Copyright PEER.tamu.edu

Why classify things? Say you go to the mall to get some new clothes. Where would you go? How would you know to go to that particular store?

How is a mall organized? Food Court Big Department Stores Specialty Clothing Stores Jewelry Stores Electronics Stores Shoe Stores Toy Stores Kiosks

Can you imagine if the mall was just one big store and you had to go through rows and rows of “stuff” to find the right clothes in the right brand and the right size for you? How long would that take?

Big Idea: The mall, your city, your school, and your closet (hopefully) are all organized so that you and other people can get things done without wasting extra time and effort. Scientists also organize or classify things so that they are easier to investigate and understand.

Here are some things that scientists classify or organize: The human body The elements Interactions in Ecosystems

Scientists also Classify Living Organisms How could you classify these living things?

Quick, organize these living things into groups:

Did you do it like this?

Or this? Are there any other ways to group these living things?

Veterinarians classify organisms for many reasons: Veterinarians have to classify infectious organisms so that they can understand how to treat them, according to their characteristics. It is important to know if they are bacteria, protozoa, prions, or viruses. Veterinarians have to classify their patients so that they can understand how their patients’ body systems work and how to treat those systems. Different species, and even different breeds, react differently to treatment.

The most basic classification system is based on Domains and Kingdoms. Organisms are classified into Domains or Kingdoms based on these characteristics: 1. Whether they are unicellular or multicellular 2. Whether they are prokaryotic or eukaryotic 3. Whether they have a cell wall or cell membrane 4. Whether they have membrane bound organelles 5. Whether they are autotrophic or heterotrophic 6. Whether they reproduce sexually or asexually 7. How they tolerate heat, salt, or other extreme conditions

Basic Classification Domains: There are three Domains of living organisms based on their characteristics: Archaea (also called Archaebacteria) Eubacteria (also called Bacteria) Eukaryota (also called Eukarya) Archaea Eubacteria Eukaryota

Basic Classification Kingdoms: The Domains can also be split into Kingdoms which further divide the organisms by their characteristics.

Domain Archaea “Archaea” means “ancient” bacteria. Organisms in Archaea are: Unicellular Prokaryotic Autotrophic or heterotrophic Organisms that reproduce asexually Bacteria that have adapted to extreme environments. Some can survive in extremely hot environments, like around hot springs and geysers. They are called thermophiles. Some can survive in extremely salty environments, like The Great Salt Lake in Utah. They are called halophiles. The Domain Archaea has one Kingdom, also called Archaea Aerial view of hot spring at Yellowstone

This hot spring is flowing into the Firehole River in Yellowstone. The colors are caused by different varieties of archaebacteria and other microscopic life forms. Scientists can distinguish temperatures of water by the colors present.

Domain Eubacteria “Eu” means “true” bacteria. They are: Unicellular Prokaryotic Autotrophic or heterotrophic Organisms that reproduce asexually The most abundant organisms on earth. One bacterium can give rise to 10 million in 24 hours. Found in almost every habitat on earth. The Domain Eubacteria has one Kingdom, also called Eubacteria. Many are common infectious agents.

This is a picture of bacteria on the skin. Bacteria can be shaped like a sphere (cocci) like this picture, like a rod, or like a spiral. The structure in the middle of this picture is a hair follicle with a hair growing out of it.

Terminology: The Domains Archaea and Eubacteria are commonly grouped together in discussion and called prokaryotes because they lack membrane-bound nuclei and membrane-bound organelles. Nucleus and Organelles

Domain Eukaryota (Eukarya) Eukaryotic Very diverse Unicellular or multicellular Autotrophic or heterotrophic Reproduce sexually or asexually Can be split into 4 Kingdoms- Protista Fungi Plantae Animalia

The 4 Kingdoms in Eukaryota Protista Mostly unicellular and microscopic Autotrophic or heterotrophic Can be infectious agents Examples: Amoeba Algae Daphnia Plasmodium (causes malaria) Plantae Multicellular green plants Autotrophic through photosynthesis Have a cell wall Examples: Mosses Ferns Trees Flowering Plants Fungi Multicellular Heterotrophic Decomposers Can be infectious agents Examples: Mushrooms Athlete’s foot Bread Mold Animalia Multicellular Animals Heterotrophic No Cell Wall Examples: Insects Spiders Crabs Birds Humans

DOMAINSDOMAINS KINGDOMSKINGDOMS

Think Break: Where do Viruses fit in this classification system? Where do Prions fit in this classification system?

How would you classify these? A organism that can exist in extremely hot temperatures and that is made of only one cell with no nucleus Domain: ArchaeaKingdom: Archaea A green organism growing from the ground that is multicellular and that undergoes photosynthesis; its cells have nuclei and cell walls Domain: EukaryotaKingdom: Plantae

Try two more: This microscopic and one-celled organism lives in colonies with millions of others like it. It does not have a nucleus and cannot survive in extreme conditions. It could be an infectious agent. Domain: EubacteriaKingdom: Eubacteria This organism is a multicellular decomposer; its cells have nuclei. Domain: EukaryotaKingdom: Fungi

Classification Systems Can Change! Can you guess why? Classification systems change as new organisms are discovered and as more information is gained about known living organisms. Science is a “work in progress” and things change as new evidence is found.

Even though classification is not an exact science, it is a part of almost every aspect of our lives. Which one would you choose? Why?