of Classification • Drugs – narrow your search for pharmaceuticals to closely related species that produce valuable proteins/chemicals • Disease – trace the transmission of diseases; disease spread more rapidly between species that share common genetics • Agriculture – increase crop yield and resistance by cross-breeding related species; biological control of natural predators, parasites, disease • Conservation – ex: In 2001 African forest elephant, Loxodonta cyclotis was declared a different species from African bush elephant, Loxodonta africana; only Loxodonta africana was protected

21. Homework • Create a table to compare the three different species concepts. Include the advantages and disadvantages. • Construct a chart that differentiates the three main types of evidence scientists use to determine relationships among species.

22. Homework con’t 3. In northwestern Ontario, there are two similar-looking garter snakes: the red-sided garter snake and the eastern garter snake. The two interbreed successfully in nature in that part of Ontario, producing offspring that have a mix of physical traits of the two. The eastern garter snake also co-exists in southern Ontario with another very similar snake, the eastern ribbon snake. However, these two snakes are not known to interbreed successfully. Infer whether these three snakes are the same species or not. Explain your reasoning.