Fossils

Steven Dutch  University of Wisconsin - Green Bay

Fossils - Remains of Ancient Plants And Animals, Evidence of Life

Commonly Preserved
Hard Parts of Organisms:

Rarely Preserved
Soft or Easily Decayed Parts of Organisms

Types of Fossils

Pseudo-Fossils: Look Like Fossils But Aren't

Fossils Occur Almost Exclusively in Sedimentary Rocks

To Be Preserved, Organisms Have to Be:

These Are Difficult Requirements! Probably Only One Organism in Millions Ever Gets Fossilized

Good Index Fossils

Classification of Organisms (Taxonomy)

Classical System - Linnaeus, ca. 1760

Organisms are known by their genus and species names

Why use this system?

Classification - The Modern System

Once upon a time, kingdoms were pretty trivial: Elephants were animals, Redwoods were plants. But in the last few decades the most interesting concepts in taxonomy have been happening at the highest levels.

For years, some biologists were frustrated by microorganisms that had characteristics of both animals and plants. They urged putting these organisms into a separate kingdom.

As long as we're on the subject, why are fungi plants? They don't respond to stimuli like animals, but they lack chlorophyll and most of the structures of green plants. Some biologists began treating fungi as a separate kingdom.

Bacteria differ from all other organisms. If fungi deserve a kingdom, so do bacteria. Thus, about 20 years ago, many biology texts adopted the

Five-Kingdom Classification

Domains and Superkingdoms

Bacteria differ from all other organisms in not having a cell nucleus. Their DNA floats freely within the cell. The difference between bacteria and everything else suggests we need something even higher than the kingdom.

What's bigger than a kingdom? Maybe an empire, but most biologists prefer the term Domains. Some use Superkingdom. The current system of domains and kingdoms is:

Why didn't Linnaeus think of this?

Easy. You need molecular biology and electron microscopes to see the defining characteristics at the domain level.

Classification of Animals

There Are About 25 Phyla of Animals. Most Important Are:

Fossil representatives in parentheses

Classificiation of Plants

There Are About Ten Plant Phyla - Most Important Are:

Plant Fossils Are Rarer Than Animal Fossils.
Leaves And Woody Parts of Higher Plants Most Common.

Evolution

There Are Over 1,000,000 Species of Animals (90% of Them Are Insects!) And 350,000 Species of Plants

Scientists Believe All These Species Arose Through Evolution

Development of Evolution Theory

Early Developments

Originator of Modern Ideas on Evolution -Charles Darwin

Natural Selection

All Living Things Are Made up of Cells. Most Cells Have a Nucleus Which Contains a Complex Molecule Called DNA. The DNA in Cells Contains a "Code" When The Cell Multiples, The DNA Code Governs The Makeup of The New Cell.

Sometimes The DNA Is Damaged by Chemicals or Radiation, or The DNA Code Isn't Copied Exactly in The New Cell. Either Way, The New Cell Is Slightly Different From The Old Cell. Such a Change Is Called a Mutation. 

Mutations Cause DNA Code to Be Changed in Passing From Parent to Offspring. If Mutation Is Major, it Usually Causes Offspring to Be Less Well Adapted Than Parents. Mutation Tends to Die out. If Mutation Is Minor, Has Little Immediate Effect on Offspring. Mutation Doesn't Die Out, But Is Passed On.

Most Organisms are already Well-Adapted, so any change is likely to be harmful. Mutations rarely have any immediate effect. If conditions change, then the mutation may be better for the organism, and those organisms without the mutation may die out.

For the historical context and responses to evolution see:

Mass Extinctions

Permian

Cretaceous

Causes ?

Were the Dinosaurs Failures?

We often use the term "Dinosaur" to denote something clunky or obsolete, but consider:

Written History Lasted 5000 Years The Dinosaurs Lasted 150,000,000 Years
For Every Year of written history: The Dinosaurs had 30,000 Years
For Every Day of written history: The Dinosaurs had 82 Years - a long human lifetime
For Every Minute of written history: The Dinosaurs had 3 weeks
For Every Second of written history: The Dinosaurs had 8.3 hours

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Created February 26, 1997; Last Update October 19, 1998