How Do Scientists Classify Life on Earth Life

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 Bacteria • No nucleus (prokaryotes) • Microscopic cells • Adapted to life in extreme environments: • No nucleus (prokaryotes) • Microscopic cells • Some bacteria: • • • Deep ocean thermal vents Hot springs Very acidic or salty water Bottom of the ocean Petroleum deposits deep underground • Other planets? ? ? • 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 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