General Biology 101

General Biology 101

Chapter Outlines

Starr & Taggert

10th edition

Chapter 19

Section 19.8

Taxonomy & Classification

Taxonomy – The field within biology that attempts to identify, name and describe species.

Manner in which living things are named:

Formulated by Carolus Linnaeus

Binomial system (meaning each species has 2 latin names to distinguish it).

-Genus – 1st letter is always capitalized

-Species (specific epithet) – letters are all lower case.

Groupings of species – The Higher Taxa

Originally everything was divided into two groups: plants and animals.

Higher taxa – everything that is ordered above genus and species level i.e. family, order, class, phylum and kingdom.

Phylogeny – Evolutionary relationships among species.

Based on clues from:

-Fossil record

-Geologic record

-Morphology

-Biochemistry

Classical taxonomy – uses degrees of morphological divergence to make model tree diagrams to show relationships amongst the members.

Cladistic taxonomy – Branches of tree show similar groupings.

Derived trait – A novel feature that evolved once and is shared only by descendants of the ancestor in which it first evolved.

Cladograms – evolutionary trees based on groups that share derived traits.

Monophyletic group – All descendants from an ancestral species in which the trait is first evolved. “Single tribe.”

Classification Systems:

1. 5 Kingdom systems (R. Whittaker).

Includes:

1)Monera – single celled prokaryotes (includes producers), pathogens, and decomposers.

2)Protista – single and multicelled eukaryotes (microscopic usually).

3)Fungi – e.g. mushrooms and yeast

4)Plantae – all green plants, including most algae forms

5)Animalia – e.g. humans, insects, worms

1. 3 Domain system (one that is most current and is based primarily on biochemical evidence deciphered by molecular genetics).

1)Eubacteria – true bacteria

2)Archaeabacteria – a.k.a. (archeans) include prokaryotes that live in extreme environments. Differ based on their cell wall compositions.

3)Eukarya – include protistans, plants, fungi and animals.

There is a proposal to go to the 6 kingdom system with monera being replaced by Archaebacteria and Eubacteria. [this proposal is based on modern biochemistry].

Section 19.8

Constructing a Cladogram

Depends upon looking at selected, various traits e.g. morphology (shape), physiology (function), and behavioral traits. Cladograms represent relative relatedness, not ancestry.

Related vocabulary:

“In” Group – A group of related taxa (groupings) that share certain traits.

“Out” group – the organism in a cladistics analysis with the fewest derived traits.

Other terms introduced in this section.

Ancestor

Nodes (intersection of derivation).

Note: The higher up (or typically to the right) one is on the tree the more derived traits that are shared. Cladograms don’t correlate with geologic time, they are used to show relative ancestry.

Note: Modern, existing species are neither ancestors nor descendents of one another e.g. gorillas and humans.