There are actually eight main levels used by scientists to classify organisms, not seven. They are:

1. Domain: The broadest category, grouping organisms based on fundamental cellular differences. Examples: Bacteria, Archaea, Eukarya.

2. Kingdom: A major grouping within a domain, based on general characteristics like cell type, nutrition, and body structure. Examples: Animalia, Plantae, Fungi.

3. Phylum: A group of closely related classes sharing common features. Examples: Chordata (animals with a backbone), Arthropoda (insects, spiders).

4. Class: A group of closely related orders sharing common features. Examples: Mammalia (animals with fur and mammary glands), Aves (birds).

5. Order: A group of closely related families sharing common features. Examples: Primates (monkeys, apes, humans), Carnivora (meat-eating mammals).

6. Family: A group of closely related genera sharing common features. Examples: Felidae (cats), Canidae (dogs).

7. Genus: A group of closely related species sharing common features. Examples: *Homo* (humans), *Canis* (dogs, wolves).

8. Species: The most specific level, defining a group of organisms that can interbreed and produce fertile offspring. Examples: *Homo sapiens* (modern humans), *Canis lupus* (wolves).

Mnemonic: You can remember these levels with the mnemonic "King Philip Came Over For Good Soup."