Modern Classification17.2

What is a species It used to be thought that anything that

looked different were considered to be different species.

We now know that any given species has variation.

In the 1940’s scientists defined a species as a group of organisms that can interbreed and produce fertile offspring

Phylogenic Species Concept Phylogeny- the evolutionary history of a

species

The phylogenic species concept defines a species as a cluster of organisms that is distinct from other clusters and shows evidence of a pattern of ancestry and descent

But like all things they add to it Phylogenetic species concept. This deals

with species in terms of populations and ancestry.

It says two or more groups that evolve independently are classified as different species.

What's that funny P word mean? Phylogeny- the evolutionary history of a

species.

Remember all this classification starts with identifying characters A Character is a inherited feature that

can vary in a species.

There are 2 types of Characters you need to know. Morphological Characters-The size,

shape, and structure of an organism or one of its parts. Bone structure, coloration.

Biochemical Characters-molecular similarities and differences among organisms. Ex DNA, RNA

Quick Check! What's a species? We classify things based on their….? What are the different types of

characteristics?

Ok now I have all this classification stuff down what do I do with it??

Dichotomous Keys

Phylogenetic Trees

Cladograms

- a device used to identify organisms - uses couplets, which are pairs of highly organized statements

- a tree showing the evolutionary relationships among groups

- a diagram that represents the evolutionary tree of life- also includes characteristics

Taxonomic Devices

Cladistics Cladistics is the method that classifies

organisms according to the order that they diverged from a common ancestor.

CLADOGRAM

“clade” a group of organisms that includes an ancestor and all descendants

Scientists use Cladistics to make a cladogram.

Cladistics-a method of classifying according to when they diverged from a ancestor.

A cladogram (aka phylogenetic tree)- is a branching diagram that shows a proposed evolutionary history.

What taxon is most closely related to birds?

Which taxon is least closely related to humans?

Which taxon has the least recent shared ancestors with humans?

DO: What are the relationships between A, B, C, D, and E?

Character types Ancestral- a character found within the

entire line of decedents Derived-characters that are present in

one group but not the ancestor

How to read a cladogram

How to Build a cladogram. http://

ccl.northwestern.edu/simevolution/obonu/cladograms/Open-This-File.swf