How Do Scientists Classify Life on Earth?

Life On Earth Scientists have identified approximately 2.5 million species of organisms on Earth, but estimate that there may be as many as 10 million inhabiting the Earth! Of these organisms, the largest percentage are single-celled bacteria!

Why Classify? It help us understand more about the diversity of living things on Earth To understand how organisms are related to one another and how they are different from one another.

Who Invented the First System for Classifying Living Things? Organisms were first classified more than 2,000 years ago by Greek philosopher Aristotle. He classified things as either Plant or Animal.

Aristotle’s System He grouped animals into Land Dwellers, Air Dwellers, and Water Dwellers. Can you think of any problems with Aristotle’s system?

The New System: taxonomy The discovery of new living things (thanks to better scientific tools) has resulted in a new classification system. The science of classifying living things is called taxonomy. Scientists developed a a ranking system for classifying organisms consisting of groups within larger groups. Today we will learn about Domains & Kingdoms.

THE THREE DOMAINS All living organisms are organized into:  Eukarya – Eukaryotes – cells with a nucleus  Bacteria – Prokaryotes – cells without a nucleus  Archaea – Prokaryotes – cells without a nucleus

EUKARYA DOMAIN Animal Kingdom Plant Kingdom Fungi Kingdom Protista Kingdom * Most organisms that we can see and that we are familiar with are in the Eukarya Domain.

Archaea and Bacteria Domains Archaea No nucleus (prokaryotes) Microscopic cells Adapted to life in extreme environments: Deep ocean thermal vents Hot springs Very acidic or salty water Bottom of the ocean Petroleum deposits deep underground Other planets??? Bacteria No nucleus (prokaryotes) Microscopic cells Some bacteria: are decomposers in the food chain are used to make food (yogurt, cheese, etc.) produce antibiotics cause disease in humans and animals

Plants Eukarya Domain Trees, grass, flowers, ferns and mosses are examples of plants Multicellular Cells have a Nucleus Make their own food using water, carbon dioxide, chlorophyll and light energy Cells have a boxy shape and contain a green chemcial called chlorophyll

Animals Eukarya Domain Humans, Insects, Birds, Reptiles Multicellular Cells have a Nucleus Do not make their own Food Over 1,000,000 on the planet!

Fungi Eukarya Domain Yeasts, mushrooms, and molds Multicellular Have a Nucleus Do not make their own food- they decompose other organisms

Protists Eukarya Domain Parameca and Euglena are examples Mostly unicellular Have a Nucleus Some can make their own food, some can’t Microscopic but larger than bacteria Have different shapes Most are able to move

Bacteria Bacteria Domain Some are beneficial to humans (l. Acidohpilus) Some cause disease (e. choli) Unicellular No Nucleus Some can make their own food, some can’t Microscopic