1. Modern Evolutionary Classification
Section 17-2

2. Problems with Traditional Classification
Originally, organisms were grouped according to their physical features.
Biologists now group organisms into categories based on their evolutionary history, not just physical similarities. ≠

3. How are evolutionary relationships determined?
Structural similarities
Geographical distribution
Biochemistry
Similar DNA and proteins
Chromosome comparison
# and structure of chromosomes
Breeding behavior
Ex. Different calls keep mates from within same group
Embryonic development

4. Phylogeny What is it? How is it shown?
The evolutionary history of a species
How is it shown?
Using models called phylogenetic trees

6. Cladistics A system of classification based on phylogeny
It classifies organisms according to the order that they diverged from a common ancestor.

7. Cladistics
Scientists look at ancestral characters, those found in the entire line of descent
They also identify a group’s derived traits (unique inherited characteristics not found in a common ancestor) and use them to construct a branching diagram called a cladogram, a model of the phylogeny of a species.

9. How does a cladogram work?
2 groups on diverging branches probably share a more recent common ancestor than those groups farther away.
They show a probable evolution of a group of organisms from ancestral groups.

10. The Six Kingdoms of Organisms
Archaebacteria
Eubacteria
Protists
Fungi
Plants
Animals

11. Kingdom Archaebacteria
Prokaryotic
Unicellular
No membrane-bound nuclei
Most live in harsh environments
Swamps, deep-ocean vents, etc.
Mostly no oxygen (anaerobic)

12. Kingdom Eubacteria Prokaryotic ~5000 species Very strong cell walls
Live in most habitats, except extreme
Some causes diseases, most are harmless

13. Kingdom Protista Eukaryotic Lacks complex organ systems
Lives in moist environments
Some unicellular, some multicellular
Example: kelp

14. Kingdom Fungi Eukaryotic
Heterotrophic—absorbs nutrients from organic materials in the environment
Immobile (unmoving)
Unicellular or multicellular
Over 50,000 species

15. Kingdom Plantae Eukaryotic Multicellular Photosynthetic Immobile
Cells tissues organs organ systems
Over 250,000 species

16. Kingdom Animalia Eukaryotic Multicellular Heterotrophic
Mobile (move from place to place)
Cells tissues organs organ systems