Living organisms on this planet are "organic." This means that they contain carbon, and are therefore "carbon based." But that's not enough to just be alive. For something to be considered "alive," it has to have several distinct features: A living organism must be able to metabolize food for energy, grow, reproduce themselves, and respond to stimuli. Your cat, your goldfish, your little sister or brother, your uncle carl, a mouse and a moose, as well as the tiny Malaria parasite Plamodium vivax, can all do that, and are thus alive as we understand it. Even plants can do this stuff, and they are alive as well.
Living things are classified in an order first suggested by Carol Linnaeus in 1737 when a book of his was published that suggested a two-part naming system for living things, now known as Binomial Nomenclature. Let's look at Genus and species, the last two definitions on the table below. They define a distinct organism, different from all others. An example might be Tyrannosaurus rex. You are a Homo sapien. There can be many organisms within the same genus, but only one species. Please notice that genus is capitalized, and species is lower case. The definition of a species is whether it can interbreed with other organisms from the same genus. If no, it's a separate group.
This binomial nomenclature was eventually expanded to contain the following in order to further classify living things.
Domain: There are three domains; Archaea, Bacteria, and Eukarya.
Kingdom: "Animalia, Plantae, Fungi, Protista, Archaea/Archaebacteria, and Bacteria/Eubacteria."
Phylem: Is a way of grouping related organisms together. All members of a phylum share a common ancestor and physical similarities. "The animal kingdom Animalia (animals), contains approximately 32 phyla, the plant kingdom Plantae contains about 14, and the fungus kingdom Fungi contains about 8 phyla." - Wikipedia (don't trust Wikipedia).
Class: A class is a narrowing down traits and characteristics. For instance, the class Chordata includes mammals, reptiles, and amphibians. The class arthropoda includes insects and arachnids.
Order: "Organisms in each class are further broken down into orders. A taxonomy key is used to determine to which order an organism belongs. A taxonomy key is nothing more than a checklist of characteristics that determines how organisms are grouped together." - http://www.softschools.com/science/biology/classification_of_living_things/
Family: "Orders are divided into families. Organisms within a family have more in common than with organisms in any classification level above it. Because they share so much in common, organisms of a family are said to be related to each other. Humans are in the Hominidae." - http://www.softschools.com/science/biology/classification_of_living_things/
Genus: "Genus is a way to describe the generic name for an organism. The genus classification is very specific so there are fewer organisms within each one. For this reason there are a lot of different genera among both animals and plants. When using taxonomy to name an organism, the genus is used to determine the first part of its two-part name." - http://www.softschools.com/science/biology/classification_of_living_things/
Species: "Species are as specific as you can get. It is the lowest and most strict level of classification of living things. The main criterion for an organism to be placed in a particular species is the ability to breed with other organisms of that same species. The species of an organism determines the second part of its two-part name." - http://www.softschools.com/science/biology/classification_of_living_things/
subkingdom Eumetazoa
symmetry group Bilateria
embryonic subgroup Deuterostomia
phylum Chordata
subphylum Craniata
family Hominidae
genus Homo
species Homo sapiens sapiens; Linnaeus"
- https://projects.ncsu.edu/cals/course/zo150/mozley/humans.html
We humans have to classify everything to keep stuff straight. We divide the one big patch of liquid water on this planet into seas, oceans, sounds, gulfs, fjords, etc. Taxonomy is the way we classify living organisms. And yes, plants, seaweed, mushrooms, and bacteria are all alive and therefore organisms that we classify.
1. What makes something alive? Is a rock alive? Is a snake alive?
2. "Kingdom" on the above list is the major deciding factor in classification. It first separates organisms by whether they have a spine or not. What word describes an organism with a spine? Without a spine?
4. Why would scientists choose to study only one particular subject in biology? My daughter does DNA research to look for things that might help people with diabetes. Is she a biologist or a chemist?
5. What is the defining factor on whether there is a difference between species?