18.1 Classification

The need for systems.

I. Taxonomy- the science of describing, naming and classifying organisms.a. this is necessary because there are millions of organisms we haven’t classified yet.b. so far 1.7 million have been named.

What kind of bird is this?

This is a robin to Europeans!

The need for systems. This is why common names are not

used to classify. Scientists classify organisms into

different categories called taxa.(singular taxon).

Scientific Naming Carl Linnaeus popularized a

system for naming all species in the 1750’s.

Binomial nomenclature=was his two part naming system.

Every species has a two part name:a. Homo sapienb. Felis domesticus

Scientific Naming Linnaeus once said that “binomial

nomenclature is one of the greatest achievements in science.”

Carl Linne was his original name until he decided to “latinize” his name!

Rules for scientific naming:

1. No two species can have the same name.

2. Always made up of two Latin or “Latin like” terms.

3. The first word is made up of the organism’s genus.

4. The second word is the “species identifier” (the completely unique part).

Rules for scientific naming:

5. The first word should be capitalized.

6. The second word should be lowercase.

7. Both terms should be italicized.Make a scientific name for yourself:

Equus caballus

Acer rubrum

Zea mays

Canis familiaris aka: ALLIE STIPANOVICH

The Linnaean System Linnaeus grouped organisms

according to their similarities in form and structure.

He categorized them into eight levels:Domain, Kingdom, Phylem, Class, Order, Family, Genus, Species.

The Levels:

1. Domain- differentiates between cell type. (3 categories)

2. Kingdom-Large groups such as:plants, animals, fungi (6 categories).

3. Phylum-Exist within kingdoms. Humans in phylum chordata.

The Levels4. Class- subgroups of phylums.5. Order- subgroups of classes.6. Family- subgroup of orders.7. Genus-subgroup of families. Very

closely related species.8. Species- A unique group of

organisms united by their ability to breed. Also has unique characteristics.

Lets review!

1. Why do biologist use the classification system?

2. What is the naming system called?3. How many domains and kingdoms

are there?4. What kingdom do humans reside

in?

MODERN SYSTEMATICS 18.2

I. Traditional Systematics II. Phylogenetics III. Cladistics IV. Inferring Evolutionary

Relatedness

I. Traditional Systematics Scientists traditionally have used

similarities in appearance and structure to group organisms

EXAMPLE: Ungulate Mammals

BUT, this approach has proven problematic b/c some organisms LOOK similar but turn out to be DISTANTLY related

EXAMPLE: birds were thought to be a completely separate group, unrelated to reptiles(this is a Norfolk Island green parrot)

Norfolk Island- off the northeast coast of Australia

Fossil evidence now shows that birds are descended from a subgroup of dinosaurs (reptiles) called theropods

Systematics is the revision of classification and procedures. This is necessary as more (fossils) are discovered

EXAMPLE of a FOSSIL: Conifer plant fossil found in Thompson Springs, Utah

II. Phylogenetics Grouping organisms by similarity is

often assumed to reflect phylogeny, but inferring phylogeny is complex in practice.

PHYLOGENY=the ancestral relationships between species

EXAMPLE: Modern phylogenetic tree that hypothesizes the relationships between several groups

Misleading similarities-not all similar characteristics came from the same ancestor

EXAMPLE: The wings of insects and the wings of birds did not evolve from the same CA (common ancestor)

* Insects had wings long before birds*

Judging relatedness- are some characteristics more important than others?

Different scientists have different answers!

young lady or old lady???

III. Cladistics Cladistic analysis is an OBJECTIVE

way to select the most likely phylogeny among a given set of organisms.

Cladistics is a method of analysis that infers phylogenies by careful comparisons of shared characters.

Comparing Characters: ancestral character/derived character

Seeds:

Shared by all living conifers

Flowers: shared only by flowering plants

This is a “meat flower” found in Indonesia that has a scent of rotting meat…

Why????

Constructing Cladograms-All groups that arise from one point belong in a CLADE Each CLADE is usually compared with

an OUTGROUPCLADE

OUTGROUP

IV. Inferring Evolutionary Relatedness Biologists compare many kinds of

evidence and apply logic carefully in order to infer phylogenies.

Morphology refers to the physical structure or anatomy of organisms We can compare morphology to

determine relationships

What other animal’s morphology can we compare to this horse’ morphology????

Molecular evidence includes DNA, RNA, and proteins that can be compared to infer phylogenies

The principle of parsimony holds that the simplest explanation for something is the most reasonable

Given 2 possible cladograms, the one with the fewest changes is preferred