Human Impact on the Evolution of the Cheeta!!

Chapt. 22:“Constructing and Using Phylogenies”

One Species from Another!!I DON”T BELIEVE IT!!

Systematics-- the study of the evolutionary relationships of organisms;relationships of present-day organisms with the past.

How can we tell what species came from another? What species are more closely related than others?What species will persist into the future?

Taxonomy- the classification of different speciesTaxon- a unit in a classification system

Carolus Linnaeus- the binomial nomenclature system

I.e. Genus, species-- Homo sapiens

Binomial Nomanclature:Genus name is capitalized, species name is not, both are italicized. e.g. Escherichia coli, Drosophila melangaster, Agropyron smithii

(also E. coli, D. melangaster, Agropyron spp.or sp.)

What is the “true” phylogeny of a particular group of organisms?Evidence: fossils (extinct) and living (extant) organisms

Systematics:(1) Determine evolutionary relationships and express them in

phylogenetic (family) trees(2) Express evolutionary relationships in a classification system

Hierarchical Classification (order of taxons in the Linnaean system):Species--Genus--Family--Order-- Class--Phylum--Kingdom

(see Fig. 22.2 for the moss rose, Rosa gallica)

Cladistics and cladograms-- evolutionary trees; points at whichbranches occur, respectivelyClade- a complete portion of the phylogeny that comes from

a common ancestor

Phylogenetic tree- cladogram with dates of branches; common ancestor at bottom (Fig. 22.6)

Systematists must determine ancestral (original) versus derived (changed from original) traits

Special versus General homologous traits-- shared by a few vs. shared by many

To construct a cladogram-- (1) select group of organisms(2) choose traits to compare(3) determine if they are ancestral or derived

Outgroups- a group branches off due to Special homologous traits, but still have General homologous traits in common

Most challenging task of a cladogram- recognizing divergence versus convergence in ancestral traits, e.g. homlogous structures (cactus spines and bat/bird wing).

PROBLEM: Homoplasy = convergent evolution of same trait more than one time (e.g.modified leaves and analogous wings of insects and birds, Fig. 22.4). Homologies from Analogies, Fig. 22.5)

Table 22.1 and Fig. 22.6-- Derived traits in vertebrates and a probable cladogram.

I.e. jaws, lungs, claws/nails all derived traits; feathers and fur (birds/mammals) derived from claws and nails (reptiles).

Molecular Evolution and Phylogeny-- ancestry and cladograms based on differences in proteins and nucleic acids (RNA and DNA), no longer just gross morphology

MICROEVOLUTION-- alleles change = changes in DNA & proteins(Review Chapt. 12)

e.g. all land plants have 100 genes for making RNA to controlsynthesis of photosynthetic enzyme production

DNA Hybridization-- mix DNA of two species--denatured--reassociated-- degree of reassociation =closer ancestry (Humans and chimpanzees,

1.6 % difference in DNA sequences; cow/pig = 20%)

Table 22.2 and Fig. 22.9 (panda bear ancestry; dogs split with racoons-pandas-bears)

Figure 22.10, Horseshoe crab evolution from over 600 mya !!Figure 22.13, Phylogeny of the Domains and Kingdoms

Where are the fungi in terms of being a plant or animal?