This simple cartoon shows general similarities and differences between eukaryote and prokaryote cells. Click on image for full size (24K GIF) Image modified from NIH

The Cell Theory states that all living things are made of cells, which are the basic units of life, and that cells come from other cells.

Prokaryotic cells have no nucleus or organelles enclosed within membranes. Species in the domains Archaea and Eubacteria have prokaryotic cells.

Eukaryotic cells have a nucleus and organelles that are surrounded by membranes. Each organelle does a specific cell function. All species in the Eukaryota domain (protists, fungi, plants, and animals) have eukaryotic cells. Individual protists are small and have only one cell, while individual plants and animals can have trillions of cells. Complex creatures like humans have special cells for particular functions such as carrying oxygen around the body, digesting food, or making bone.

One theory about how cells originally formed states that the first life on Earth consisted of several types of tiny, simple prokaryotic cells. Over time, prokaryotes with different specializations became engulfed within larger prokaryotes. This was beneficial to both the larger prokaryotes who were able to perform more functions with help from the smaller ones trapped within and the smaller prokaryotes who were protected within the larger one. Over millions of years the smaller prokaryotes became the organelles within eukaryotic cells.

This simple cartoon shows general similarities and differences between eukaryote and prokaryote cells. Click on image for full size (24K GIF) Modified from NIH

The Cell Theory states that all living things are made of cells, which are the basic units of life, and that cells come from other cells.

Prokaryotic cells have no nucleus or organelles enclosed within membranes. Species in the domains Archaea and Eubacteria have prokaryotic cells.

Eukaryotic cells have a nucleus and organelles that are surrounded by membranes. Each organelle does a specific cell function. All species in the Eukaryota domain (protists, fungi, plants, and animals) have eukaryotic cells. Individual protists have only one cell, while plants and animals can have trillions of cells. Complex creatures like humans have special cells for special functions like carrying oxygen around the body, digesting food, or making bone.

This simple cartoon shows general similarities and differences between eukaryote and prokaryote cells. Click on image for full size (24K GIF) Modified from NIH

All living things, from tiny bacteria to giant elephants, are made of cells. Tiny bacteria have only one cell while larger animals and plants can have trillions of cells.

Where do cells come from? New cells are made from old cells. Right now, even without your knowledge, your cells are making new cells!

There are two different types of cells.

Prokaryotic cells are bacteria cells! Species in the domains Archaea and Eubacteria have prokaryotic cells. Each cell contain everything the bacteria needs, but the stuff is not organized very much, just like a messy room!

Eukaryotic cells are the cells of plants, animals, fungi and protists (living things in the Eukaryota domain). Protists are usually quite small and have only one cell. But plants and animals can have tons of cells! These cells can be complex and are very well organized, just like a tidy room! Different parts of the cell do different things. Complex creatures like humans have special cells for special functions like carrying oxygen around the body, digesting food, or making bone.