Chapter 17 Classification Section 2 Systematics

1. Chapter 17 ClassificationSection 2 Systematics The goal of systematics is to classify organisms in terms of their natural relationships.

2. Phylogeny- evolutionary history of a species or taxon • Phylogenetics- the study of the evolutionary or ancestral relationships among taxa

3. How do systematists hypothesize about phylogenetics? • Compare visible similarities in fossils or living organisms • Homologous and derived characters • Chromosomes and macromolecules DNA, RNA, amino acids

4. Although analogous structures may infer a distant ancestor they are not used by biologists to classify organisms.

5. Embryo development

6. e • The relationships they propose are represented by a phylogenetic diagram a.k.a. family tree

7. Homologous features- items that share a common ancestry • Analogous features-similar function but not a similar lineage-infer a distant common ancestor • Scales in snakes and pangolins are an example of analogous features

8. Cladistics • A system of phylogenetic analysis using shared and derived characters as the only criteria for grouping taxa Derived character-a feature that evolved only within the group under consideration Shared character- a feature all members of a group have in common

9. Cladogram- an ancestry diagram • Used to hypothesize the sequence in which different groups evolved

10. In constructing a cladogram, one group is used for comparison that is very different than the rest- out-group • Cladists assume that organisms that share one or more derived characters probably inherited those characters from a common ancestor

11. No phylum or class names are used in cladograms • A cladogram represents the relationships between a group of organisms based on shared and derived characters